johnsmachines

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.

Category: 3d printer

The (non) gripping power of rubber

In order to increase the head pressure of molten aluminium during my casting pours, I increased the height of the casting cylinder to 250mm (previously 100 to 150mm).

That meant that the weight of the casting investment mix increased to 5.25kg. per 250mm cylinder.

This was the result today, when I poured the investment mix, then moved the cylinder with the rubber cap at the bottom.  It would have been OK if I had waited for the mixture to set. (about 20″).

PANA4000

The rubber end cap slipped off, the investment mixture came out, the 3D printed parts tree fell apart, and an horrendous mess resulted.

After a barrage of unprintable expressions, I hosed the 3D prints down (outside), and washed the cylinder and end cap (outside).

By then the mess on the bench and floor had set, so I was able to scoop most of it up with a BBQ spatula.  Then multiple wipe downs to get the very fine powder off the surfaces.

I still wanted to prepare the moulding cylinder(s), and for some reason I had lost my desire to use the 250mm cylinder, so I made 2 trees with the parts, and split them into two 150mm cylinders.   Without further incident.

While waiting for the investment mixture to set, I did some further work on the previously cast parts.

PANA4001

Applying some JB Weld  onto one of the cast rear wheel bracket and column assemblies.

Second Pour.

One definition of stupidity  is repeating a set of actions and expecting a different outcome.

Well, after my partly successful first molten metal pour, I repeated the same steps, (with some minor corrections), and hoping for a more successful result.

The day was entertaining, with one of my daughters videoing the exercise.  But this was the result…..

PANA3967

The aluminium melt has not properly filled the cavities at the top (nearest the funnel).  The bottom cavities have filled nicely, with good definition of the printing details.

PANA3968

The second flask with the same  result.

PANA3965

My daughter found the exercise very interesting, particularly the pour and the boiling out of the investment material.  But she was a bit disappointed that the end result was not better.

So, I am considering how to change the process.

I believe that I need to increase the filling pressure in the upper half of the flasks.

Possible methods:

  1.  Install a vacuum system for the melt pour
  2. Use a vertical extension for the melt funnel, to increase the height of the column
  3. Increase the diameter of the funnel tube
  4. Increase the number of the funnel tubes
  5. Don’t place tree branches close to the funnel

I had previously considered 1. as recommended on YouTube by several contributors.

The investment powder is a significant cost, so I would prefer to use as much of the volume of the flask as possible, which makes 5. an unattractive proposition.

There are difficulties with instituting 2. but I am thinking about this one.

And possibility 6, is to try bronze or brass, which has a much greater density, and probably less viscosity than aluminium.  I am waiting for some more furnace graphite crucibles to arrive before I can try this one.

Meanwhile I have to 3D print some more PLA parts.

 

Repairing Failed 3D Prints

As a beginner, I have a fair percentage of unsatisfactory prints.

Print breaks free of plate.

Supports fall over.

Overhanging areas insufficiently supported.

Holes appearing due to wrong settings.

etc. etc. etc.

Most of the time I just bin the failure, change the settings or setup, and make another print. And wait another 2, 9, 12 or 24 hours……  Not a huge financial cost, but does involve waiting.  And I am not very good at that.

I used to grow olives and make olive oil.

Sometimes the bottles of oil were sealed with wax.  Melting point 85ºc.

After a failed print of 6 items today, due to inadequate supports of overhanging areas, I wondered if the holes and thin areas could be fixed with the bottle sealing wax.  After all, lost PLA casting is just a descendant of the lost wax method in the metal casting process.

So I found the left over remnants of the bottle sealing wax, and heated up a soldering iron.

IMG_8520

One of the failed prints.  This is a wheel trolley bracket for the model Armstrong cannon.  The moth eaten area was overhanging, and the support had fallen over.  The area was thinned and the holes were not properly formed.   If a brass or bronze casting was made from this, it would have been unusable.

IMG_8522

The 850g slab of bottle sealing wax, and soldering iron.  I do not know if this supplier is still available.  It was not expensive.

The soldering iron is heated, dipped into the wax, and the molten wax carefully dripped onto the deficient area of the print, gradually building it up.

The wax can then be shaped with the soldering iron, or a heated knife, or even a finger or thumb.  I also tried a blade shaver and sharp knife.  I think that my soldering iron, and finger were the best tools.

