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week 14. Molding and casting

This Week, I created several molds and casted a coin, a Finger Tip replacement and some dice.

In our group assignmentWe showed, how to work with silicone, reviewed the Datasheets of different Silicone and Resins and compared different Molding-techniques(DLP and FDM). I was responsible for the Coin-Mold and the process of 3D-Printing.

Mold Design

I created a Mold of a Coin we designed in the Group. On one side the FabLab Logo and on the othe side our initials and the Year 2025. Size wise we orientend us on a european 50cent piece, because we can use it as Chip for Shopping Carts here in germany

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Then i created the mold around it. I first split the coin in the half to have both faces. This was followed by adding walls, a registration edge and a "sealing" lip. The sprue/reservoir and vent where added at the End.

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FDM Printing

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PrintSettings in PrusaSlicer

DLP Printing

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Slicing in ChituBox

As Slicer i used ChituBox because this is one of the two Slicers recommended from Eleegoo and i alsready used it for my own Resin Printer the Halot One, which unfortionatly doesnt survived my moving . The First recommended was there own: Satelite.

These Settings for the Resin found to be working with the Eleegoo Saturn 4 Ultra with 28mm Tabletop minis(i tested them before ), so i used them for that as Test

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with the Srttings for the resin, i Imported the model of the mold and orientarted, how i belived it would print good and doesnt need support in the actual coin area.

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Then i switched to the Support Tab(red circled), selected middle support settings and clicked auto spupport.

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last step was to go back to the overview tab(left of the before red circled tab) and click on slice

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The then saved .cxdlp can be used on the Saturn 4 ultra to print the Mold.

Post process

You already saw in the beginning of this Charpter, that the part warped a bit. This was due to underexposure, anyway, we used this mold to get done. and the result was not bad

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After the Print was finished, i removed the supports and washed the mold in our Formlabs Washing machine for 20 minutes.

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After Washing I cured the part by 60°C for 15 minutes

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Casting the negative mold

In our group assignment we already showed, how to make molds(and also how to cast this particular one)

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Here is also an image of both Molds from the FDM(top) and DLP(bottom) Printer:

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small comparison of both

1. Surface Finish

FDM (Top):

DLP (Bottom):

2. Detail Reproduction

FDM (Top):

DLP (Bottom):

Casting the Coin

Making it "Bunt"

I wanted to make the cast more appealing, so i "painted" the indentations with mica powder in the respecting colors.

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The Logo was getting the three colors blue, green and red. The Writing and the brim where colored in Gold

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The Casting

I used some epoxy, Ive got for dice casting. It was the Exposi-Hartz Diamond. Also differently to the methode for filling the mold like in our Group Assignment. i just overfilled both halfes of the Mold and squished them together and wrapped tape to "clamp" it tight.

Results

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So even even we I used the Mold printed on the FDM-Printer, which looks way sharper, The coin came out realy smooth. Yes you see some artifacts in the Logo area, but for the size, i think its pretty good.

Design files

CoinMold Fusion Archive
Coin Mold STL

Used resin and Silicone

As resin i used Exposi-Hartz-Diamond Eppoxyresin and as Silicone i used the ProtoSil RTV 245 from Altropol

As stated on the Website of Exposi-Hartz the Resin is a rebranded. The original manufacturer is DipOn and the resin in particular is the EpoxyPlast 100 P Diamond

Safety Datasheet Silicone

Safety Datasheets DipOn EpoxyPlast Diamond Clear

ProtoSil RTV 245

The Datasheets are unfortionatly only in German

more Molds and Casting

The FingerTip

"The FingerTip" is a Test, thats wy i printed it realy rough(what gave me a hard time demolding). The Story of it is, that a StaffMember lost part of his left middlefinger and he wants to play guitar again. I designed something crude to help him and play a bit with prosthetics.

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First i needed to tap the mold at the bottom, because this was hole needed to be plugged, to help demold later with pressured air. I tapped it with an M4 thread.

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Here is the screw from the Bottom.

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After Filling the mold, i pressed the top piece into the mold for the finger cavety, and clamped the mold with 2 M3 Screws.

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While demolding, i destroyed the upper piece. It was a sacreficial mold eitherway.

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To help demolding, I removed the Screw at the Bottom and injected pressured air into the mold, which catapulted the cast out. but it was silicone and just hitted a box, i placed, to catch the FingerTip.

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Demolded you see the roughness. But its a first fitting Test, if the Prosthetic fits him.

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DiceMoldMaker

I made two Versions. the First one was a Slabmold for 7 Dices (normaly: D4, D6, D8, D10, D%, D12 and D20) which is ment for a DND Dice set. The 2nd version is for a single Dice.

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Prepwork

Some years ago i printed the Facets Dice by sablebadger with my DLP Printer and now i wanted to make Mold out of them.

The First step was to drill a 2mm Hole into the ugliest side of the dices. Followed by glueing a piece of Filament(1.75mm) into this hole long enough to have excess later.

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I just inserted the dices into the hole in the bottom piece of the mold(SlabMoldA).

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Last Prep step was to close the mold with two printed SlabMoldB parts and. putting a bead of hotglue over the exposed parts of the Filament sticking out the Bottom

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Main Mold

I poured Silicone into the mold and let it cure

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Here i removed the mold but keeping the Dices with the "Sprue" untouched. Thats why just i used a tiny bit of Hotglue at the tip of the Filament pieces. I also needed to remove some Flashing and coating the whole top side of the Mold with Vaseline, to prevent the next layer of Silicone of sticking to this layer.

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Lid

The Lid part was easy. Just a bit of Silicone on top, while having the outer shell again in place with some margin to the bottom

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Here you see the Lid seperated after curing

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Result

For casting i just overfilled the mold and Squished the cap onto it. the hole in the top acts as vent to prevent the introduction of more bubbles. But it doesnt helped, I degased the Resin too short.

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After Demolding:

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