machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment. I read every comment and respond to most. n.b. There is a list of my first 800 posts in my post of 17 June 2021, titled "800 Posts"
I watch YouTube videos about megalithic sites around the world, including Peru, Cambodia, Russia, Bolivia, and especially, Egypt. I have been fascinated in the subject for over 50 years, since reading an article in National Geographic as a teenager, about the almost unbelievable stone work in Peru which was then ascribed to the Incas, (but that Inca origin theory now has many serious doubters).
One of those YT sites, “UnchartedX” , (to which I subscribe and support), frequently refers to the book “Lost Technologies of Ancient Egypt”, and recently did a 2 hour interview with the author, Christopher Dunn. The book was published in 2010, based on many visits to Egypt by the author. The interview led me to purchasing and reading the book. Although now 9 years (oops 11 years) since publication, his work is respected by Egyptologists, academics, and more free thinking enthusiasts such as YouTubers like Ben of UnchartedX, quite an accomplishment considering the degree of hostility between the opposing views.
Christopher Dunn is/was a toolmaker, engineer, and manager in the US aerospace industry, and expert user of CAD, CAM, lasers, metrology, and photogrammetry. He is also into ancient history. So when he visited Egypt he looked at the pyramids and other buildings and monuments, with the eyes of an engineer, and wondered how they “did it”. Over the course of many visits, he took increasingly sophisticated metrology devices and started to measure and take detailed photographs of monuments, temples, statues and quarries. He was staggered to discover the degree of precision to which many of these huge objects were made, in many cases of granite or basalt some of the hardest of all stones.
And he examined magnified views of the surfaces, to see the marks which remained, which might give clues about the tools which were used to create the objects, which in some cases are at least 4500 years old.
He carefully analyses the Egyptologists’ views that the tools were simple and primitive. Like copper chisels, and stone pounding rocks, and while not dismissing those views out of hand, leaves us with the impression that such results would be almost impossible in this CAD CAM era, and much less with copper tools and stone pounders. He does not mention aliens or pre-dynastic civilisations, but just states that the tools which made the pyramids, obelisks, huge precise statues, and stone boxes, those tools, unlike the copper chisels and stone pounders, have never been found.
He does point out evidence of large circular saws with a 38 feet diameter blade, hole saws up to 6″ diameter, and straight saws which have left tell tale marks in stone objects and quarries in many places.
In many cases, such as the huge, incredibly precise stone boxes in the Serapeum, and the absolutely identical pair of 40′ statues of Rameses 2, he just states “we have no idea how this was done”. The precision is not just in linear measurements, but in complex curves, and surface shapes and areas.
Dunn’s analysis is principally about the tools and engineering of Ancient Egypt. Equally fascinating, but not covered in this book, are the mathematics associated with the pyramids, but that is another story. Also, he does not believe that the Great Pyramid was designed as a tomb, but as a machine. But that also is the subject of another of his books, which I have not, as yet, read.
“Lost Technologies” is 360 pages, paper bound, illustrated with many black and white photos of variable quality, many excellent diagrams, and 16 pages of good colour plates.
The text is technical, but quite readable cover to cover. I found it difficult to put down. If you enjoyed Simon Winchester’s “Exactly” you will probably like this one.
This is not an in-depth examination of the question. It is rather my experience with a particular 3D printer. But I believe that my experience has been experienced by many other 3D printer owners, so I have decided to make this record.
The printer which I purchased was a Creality CR 10s. I bought it in January 2020. I had been considering such a purchase for a year or more, and finally took the plunge when faced by making components for the model Armstrong cannon which featured in this blog over the past 18 months, I realised that I would have to metal cast quite a few complex parts. And the “lost PLA” method seemed like the best option to cast those parts.
So I accumulated the equipment for printing the PLA, making the molds from jeweller’s investment medium, a potter’s oven for burning out the PLA and baking the moulds, a furnace for melting the aluminium and bronze, and assorted other necessary paraphernalia.
Choosing the 3D printer was difficult, coming from a knowledge base of close to zero. I asked members of my model engineering society which printers they chose, and why. I watched numerous YouTube videos, and read reviews. As usual, I discovered that the more information you absorb, the more confusing it all becomes. I have the same feelings when researching which car or camera to buy. Eventually, I decided to buy a lowish cost printer, with the idea that I would eventually replace it with a better unit for long term use.
For this first 3D printer I wanted a well known brand with a good reputation, a build volume which would allow me to print the biggest component of the model cannon (the barrel, which is 300mm long x 65mm x 100mm).
I was still mulling this choice when Amazon advertised a special deal for the CR10s, and I made a snap decision to take the plunge. Would I make the same choice today? Quite possibly (actually, no. see below). Although technology has advanced. I am now considering whether to add an Elegoo Saturn resin 3D printer to my ever growing list of machines.
So this is what I bought. It is an open frame 3D printer, with a separate box for the motherboard and controls, and a side mounted spool. Single extruder. Advertised as an auto self levelling base (but it is not. It is manual, time consuming and fiddly). Filament end detection (hence the “s” after the 10), which works well. The build volume is 300x300x400(h), which is at the high end of low cost 3D printers, and bigger than any of the low/medium cost resin printers. I used close to the full extents of the volume on several occasions.
Actually, the very first modification was the slicer software. The printer came with a free version of “Cura”, but I accepted some expert advice to use “Simplify 3D”, which I purchased ($AUD 175) and used exclusively until recently. More about that later.
The instructions for using the printer were in an illustrated 10 page booklet, and a pdf file. As instructions for assembling the printer, they were just OK (do manufacturers EVER test their instruction booklets on novices??). As instructions for fault diagnosis they are hopelessly inadequate. In my previous post I showed a paper back book which would have been immensely useful when I started this 3D printing journey, and HAS been immensely useful after almost 2 years of wallowing about in ignorance. (“3D Printing Failures” by Sean Aranda).
By trial and error (mostly error), I printed the parts for my model cannon, and also came to grips with the casting processes.
BUT. When I started printing components for my next project I experienced failures and frustrations which I could not overcome. The Ottoman bombard has only 2 components, the breech and the barrel, which I intend to cast in bronze, using the lost PLA technique. These will be the biggest castings, and biggest 3D prints which I have attempted. Not surprisingly, I had problems with the 3D prints. Some of my attempts at fixing the problems caused further problems. After reading Sean Aranda’s book, discovered that my problems had ALL been described, catalogued, and fixes known.
