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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.

Tag: CNC milling

How Many One Off Parts Can You Make Per Day?

Obviously it depends how many machining operations are required per part, but these days I find that one or two parts per day is about all that I can manage.  That includes deciding on then finding the material,  drawing up the part in CAD, mounting the material and the cutter(s), then machining and finishing time.

Take today for example.  My aim was make a steam pressure valve for the Trevithick Dredger Engine.   It consists of a lead ball weight 30mm diameter, a lever arm with a hook, a simple stand with a M6 male thread, a movement restrainer, and the seat and valve.  6 fairly simple parts.  I thought that I might get it all done in one day.

But at the end of the day, all that I had made was the arm, stand and restrainer.  3 simple parts.

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The pressure valve arm, stand and restrainer in place.

Admittedly the arm is stainless steel of unknown grade.  I broke 2  (4mm) cutters before I had slowed the milling feed rate to a snail’s pace 40mm/minute.  Machining time for that part was over an hour!  Then at least another hour of hand filing and finishing.

It is just as well that the worst day in the workshop is better than the best day of working!

And next will the interesting job of making the 30mm diameter lead ball weight.  Still thinking about that one.

Trevithick Dredger Engine- bronze brazing and some milled parts.

 

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The copper tube which I am using for boiler shell has 6 holes, intended for another project by the previous owner.  Here I am trimming the length, so 2 of the holes will eventually be removed.  Using a drop bandsaw, with a wooden plug so the tube is not bent by vise pressure.

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Bronze brazing the domed boiler end to the boiler wrapper.  The assembly absorbs a huge amount of heat before it reaches brazing temperature.  Showing the temporary forge, and the torch head for the oxy-propane fuel.  The join has been completed in this photo.

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The join in progress.  Note the positioning copper rivets, and the tacking points.  At this point I ran out of oxygen and had to finish the braze on the following day.

And today I made some parts for the boiler’s removable flat end.  My CNC mill is out of action, so GSMEE President Brendan kindly allowed me to use his machine.

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CNC spotting 3.2mm brass plate.

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The almost completed firebox door base.  Spotting did not allow for the removed material in the rebate, and the drill ran out in one hole- some repair required.  I will plug and redrill that hole.

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The manhole cover.  It will eventually be painted.

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Sitting in intended positions.  Fastener holes spotted, yet to be drilled and threaded.

Turkish Bombard – the barrel mouth

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Except for a name plate I have finshed the bombard.  The floral design at 12, 4 and 8 is not as clear as I wished, and the Arabic script at 2, 6 and 10 is even worse.  But it is cut in wood, and it is a first effort at such work, and it is not easily seen in a model only 106mm 4.2″ diameter, so I am reasonably satisfied.

Also, this was always a prototype, in wood, and I have not totally dismissed the idea of making it in cast iron or brass.  In metal I am sure that the detail work would be a lot finer.

Turkish Bombard. The Barrel Script

Well, I bought a pair of NSK bearings for the Z axis of my CNC mill, and removed the old ones and inserted the new ones.  Cost $AUD 200.  Plus 2 or 3 half  days of  dirty heavy work.    And the problem persisted!!@!@

OK.  Time to get an expert opinion.  Here comes the cavalry.  Thank goodness for my expert friend Stuart T.

Very puzzling.  Even for Stuart.  There was some unwanted movement in the Z axis (about 2mm), despite being apparently properly installed.  Not a problem with the ballscrew or ballnut.  Even Stuart was puzzled.

“have you got any left over bits and pieces?  Is it all installed the way it was before?”

To cut the story short, we installed a thicker washer below the locknuts, and it seemed the problem was fixed.  Or was it?

Today I did another test run of the bombard mouth Arabic script.  Worked fine.  OK.  Time to finish the bombard.

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Here is the finished result, ready for painting.  I have used a 20 degree engraving carbide bit with a 0.2mm flat end.  There is some loss of fine detail but it is I think, adequate.  When it is painted, the filling putty above the pin screws (the white circles) will be invisible.  The engraving took a total of about 60 minutes, at 500mm/minute, 15,000 rpm.

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The setup.   A large angle plate clamped to the table.  The work clamped to the angle plate.

The translation of the Arabic script is “Help O God the Sultan Mehmet Khan son of Murad. The work of Munir Ali in the month of Rejeb. In the year 868.”

Turkish Bombard. The Arabic Script.

