[CoolHand]

This isn't a charity case, I'm happy to pay you to do it.

I need someone who can print a master pattern for me, solid enough that I can cast it in rubber/silicon to create a mold that I can use to make urethane working patterns for sand casting. The pattern would be ~18" wide x ~20" long x ~8" tall, shaped like a flat topped hollow dome (it's a brake drum) with attached runners/risers/sprue/etc.

What I need is someone who can accept a solid model (or STL file or whatever computer file you need) from me and produce a printed solid that is within just a very few thousandths of an inch of being exactly the size of the model.

Accuracy is very important here, because I'm casting to near net size. There will be machine work allowances built in, but you gotta be within -+0.010" pretty much everywhere (except the casting runners, sprue, etc, that stuff gets sawed off and remelted, so a bit of distortion in those parts is fine).

So, any takers?

If you're up for the challenge, PM me your email address and we can discuss our options.

Anyway, thanks for looking. I appreciate whatever help you all can give me.

[awerby]

Are you sure you want a 3d print and not a CNC-machined pattern board? I don't see any advantages to additive manufacturing for this so far. The cost will be significantly higher, but the surface quality likely won't be as good. Your size is at the outer limit for printing, but well within CNC range. Accuracy is better with CNC machining too. Casting to near-net size is risky, because differences in the heat of the metal as it's poured can change the shrinkage factor significantly (you have calculated the shrinkages for the silicone, urethane and metal and incorporated those into your model, right?). Shrinkages can be irregular too, depending on the model's configuration and how it's gated. If you're machining it post-casting anyway, it's usually better to shoot for a bit bigger than you need rather than try to hit a bulls-eye each time.

Andrew Werby
www.computersculpture.com

[CoolHand]

Yeah, I'm sure I want to print it VS cnc machining.

I own a VMC, and it would take the better part of a week to machine it, nevermind the hundreds of dollars of long reach tools I'd need to purchase, and at least one fixture I'd have to build to machine it.

It's a finned brake drum with all the associated runners/risers/gates/etc attached, not something simple or solid.

If it were easily machined from solid, I'd do it myself, but it really isn't.

Spare me the armchair design lectures and either speak up to quote the job or don't.

So far, you've been of no help at all.

Anyone useful want to weigh in?

Nobody willing to take a crack at it?

[SPEEDRE]

I am a retired Master Pattern Maker for the sand cast trade. I must ask, why a 3d print, when a real urethane master pattern mounted on cope and drag mold boards might just be the recommended tool for this application. Please consider consulting a Pattern Design Engineer, or Foundry Eng. I can recommend a real good pattern shop for you, if you'd like. P.M. and we'll have a conversation.

[CoolHand]

As it turns out, the foundry must use a metal match plate, as all their molding is done by automatic machines.

Thanks for the input though.

[Me2]

Well I hope I might be "usefull". Having done many large patterns for sand casting outside the scope of my CNC I cut them in waffers with each waffer having a dowel hole to align to the next waffer, glue them up with a light sand and done. Its worked perfectly for me over the years, but then again I might just be an armchair designer.

[CoolHand]

No, that's actually a really good suggestion.

It would be useful if the foundry didn't need alum matchplates for their machines.

I talked it over with them and they said if I delivered to them a wood/plastic master pattern, they'd have to have their matchplates pressure cast off of it to run in their machines, so it was just cheaper to let their pattern guy machine one from bar stock.

[mactec54]

CoolHand

What company are you using for your casting, they sound like they are up with technology

[tjb1]

CoolHand, I tried to PM you but it says you are not allowed to receive PMs. I can print this for you but I can only do PLA and the sections will need glued together with super glue as I can only do a 6"x6"x5" print area. You will be very hard pressed to find someone with a printer that can print the whole form in one piece. If you can PM me your email, we can discuss further details.

[CoolHand]

Company name is Rexite in STL.

The tech is early 1980's though, not cutting edge by any means, just a lot more modern than squeezers and wooden patterns on a mold board.

That's 1930's technology.

Don't worry about my pattern anymore guys, the foundry has a pattern maker, and I found a friend from another board who was willing to print anything I needed.

I don't know what the deal is with the PM's, I've been a member here basically since the forum started, I just don't post very much. Not sure why they'd deny me the use of PM's.

[slowlearner]

Pressure cast matchplates are 1950's technology . I machine all the matchplates I sell from 6061.

[CoolHand]

That's what the foundry told me as well. Nobody casts their matchplates from a wooden master anymore, they're all machined from bar stock.

It's much cheaper, and less trouble too.

That's how we'll do this one as well.

[slowlearner]

Do you purchase a lot of tooling? If so I can give you some very competitive pricing.

[CoolHand]

This is the first time I've had commercial castings made.

Depending on how this project goes, I may do them more often.

It all depends on how this first one turns out.

[3D Accuracy]

Good evening Ryan,

I just caught this thread this evening. It looks like you may have found someone to fill your 3D Printing needs but if you're still looking please connect with me, I can help you.

Have a terrific evening!
Robert
3D Accuracy
3D ACCURACY