The problems were:
1. Poor plate adhesion causing models to break free during printing.
2. Poor adhesion between layers causing gaps and structural failures.
3. XY shifting between layers
3. Gaps between filaments which would cause casting holes.
4. Excessive stringing.
5. Lumps on surfaces.
And this was typical of the failures….
Then I decided on some upgrades….
An enclosure to prevents drafts, and keep the printing environment warm during cold nights. $AUD155. A temperature and humidity logger kept a record of overnight temperatures. The heated printer bed provided the heat. I noted that temperatures remained between 22 and 26ºc inside the enclosure.
An all-metal fully geared extruder. $AUD25
A filament dehydrator, and warmer. “Sunlu” brand. $AUD60. Old filament can be reconditioned by warming at 50ºc for 4-8 hours. The same machine can hold the filament during printing to keep it warm and dry.
Around this time I experienced a serious filament leak and blockage which bent the hot end enclosure, broke the wire to the thermostat, and broke some insulating material. The leak was caused by a loose extruder nozzle, and an imperfectly seated Bowden tube. It was probably repairable, but when I saw that the cost of a replacement unit, including the wiring loom, hot end, 2 fans, silicon boot, etc was only $AUD35. So I bought one, had it installed easily in a few minutes. It came very well packaged, and quickly.
Also about this time I read Sean Aranda’s book. It has been a game changer.
Aranda uses “Cura”, and although his fixes can been used by any other slicer, one of my problems was holes between walls and internal surfaces. He says that this is a problem which is worse with “Simplify 3D” than with “Cura”, and he also thinks that “Cura is a better program overall, mainly due to the quality and number of online updates. The fact that “Cura” is free is an added bonus.
4. Sean Aranda’s book. “3D Printing Failures”
5. Changed slicer to “Cura”. Although it is called “Ultimater Cura” it works on most if not all 3D filament printers.
6. Changed the stick-on printing surface to a new 3M cover. This was after I read the product information which stated that these surfaces last for only 10 prints! I am quite sure that mine lasted for at least 50 prints before becoming unusable. Now I print on different areas of the surface, and keep a record of the number of prints at each location. Since then I have bought a magnetic cover which I will use when the current 3M cover starts to fail. (p.s. I have now installed the magnetic base, and so far, it has been wonderful!). No break aways despite not using brims or platforms, and easy to remove prints
After all of those changes my prints have been excellent. No break aways, no X-Y layer shifts, good adhesion between layers, better surfaces, and no holes/gaps between filaments. The only problem is that I am not sure exactly which changes were effective and which ones were not. Probably they have all helped to a degree.
Postscript. I have been considering buying an Elegoo Saturn resin printer, or maybe even substituting the Saturn for my Creality CR-10s. From the reviews the Saturn produces much smoother surfaces, and more precise dimensions. And the prints are much faster. My 3 and 4 day barrel prints could be printed 5-10 times faster. The known down side is the is the cost of the machine (on special at Amazon at present for $AUD639), the smell, the need to avoid skin contact with the uncured resin, the desirability of a print washer/UV curer, and the need for extra space. The other major consideration for me is the smaller maximum print size. 200x192x125mm. The bombard parts would need to printed in halves and glued together in order to make the molds. So, while the CR 10s is working well, I will hold off buying the resin printer. There is some advantage in waiting because 3D printing is a constantly evolving and improving technology.
So, were the upgraded components worth it? A resounding yes, as far as I am concerned. Still pondering the Elegoo Saturn
I guess that title should read “2 Person Tongs” but I doubt that SWMBO will be volunteering.
I am still planning to pour a model bronze Ottoman bombard.
The plastic model has been 3D printed, the flasks for the investment powder mould are ready, and I have the potter’s oven ready to dry, burnout, bake, and heat the moulds.
I have borrowed a melting furnace from Stuart Tankard, which is large enough to fit the crucible. The crucible has 14kg capacity. The crucible itself weighs 4kg. Unloading the furnace from my Toyota Landcruiser cost me a couple of broken ribs, which set back the project a few weeks.
Then I wondered about tongs to insert the crucible into the furnace, and, more importantly, how to lift the crucible full of molten bronze out of the furnace and pour the bronze into the moulds. The weight to lift and pour I estimate to be: bronze 10kg, crucible 4kg, plus tongs say 4kg = 18kg. The crucible with its bronze load will be at approx. 1100ºc / 2000ºf so some distance will be required for the gloved hands from the red-hot load.
I have several pairs of tongs for smaller crucibles, but nothing approaching a 14kg crucible. So I asked Stuart T for his thoughts on the matter. He recalled seeing a video by an MSMEE member and suggested that I check it out.
John M’s tongs looked like they had been designed by an engineer, which was actually the case. I contacted him (by email because Melbourne is in Covid lockdown), and he generously offered to send photos, a video and a drawing.
I copied his design, with a few modifications based on the materials which I had on hand, and also to enable a 2 man lift and pour. In retrospect, I could have fabricated a one man pouring apparatus, using a swivel on a frame, but to be honest I would prefer someone else present for safety reasons.
The remainder of the tongs construction was basic cutting, welding, and drilling.
I used to be a half reasonable amateur welder, but lack of ongoing practice lately, and dodgy eyesight is my excuse for the lumpy welds and essential use of an angle grinder.
Next steps…. I need some dry, non windy weather, and availability of assistance for the pour. I will make the first mould, of the breech since it is shorter than the barrel, dry it, burn out the PLA, and bake it at 750ºc. That will take most of a day. While the baking is in progress (about 4 hours), I will start the melting of the bronze ingot. Stuart says that I will require 2 full 20kg cylinders of propane.
Then the pour. Then after some cooling with fingers crossed. Camera running…..
The 6th Victorian Covid lockdown was the shortest, but seemed to hit me the hardest. It was unexpectedly relaxed after only 5 days in regional Victoria, where I live. With escalating numbers in Melbourne, and Sydney, and NSW reacting by putting its collective heads in the sand we expected the be in lockdown for weeks or months, and frankly it was quite depressing. For the first 3-4 days I did a bit of garden tidying (with a chainsaw, much to SWMBO’s horror), and time on YouTube, Ebay, Banggood and Amazon. A fair bit of impulse buying, as follows.
Paragraph deleted. My political and religious views have predictably caused offense to some of my readers. While I do not resile from any of those views I accept that others have different views, and me having a rant is unlikely to be at all persuasive. So I have removed the paragraph. For those who agree with my views, my apology. Any further conversation about Trump, Liberal and labor politics in Oz, and religion, will have to be in private. (I still consider Trump to be a lying, ignorant, con man, and a disaster for USA and western democracies.)
