Assignment requirements:

Group Assignment

• Review the safety data sheets for each of your molding and casting materials, then make and compare test casts with each of them.

Individual Assignment

• Design a mold around the stock and tooling that you'll be using.
• Mill it (rough cut + (at least) three-axis finish cut).
• And use it to cast parts.

Learning outcomes:

• Design appropriate objects within the limitations of 3 axis machining.
• Demonstrate workflows used in mold design, construction and casting.

Assessment criteria

• Linked to the group assignment page and reflected on your individual page what you have learned.
• Reviewed the safety data sheets for each of your molding and casting materials, then made and compared test casts with each of them.
• Documented how you designed your 3D mold and created your rough and finish toolpaths for machining, including machine settings.
• Shown how you made your mold and cast the parts.
• Described problems and how you fixed them.
• Included your design files and 'hero shot' of the mold and the final object.

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Individual Assignment

Design

I wanted to design some cute animal model with blender to know more about blender so I followed this tutorial but I was able to get an STL file for a panda from it but couldn't make the mold on it because I'm still a beginner, also, I couldn't use the STL in another software and edit on it to make the mold.

So I went to the software I'm familiar with 'Solidworks' and started to design another Panda, and added extension to both legs so one of them acts like a Sprue and the other acts like Riser, I used this picture to get the ratio of the panda drawing.

Then I cut the model into 2 parts to make a mold of each part (I used 2 halfs because it was not symmetric).

I made 2 blocks to put each half inside them to get a 2 parts mold, I set the dimensions of the blocks so the output silicone mold parts one can fit inside another one (instead of taps).

Then to get sure that everything is working will I drew a solid block and assembled it inside each mold part, and used a feature in solidworks called Cavity to subtract the positive molds from the block to get the expected shape of the output silicone mold.

After getting the 2 silicone mold parts ready I assembled them the way they should be assembled in real, then used the same cavity technique to check how would the output resin look like.

Actually this was one of the good things I did, because the first time I did it I forgot the panda isn't symmetric and made one half in both mold parts so I got a deformed output which lead me to get 2 seperate halfs of the panda model.

Ok, all set and ready to mill so I exported both parts of the positive mold as STL file to use them.

Milling

To start milling I have to choose the endmill, I made my design minimum clearance to 3.2mm so I can use the 3.175mm (1/8 inch) endmill in everything.

We used chemical Wood.

The most important parameter in milling is the feed rate, to get the feed rate I went to the Chip Load calculator again so I found that 1 m/min is good for hardwood (ourwood wasn't hard but I calculated at hardwood for safety) which means around 16 mm/sec But the modela player didn't accept more than 15 so I used 15.

Set the orientation of the model.

Set where the origin is located (I use the bottom left corner) same as the machine.

And generate the toolpath.

Then Set the home coordinates of your model on the machine (Z axis manually).

I fixed the wood same as the PCB (paint tape and double face).

Then Press Cut.

Repeat the same steps for finishing process, but this time I used the 3/32 endmill (I was able to use the 1/8 in finishing too but I wanted to explore more).

I changed the path interval from default value of 0.1mm which gives best results to 0.2mm to speed it up.

Nice, now repeat the whole process for the 2nd part of the mold, but this time I used the 1/8 endmill for both roughing and finishing.

ok I see that you have noticed that the machine the whole outline of the 2nd part of the mold which will give the silicone mold walls to fit with the other mold part, I don't know why this happened because I made this distance to 3.2mm to be bigger than the tool.

So I have to use the minicraft to fix this probelm and make the mold look ugly.

Silicone Mold

Now we are ready for silicone.

To know what is the mass of the silicone we need we should put some material we know its density and use the formula which says density = mass/volume, or use your sense.

I made 45 gm of silicone and 4.5 gm of the hardner to satisfy the 1:10 ratio.

Then use silicone spray to help easily remove after curing then pour the silicone resin.

Then I used a vibration sander without a sanding paper to release bubbles.

Ready for resin.

Resin part "Polyester"

Now I will pour polyester inside the silicone mold, I used 1:10 ratio for the polyester resin and its hardner too

I fixed mold parts together with a rope which was not a very good idea because I squished the mold harder than I should, and got a thin banda at the first trial.

After getting the stressed Panda I tried to make a setup with wood which will gently press the mold.

I got a few leakage in this trial but generally it was a better idea

Hints I got from this trials that as I don't have a vacum champer I can't completly release bubbles which leads that over time bubbles go up and my panda leg disappears.

Resin part "Epoxy"

This time I used Epoxy with mixing ratio 1:3.

Also I used a rubber band this time as I though it would work and also faster, and when I poured the Epoxy it didn't leake.

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Downloads

Blender Panda project All Solidworks Panda and mold parts Panda picture I used

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