A little unfinished business on my model bombard is the Arabic script and floral decoration around the barrel mouth.

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XIX.164 / 19-00164 Detail of muzzle of a great bronze gun. Turkish, dated 1464 Royal Armouries Museum, Leeds LS10 1LT Transparency tr-1185 Imacon Flextight Precision II

This is what I have managed so far….

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It is a practice run in scrap wood.

Some of the detail has disappeared because I used a milling cutter with an end width of 0.5mm.  Next time I will add another step using a cutter with a sharp point, and a lot more of the fine detail will appear.

That pattern took a total of 80 minutes to CNC mill, with the feed rate set at 500 mm/min.

Unfortunately my CNC mill developed a problem with the Z axis, probably due to a worn out end bearing.  I am hoping that it is not the ball screw nut.  Now in the process of removing the bearing. A heavy, awkward, dirty job.

When the mill is working again I will mill the actual bombard model and post some pics.

Computer graphics is not my strong point.  To get the CNC mill to cut that pattern I did the following..

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  1. Enlarged the photo, outlined the tracery and the script, then traced the outline onto tracing paper.  That 550 year old pattern is worn and hard to define in many places.  Quite a bit of guess work.  Lucky that almost no-one can read ancient Arabic script these days.
  2. Scanned the tracing and loaded the scan into Corel Draw
  3. Used Corel Draw to smooth the curves, and make 3 copies in an array of the floral design
  4. Converted the drawing to bitmap file (bmp)
  5. Used V Carve Pro to convert the bmp file to vectors
  6. Used V Carve Pro to generate the CNC G codes
  7. CNC milled the scrap wood at 16000rpm, using a 3.2mm carbide cutter

Modelling a Turkish Bombard -4 Decoration

The decoration around the barrel is formed by a repeating pattern, which when milled, very cleverly forms 2 identical patterns.  One is excavated and one is the original barrel surface.  You will see what I mean if you look at the pictures in the earlier blog, and the video below.

It took me an evening of experimenting on the computer to work out the system and draw it.

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Then I measured the diameters of the 2 gun components, calculated the circumference, (OK it is not rocket science.   3.142 times diameter), then working out the number of identical shapes which would fit around the 2 different diameters, at the same size and spacing.   Amazingly, it took 18 shapes to fit almost exactly around the barrel, and 16 of identical size almost exactly around the breech.  the angular spacing was 20 degrees and 22.5 degrees.

Then the shape was imported into V-Carve Pro, and G codes were generated.

My CNC mill does not have a 4th axis, so I used a dividing head to move the workpiece at the precise angles.  See the setup in the video.  That meant that the pattern was engraved into 16 and 18 flat surfaces, rather than a continuous cylinder as on the original.

It worked very well.  There were minor compromises due to the shapes being milled with a fine end mill but when you look at the pics I hope that you will agree that it is effective.

I calculated that the milling had to be at a maximum depth of 2mm in order to cope with the curvature, but if I do it again,  I would reduce the depth by 25%.

The first part of the video is a shot of CNC drilling.  Then the CNC routing of the repeating patterns.  Each angular setting of the pattern took 4 minutes to complete.  136 minutes altogether.  In reality, it took a whole day, most of which was spent doing the setups.

 

 

COMPRESSED AIR ON THE CNC MILL

Compressed air is very, very useful on the milling machine.  The tool changer uses air for fast tightening and release.  And I often use air to clear the field of swarf, and shavings (yes, I use my mill for wood  too).

Recently, at the suggestion of Stuart L  of stusshed.com fame, I installed 2 semipermanent nozzles on the mill, with adjustable direction and pressure adjustments.  It has been a quantum leap improvement.

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The pic shows the jets aimed during CNC end milling of wood.  The wood shavings are blown away which makes it easier to see how the milling is progressing; blows them away from me which is safer and cleaner; and stops the chips being machined into the work, which leads to a cleaner cut.  It also improves any video or photo of the progress.  It must also cool the cutter, although not as effectively as a liquid coolant.  I have not tried using the misting attachment, which would improve the cooling, but at the cost of dampening the area and the work.

I particularly like the improvement experienced when machining brass or steel.  The swarf is removed from the advancing cutter, preventing it being re-machined and squashed into the workpiece.  I am noticing better surface finishes.  I also adjust the air direction to keep the swarf away from me;  particularly valuable when brass needles otherwise would be flying at me.

