3D Printing - whether to buy, what to buy and how to use it?

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simond

simond

Western Thunderer
Another question, which might be of more general interest than my workbench.

has anyone used 3D printing to make masters for Lost Wax casting?

I know it’s a known industrial process, but I’m thinking of hobby volumes. Like two sets.

and if so..

which resin?
who would you send the masters to for casting?

I'm thinking Walschaerts valve gear in 7mm

cheers
Simon
 
richard carr

richard carr

Western Thunderer
Simon

I don't think that it is very cost effective to only have 2 copies cast. I once had some wagon coupling hooks cast, about 500 I think that worked out at about 50p each, but they would have charged me 75% of the total price for just 2.

Richard
 
Mike W

Mike W

Western Thunderer
Not having a 3D printer I've not printed patterns for casting, but I've used plenty of printed patterns for casting. Don't think the resin matters so long as its as smooth as possible and much better to at least give them a coat of paint because the printed surface has lots of crevices to catch and tear the rubber. I'd use Plataurum in Birmingham, Abbey casting in Essex, or Devon Metalcraft. All are capable of a first class job. Others are also capable, but don't always do it. Probably the best is Iain Young of Sanspareil, but his lead times are years rather than weeks.

Whether its cost effective only you can know, but I have had single or pairs of castings done.

Mike
 
Rob R

Rob R

Western Thunderer
simond said:
Another question, which might be of more general interest than my workbench.

has anyone used 3D printing to make masters for Lost Wax casting?

I know it’s a known industrial process, but I’m thinking of hobby volumes. Like two sets.

and if so..

which resin?
who would you send the masters to for casting?

I'm thinking Walschaerts valve gear in 7mm

cheers
Simon
Click to expand...
Simon
The chap who did the 7mm Old class I manning wardle thread earlier this year on WT printed masters for lwc. Sorry, brain fade, cant remember his name or the thread title..
 
Dog Star

Dog Star

Western Thunderer
Simon, (@simond),

Chris Brown (@ChrisBr) produced, for me, a 3D drawing of a BR period brake lever guard and that drawing was sent to Slater's Plastikard. David White arranged for some wax prints to be made from the drawing and then used those waxes to produce a "tree" suitable for Slater's casting capacity. I was happy with the charge for making the wax tree and the charge for casting the lever guards, the work was done about six years back and so the price is not appropriate to today.


Whilst I asked for just ten castings the mould for the wax tree has been used several times in the recent past - so initially just hobby quantities although the quantity has now exceeded fifty items!

regards, Graham
 
Dan Randall

Dan Randall

Western Thunderer
simond said:
Another question, which might be of more general interest than my workbench.

has anyone used 3D printing to make masters for Lost Wax casting?

I know it’s a known industrial process, but I’m thinking of hobby volumes. Like two sets.

and if so..

which resin?
who would you send the masters to for casting?

I'm thinking Walschaerts valve gear in 7mm

cheers
Simon
Click to expand...
Hi Simon

Mike Hopkins has been getting impressive results, using a printable wax, to produce the patterns for lost-wax castings and some examples of his work can be seen here….

7mm - Mike Hopkins workbench - GNR Artic Coaches

I have been working on this project for quite some time now the whole thing is designed in Fusion 360 using the sheet metal function as well as solid modelling for 3D printed for castings and coach bodies. I was at first going to do the whole thing by 3D printing the chassis bogies and bodies...
www.westernthunder.co.uk

I don’t know which wax he’s using, or indeed, which casting company, but with some lost-wax projects of my own in mind, I’d be interested in knowing myself. :)


Regards

Dan
 
David Halfpenny

David Halfpenny

Western Thunderer
simond said:
has anyone used 3D printing to make masters for Lost Wax casting?
Click to expand...
Simon,
I can answer this slightly different question:

"has anyone used 3D printing to make Lost Wax Castings?"

with, "Yes, I have, by sending my 3D design files to a print agency."

I got back some very nice little 1:32 bronze auto-couplers, with one caveat: small file marks where the technician had removed the sprue not quite as carefully as I would have liked. (There are various ways round this.)

