3D Printing for Lost Wax Casting

[CHARLES lipscombeParticipant @charleslipscombe16059]

Following several pieces of very valuable advice from different forum threads, I am currently trying to make 3D printing work in conjunction with lost wax casting,

Current state of play is that the finished stainless steel castings (prepared from PLA "waxes" are often rejects, being incomplete in some areas or deeply pitted.

The foundry blames porosity in the 3D prints while the 3D print guy blames the foundry for not completely melting out the "wax". Doubtless this situation can be resolved by more time and effort, but I would like to negotiate from a position where I know what I am talking about

SO MY QUESTION IS: IS POROSITY IN 3D PRINTS A KNOWN CAUSE OF PROBLEMS WHEN USING THEM FOR LOST WAX CASTING?

I have seen Neil's articles on 3D prints to Lost Wax castings but whilst excellent for Neil's needs they look much to low a standard for what I do – which is:

Making otherwise unobtainable parts for vintage and veteran motorcycles, especially control levers etc, so the parts are often about 50x50x10 mms in size and complex shapes.

In conclusion, I agree that I should be doing my own 3D printing so that I have control over the quality but an often unstated fact with 3D printing is that for model-making purposes etc you first need to create a CAD drawing. For someone like me starting from ground zero this is a considerable handicap.

Best wishes to all those forum contributors who have helped me in the past, especially to mechman48

Chas

Edited By CHARLES lipscombe on 14/04/2018 10:16:12

Edited By Neil Wyatt on 17/04/2018 13:52:00

[David JuppParticipant @davidjupp51506]

For high quality finish, there are 3D printable waxes designed especially for lost wax casting. Not sure if such things are available for 'home' printers. It might be worth checking what the bureau services can provide.

Edited By Neil Wyatt on 17/04/2018 13:52:27

[CHARLES lipscombeParticipant @charleslipscombe16059]

Finish per se is not really the issue because the final stainless castings have a sand-blasted finish and I need to polish this off anyway. However useful to know that such waxes exist. Thanks, Chas

Edited By Neil Wyatt on 17/04/2018 13:52:32

[David ColwillParticipant @davidcolwill19261]

I wonder if you could use some kind of wax as a filler for the 3d prints, you are after all only filling smallish holes. I would have thought just rubbing a hard wax into the print and wiping off the excess would leave a pretty good finish.

Also it may be an idea to try a test run of something in aluminium which would be cheaper to do initial testing with. Once you were happy with that, then try the stainless.

These are just my thoughts and are not based on any real world experience.

David.

Edited By Neil Wyatt on 17/04/2018 13:52:37

[JasonBModerator @jasonb]

May be better to take a mould of the PLA printed part and then cast proper waxes particularly if more than one item is required.

Also are you using the PLA part straight off the printer or are you doing any work to the surface to get a better finish?

Edited By Neil Wyatt on 17/04/2018 13:52:42

[Neil WyattModerator @neilwyatt]

Hello Charles, it would help to see a finished casting.

Porosity shouldn't be an issue, the outer skin of a good print should be virtually airtight. The limit on the castings I'm getting is caused by using plaster as the moulding medium, also bear in mind the parts I have done are very small. Hopefully the image below is closer to 'actual size'.

My advice would be to seek a company who will print and cast the part themselves – they are out there and if their prints go wrong they can only blame themselves.

Edited By Neil Wyatt on 17/04/2018 13:52:23

[CHARLES lipscombeParticipant @charleslipscombe16059]

Thanks to all those who responded.

Neil: The photo shows 2 original parts (brass), the 3D print and a failed stainless casting. The part is a lever fulcrum for a carburetter control which was current from 1909 to 1914.

Typically about 50% of the S/S castings I get back are OK and the other half have the "lace curtain" effect shown.

Thanks for clarifying what you did with your casting – a good example of horses for courses I think

The prints were originally 2-shell i.e. the walls were 2 layers thick with a hollow centre. I went to 5-shell then solid prints but without any conspicuous sucess. I believe it is usual for foundries to apply vaccuum at some stages of their process and this would mean that a small pinhole could lead to a major defect in the casting.

I agree that it would be better to use a company that did the printing and casting in house but the few companies that I have found in Australia to do this, all charge like wounded bulls. I am a hobby-level producer, basically in it for the fun and the satisfaction of creating things with my hands so high costs are not on.