When cutting pockets, the air keeps the pocket free of swarf, and when using tiny endmills at high speeds I am experiencing fewer tool breakages.

This gadget was inexpensive ($AUD12) from China.  It does not work the compressor too hard when the volume is turned back as far as possible, but still adequate.  Although there are 2 jets, I find that only one at a time is adequate.

Recommended.

As an afterthought.   I rarely use coolant on my lathes, but an air stream on the cutter and workpiece would probably have similar advantages to those listed above.  I particularly wonder if it would assist during deep parting…   always a tense procedure.  I suspect that the cutter becomes hotter and expands more than the workpiece parting slot if there is no coolant.  I will mention the result of air cooling and chip clearing on the lathe in a later blog.

CARRONADE 1

It has been a while since I posted, but I have been busy.

Some of that has been in the workshop making a scale model carronade.

A carronade, in case you are wondering, was a muzzle loading cannon, made 1776-1852 in the Scottish town of Carron, by the Carron company.  And subsequently much copied elsewhere.

It is a cannon which is short, squat and ugly.

Weighs about 1/3 as much as an equivalent bore long gun, (see previous posts), requires only 3 men to operate (compared to 9-11 for a long gun), and can fire balls or other nasties at 3 times the rate as long guns.

2 carronades, 68 pounders,  were on the foredeck of Nelson’s “Victory”, and they caused huge damage  at Trafalgar.   Can you imagine loading a 68 pound cannon ball into the muzzle of a hot cannon?   Many actions proved the killing power of carronades, and the British Admiralty were so impressed that they replaced long guns with carronades on many of their ships.

The French, and Americans were less rapid to  access this new technology, although Napoleon, who was an artillery officer, was adamant that the French navy should have the carronades installed as quickly as possible.

The British equipped some of their ships almost exclusively with carronades, and at close quarters they were devastating and they won some notable victories.

Unfortunately, although they were devastating at close quarters, they did not have the accuracy or range of long guns beyond about 500 meters.

So in the war between the Brits and the Yanks in 1812, the Americans found that all they had to do to win at sea and on the Great Lakes, was for their frigates to remain beyond the carronade range, and shoot their long guns, with many victories, and great frustration of the Brits, who were not used to losing naval battles.

Carronades were commonly installed on merchant ships, privateers, pirate ships, and small naval vessels, due to their relatively light weight, and small gun crew. But the Royal Navy stopped using them from 1852, when breech loaders were the latest new technology being installed wherever possible.

I decided to make another 1:10 scale model cannon.  A 32 pounder carronade, the same scale as the previously blogged 24 pounder long gun, to put them side by side for comparison.

It is almost finished.  I will post some photos soon.  Look forward to squat and ugly.

 

 

Video of Making the Model Naval Cannon

Click on the arrow in the screen link below to connect to the YouTube video of the making of the 1779 model cannon.  Probably of interest only to machine aficionados, but it does feature some very pleasant music composed and played by Lis Viggers.

The labels appear too briefly, so use the pause button to read them.

The segment on boring the barrel is really boring. (really)

And a few editing errors appeared.  I typed cascobels when it should have read astragals.  Not prepared to delete, re-edit and re-upload given my very slow Internet connection.

 

And this is a link to another YouTube video with an excellent description of how these type of cannons were made originally.  Definitely worth watching.

Cannon, final parts.

The 1779 model naval cannon is complete, finished!

Photos of finished project in next blog.

The last task was to make the bolts, hinge and keys which hold the barrel to the carriage.

These small items took 2 days to make, demonstrating that the size of parts has no relation to the the time taken to make, except in an inverse relationship.  ie. the smaller the part, the harder and longer it takes to, make it.

The bolts which hold the barrel trunnion to the carriage have small rectangular holes which hold a key.  The holes are 2.4mm wide and 3.6mm high.  That is smaller than my smallest file.  My smallest endmill is 2.38mm diameter, so that determined the size of the rectangular holes.

I drilled the holes with the endmill, then elongated the round hole to a rectangle by filing.

The problem was that my smallest file was a square file 3x3mm.

Solution!  I ground the teeth off two surfaces of the file, leaving 2 faces 2.4mm apart, and 2 cutting faces 3mm apart.  (using a surface grinder).

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Finished rectangular hole on right.  FIling in progress on LHS.  The head of the bolt was silver soldered to the shaft.  Second soldering effort worked.