So, having offended and lost 3/4 of my readers I will get back to my little buying spree…..
Firstly, a book.
I read some good reviews about this book, and since I have had considerable frustration with my 3D printing of late, I decided to buy it. 3D PRINTING FAILURES by SEAN ARANDA.
Paper back, 298 pages, large format, large print font size, 2020 edition. Under $AUD30 including postage from Amazon.Australia.
And it looks excellent. Clearly laid out and written, lots of pictures and diagrams, and the author even gives his email address and offers expert help if there should be a problem not covered in the book.
Some of the pictures admittedly are not great quality, but the author has a service which astounded me. If proof of purchase is emailed to him he will send high definition colour photographs for download. He sent me all of the photographs within 24 hours of my request. AND, a pdf version of the entire book. AND, a promise to send me free of charge a PDF version of the 2022 edition which will be published near the end of this year!
I have cherry picked some of the chapters and I am VERY impressed. They are VERY helpful. Some random pages follow….
This book should be included with every 3D filament printer purchased. Note that it does not cover liquid 3D printers.
In my previous post I showed a photograph of the enclosure which I cobbled together from cartons and a blanket to try and avoid printing problems arising from overnight temperature drops, and draughts. I intended to make an enclosure from MDF and perspex, but while browsing Ebay came across this one.
As you can see it was not a trivial cost. But when I factored in the difficulty in obtaining the materials during the lockdown, and the fact that the commercial one claimed some fire resistance, I bought it.
It came today, and with some levering of the cover on the frame, it assembled quite neatly, tightly, and well. Here it is with my printer.
As you can see the electronic control box is outside the enclosure. There is a flap on top for those who prefer the filament reel on top.
The front and top zip open. And there is some spare room for bits and pieces. It does look slightly neater than the previously used cardboard boxes. The printer is fully enclosed, even with a build in floor. The price seems to have risen a bit since I paid for this one. Time will tell if the print quality improves. I am predicting that the print quality will improve. After reading the chapter on fire safety and 3D printing in the book above I will feel more comfortable about leaving the printer unattended with this “Fire proof” enclosure. I suggest interpret that as “fire resistant”. I will be watching temperatures closely for the first few runs.
Still on the subject of retail therapy, a couple more purchases….
This is a woodworker’s gauge from Banggood. I bought it after watching a YouTube video about its uses. Nicely made, and reasonably accurate by wood working standards. I will do a separate post about it when I have more fully explored its applications. (it is for making perfect grooves and lap joints on a table saw).
And finally, this one was a splurge, impulse buy. But something that I had wished I had on quite a few occasions when making models.
As you can see it is a pin gauge set. It is Imperial because it was a fraction of the cost of a metric set. 190 pieces of ground and laser labelled cylinders, up to 1/4″. They seem to be as accurate as my Mitutoyo micrometer can assess. It does mean that I will be committed to a moment of calculation to metric when in use. Cost? About 50 cents per piece, including the case and postage.
Fortunately for my credit card, the lockdown ended 2 days ago. I have spent a couple of short sessions in the workshop, tidying up and doing some machine repairs and maintenance. Nothing really to show. But it is nice to be back.
It has been cold here during the current lockdown. And I mean temperatures. Not by American midwest standards by any means, but since we are confined to our homes except for limited predefined purposes, some days and nights are chilly. Down to 5-8ºc here.
I have been spending a lot of lockdown time doing 3D prints. And really struggling to get decent results.
Some of my GSMEE colleagues have been urging me to make an enclosure for my 3D printer. To be honest, Stuart T had urged me originally to buy a printer with an enclosure, but I pressed ahead and purchased an open structure model because I wanted the extra print size it offered. The Creality CR10s can print up to 300x300x400mm which I have fully used for my Ottoman bombard prints.
But in recent weeks, with the onset of the cold weather, I have noticed a distinct deterioration in print quality, particularly with poor layer adhesion when printing overnight, when the house heating is turned down or off.
So I decided to make an enclosure!
But, I did not have the materials on hand, and visiting hardware stores is verbotten with lockdown rules.
So, don’t laugh. This is what I cobbled together……
A couple of cardboard cartons, an artist’s A0 paper case (SWMBO hasn’t noticed it missing yet), and a blanket.
The heated printer bed is the heat source, at 50ºc. And I was surprised at the temperatures reached inside the rickety construction.
The steep temperature rise on the left is inside the enclosure after printing started. As you can see, the temperature rose from about 18ºc (room temp), fairly quickly to over 30ºc. After midnight, when the house heating was turned off there was a slow drop to 25ºc, and then a further drop to 18ºc when the printing finished and the bed self turned off.
The temperatures were measured with this gadget. A temperature/humidity logger.
And the printing result??
This is the best quality print which I have had since the onset of winter weather. It is solid, water tight, and a reasonable finish. 0.2mm layer height. It is a molten metal pouring funnel, so I was not trying to get a super smooth finish, just an intact water tight object.
As soon as I can get access to Bunnings, I will make a more purposeful enclosure. Meanwhile, the cartons and blankets can remain in use.
I have given some thought to how to manage the bronze pour for the barrel of the Ottoman bombard. It will be at the size limit of my potter’s oven for the PLA burnout.
The red 3D printed PLA is the barrel. The breech, although significantly shorter, weighs almost exactly the same, but being shorter, should be less problematic. The wall thickness of the breech is greater than the barrel.
I had thought that the steel cylinder would be adequately long to cast the barrel, but it is about 50mm too short when I take into account the bronze feeder reservoir which will be required. So I will add a 50mm length, probably by arc welding another bit of tube to one end. It wont matter if it is not a perfect join. I will make it waterproof with duct tape. The tape will burn off during the investment melting/burnout.
I will cast the barrel with the threaded end downmost. The molten bronze feeder reservoir will be 60mm deep which I hope will provide adequate pressure and extra molten bronze if required during cooling contraction.
I decided that the usual rubber pouring funnel (pictured above at the bottom of the steel cylinder) would not have an adequately large bronze opening or reservoir depth, so have 3D printed one in PLA. The PLA will disappear during burnout, but will leave its shape in the investment medium and become the funnel and reservoir.
Hard to get your head around that one? It certainly was for me when designing it.
You (and I) need to remember that any space around the PLA will become investment medium. The PLA will disappear and become a void which will be filled with bronze.