And yes, even one casting would have been economically viable (though not necessarily cheap as chips).

It's a big thing in modern jewellery - see CooksonGold for example - but there's a usefully clear description at:
www.shapeways.com

3D Print Lost Wax Casting - Shapeways

Shapeways customers can choose from a range of metals for Wax Casting, including brass, bronze, copper, gold, platinum, and silver. Learn relevant applications and criteria for 3D models.
www.shapeways.com www.shapeways.com

where you can also get a quote without obligation simply by uploading your design file.


To answer a rather more radical question:

"has anyone used 3D printing to make metal parts directly?"

again the answer is yes, with aluminium being my all-round favourite for strength, machinability and finish, but the slight roughness of steel prints better representing sand-castings.

David 1/2d
 
JimG

JimG

Western Thunderer
You might be interested in what the S Scale Society did when it wanted brass versions of its plastic chair sprues. We sent the required number of sprues to Slaters and they made castings using the sprues as a total loss process by burning them out of their moulds. The brass results were excellent, being as good a fit on the rails as the originals. There was also no sign of marking from ash deposits. If I remember correctly the cost was about £3 per sprue casting. That was a few years ago so might be a bit more today.

It might be a good way of doing your job especially if you are doing your own 3D prints.

Jim.
 
David Halfpenny

David Halfpenny

Western Thunderer
Simon,
You'd be very welcome in the Gauge One 3D Circle, an email+web forum that covers all forms of digital modelling, with especial regard to 45mm between the rails.
gaugeone3dcircle.groups.io

home groups.io Group

*The Gauge One 3D circle is a discussion group for railway modellers working to a track gauge of 1 3/4 inches or 45mm who are interested in modern manufacturing technologies. The* *group aims are * *(I) to share expertise in all forms of Computer Aided Design and Manufacturing as applied to...
gaugeone3dcircle.groups.io gaugeone3dcircle.groups.io

It's an active group that shares experiences such as choice of printer, software and consumables, problem-solving etc. and also shares 3D print files among members.
We also cover CNC and Control, albeit to a lesser extent.

While naturally the quality of individuals' offerings varies with their skills, tastes and investment, you can assess that for yourself before committing any dosh - (unlike the pot-luck of buying prints sight-unseen).

Membership policy is to remain free of charge for as long as possible.
Though we cannot accumulate 3D files indefinitely without somebody putting in pennies.

(Admin is by G1MRA, so membership of that forward-thinking organisation is encouraged, but not required.)

David 1/2d
 
John Baker

John Baker

Western Thunderer
simond said:
Another question, which might be of more general interest than my workbench.

has anyone used 3D printing to make masters for Lost Wax casting?

I know it’s a known industrial process, but I’m thinking of hobby volumes. Like two sets.

and if so..

which resin?
who would you send the masters to for casting?

I'm thinking Walschaerts valve gear in 7mm

cheers
Simon
Click to expand...

Hi Simon,
As Rob & Graham have mentioned, I used 3D printing for lost wax casting for my Manning Wardle Old Class i. In fact having done V2 of the etches, I'm just about to print another set of masters for the castings for the next test build.

I used PowerCast Zero, and I'll use it again as I've still got lots left. It gave very good, clean results. It suffers from very little shrinkage and therefore makes it very good for parts that require accuracy like valve gear. It's capable of very fine, detailed prints which cast well. All that's on my little Mars Pro, so you'll have no problem on the Saturn. It has to be said though that it is expensive stuff - I bought it whilst there was a good deal on it - but would certainly look for something cheaper once I've used it all. SirayaTech castable gets very good reviews, and I'll be trying this next. There are loads of options out there for castable resins now, and there have been lots more to hit the market since I bought the PowerCast.
Last time I spoke to Mike Hopkinson, he was using FormLabs castable resin on his FormLabs printer.

As for the casters, I used Jewellery Casting Scotland. Very helpful people who run it, and a pretty quick turn around too.

