Mold and pour mendel parts

why not use clay to fill and smooth the printed part and spray something over the whole thing then sand it to prepare it for the mold?

That's rather a good idea! Automotive filler might be a good choice to use.

The problem with getting this show on the road is the same problem this solution looks to solve, I can't find anyone in 500 miles with a working mendel or willing to send me a few parts to test the process out with. There are a few folks with cupcakes but I haven't really had a chance to coordinate with them.

If someone sends me the parts I promise to return twice as many or redistribute them to someone else. If anyone part is going to be sent please send the single piece mendel extruder carriage. That is the most valuable from a bootstrapping standpoint and the 'keystone' in terms of a repstrap (you need an extruder carriage to build an extruder carriage).

[wooden-mendel.blogspot.com]

---

-----------------------------------------------
Wooden Mendel
Teacup Firmware

Triffid,

I think that is great but if I understand correctly it needed a bandsaw, drill press, router and presumably some jigs? I think that still has the barrier too high, it would be easier to just spend the $60 at protovantage. I would also have some concerns about temperature (though I guess it only needs to work long enough to print a plastic extruder carriage). The barrel mounting area on my extruder gets to 400F if I have been printing a long time.

I think hardwood survives those temperatures about as well as printable plastics do- maybe better.

If you're careful you could make that block with a chisel and a hand-drill.. the bandsaw was just used for the corner cut-outs- it's the inner cut-out that's tricky without a mill/router, and the vertical 1/8" hole needs to be fairly precise

---

-----------------------------------------------
Wooden Mendel
Teacup Firmware

Well most bits could be produced with a coping saw and lot of time and care. 3D objects aren't too easy though.
What if the parts were reformatted into arrangements of flat sheets? Cut out from, say, 12mm MDF, then glue the layers together to make the 3D part. Just print the 2D plans, glue them to the board and cut around. Relatively easy if someone can modify the design files.

So far I've got the frame vertex piece made. Editing and printing pepakura layouts works ok so far on the simpler ones.

I think that is great but if I understand correctly it needed a bandsaw, drill press, router and presumably some jigs? I think that still has the barrier too high, it would be easier to just spend the $60 at protovantage.

People make this thing every way possible, out of many different materials. The wooden stuff is utterly great, for the millions of people with that tooling available.

---

-Sebastien, RepRap.org library gnome.

---

Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

So, I got down to it and built the mold I proposed. Built from 1.5mm styrene sheet, all the faces are sheathed with vinyl duct tape as a release agent. The removable cores are the barrels of cheap fibre tipped pens, because they're very close to 8mm diameter and they're slightly tapered, I assume because that's the draft for injection molding. I wrapped them in aluminium kitchen foil as a barrier film rather than using a release agent on them. The collar stops the resin getting down the sides if I'm sloppy. Gonna go pour it now. Wish me luck.

I think the idea of using kitchen foil as a release foil was inspired. The inserts slid out without any resistance at all.
A good enough result to be going on with.

Edited 1 time(s). Last edit at 03/09/2010 11:07PM by murd.

Nice bit of work, murd. Try using modeling clay proactively as a leak-stopper.

Interesting that duct tape works as a release agent for ?urethane plastic resin?. I'd just have used vaseline.

Food-type plastic wrap works well for in molds as well.

Nice bit of work, though. Going to ebay them?

It's polyester car body filler. I didn't put enough hardener in the mix in two of the three mixes that I filled the mold with, it was a cool day and the end result is that only one of the pieces has fully hardened today! Maybe they'll set overnight with a bit of warmth from a light bulb, if not I'll have to do it again. At least the mold's reusable...
I'll probably use food wrap as you suggest instead of the vinyl tape. Food wrap is PE. The solvents in the putty I used passed through the tape and softened its adhesive, which separated from the mold. Doesn't happen with epoxies. Another lesson learned. When I can put all this learning into practise, maybe ebay then. I wouldn't be happy if I bought today's effort myself though.

Murd great design! You should pick up some Polyurethane Resin from an arts supply store. Extremely simple to work with and will set up in 15 minutes. I'm using it to test all my molds because it's so quick and easy to mix.

I had better success today. Woohoo, I can put some bits together! The mold design works well to align the studding holes, but polystyrene sheet was the wrong choice to use with polyester resin, which dissolves it. I designed it as a grandpa's axe mold, so that deteriorating parts can be replaced, so I'll replace them with polyethylene sheet (milk bottles!), which doesn't react with the solvents and is even more commonplace than styrene sheet. Polyester body filler is available everywhere here, car parts stores, discount chains. Polyurethane is available, but not so conveniently or cheaply. I've just got to take more care over the catalyst proportion and mix and fill faster, the stuff is plenty tough enough done properly.

Regarding Polyurethane Resin, I just discovered that (oven-dried) sand is apparently a good filler.

Via:
[www.smooth-on.com]

Also, here's a bit of a verbiage-dump by a guy who sells filler.
[stores.shop.ebay.co.uk]

This is also promising, but I haven't tried it:
[objects.reprap.org]

... i used hollow glass-spheres (around 50 microns and smaller in diameter) with waterglass/sodium silicate as air-hardening/heatcuring paste - it's very good dimension-stable, behaves like styrofoam when hardened but is heatresistant until 600 centigrades and can be crushed away if needed ...

---

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

murd Wrote:
-------------------------------------------------------
> Polyurethane is available, but not so
> conveniently or cheaply. I've just got to take
> more care over the catalyst proportion and mix and
> fill faster, the stuff is plenty tough enough done
> properly.

For 20 bucks you can get enough Polyurethane resin to pour an entire set of Mendel parts with a 30% failure rate if you needed it. That's pretty cheap.

>I think the idea of using kitchen foil as a release foil was inspired. The
>inserts slid out without any resistance at all.
>A good enough result to be going on with.

Hey, this seems very nice idea.. I'll try it with my shapeways mold as well. Maybe I should also try polyester resin.