The 3D print took over 8 hours. 0.2mm layers, 210ºc extruder temperature, 3000mm/min. I will need to do a similar 3D print for the breech. If either or both pours fail the whole process will need to be repeated.
Still in lockdown. Cannot visit my workshop due to the 5km travel limit. So 3D designing and printing at home is fairly good use of my time.
I have been attempting to print a 1:10 scale barrel of the Ottoman bombard, in PLA, so I can make a cast in jeweller’s investment, and use that to pour a bronze version of the cannon.
I borrowed a big furnace to melt the bronze, and broke 2 ribs unloading it from my vehicle. That was about a month ago. They still ache a bit, but apart from careful positioning in bed, are steadily mending. I have to sleep on my back, which would normally make my snoring unbearable, but the CPAP machine is working quite well. SWMBO absolutely insists that it is in constant use.
And I have purchased a length of 5″ stainless steel pipe to make the mold.
I have featured the Ottoman bombard in previous posts, having made a wooden version some years ago. It is over 500mm long, and 107mm diameter. In 2 pieces with a big thread joining the pieces.
I can’t really justify a bronze version. It will weigh close to 20kg. But it is a challenge. And I think that it will look more authentic in unpainted bronze.
I printed the breech part a few months ago.
3D PRINTING THE BARREL.
The barrel is 315mm long. My printer has a maximum print size of 300x300x400 mm so I was not anticipating any problems. I knew from the slicer program that it would take 2/3 of a 1kg reel of PLA, so I bought some new transparent PLA, thinking that it might melt/vapourise more completely in the burn out cycle of the production than the coloured PLA.
So I tried to print it. I have lost count of the number of unsuccessful attempts. Each time the print would start well, but at some point, sometimes after a whole day or 2 of printing, the print would come loose from the printer base and I would have clean up the mess of PLA spaghetti, and start again. I cleaned the printer base thoroughly. Scraped it. Wiped with acetone. Re-levelled it multiple times. But every time the print would break free.
I also noticed that I was getting a lot of stringing, and lumps of PLA would form on the printed surface, cool and harden, and sometimes the print nozzle would hit the hard lumps. That is when the print would loosen from the base and eventually break free.
I have been using a 3M printing cover over the aluminium printer base, quite successfully for over a year. Maybe the cover had worn out. I looked up the P.I. for the cover, and yes, it has a stated expected life of 10 uses! So that was likely the cause of the adherence problem because I must have used that cover at least 50 times!
I had no replacement 3M cover, so I reverted to the original cover supplied with the machine, which was boro-silicate glass. Initially it worked well, with good print adherence, but the hard lumps were still forming, and when the nozzle hit them, there was enough force to break the glass plate free.
What could be causing the hard lumps?
I watched multiple YouTube videos. Re-levelled the bed again. Checked every nut and bolt on the printer for tightness with no problem found. Checked the Z axis for level.
By this stage I was contemplating buying a new printer. Maybe one of those liquid + UV light jobs. But one of those big enough to make my barrel would cost thousands. So I got a quote from a professional printing service to print the barrel…. almost $AUD600. I would have done that, but the print is destroyed in the making of the cast, and it is possible that more than one attempt of bronze casting will be required. I was considering abandoning the entire project.
One last try at a print. I replaced the 3M cover with a new cover, and started a new print with a new reel of red PLA.
All seemed to be going well.
The print was adhering solidly to the new 3m cover. The hard lumps were still appearing, but the print head ploughed through them or knocked them off completely. The problem was, that after 3 days of printing, with 10% of the barrel still to go, the multiple jarrings were producing axis shifts. The appearance was pretty bad, but I figured that I could fix it with some extensive post printing hand finishing.
By this stage the print was almost 300mm high, and I could watch the laying of the PLA extrusion from the print head directly. In retrospect I should have used a mirror to do this at a much earlier stage.
What I saw explained the issue of the hard lumps appearing.
PLA was slowly oozing from around the base of the extruder nozzle. It was gradually building up into a pea size lump, and eventually falling off onto the print face!
So, I paused the print, picked off the accumulating lump, and watched some more. The same thing happened.
Why was the base of the nozzle leaking? Another pause. Checked the tightness of the nozzle. It was totally loose. About a full turn!
Tightened it up. Resumed printing.
The next layer did not adhere at all to the previous one, because tightening the nozzle had lifted it at least one mm.
I thought that I could start a new print of the final 10% of the barrel, and glue it to the part pictured, but when I examined it, the layers were poorly adherent, and falling apart. It went into the plastics bin. I expect that the loose nozzle caused multiple print faults in x, y, and z axes.
So, I am now 32 hours into the next attempt, with 47% completed.
Now that the Model Armstrong cannon is finished, I feel able to move onto some smaller projects which have been hanging around on my to-do list.
4-5 months ago I had these parts laser cut from 3mm and 4mm plate. GSMEE members have been making the Kant Twist clamps, and over the past 3 workshop sessions I have made a pair of the larger clamps.
The machining of pins and jaws was very basic so I did not record those processes. The laser cuts holes were accurate enough to be reamed to size. I found 2 annoying mistakes, neither of which was fatal. There is an extra hole in the small side arm. And the position of the pivot hole in one of the arms is about 1mm out. Not sure how that mistake crept in. Neither of these mistakes will affect the functionality of the clamps.
I would suggest one design change to the clamps, which I will apply to the small ones when I make them. I would add a small extension to the handle boss, say about 12mm, and knurl it. That would facilitate speedy changes to opening settings, before tightening with the handles.
Time and use will tell whether my choice of brass was sensible.
I know that these clamps can be purchased on Amazon and other sites, but this was a very satisfying project, and I have no regrets about deciding to invest the time to make them.
Small drill bits (up to 3.2mm diameter) are almost impossible to sharpen. Most of us just just buy new ones when our bits get dull. They are not expensive even in packs of 10.
But, sometimes we have parts which require sharp bits. (see recent post on installing model cannon sights). Even new bits are not necessarily correctly sharpened. I use Sutton drill bits which in small sizes cost ~$AUD18-20 for packs of 10 bits, but for crucial jobs I would like to touch up even those quality bits. The Sutton bits which I used for the cannon sights worked well, but the tense job made me very aware that in future I NEED to make sure that the bits are sharp.
So, I made a jig for sharpening small drill bits. The plans were published in Model Engineer 29 Dec 2000 and 26 Jan 2001.
