Using 3D prints for casting

[DMBParticipant @dmb]

Last year I saw a 3D printed pattern in plastic for a ring of brake blocks and the resulting iron castings @ Brighton & Hove clubs wrinklies day.
John

[AndyPParticipant @andyp13730]

I have found pla burns out nicely when printing lots of precious metal items (it's the day job) but more importantly things like this:-

or

which is the pump body for a sweet pea so I could practice on one before butchering the the real thing on the left since it is for the new club loco.

This shows the model sprued up ready to invest with another scaled up model and the original brass cylinder with a 1 to 1 copy in pla. All steam passageways are cast in but I should leave some meat on the valve openings to clean them up.

 

cast in gunmetal as a test and the brass pair now adorn my MarieE, it is the normal method of address for my particular SWMBO.

Now if I could just melt cast iron ………

Andy

Edited By AndyP on 19/02/2015 21:43:00

[Bob YouldonParticipant @bobyouldon45599]

Hello all,

Following on from DMB's post re the Brighton and Hove SMLE brake shoe rings please see attached photographs of the said shoes, including the CAD 3D drawing, the CI rings and pattern and an as received cast iron ring.

Regards,

Bob Youldon

[Chris Pattison 1Participant @chrispattison1]

Bob,

Personally, I would have gone the laser cutting route for those brake shoes. It may have been easier. Provided of course that you could get cast iron solid, to then cut into slices of appropriate thickness.

Regards,

Chris P

[EnnechParticipant @ennech]

Seems a shame getting a pattern done like that without taking the opportunity of getting a bit more detail into them.

Eric

[Neil WyattModerator @neilwyatt]

I fancy printing tank tracks. The thought of milling 200 links from aluminium and then having to anodise them to make them a decent colour fills me with dread.

A dark grey ABS print would be fine for what I want, and only a few holes to drill in each one.

Neil

[Bob YouldonParticipant @bobyouldon45599]

Good morning all,

Re:

Personally, I would have gone the laser cutting route for those brake shoes. It may have been easier. Provided of co urse that you could get cast iron solid, to then cut into slices of appropriate thickness.

Chris, laser cutting was considered and in the prototype passenger car the shoes were originally laser cut in steel, but it was the opinion of the building group cast iron against the steel bogie wheel is a much better propersition so therefore the decision was taken to go the cast iron route.

Seems a shame getting a pattern done like that without taking the opportunity of getting a bit more detail into them.

Eric, as the shoes are destined for use under passenger cars, there was a need to produce a simple repeatable component, there was a requirement for in excess of a hundred and in normal use they will never be seen.

I will say the effectiveness of eight shoes per car in stopping a loaded vehicle is very impressive.

Regards

Bob Youldon

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 20/02/2015 11:11:35:

I fancy printing tank tracks. The thought of milling 200 links from aluminium and then having to anodise them to make them a decent colour fills me with dread.

A dark grey ABS print would be fine for what I want, and only a few holes to drill in each one.

.

Neil,

That would be a printed product wouldn't it ?

… I thought the idea here was to use the print as a pattern.

Is it 'efficient' to print 200 identical items ?

MichaelG.

[Neil WyattModerator @neilwyatt]

> Is it 'efficient' to print 200 identical items ?

If the alternatives are:

• Milling them
• Fabricating them(!)
• Paying for 200 little castings

Then yes!

Neil

[Peter BondParticipant @peterbond14804]

Mill one mould in Al and build a small injection moulder?

[WALLACEParticipant @wallace]

Hello Bob.

Wrt to the castings – they look very clean and tidy. This is probably a silly question but I can’t see any signs of risers or sprues on them – any idea on how they were cast ?

Thanks.

W.

[Neil WyattModerator @neilwyatt]

> Mill one mould in Al and build a small injection moulder?

That was the fourth option I meant to reject!

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 20/02/2015 22:18:45:

That was the fourth option I meant to reject!

.

Neil,

Do you already have a 3D Printer?

… Or are we witnessing the 'Purchase Justification' process?

MichaelG.

[Bob YouldonParticipant @bobyouldon45599]

Good evening Wallace,

Re the castings, as received from the foundry they had been fettled and any risers or in gates had been removed, they must have spent some considerable time on them; the photograph of the stack of brake shoe rings is exactly as we received them from the foundry. I'm afraid I cannot help with their moulding and casting process, off went the pattern, back came the rings, simple as that!

Regards,

Bob Youldon

[Peter BondParticipant @peterbond14804]

Posted by Neil Wyatt on 20/02/2015 22:18:45:

> Mill one mould in Al and build a small injection moulder?

That was the fourth option I meant to reject!

OK, print 1 mould, lost PLA cast it in Al and build an injection moulder?

Less costly & time consuming than printing 200 of them!

[JasonBModerator @jasonb]

It all comes down to the job in hand as to what will be the most ecconomic and that will also vary from one person to another depending on what equipment they have and what they would have to buy in.