Then I had to make the keys. These are truly minute!

So I cheated.  I CNC’d the shape on the end of a piece of brass rod, then parted off the keys in the lathe.

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Parting the first key.

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That key is 9mm long and 6mm high.  It still needed some filing, which I accomplished in this tiny toolmakers’ Starrett vice.  That file is 3x3mm.

 

Cannon trunnion shoulders, flash pan and trunnion brackets.

Another couple of long and very enjoyable workshop days, making various bits for the 1779 24 pounder model naval cannon.

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The trunnion shoulders were bored to a close fit on the trunnions, then the barrel curve was machined on the vertical mill.

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Using a boring head to make the barrel curve.

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Testing the barrel curve.  A good fit.

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The trunnion shoulders were glued into position with Loctite.

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The trunnion bands were difficult and fiddly.  The 3 components of each were joined with silver solder, then several hours was spent with tiny  files to achieve the shape pictured.

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The square cap trunnion bolts are yet to be made.

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Milling the powder pan enclosure with a 2.3mm end mill.

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The powder pan, sculptured from bar stock.  The base gets milled away.

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The powder pan is glued into place with Loctite.

As you can see, this cannon project is almost completed.  A few more hours to make some bolts and fittings.  I am considering adding some ropes and pulley blocks.

More Naval Cannon

Some temporary bolts inserted until I get around to making the permanent brass fixtures.  And the quoin and bed finished.  And the wheel halves joined with brass pins.

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The quoin is the wedge which is used to set the elevation of the barrel.  It has a dovetail connection to the bed underneath.    The brass pins which connect the wheel halves are also seen here.

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The dovetail groove was smaller than any commercially available router cutter.  That top opening is only 3mm (1/8″) across.  After considering options I elected to cut the bed in half and then machine a 60 degree groove into each half, then superglue the halves together.   The tongue in the quoin was similarly machined, but in one piece.   That handle hole in the quoin is not centered, despite careful positioning.  The wood grain must have pushed the drill bit laterally.  I will use an end mill to get a bigger, centered hole and glue in a patch.

 

The barrel is 300mm-12″ long.  It has straight sections, a taper section and several curved sections.  Plus several types of bands called astrogals.  It would be ideally suited to turning on a CNC lathe, but is much too long for my Boxford.  So I am asking around, to locate a larger CNC lathe for hire/loan.  If all else fails I will use my manual lathe, but I expect that the finish would be better on a CNC.

I will drill the bore first, and after considering the options, will use the Jerry Howell recommended method, which is to use a D-bit.

DESERT IRONWOOD

Some decades ago I made a table for our kitchen.  (cannot find  photo just now, will add one later)

I bought the wood from a wood recycler.  He removed trees from Melbourne suburban gardens, then cut them into slabs and air dried them.

I recall that I paid about $AUD 1000 for the 6-8 planks.  They were about 40mm thick and 300mm wide and about 2.5m long.  They were so heavy that I could barely lift them.

I have since learned that they weigh 1.1 to 1.4 tonnes per cubic metre, which is at the high limit of wood densities.

The tree must have been 400mm diameter, because some slabs still had the bark attached to both sides.

The wood has a beautiful dark brown colour, with almost white sapwood solidly attached. It is unbelievably hard, and I struggled to machine it with my thicknesser/buzzer.  Also, it was the most reactive wood I have ever worked.  When planed or thicknessed it would bend and react totally unpredictably.   My 40-45mm thick planks ended up 25-28mm thick and even then they were not totally flat.

But SWMBO liked the table, and it still is the main meal table in out house.  One of my daughters requested a similar table, which I made from Gippsland Blue gum, another spectacular dense hard Australian wood.

The ironwood has survived kids dancing on it, steam engine demonstrations, being used as a work bench, not to mention many meals with never a table cloth.   And the wood itself is unmarked!  The polish has disappeared in places, but the wood itself seems impervious to damage.

To get to the point of this post, I am currently making a 1779, 24 pounder, 1:10 scale naval cannon.  Jerry Howell design.  About 300mm (one foot) long.

When I was looking in my shed I considered various woods for the carriage-base.  I considered some black walnut, which was recommended, but it seemed a bit light in weight and colour.  I considered some Australian redgum, which polishes beautifully, and is dense and tough, but it is a bit too red.  Some African Odum looked possible, but the figuring is a bit plain.  Then I found some ironwood offcuts from the table job, and the decision was made.  Ironwood it is.