It was a simple build. Took me 2 workshop sessions of about 2 hours each. I had the jig plate laser cut, very inexpensively from 2mm mild steel plate. Distributed to interested GSMEE members. The drill bit holder is an Asian copy of the English “Eclipse” pin chuck original. Also inexpensive. Came with 3 collets, to hold sizes up to 3.2 mm diameter. Cost $AUD10 inc postage. Note that the 1/4″ shaft actually measures 6.25mm diameter.
I used M2 and M3 metric fasteners in preference to the specified BA10 and BA8 fasteners.
The pin chuck should be through drilled in order to accomodate longer drill bits. The Asian pin chuck was not difficult to drill with a 3.5mm cobalt bit. It appeared to be case hardened only. And I used 2mm mild steel plate instead of the specified 16g brass plate for the jig. The wheel mounts were modified to cope with the different plate thickness.
The plans and instructions for use are in the articles in Model Engineer listed above.
p.s. GSMEE members who intend to use the laser cut plates. The drilling positions marked by the full thickness crosses can be successfully drilled to 1.6mm and 2.5mm by using sharp drill bits at high speeds- 3000rpm, slow feed rates, and cutting liquid. I used TapMagic.
And, it works! Here I am testing a 1.5mm bit which has been sharpened with the jig. Drilling through 4mm mild steel.
The sights were the final parts to be made for the model Armstrong RML.
There were reasons for delaying these items. They are tiny, easily dropped and lost, have tiny almost invisible details (to my eyes), and involve fine and very deep drilling into the barrel, on which many hours have previously been expended.
First I looked up every reference I could find about the full size originals. I could find no picture of the sights on the 80pr Armstrong, but I did find some diagrams of the sights on the Armstrong 64pr, on which the 80pr was based. Another problem was that there were rapid developments in sight technology, and I had to decide which period I would choose. The later periods (after 1880) had complexities which did not exist in 1860. In the end I just made decisions, knowing that they might not be exactly correct, but thinking that if further information surfaces I could make and install new sights.
The next step was to drill some 2mm and 3mm holes into the barrel.
First I milled 3mm flats. The first milling bit, solid carbide, just snapped as it bit into the barrel from the side. A HSS bit was more long lived.
Next, a 2mm hole was drilled right through the barrel, missing the bore, and exiting through the bronze bracket which supports the elevation quadrant gear. At 40mm deep that hole qualifies as deep drilling. Tension drilling.
Most hobby modellers who use a CNC lathe, run the lathe with Mach3 software. Some have progressed to Mach4, but apparently 4 is not straight forward, and my expert advisor says that it is best to stick with Mach3 for the time being.
Mach3/4 requires instructions to control movements of the lathe carriage (X and Z movements), spindle on and off, spindle speed, coolant on and off etc, and those instructions are in the form of G codes.
G coding is not difficult to learn. There are excellent YouTube tutorial videos on the subject, Udemy courses, books, and so on.
The problem is that mistakes in G coding can be easily made, costly, and sometimes scary. The biggest problem is that G coding is time consuming.
Fortunately, software is available to make G coding automatic, fast, and reliable. This post is about the program which I use for G coding. It is called Ezilathe. It is available at no cost as a download from CNCZone. (see details of downloading later in this post).
Ezilathe was written by Stuart Tankard, who I met a decade or so ago at a meeting of GSMEE. Stuart gradually persuaded me to get into CNC, and frankly, the decision to do so has resulted in a quantum leap in the scope and standards of my model engineering efforts. Now I use a CNC lathe, CNC mill, CNC rotary table, CNC 3D printing.
But I digress. This post is about G coding for CNC lathe. Until Ezilathe came along, I was programming G codes manually, making mistakes, and consuming lots of time. And experiencing crashes. Exciting, damaging, and sometimes dangerous.
To CNC turn an object, the profile must first be drawn with a CAD program such as AutoCAD. There is a very basic CAD drawing facility in Ezilathe, but it is so basic that I prefer AutoCAD. In AutoCAD I then rotate and move the object as it would be held in the lathe chuck, and move the tailstock end of the profile to the X=0, Y=0 position. Only half of the original drawing is required, so I delete everything below the X 0 line. I delete or hide all lines which are not part of the profile. The profile can be saved as a polyline, or as separate lines, arcs, splines etc. It is named and saved as a dxf file.
Then Ezilathe is opened, and the dxf file is imported.
The stock diameter is entered. The z position of the tailstock end of the profile is entered (usually Z=0). Feeds and speeds are entered using the tables in Ezilathe or another source. I use an app named “FS Pro”. Also select which lathe tool is to be used (the lathe tools are all entered in advance) or select a “point tool” which has an infinitely sharp point, and no width. In the example shown in the pictures below the turning was achieved with one tool. If multiple tools are required on one job, each tool will have to been set in the tool editor. So far I have not used the tool editor, but I can vouch that it works well, having seen the superb results which have been achieved by Stuart.(see the photos below)
Then the polyline of the profile, OR, each line and arc etc is selected in the machining sequence. Important not to miss any small lines or arcs as unintended results can occur. That is why it is sensible to save the original drawing as a single polyline. (Stuart tells me that any gaps will be automatically filled by Ezilathe as straight lines.)
Then go to the simulator, and see how Ezilathe will manage the sequence of cuts. In the picture below, the cuts are the straight lines, and there are 2 finishing cuts along the profile.
If all looks well, generate the G code. I usually visually scan the G code, looking for obvious errors. Usually there are no errors. Save the G code. Then ready to use the G code to make the part.
AN air cut with no work stock or cutting tool is sensible for beginners.
There is a lot more to Ezilathe. This has been a very brief introductory summary. Creating a lathe tool library, and entering startup strings for different lathe setups for example.
To download Ezilathe, you need to register at CNCZone. It is quite a good, useful site. In CNCZone go to downloads, Postfiles, Page 2. Select Ezilathe, and Ezilathe.pdf. The pdf is a comprehensive manual. Save them to a directory named C:\Ezilathe and unzip them. The program has been fine tuned, and updated. The latest version is 1.7.3. Then, on page 1 of Postfiles there is a small bug fix, Version 18.104.22.168. 22.214.171.124 is an executable which should be run after 1.7.3 is installed. If there are problems or questions Stuart can be contacted via CNCZone.
I have no hesitation in recommending this excellent program. It is just amazing that it is free.
Well, that heading is bit misleading. I had no pre-existing plans. I drew plans up myself, using the original cannon to measure, scale down and get my model dimensions.