If plastic is suitable for Neil's tracks and he had a 3D printer then his only cost is a reel of filament and he could go and walk the dog while it was printing. If Neil also had a CNC mill then he may look differently at the milling option as that could be making a pile of swarf while he walked the do and his costs would be the raw material and a cutter or two.

Now if somebody else wanted 200 track links but needed them in metal then they could outsource them to be CNC cut, printed in metal from the likes of shapeways. Print one off in plastic then take an RTV mould, cast up 200 wax replicas and make them into a tree and have them lost wax cast, or if they were big tracks (neil has not given a size) then maybe print oversize, cast an alloy pattern and then sandcast 200 from that pattern, still cheap if you have a home foundry but pricy if you sub it out.

Or just go out and buy some aftermarket tracks in either PU resin or light alloy as they are readily available for the AFV and site plant modeler.

All the above and more would have plus and minus points so you can't generalise. Though from Andrews earlier post it looks like it was more econonic for him to print out several hundred of his component housing boxes than have them moulded.

J

[Neil WyattModerator @neilwyatt]

They would be anything from 3/4" to 1 1/2" long, I haven't decided on a scale yet.

I reckon it would be possible to print them in quite big batches at a time. As Jason says I could get on with real life while they printed and anyway the length of time is irrelevant as it's something I've been musing on for years – a Vickers Light Tank, My main interest is in making working suspension units, but a bit pointless without a route to a full model!

I also want something a bit more space-friendly than TIger tank.

Neil

Edited By Neil Wyatt on 21/02/2015 12:55:35

[WALLACEParticipant @wallace]

Hello Bob.

Thanks for the reply – I’m still impressed by the castings however they were done !

Presumably its easy enough to print out the pattern slightly larger to take shrinkage into account as well ?

W.

[JasonBModerator @jasonb]

Shrinkage allowances are easily catered for, you just draw the part teh size you want it in your CAD package and then hit a button that will allow you to enter a percentage to increase the item by so you just enter a suitable figure for the intended metal. Same with draft angle if sand casting you can enter an angle when you extrude the basic shape. and then if you want to can superimpose the pattern over the part to make sure it will fit and has machining allowance where needed, I do this by making one part semi transparent.

[Bob YouldonParticipant @bobyouldon45599]

Hello Wallace,

It's simple to draw the draught angle on to the CAD image and as JasnB has said, machining allowance can also be included where required. What is essential is a good 3D printer, better the printer the better the 3D print.

Regards,

Bob Youldon

[Chris Pattison 1Participant @chrispattison1]

I am astounded at the response my original posting has made. It has certainly stimulated the thinking of a lot of you out there. If you don't have your own printer, I am certain that there will be companies out there that will 3D print your items to order.

I note that just recently, a specialised tool was needed in the Space Station, and as they did not have this on board, they uploaded the necessary file and just printed out the required tool on their onboard printer.

Looking forward, maybe there should be a databank created to store all the programs for various items. To be downloaded and used by others, maybe for a small fee? Certainly cheaper than shipping.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Chris Pattison 1 on 22/02/2015 05:50:15:

… To be downloaded and used by others, maybe for a small fee?

.

I wonder if Neil conducted his recent survey with that possibility in mind.

MichaelG.

[JasonBModerator @jasonb]

Neil, biggest problem I see with your tracks if printed on a home machine is that the "teeth" that stick up will be very weak as the print could fracture between layers a bit like short grain on wood.

Is it for a static model or RC?

As I said if you are not going for a perfect match (two different drawings) then you can buy aftermarket tracks for the RC tanks, about £10 for a set of plastic and from £40 for metal at 1/16th scale which would fit within your scale range.

Edited By JasonB on 22/02/2015 08:01:41

[Andrew EntwistleParticipant @andrewentwistle]

I printed the 3/8" ratchet that was also printed on the ISS – incidentally it was not needed there, it was an exercise in designing something remotely to where it might be needed. Anyway you would think the 3/8" square drive would shear off easily since as Jason suggested it was printed as layers, but I found that it withstood the kind of force that you would expect to shear the same part if it was moulded. With ABS I often treat the print to an acetone vapour bath which fuses the exposed edges and reduces the propensity to delaminate.

Andrew.

[Neil WyattModerator @neilwyatt]

> I wonder if Neil conducted his recent survey with that possibility in mind.

No…

> Is it for a static model or RC?

R/C. The crude drawing was to help me figure out what a link looked like from photos of the outside of the track, the lower drawing is obviously from a contemporary manual. It's surprising how different the links look from the inner and outer faces – the major one being that the central hole is a large round scoop on the outside with another 'layer' on the inside with a smaller, squarer, hole. I misinterpreted this in the pictures as part of the sprocket wheel, and I hadn't understood the 3-D shape of the teeth at all well. I'd obviously have to redraw it in much more detail.

I don't think it would do any harm to make the 'pyramidal' teeth a bit broader at the bottom and rather less hollow to make them stronger

Neil

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