So here are the initial photos of the carriage parts.  They were machined on my metalworking mill, using HSS cutters.   I CNC’d where possible.

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Ironwood after conventional thicknessing.  Tearouts are a problem.

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Ironwood after surfacing with a 1″ endmill.  Here I am CNCing the profile of the carriage.  3000rpm, 500mm/minute.

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After milling, I am tempted to just oil the surface.  The edges are sharp, like milled metal.

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CNCing the wheels.

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A little deburring or with wood is it called defuzzing? required

Watch this space for progress on the cannon.

There are some technical challenges, including deep boring 14mm diameter 275mm deep, making a tiny dovetail in the ironwood,  and turning the barrel from 50mm diameter brass.

TAPPING GUIDE

I took another break from the triple to make this tapping guide…

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The tapping guide in use.  BA7. (staged photo)

 

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CNC drilling and reaming

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CNC milling the flanges

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The completed arms and flanges

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Milling the jaws manually

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The jaws in position

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Showing the jaws holding a tap. The jaw cover is removed.  The  hole in the side of the chuck is for the M5 grub screw which opens and closes the jaws.

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Showing the jaws cover in place.

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The 3 jaw chuck provides a convenient and accurate base. Alternatively, the guide could be supported in a hole in the bench.

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Very handy for tapping threads in items not readily held in a vise.

The biggest problem with tapping threaded holes is taps which break in a job.  Sometimes after many, many hours making a part.   Sometimes the broken tap is able to be removed, and sometimes it cannot, resulting in a ruined part, wasted time and much wailing and gnashing of dentures.

Keeping the tap vertical at all times during the tapping procedure, and using a sharp tap, suitable lubricant, and appropriate torque, are the keys to not breaking taps and saving teeth.

Usually I do my tapping with the tap held under a spring loaded guide in the chuck of the drill press or mill, and the workpiece in the vise.  This method prevents any inadvertent bending of the tap, which avoids one of the major causes of breakages.

But sometimes it is just not possible to hold the workpiece in the mill or drill press and the tapping has to be done freehand, aligning the tap by eye.  I am rarely satisfied that the tap is vertical after using this method.  Lack of accuracy, and higher chance of a broken tap is the consequence.

So when I saw this tapping guide in “Model Engineer”, and saw the possibilities for its accuracy and versatility, I decided to make one.  The fact that much of the machining could be CNC’d was an added attraction.   Also the 4 jaw chuck was intriguing.  I had seen one made by a colleague in the Melbourne Model Engineering Club, and I was keen to see if I could manage it.

The design was by Mogens Kilde and the plans were published in the August 2015 “Model Engineer”.    I made a few minor changes to the design, mainly using thicker aluminium in the arms and flanges.  I used stainless steel for the chuck body because that was the only free machining steel which I had in the size.  I used key steel for the chuck jaws, again because that was what I had available in my workshop.

The double parallelogram arms keep the tap vertical within the limits of the arm movements.  Using a 3 jaw chuck as the base of the unit provides a lot of flexibility in positioning the guide.

I will not comment on the actual building, because that is clearly explained in detail in the original ME articles.

Making the Lathe Spider

Drawing the chuck, the bore, and the 3 spider components.

Drawing the chuck, the bore, and the 3 spider components.

Using CAD to measure the dimensions.

Using CAD to measure the dimensions.  The main requirements are that the 3 components are identical, and the 30/120 degree angle.  (360/3).

Transfer the dimensions to Vcarve pro, to generate the G code. (not essential to use Vcarve pro. This simple shape could have been entered directly into the CNC mill)

Transfer the dimensions to Vcarve pro, to generate the G code. (not essential to use Vcarve pro. This simple shape could have been entered directly into the CNC mill)

Simulation of the process, using VCarve pro. Again, not essential, but it is fun. I use an iphone App called FS Wizard to calculate the feeds and speeds.

Simulation of the process, using VCarve pro. Again, not essential, but it is fun.
I use an iphone App called FS Wizard to calculate the feeds and speeds.

Milling the components.

Milling the components.

The sacrificial holding plate, and the components. I tried a wooden sacrificial holding plate, but it was just not adequately rigid, and the finish was poor.