In my posts over the past 18 months you have seen plenty of pictures of the original cannons, and the models.
I decided to model the particular cannon because I liked the shape, the degree of mechanical complexity with gear trains, riveting, etc, and because of the association of the town (Port Fairy) with my son in law. Also, because Port Fairy is within driving distance, if further dimensions and details should be required, which they were.
I thought that a model would look interesting and impressive. And it could be built in 3 distinct stages. Chassis-slide, carriage, and barrel.
So, in the order in which things happened……. (this info is all in older posts, so turn off now if the repetition is boring. I am writing this post for an overseas reader who wants to know how it was all done.)
I used a digital camera and iPhone to take photos of the entire cannon and its components. Close up, and from a distance showing the relations. The straight lateral, front and rear photos were particularly useful. In total, about 200 pictures. The photos were printed A4, and catalogued. As the model building progressed I realised that I had missed some components, and 2 further photo sessions were required. That was complicated by the Covid restrictions, but managed with some delay. The best photos were in overcast weather conditions, with and without flash.
I measured as many dimensions as possible, using a builder’s tape measure. The dimensions were recorded on hand drawn sketches in a note book, and a phone app (<My Measures Pro>. Very useful). On a later trip I used digital callipers for some small details. The barrel was measured using circumferences, and calculating diameters from those.
Using AutoCAD, I drew up a simple side profile plan. In that process I realised that many more measurements were required, and repeat visits were made. Actual components were later modelled using 3D CAD and saving as STL files. The STL’s were used to make 3d prints for casting, and in some cases just to see how the part would fit into the cannon assembly.
I searched the Internet for any references to the particular cannon. In that process I discovered that the particular cannon was unusual, and it appeared that all 26 examples from the Royal Gun Factory had been sent to colonial Victoria. Identical cannons were to be found in 2 other towns close to Port Fairy, and in 2-3 locations elsewhere in the state of Victoria. The design (of the 80pr original) was very close to a smaller capacity cannon (64pr) of which examples are still located in Hong Kong, Singapore, UK and probably elsewhere. It gradually dawned on me that the differences between the 64pr and 80pr related only to the construction method of the barrel, and not its appearance. Google, Google Images, Wikipedia all had information. I even discovered some images of simple plans with dimensions of the 64pr cannon, which corresponded very closely to the dimensions which I had obtained from the Port Fairy original.
As I posted progress of the model build on this blog, various readers offered further information, some of which was very useful. I have had some very satisfying subsequent correspondence with model cannon builders. In fact, the blog correspondence has led to some very useful experts who have been of immense help. One even supplied me with a copy of the original operating instructions for the Warrnambool 80pr cannons.
Searching for books on the subject of artillery in the 19th century has produced two which were published in 1877 and 1897. These are available free of charge as downloads, and bound reprints were purchased in addition. The cost of the bound books was very reasonable ($AUD20, and $AUD50). These have been thoroughly read, thumbed, dog eared, and used. So much so, that one of them is due for replacement.
Discussion with several experts has provided further great information, and resolved some of my questions. I had been mislead by some inaccurate restorations of the cannons at Warrnambool and Portland, and my suspicions about the restored details were confirmed in those discussions. The cannons at Port Fairy have had no restoration, which has resulted in severe rusting, but at least the remains are original and genuine.
Steps 1,2 and 3 occupied me on and off for about 5 days. 4,5,6 and 7 occurred progressively over the following 12-18 months during the model construction.
Regarding the accuracy of my scale models compared with the originals, I make the following observations.
As far as possible the linear dimensions are at a scale of 1:10. That was the scale of the first cannon I modelled, and I have stuck with that 1:10 for consistency, comparison between different cannon models, and simplicity of conversion. Of course that means that surface areas are 1:100, and volumes and weights are 1:1000. I have made some compromises to enable use of standard fasteners, shafts, and bevel gears, but have kept the compromises as small as possible consistent with the visual appearance.
Materials. The original cannon was constructed of wrought iron, cast iron, bronze/brass and wood. Steel was used only for the top surface of the slide. I used mild steel for the slide, the chassis, the carriage and the barrel. I used bronze or brass where the original had bronze. The wheel assemblies were cast iron on the original. I was restricted to cast aluminium and later cast bronze, but since these components were painted, the exact metal is not detectable, and probably irrelevant. The original wooden chassis/slide was made in the UK. The later iron chassis/slide was ,made in the UK but modified in Melbourne. That is the slide which I modelled. I imagine the original wood components to have been oak, but with no certainty. Scaling wood is difficult, due to the problems of scaling the figuring. I have some European oak offcuts, but decided to use Australian jarrah, because of its fine grain and attractive reddish colour.
Colours. I could find no reference anywhere regarding original colours. The experts had no hard information about colours and neither of the books mentioned colours. Some opinions were that black was most likely, and for cooler climates that seems reasonable. But in a hot Australian summer, black iron objects can be too hot to touch. I therefore suspect that white or at least a lighter colour would have been most likely used. But, you know what? SWMBO offered the most sensible advice. She said that if the model is to be on display it has to look attractive. She recommended painting the boring bits flat black (carriage sides, recoil tube, wheel assemblies), and leave the remaining metal uncoloured. Even the copper rivets, which would have been iron in the original. And to polish the bronze and brass components. So that is what I have done.
The base. A lot of thought went into this. The original ran on circular iron tracks which were set into concrete slabs. I rejected a circular track on the grounds that the model would have been too wide for convenient storage and display. I also rejected concrete or model concrete in favour of the eventual choice. That decision, (incidentally, not “set in concrete”…. might be changed at a later stage), was for a single piece of 12mm thick gloss black cast acrylic Lexan, sandwiched to a piece of thick plywood which is painted flat black. It looks good IMO, is hard wearing, and reflects the internal components so they can be seen. The first model Armstrong which I made was set on a wooden base with oil polished top and black painted sides. That also looks quite good. (IMO).
I might add to this list if further memories surface of the various processes used in the planning stages.
Just one picture for those readers who never read the text….
I made them promise to not make me laugh or cough or do any heavy lifting. And it was a pleasure to attend another face to face GSMEE meeting after a few weeks of Zooming.
And Swen Pettig brought along his Grasshopper beam engine for a progress assessment.
Swen has also recently made this sphere making lathe attachment. The cutter is a 6mm diameter TC disk. He showed us an example of a job, which has a lovely finish and excellent shape, but a rather thick neck. Swen plans to make another cutting tool with a sharper point to make thinner necks on the spheres. Chatter has not been a problem with this tool.