Some useful links:
Clearmind Jewellery has some good reviews on their YouTube channel, and have 'ranked' many of the resins they try. It's all from a jewellery point of view, but I have found that if something works for jewellery, it generally works for models too.
YouTube Playlist: https://www.youtube.com/playlist?list=PLJ5braxcEk8zn3EEOdha3QeozAxtciYul
Ranked resin list: Castable Resin Ranked List

VOG (now called VOGMan) also makes and casts using castable resins - again jewellery. Excellent videos to watch!

There'll be plenty of others online too - these are just two that I follow. Not found anyone doing videos about casting models yet.....maybe I'll do one for my next set of castings!

Hope that helps!
John
 
simond

simond

Western Thunderer
John, all, thanks very much.

Maybe this is a better way forward than NC milling the valve gear from steel (or myriad other metals). It’ll certainly be easier from a programming point-of-view because Chitubox does the hard work. No g-code to write.

OTOH, part of the plan was to gain some competence and confidence in g-code & micro milling….

Then again, it would be nice to get the Garratt finished.

thanks again to all!
Simon
 
A

Arun Sharma

Western Thunderer
Yes Simon, I've had hundreds of 3D printed masters used as masters for lost wax casting in silver, nickel-silver and brass in my kits. There are two essential methods - The first is just to use the 3D printed master in the normal way and make a mould from which wax intermediates are extracted and then burnt out. The second, which is ideal for very small runs where no mould is required is to use a printing resin designed for jewellry where it will burn out once invested in plaster without producing any ash. Technically that wouldn't be lost wax casting as there is no intermediate wax but the basic casting process is the same.
The only adaptation required for either of these two processes over normal 3D printing is to add a scale factor to take into account wax shrinkage on setting and also metal shrinkage on cooling. The exact percentage figure depends on the metal used, the ratio of length to width [if dealing with something especially long and thin like a piece of railway line] and the requirements of the foundry. In practice it's only a couple of percent or so.

Simples!
 
G

GrahamMc

Western Thunderer
simond said:
masters for Lost Wax casting?
Click to expand...
With regard to shrinkage a little care is required as it depends on the mould material for the waxes. Just to clarify the process for those not familiar with it the standard process is to create a master/pattern in a fairly robust material and this is then embedded in a mould, silicone rubber or rubber. The pattern is removed and wax injected into the void. The waxes are then embedded in plaster, burnt out at around 700 degrees C leaving a hole and the metal is cast into the plaster, which is destroyed when the casting is removed.
Now, back to the moulds. If it's a self curing silicone mould the shrinkage isn't too much and the mould shrinkage is usually specified on the packaging. If a vulcanised mould is used then layers of unvulcanised rubber are built up around the pattern to make a rectangular block. This is then put in an aluminium frame and the whole lot vulcanised under pressure and heat so you end up with a solid block of rubber with the pattern (and a sprue) embedded in it. You then cut the pattern out to leave the cavity into which the wax is injected.
So, if your caster goes the vulcanising route you get shrinkage in the rubber mould as it cools, a little shrinkage in the wax and finally a little shrinkage in the cast metal. I always used to reckon on 7% total shrinkage for this route but it will vary depending on what is being cast.
With a silicone mould it's going to be a lot less. I've no experience of this but that's been very helpfully covered in the post above this one.
 
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Giles

Giles

Western Thunderer
My 37 has a silver brake block, as I lost one - so I borrowed another from the loco and took a mold using a low temp silicon, which in turn I used to make a wax from. I made this up onto a wax sprue with a gate and cast in in investment plaster, burned it out in a microwave (within a ceramic case) and cast it in silver as being a very easy metal to cast. The sprue etc was of course recycled!

If anyone is interest in using a microwave for smelting.....

 
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Giles

Giles

Western Thunderer
Simon, apropos your motion, the other technique I would consider if I were you, is to have them water jet cut from steel (or any other material). Most companies wouldn't look at an order such as this, but there is one SCISS Ltd in Staplehurst, who are railway people, and have done modelling stuff for me in the past. The advantage is that it's a cold process, should be accurate, clean etc... also an excellent way to do frames.....
 
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