 

IMG_8521

The repaired area.  It looks unsightly, but of course the wax will all disappear during the casting process, along with the PLA.

I am probably reinventing the wheel with this idea.  Again.  But have not seen it used anywhere else.  So there it is.  I think that it will be useful to me.

PS>. 12 hours later.  I now realise that this is so old hat that I am embarrassed that I posted this.  Reinventing the wheel,… that’s me.

 

 

3D Printing a Cannon Barrel

There is quite a learning curve to 3D printing, and most of my prints so far have exhibited considerable room for improvement.  There are some helpful YouTube videos on the subject, but at my beginners level there is still a lot of trial and error.

I am still planning my next cannon model build, and printed some cannon barrels to improve my printing skills, and also to have a plastic model of the barrel to help decide about construction methods of the metal model.

P1053560

This is a 1:20 print, but was unsatisfactory because the cascable, and the rifling did not print.

The next prints took 22 hours (vertical orientation) and 24 hours (horizontal orientation) each.

Firstly the vertical orientation..

P1053570

It starts with a thin line which marks a little beyond the outside outline of the model to ensure that it is properly located on the printing plate.  Then a thin base to ensure adherence of the model to the printing plate, for the duration of the printing.  My plate is heated to 60ºc, which is not essential with the PLA filament which I am using.  I changed the filament colour for aesthetic reasons.

P1053571

Each layer of filament adds another 0.2mm of height.  The rectangular columns support the overhanging parts, and increase the overall support of the model during printing.

P1053574

The printing is finished after 22 hours.  I can already see some mistakes.  The barrel should be smoothly rounded, instead of faceted.

P1053584

After breaking off the supports.  Next to a bit of workshop rod  which I will use to make the actual cannon model.   Not quite long enough, but the rifled gun tube and cascabel will be made separately so the steel rod will be long enough for the rest of the cannon.

The next print was horizontal…

IMG_8505

IMG_8507

I made the supports more densely placed to improve the support.  The cannon barrel is just appearing in the centre.

IMG_8509 2

I left the printer to continue overnight, and this is what I saw next morning.  Note the longitudinal placement of the plastic fibres.  Infill set at only 3%, which was adequate.  I increased the outside wall thickness to 5 layers, which was plenty thick enough.

IMG_8511

P1053590

The finished horizontal print on its supports (front) and the vertical version (behind).   Apart from the facets, the appearance of the vertical version was better IMO.

Now I am ready to turn the barrel in steel.  I have obtained a facsimile book about naval artillery which was written in the late 19th century, it reveals that the Armstrong barrels were made in concentric pieces, and heat shrunk together.  I will adopt a similar method, making the cascabel and the central rifled tube separately from the breech sections.   Not decided whether to heat shrink them together, or silver solder, or Loctite. (ps. a week later.  Changed my mind.  Making the barrel from a single piece of steel)

The artillery book also answered my question about 64 -80 lb cannon and bore sizes.  When round shot was replaced by pointy cylindrical projectiles, the projectile weight could increase by increasing the length rather than the diameter of the projectile.  And some 64lb cannons were redesignated as 80 lb cannons, after modifications which did not necessarily alter the bore.  Unfortunately the book does not answer how the rifling was accomplished with a closed breech.

And I made another workshop tool.   This one is a lathe tool height gauge.

P1053566

I expect that the tough PLA will stand up to workshop treatment quite well.  It is light, very visible, will test upright and upside down tool bits, and will hang on a conveniently placed hook. Also, it is within 0.01mm of the required 38.05mm tool height.  A light rub of the base over fine emery paper will get the dimension right on.

 

 

3D Printing is FUN! (but still slow)

IMG_8498

My 3D printer.  Bought from Amazon on a special offer.  $AUD279.  Worked straight out of the box after minimal assembly, and using the supplied plastic filament (PLA).  You can see the large gear on the platten which I drew up using a CAD program.  I used the software (Cura) supplied by the printer manufacturer (Creality).   The printer is a Creality CR -10S.  The “S” refers to a “filament out” sensor which I have not yet installed.  I read some reviews of the printer before spending my money, and so far I am very happy with it.  You might notice some bracing bars which I bought separately on Ebay.  Not sure if they are necessary, but they might improve the print quality by reducing vibration in the printer.