I am not quite ready to show the Armstrong RML gun, because it is still waiting for me to get back into the workshop for some finishing touches, so I brought some goodies to show which I recently bought from Banggood.
And this one is a woodworking tool, which I have wanted for some time, but the US version is about x4 the cost , and postage is an extra deal killer. The costs mentioned all included postage.
Today I picked up the laser cut metal plate which will become the small drill sharpening jig. For drills bits up to 3mm. You might ask why bother? Well, I can see the jig being used where I want a really sharp tiny drill, on a critical job. I would touch up the cutting edges on even a new bit.
The drill bits to be resharpened will be held in a small collet chuck, purchased commercially for about $10, including 3 collets. The lasering cost about $5 each.
Several weeks ago one of my grandsons broke his wrist. In a discussion about the accident with SWMBO I mentioned that I had never experienced a bone fracture. (mistake #1).
Some days after that I collected a metal melting furnace from Stuart Tankard. A loan, so I could melt enough bronze to cast the Ottoman bombard. My own furnace has a capacity of 3kg of bronze, but I needed to melt about 10kg for each of the two parts of the cannon. Stuart’s furnace is gas fired and will take much larger crucibles than mine. He readily agreed to the loan of the furnace, but I noted that he hesitated when I rang to arrange the pickup. I discovered why when we loaded it.
It is bloody heavy!! The two of us could not lift it more than a few centimeters. It must weigh around 200kg.
So, we manoeuvred it onto a hydraulic lift trolley, and used that that to roll it to my Landcruiser, jacked it up, and slowly and progressively moved it into the back compartment of the cruiser. I assured Stuart that I would be OK unloading it. (error #2) I have an identical hydraulic lift trolley. And I was sure that I could carefully manoeuvre the furnace onto the trolley.
So, at my workshop I backed the cruiser to the concrete pad where the trolley was positioned, jacked up the trolley platform to the level of my cruiser and slowly pulled the furnace towards the trolley. But it would not budge.
The furnace has a handle for rolling it around. The handle slips into position quite neatly. So I climbed onto the cruiser floor, and started pulling and manoeuvring (error #3). Suddenly, the handle came free, and I was flying through the air tumbling backwards. Fortunately the furnace stayed where it sat.
But I hit the concrete pad.
With my chest.
Initially I was winded. And my chest hurt like hell. And my head hurt. When I stood, I realised that I was conscious, bit giddy, and in PAIN from my chest. Oh shit. I knew that I had probably broken a rib(s). It hurt to breath. I took shallow breaths. No bleeding, but I was sure that there would be some impressive bruises.
As was alone, with no-one nearby, I rang my wife. By then I had regained my breath and I reassured her that I was not seriously hurt, and did not need an ambulance. But if I did not turn up at home that evening maybe she should come and find me. (sensible#)
As time passed, the pain did not seem too bad, so I had a cup of coffee, some Aspirin, finished unloading the furnace, and a couple of hours later drove home. I took some more aspirin, and started cooking dinner as usual. My wife said that I should see a doctor, but hey, I used to be a doctor, and I knew that nothing serious had happened. (error #3). Also it was a public holiday. My doctor would have either been on call, or arranged suitable cover. But I figured that it could wait until the next day.
After an uncomfortable, restless night, the next morning I felt sore, but not in severe pain, and it settled with some more aspirin. We were child minding that day, so seeing the doctor would have been very inconvenient. So I did the child minding with my wife, with no great problems. Then another restless night. I planned to see my GP the next day. Or at least to talk to him with a phone consultation.
Next morning, I sneezed. Hay fever. The chest pain was suddenly much worse. Aspirin hardly touched it. Some movements were very painful. I was terrified that I would sneeze again. Deep breaths were out of the question. I rang for an urgent appointment with my GP. It was made for late that afternoon. I knew that I needed an X-ray of my ribs, so I sent an email to my doctor. It is almost impossible to get to talk directly to a doctor without a prior appointment but I thought that an email from an ex-doctor might might get through. And it did. I had a phone call from him within minutes, and the X-ray was arranged. He also arranged an electronic prescription for a stronger pain killer, which my wife collected. It helped.
I had the X-ray, driven there by my wife, who by this stage was very concerned.
At the pre-arranged consultation the GP examined me. Clinically he agreed that at least one rib was fractured. However the X-ray report said that there was no fracture. He invited me to view the X-rays, and I was certain that I could see a fracture. I was no radiologist but I had seen a lot of X-rays in my medical career. A second radiologist opinion would be obtained. (the second opinion confirmed the fracture). My lungs were intact at that time.
I did not require hospital admission. I was given a prescription for more pain killers, instructions about keeping active, taking laxatives (to avoid the analgesic induced constipation), and to stay in touch for the 6 or so weeks that healing would require.
The next day the situation changed. Despite the strong pain killers, the pain progressively worsened. By evening, when SWMBO arrived home I was having frequent episodes of agony in the area of the fracture(s). I discovered the meaning of the phrase “pain bringing someone (me) to his knees”. It was worse than the root canal pain, the ski accident multiple ruptured ligaments and crushed bone ends pain, you get the picture. I was almost fainting with the pain. SWBMO wanted to get an ambulance. I did not want the delay. So she drove me to the hospital casualty. Every bump in the road provoked the agony.
At the hospital, I staggered into the casualty department while SWMBO parked the car. There was a queue at the triage assessment. I had put on a mask as per Covid regulations. I was doubled over with pain, and wondering if I would faint if a severe wave occurred. I was aware that I was groaning with the pain. Waiting people were staring. But the triage nurse was not looking. So I walked to the window and said “I am in severe pain”. She said “sit there”. I said “I cannot sit down”. She pointed to an adjacent room and said “wait in there”. So I did, while she continued getting details from the two people ahead of me in the queue. I was bothered by the attitude, but in no condition to argue. I guess that she was following protocol. I wonder what protocol would have required if I had collapsed.
Eventually, after an interminable wait (probably about 5 minutes) I was motioned to window, gave my details, and I was walked with assistance from 2 orderlies, into a cubicle. Things moved quickly then. An IV line was inserted, and I was given IV Morphine. A few seconds later the pain was almost gone. It was heaven.
A CT scan confirmed the fractures. And partial lung collapse. My liver was intact. There was no internal bleeding. Hospital admission was recommended, and SWMBO insisted that I accept, although after the Morphine I was tempted to go home. Anyway, I stayed overnight, with strong oral painkillers every 3 hours.
