Lost wax casting advice needed

[Brian AbbottParticipant @brianabbott67793]

Hello all

I have been thinking about having a small item i needed cast from brass.

I have had a pattern 3d printed and started making enquirys about the casting.

The advice given was to take the lost wax route so spoke to a couple of casting firms quickly to get a price.

Option A said he would need to make a mould from that he would cast the item.

Option B said he would just use the printed item and burn it away.

Does option B sound ok ? as its a fraction of the cost.

I fully understand the normal pattern / casting process but i thought lost wax some how gave you a finer part.

Any advice would be good.

Thanks

[Brian AbbottParticipant @brianabbott67793]

[JasonBModerator @jasonb]

If it is just a one off casting you want then option B will be quicker and cheaper. If you want a lot then once a mould has been made from your print it becomes more economical to cast as many waxes as you want rather than have to get lots of prints done particularly if you have to pay someone to print the patterns.

Either way a wax will just replicate the finish of the print and won't make it any better

[John FlackParticipant @johnflack59079]

The reason for making a mould is to allow an impression to be made this is injected with wax,the wax impresion is placed in a flask and covered with plaster. This method allows multiple items which are attached to a sprue with an ingrate to pour in the molten metal.with option B the pattern would be encased in plaster with ingate and the pattern would be lost due to the heat of the molten metal. If the cast results in a misshape you pattern will be lost. With option A if a misshape occurs you simply create wax impressions from the mould ad infinitum. The quality of the caster will be a key decision.

[Neil WyattModerator @neilwyatt]

There is materially no difference bewteen lost-wax and lost-PLA so probably option B, especially if the cost of a replacement 3D part is a fraction of the cost of having a secondary mould made.

Neil

[Senior YatesParticipant @senioryates]

Hi, if you are after just a one off option B is best but remember if you want a decent surface finish burning RP is not the best. Most RP leave an ash residue which never leads to a good finish and any printing lines will be magnified 10 fold. It's always better to ask about the size of the companies wax presses and if possible max a little tool yourself, they are only made from aluminium and brass. I had 20 years working with all types of RPs and sometimes making a little hard tool was quicker and cheaper.

Good luck

[David George 1Participant @davidgeorge1]

Hi Brian. As I worked for a tool making company specialising in investment ( lost Wax ) casting making wax dies for parts from hip joints to turbine blades for Rolls Royce it is easy to make your own die from aluminium blocks. if you ask the casting company for their die sizes and injection information i.e. Die height sprue location radius anyone could make a pattern die and then you could make as many parts as you like and possibly using inserts use the die to make other parts. We used to have a standard die and just replaced the insert to make different parts maybe they have a standard die so you could make inserts for.

David

[Brian AbbottParticipant @brianabbott67793]

Hello All.

Thanks for the reply’s,

Starting to understand the principles behind the process but I don’t understand what makes it better at creating a finer detail casting compared with a normal sand casting.

Making a mould myself is not really an option, I should have been clearer as what I am trying to achieve, attached below is a picture of the 3d printed hubs I wanted to cast.

My main concern is to try and maintain the clarity of the lettering, both companies have said that this should not be a problem so unless there is any definite benefit to the quality of the part I will try option b.

Soon as I have some progress, photos of the finished product I will post a picture for anyone interested.

Thanks,

[not done it yetParticipant @notdoneityet]

Why bother with the intracacies other than the lettering? Cast a simple embossed disc and machine the rest?

[John HaineParticipant @johnhaine32865]

As you must have cad files, why not machine it? How many are you wanting to make? How big are they?

[JasonBModerator @jasonb]

Posted by Brian Abbott on 07/02/2017 23:05:37:

Hello All.

Thanks for the reply’s,

Starting to understand the principles behind the process but I don’t understand what makes it better at creating a finer detail casting compared with a normal sand casting.

The plaster used for the investment has a much finer grain than sand so will give a smoother surface which is replicated in the cast part, this is so good that if there are and layer marks on the printed pattern they will be reproduced though it looks like you have had them printed on a decent printer not a cheap DIY one.

Ulless you have a CNC machine I can't see how having teh CAD files will help and even then it will be a job to get tight internal corners to the lettering on what look to be Minnie hubcaps at about 1.25" dia unless John can suggest how to machine them.