Jason and David Colwill: Print quality is OK but not as good as some I have seen. I don't know what thread size he prints at. Anyhow, I don't work on the surface of the prints before they go to the foundry. The foundry uses a product called Patch Wax to repair damaged waxes before casting (made by DARENT WAXES in the UK if anyone is interested). I have tried this on the 3D prints but it is difficult and time consuming to do this and get all facets of the prints covered. Again I have had limited success with this idea.

My next move is that I am waiting delivery of an el-cheapo vacc pump and vacc chamber from e-bay. I propose to immerse the castings in molten Patch-Wax, apply vacc and watch for bubbles. Then I can drain off the surplus wax and send them to the foundry for casting.

To summarise, I am finding 3D printing brilliant, even indispensible for prototype work(*see below) but I am still struggling with production

*The original is for the left-hand side of the handlebars but I wanted a right-hand version. Without 3D printing I would have to fashion a RH version, probably from solid and probably need several goes before I got it right.

Best wishes, Chas

Edited By CHARLES lipscombe on 15/04/2018 06:30:05

[CHARLES lipscombeParticipant @charleslipscombe16059]

[not done it yetParticipant @notdoneityet]

Go on, give us a clue!

[CHARLES lipscombeParticipant @charleslipscombe16059]

To not done it yet, I think somehow I have accidentally started a new thread. If you check back posts for the past few days using the same thread title you will see the start of this topic.

Sorry for that, Chas

[IanHParticipant @ianh]

By coincidence I have just finished a batch of similar levers for Morgan Three Wheelers. These are reproductions of the Amal originals. I am 3D modelling them, then making alloy tooling (CNC and conventional milling and turning) which goes to the foundry for wax injection. There is one tool for the levers, it produces either the long or short lever. There is a second tool for the bodies – this tool is designed to produce single or double levers, left or right handed. I add the Amal logo on with the CNC miller.

Ian

[IanHParticipant @ianh]

Apologies for the messy post….

[CHARLES lipscombeParticipant @charleslipscombe16059]

Ian H: I have sent you a private message.Chas

[not done it yetParticipant @notdoneityet]

It wasn’t that it was a new thread; it was that there was one pic and devoid of any text! It happens…..

[Neil WyattModerator @neilwyatt]

Looks to me that your foundry may be failing to burn out the print completely. Even if porosity was an issue I wouldn't expect so much of the mould to fail. For such a thin-walled, large object I would suggest investing in filament meant for lost-wax casting.

The answer would be to break out the part from the mould yourself and see if the missing space is filled with investment or with carbonised plastic.

If it is porosity the answer is simple – ask them to coat thw pattern with a layer of investment (no vacuum) and let this dry before preparing the full mould.

Neil

[CHARLES lipscombeParticipant @charleslipscombe16059]

Neil: Thank you for your very helpful reply. I will post again when I finally solve the problem but I feel fairly confident you have supplied the answer. Per ardua ad excellence

Once again the forum comes up trumps!

Chas

[John PParticipant @johnp77052]

Seeing your casting with the lace curtain effect reminded me of a similar
problem that i had in the past casting some of these aluminium parts
seen here in the photo ,i had on some a granular net curtain appearance.
At about that time i attended the Farnbrough airshow ,the trade
stands there are interesting to see ,i showed one of the castings to
one of the exihibitors and suggested lowering the flask temperature
before casting the metal .It worked ,the differential for aluminium was
about 300 deg C.
Whilst 3d printing is an attractive method to produce prototype parts
any voids within are likely to cause problems when investing the parts,
some useful reading can be found at http://www.srs-ltd.co.uk
navigating through the site shows some problems and likely causes
and remidies.Also to see how the process for mixing and investing
is carried out ,most of these investment powders have a strict method
that must be adhered to ie the mixing time vacuuming ,filling the flask
and vacuuming again .This is a one off deal ,i think that Neil's suggestion
of pre-coating the pattern will not work ,on a previous occasion i did not
mix enough investment to fill a flask and tried mixing some more to
fill the remainder ,it fell apart, the investment does not bond together.

Like all casting methods good patterns make good castings ,the
post by IanH using solid moulds using wax injection is the way to
go to get good casts .

The photo shows some cast aluminium parts looking closely it will
be seen that the inner parts of the moulds are polished ,when the
patterns are released from the mould the slightly translucent nature
of the wax can be viewed with the aid of a strong light to see any
voids of defects before investing.

John

[IanHParticipant @ianh]

For interest here is a photo of the tooling for the levers and a photo of the waxes for the levers and the bases.

[Neil WyattModerator @neilwyatt]

I've gathered all the bits together.

Try not to split a thread like this again, please

Neil

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