P1053563

These gears and shafts were printed.  They were used to check the sizes of parts for my next model cannon build.  I used a program called “Gearotic” to plan the gear module, teeth numbers, distance between centres etc.  Gearotic is also great fun.

P1053561

The printed gear and pinion quadrant on a background of a photo of the real cannon.  On my model the gear and pinion will be made of steel or brass, machined from bar stock.

P1053558

Another part sitting on a photo of the original.  This demonstrated that I had got the corner chamfer a bit wrong.  Much better to discover the fault at this stage! 

P1053560

A half size print of the barrel.  This was just for fun.  The final part will be ~300mm long, and will be machined from steel.  This print took almost 4 hours.

P1053557

A print of the centre column which the cannon chassis sits on and traverses around.  It is ~60mm tall.  It will be tricky to machine from solid bar.  Could be fabricated in pieces and silver soldered together, but I am considering using the printed part to make a mould and cast the part in brass or bronze……   The original cannon column has an 5-600mm extension into the concrete base which my model will not need.

So far all of these prints have been made from PLA filament, which I read is easy to use, tough, rather brittle, and has a low melting point.  It is also inexpensive (about $20-25 for 1 kg).  I am still on the supplied small roll which came with the printer.  Future prints will be in colour!

The weather is a bit cooler today, so I might get back into the workshop and make some metal swarf.

 

 

3D Printing is SLOW

P1053454.JPG

Crealty CR-10s 3D printer.  The machinists parallels were my solution to ensuring that the horizontal arm is parallel to the base frame.

So, I took delivery of the 14kg box, and spent a couple of hours assembling the printer.  It was partly assembled, as delivered, and if I had known what I was doing the final assembly would have been done in a fraction of the time.  The assembly instructions were adequate.  The wiring connections were well labelled.  The wiring connectors were delicate, and I took care not to bend or break them.

The vertical frame bolts to the base frame, and it is surprisingly rigid.  There are 2 Z axis stepper motors, and when not powered up, they can be individually turned.  It occurred to me that the horizontal arm which the Z axis motors raise and lower should be exactly parallel to the base, so I placed the machinist’s parallels as shown in the above photo and screwed the horizontal arm down onto the parallels to set the horizontal position.  I assume that the Z steppers will move the arm equally. (Hmm… I will check that assumption later.)

Next day, I downloaded the operating software.  An older version was supplied with the machine, and the newer version would not work on my old XP Pro Windows computer, so I used the old version.

I spent some time manually levelling the bed, then ran the automatic bed levelling software.

The printed operating instructions are very basic.  An Internet connection is assumed, and I did not have one available, so my first printed object was with default settings and the supplied white filament.

Somewhat to my surprise, it worked.

P1053455.JPG

The platten is aluminium.  A glass plate was also supplied, so I used that on top of the aluminium.

The filename was “dog”.  I had no idea whether “dog” was a 3D dog, a picture, or whatever.  Neither did I have any idea of its size.  After an hour, I had printed a disk about 125mm diameter and 1.1mm thick.  Then the disk came off the platten, so I aborted the print.

Today, after getting some advice from Stuart T regarding print adhesion I removed the glass platten cover and applied some special adhesive 3D printer cover.  It is called “3M double coated tissue tape 9080A”.  Then I printed 2 more items.  Neither broke free.  in fact they were difficult to remove at the conclusion of the prints.

P1053466.JPG

This tiny Tyranosaurus was printed from a 3D file which I found on my computer.  It printed in about 20 minutes.  Default settings again.  The supports were too big for the object, and when I broke them free I also broke off the T Rex arms.  Some settings for supports need to be changed.

The next print was a tool which I planned for the 3D printer…..

P1053468.JPG

The item is a speed handle for a milling vise.  It is 80mm diameter with some grippy indentations on the circumference.  The tricky feature to make is the hex hole, to fit a 19mm hex shaft.  This is the 3D drawing, imported into the Creality software, so the G code can be generated.

P1053469.JPG

First layers.  Each layer is 0.2mm thick

P1053475.JPG

The internal framework is a bit lighter than I wanted.  I thought that I had chosen 90% density.  (ps.  a couple of weeks later.  The speed handle seems to be standing up to the usual rough treatment in my workshop, despite my misgivings about its lightness.)

 

P1053477.JPG

The speed handle on the vise.  Nice fit.  The print took over 2 hours.

Not perfect, but too bad at all.