[HomeUseParticipant @homeuse]

Following on from Neil’s post I can confirm that for one off castings a core of 3D printed PLA will “burn out” satisfactory for casting purposes, but if the 3D print is ABS then the “burn out” leaves a residue which creates faults in the casting – I have not cast in Brass, using mainly Aluminium and occasionally Silver

[John HaineParticipant @johnhaine32865]

Posted by JasonB on 08/02/2017 07:42:11:

Ulless you have a CNC machine I can't see how having teh CAD files will help and even then it will be a job to get tight internal corners to the lettering on what look to be Minnie hubcaps at about 1.25" dia unless John can suggest how to machine them.

How tall are the letters? It is possible to mill out most of the waste with say a 1mm end mill and clean up into the corners with an engraving cutter, depending on the letter size and the corner definition needed.

[JasonBModerator @jasonb]

The raised part of the hub cap is about 7/8" dia so letters would be 2 -2.5mm high at the most, depth 0.5mm or less

[KWILParticipant @kwil]

As an alternative approach, Silicon Rubber is used as a mold around printed "master", slit open rubber and then wax cast in mold. Resultant wax master(s) fixed to "tree" for coating with the ceramic investment material. Wax burns out in the normal way.

Seen this used to produce fine surface model ship propellors in bronze, but of course the "master was a fine finish to start with.

[AndyAParticipant @andya]

For two off it may be worth the small extra cost of having them printed in wax which is then burnt out in the traditional way. There is a supplier of steam fitting who uses this method and may be able to help you with these.

[Brian AbbottParticipant @brianabbott67793]

Thanks all.

I do have limited access to CNC, but the spindle speeds required for such a small cutter would not be achievable on our machines.

I did think about taking the road that Richard S2 took with his Minnie using individual letters, but to be honest I just wanted to try something different, if it works then great.

The material these where printed from is liquid polymer not sure if this would burn away cleanly so I may be better taking the route of a wax model.

I will speak to the casting company again and see what they recommend.

Thanks Jason for explaining about the medium used, makes sense.

Cheers.

[JasonBModerator @jasonb]

As they are only decorative caps it would be interesting to get a price for having them printed in metal, someone like Shapeways should be able to give you a price.

Another option would be to photo etch the lettering into a turned blank.

[John FlackParticipant @johnflack59079]

Brian……there is a company called Alex Tiranti I think in Berkshire they specialise in mould rubber and cold casting materials mainly for the hobby trade…….might be a useful starting point.

[John HaineParticipant @johnhaine32865]

Brian, what speed can you do? I recently did some nameplates in brass, slightly larger letters, 5000 rpm using a 1 mm cutter. Took quite a long time but successful without breaking the cutter. I use F-Engrave which is a free program to generate the code from an image.

Edited By John Haine on 08/02/2017 16:37:48

[Brian AbbottParticipant @brianabbott67793]

Thanks all..

I did look at the etch idea and as for metal printing…what ever next…

John..thanks for the info, but i have not really enough access to these machine to experiment, be nice if i could.

I have tried emailing another couple of foundries but not really had any luck so am going to try option 1, more expensive but i have a better feeling about them.

Thanks for all the advice and i will post the results..

Next question is square threads but i till start a new thread for that one..

[Nick HughesParticipant @nickhughes97026]

Hi Brian,

A bit late, but if you haven't yet, try Dan at Union Steam Model Company:- **LINK**

I've had the castings he does for the Peter Rich Castle Class and have no complaints with the quality.

Nick.

[Brian AbbottParticipant @brianabbott67793]

I collected my brass castings today and am quite pleased..

couple of points,

Wish i have cleaned up the pattern, as was suggested to me every mark can be seen.

I did not allow for any shrinkage, there was quite a bit.

Need to decide no how to finish them, bit tight on material to machine all over and any machining to the lettering will loose the detail.

Might just machine the back face and give the rest a light rub to remove the pattern marks and leave at that.

[Neil WyattModerator @neilwyatt]

Are you able to share an idea of cost and the name of the foundry?

Neil

[Brian AbbottParticipant @brianabbott67793]

The company i used was Lunts castings.

http://www.luntscastings.co.uk/

Handy as they are only just round the corner from me, but not cheap.

£12.50 for the casting, £30 for the mould.

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