I was discharged home the next day with a supply of really strong painkillers, and arrangements for follow up. Since then, I have been slowly improving. I have a strange “clicking” sensation at the site of the fracture. Something is moving. Yesterday I visited the workshop, but not really up to anything interesting. Doing a lot of dozing.
I started with virtually no knowledge about this subject, but I had to learn quickly in order to finish my 1:10 model Armstrong rifled muzzle loading 1866 cannon. I finished the job, not perfectly, but adequately, and this is what I have learned so far.
Copper rivets are annealed when purchased, but as soon as you start hammering them, they harden.
You need one hand to hold the work. If you use a hammer, and hold a snap, that uses 2 hands. So either use a third hand or use a pneumatic hammer with the snap attached. That leaves a hand free to hold the job. The pneumatic hammer size must be appropriate for the job. I purchased one from the country of Taiwan. It cost $AUD120. Seems to be excellent quality.
The compressor pressure is critical. The air setting on the hammer is critical. Experiment on waste material first!
Hold the fixed snap in a strong vise.
The snaps need to be accurately made for the rivet size. Try them on waste material before using them on the job.
Rivets of the same size but from different manufacturers will differ in finished appearance. Get your rivets from a single supplier in one batch. Order 10-20% more than you think that you will need. You will lose some, and muck up the insertion in some.
The surface of the snaps should be smooth, with rounded edges. A polished finish is best.
A complex job, with internal rivet ends, requires custom made snaps. Be prepared to make them. For the carriage parts I used 5 different shaped snaps. For copper rivets, mild steel snaps were quite adequate.
Some rivets will not insert well. Just remove them, and try again.
To remove a rivet, grind off one head. It might then push out with a steel pin. If necessary, drill through the shaft with a small drill (say 1-1.5mm for a 2mm rivet), then punch the remains out of the job.
The rivet length must be precise. The head which is formed by the snap was best if the shaft length was 2.5mm longer than the total thickness of the materials to be joined. There are tables to determine the lengths.
To shorten copper rivets, drill a hole in steel plate which is the exact thickness of the desired rivet length, the exact diameter of the rivet. With the rivet in the hole, snip the rivet to length with wire cutters, then belt sand it to length. Push the rivet out backwards.
With grateful thanks to Neil M for expert advice on this subject.
The lettering on the muzzle reads “Marshall’s Iron”. It refers to the steel bore of the barrel, which was supplied to the Royal Gun Factory by a specialist manufacturer, Marshall Iron. The rest of the barrel was made from wrought iron, as a coil, as described in a previous post.
The barrel is 300mm long, too high for the laser machine to focus. So the setup used a low profile 3 jaw vice, hanging out from the edge of the machine, with the breech of the barrel down the front of the desk/bench.
Immediately after lasering, which took about 20 seconds, (and about 45 minutes to set up the machine/supports). The circle represents the junction between the steel bore and the outer iron coil. The vertical line was used for sighting.
The lines and lettering looked a lot sharper after a quick rub with emery paper. Those letters are less than 1mm high. A very magnified, not well focussed photo.
The cannon is now mounted on a shiny acrylic/wood base. It reflects the underneath details. And has handles.
Thanks once again to Stuart Tankard, for using his fibre laser machine to accomplish the engraving. Stuart told me that he has done more jobs for me than he has done for himself. I call it “getting experience”.
And, WordPress has now improved its program to the point that captions cannot be added to photographs, and a title cannot be added to the post. Well done WordPress. (p.s. 16 June… captions and headings have reappeared. Hooray!)
I have been tearing out chunks of hair, and gnashing teeth because prints are failing due to loss of adhesion. And the problem has progressively worsened to the point that the failure rate is now 100%.
And I am thoroughly fed up with throwing bird’s nest conglomerations of PLA in the bin.
I have tried the following remedies…….
Varying the bed temperatures and extruder temperatures up and down. Various combinations and permutations.
Cleaning the bed after every print, with acetone and scraping.
Checking and rechecking the bed for level.
Replacing the extruder nozzle.
Changing the PLA to brand new stock.
Printing on a different part of the bed rather than the default centre.
Today, I searched the net for solutions, and I decided that I had tried all of them, EXCEPT, replacing the bed surface.
I have been using a 3M product, designed for 3D printing, designated 9080A. Today I RTFM. If you do not know what that stands for, try “Read the F’ing Manual”. So I RTFM’d.
It seems that 9080A is good only for 10 uses, then should be replaced. OK. Penny drop time. I have been using the printer for 18 months with the same 9080A sheet. Maybe 50 times?
Back to Amazon, order some more 9080A sheets. Meanwhile I will revert to the borosilicate glass sheet that was originally supplied with the printer.
Well, 99% finished. I still intend to make sights, a base, and bumper components. But it now looks finished. A few pics.
It has a few differences from the first one of these which I finished for last Xmas. It has side platforms, handles for positioning the carriage on the slide, minor design changes in the rear wheel brackets, minor changes in the elevation wheel, and probably a few more that I cannot remember.
The explosive projectiles would never have been placed on the side platform. The noses contained impact sensitive detonators, and I doubt that the gunners would have risked them falling off.
The positioning gears work well, as does the elevating mechanism/gears, the elevation lock, the clutch and brake.
Oh yes, some fasteners for the rear platform too… And engraving text on the recoil tube cap, and the muzzle mouth. OK, 98% done.
Now, I am getting on with my next project too. Yes I will eventually finish the Armstrong RML cannon. But I am getting impatient to be doing something different, so I have started on the bronze version of the Ottoman bombard.
This PLA 3D printed breech is 230mm long, plus thread, and 107mm max. diameter. Still deciding whether to refine the design and print another. For one thing, the threaded section is constant diameter, whereas the original had a tapered thread. Yet to 3D print the barrel. It is 280mm long. That is a lot of plastic to burn out prior to bronze pouring. Maybe I should use transparent PLA in case the black dye (whatever it is) damages my burn out oven, or my lungs.
For another thing I have been unable to get my CAD program to convert the Ancient Arabic Script into vectors. But, I have been able to get V-Carve Pro to recognise them/
That is a tracing from the photograph. A couple of hours of effort doing the tracing. Then scanned the tracing, and imported the scan into V Carve. That worked, and I hope to remove 0.5mm of the muzzle bronze, leaving the raised script and stylised designs. V Carve predicts that will take 5 hours on the CNC mill!! Watch this space.