The aluminium sacrificial holding plate, and the components. I tried a wooden sacrificial holding plate, but it was just not adequately rigid, and the finish was poor.  The aluminium plate worked well.  It will now join the growing pile of sacrificial plates from other CNC projects.  You can also see the result of an extra milling step which removed the rounded fillet, allowing the spider to sit snug against the chuck jaws.

Cylinder Bases. Lathe or milling machine?

I read an expert treatise on making a double expansion steam engine, and I imagine that the comments applies to triples also.  One aspect emphasised the importance of accuracy in making the cylinder bases.  The parallelism of the surfaces, the concentricity of the piston rod hole and the other circular elements, and the thickness. The usual method for making these items is to turn them in a lathe with a 4 jaw chuck, then to reverse the item in the 4 jaw to turn the other face.  It is possible, but very fiddly and time consuming, and relies on expertise, patience, good eyesight, and a good lathe.   All of which are in short supply around here. A triple expansion steam engine requires 3 of these base plates, and while there are some common dimensions, the cylinder bores are all different.  Many of the screw holes are common to the 3 plates.  The thicknesses are all the same. To shorten this rather boring epistle, I decided to have a go at making the base plates on the CNC mill.  Given my previous muck ups, broken bits, crashes, this was a courageous decision, as evidenced by having to bin the first effort.  But the next 3 all seemed to work OK. First I studied the plans and noted the common elements, then I made a jig, with holes drilled at the common positions.

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The underside of the jig, showing the 5mm centre hole and the counterbored holes at the attachment points.

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The topside of the jig, after the first and second baseplates were drilled, thicknessed and shaped. The jig needed to be made very accurately, to retain position of the workpiece after it was reversed, so both faces could be milled. I am told that CNCers build up a collection of jigs over time. They are rarely used again.

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CNC milling the central boss. 20.48mm diameter, and accurate. Note the red positioning device, enabling the workpiece to be removed to check measurements, then replaced exactly in the same position.

To see a video of the CNC mill cutting the external profile click on the link below http://youtu.be/m0d5yuX96Uc

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The cylinder baseplates screwed to the columns. Some trimming of the column tops is required. The baseplates are centered accurately, as far as I can measure. Note that the central jig separating the columns has been removed, and the baseplates are now holding the column tops in position. The columns appear to be lining up correctly.

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The next example of using the CNC mill to perform a task which is normally done on the lathe. The mill cutter is travelling in diminishing circles, producing a central boss, and a flat surface.

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The boss finished to size (10mm dia) and flat surface.

BTW.  In a previous post I mentioned a 1 mm inaccuracy in a CNC milled part.  It happened again when I milled the first base plate, which ended up exactly 2mm smaller than programmed, and had to be re-made.  This time I discovered the cause of the inaccuracy….   I had used an 8mm milling cutter, but had forgotten to tell the CNC computer that I had changed from using the 6mm cutter.  The CNC machine did not notice the change, and cut the part exactly as instructed, very accurately, 2mm smaller than intended.  CNC machines are incredibly clever, but very very dumb.  They do exactly as instructed, even if the instruction is wrong.

108 Accurate holes. CNC again.

The triple expansion engine legs will be bolted to the base, with 9 bolts each.  That is 54 holes which needed to be precisely drilled so the columns are accurately positioned.  Each one of those holes needs to have a mating hole made in the base.  The base hole will be threaded to accept a stud.

Normally one gets accurately mated holes by drilling through both objects simultaneously, but that was not possible in this situation due to obstruction from the columns themselves.

So the solution??   CNC of course!

The hole positions were known from the CAD drawings, and were entered into the CAM program.  The resulting file was too big for my old CNC mill (1997 model), so I attempted to drip feed the information as the machining operation was taking place, but without success.  Several phone calls to my expert friend Stuart did not resolve the problem, so Stuart kindly came to suss it out.    A couple of hours later he had the drip feeding working as a result of a serendipitous error.

We knew that the largish file needed to be drip fed into the CNC mill, but it eventuated that we had to try to enter it directly, and produce an error message first, before drip feeding it.  A bizarre system, originating from the land of Manuel of Faulty Towers.

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A test run in scrap wood.

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Heart in mouth, center drilling in progress

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And  2.5mm through  drilling

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And the mirror image holes in the base. 2.05mm diameter, ready for BA7 threading. See how the holes line up exactly with the marking lines.  Now to make 54 BA7 studs.

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