3D print as a pattern for casting

Through some extensive pleading I have managed to get a friend to print off a 3D printed nameplate to use as a pattern for some sand casting in brass or bronze. I've done some casting in the past but never using a 3D print as a pattern.

As it was difficult to get done (I felt really bad for asking, he is a busy chap) I don't really want to have to beg for another if this one gets damaged so I'm treating the original with kid gloves. That said the surface is quite rough. So will this cast ok? Would I be best off using a light coating of paint on top to help it to release from the sand? I'm using proper casting sand. The object is relatively small, 7cm x 1.5cm.

I don't mind the surface being rough on the finished article because I deliberately asked for it to be slightly oversize so it could be sanded back. I'm nervous about sanding the original for the reasons stated earlier. Excuse the fag packet sketch, it was done standing up!

Edited By Jon Lawes on 01/10/2018 12:23:19

Cyanoacrylate glue seems to be pretty popular for smoothing PLA prints, with or without talcum powder as additional filler.

The CA can also be sanded afterwards to give an even flatter finish.

Thats a good tip, thanks, I'll try it on the reverse face to see how it works.

That pattern will barely show with a sand casting.

High build primer is good on prints made with a small layer height. It might also help with rounding out some of the tight corners.

Your problem with be sand sticking in the sharp internal corners and in the thin gaps between the letters and the border.

If it does need to get done again (it shouldn't be a lot of work, to be honest) ask for the letters and border to be extruded with a draft angle on them, and ideally with a fillet.

Neil

Hi Jon,

I thought i'd better put my money where my mouth is and had a go in Alibre Atom. This is with draft and fillets and took about 10 minutes. Most of that was me trying to fillet each bit of letter before realising I just had to click on the background surface...

If your friend's CAD won't easily do fillets etc. send me a PM with your email and I can send you the STL file.

Neil

Neil, if you do end up sending the STL file then fillet the inside of the D and O first

D O h!

Well spotted, I hadn't twigged that they count as different surfaces!

Neil

I've done one with a bigger font, too.

I do wonder if it should be a 'medium' sized font

Neil

I found standard Gill Sans at 10mm high looked about right. Oh and I buffed mine up a bit

Edited By JasonB on 02/10/2018 06:51:26

Blimey, I look away for two minutes and there has been so much effort on my behalf! Thank you all!

I'd be delighted to receive your design Neil, thankyou.

For the curious, D. Stokes was my grandfather.