molding and casting

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


  • This is a liquid based on epoxyresin
  • The pot life is about 40 minutes and the cure about 20-24 hours
  • Note:
    • The "Härter" component schould be heated to 30-40°C and stirred before mixed
  • mix both components at a ratio of 100:17 / 100:227 /100:23 /100:25 /100:30 /100:35
    /100:37 / 100:38 / 100:40 / 100:60 / 100:63 / 100:65 / 100:144 for at least 60 seconds
  • Note:
    • a flat stirring tool should be used,so the walls and the bottom of the container can be reached and left over material can be swept back into the container
  • Curing should take place for about 20-24h at 20-25°C and with not more than 70% relative air humidity
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Silastic RTV-3841 & Vernetzer RTV-3081 (VF & R)

  • This is used to create forms and casting basins, where models of silicon, ebacryl polyurethane and epoxyresin can be created
  • Note:
    • Clean the original object, and use a abhesive if the surface is porous
  • Depending on wich RTV-3081 (VF or R) the pot life and cure variy. When I use the VF-component, the pot life are about 8-10 minutes while the cure takes about 2 hours. When I use the R-component, the pot life increase to 90-120 minutes and the cure to 24 hours.
  • Mix 100 parts of the "Silastic"-component with 5 parts of the "vernetzer"-component B and stirr them quickly until component B is complelty dissolved
  • Note:
    • Do not exceed temperatures over 35°C while stirring
  • Air that is trapped insede the mass can be removed by using a vacuum machine
  • Cast the mixed liquid as fast as possible on the original object and try to not trap air bubbles in the cast
  • Curing time depends on the Vernetzer-component but should always occure at 22-24°C
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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

I first started working with our 3-axis CNC milling machine. First of all I had to repair it because it did not run in a straight line. After I disassembled it 3 times completely, I finally found out how it works and also found all the screws I needed to tighten. It took me a whole day just to find out that we only have one cutter and no one is delivered on time. Because I would like to cast the standard block of my robot system to find out if this works well. Since this would be a different production waitiante than printing all the parts.
So another solution had to be found. We now have a second milling machine, the PocketNC, which is a little more difficult to operate because it has 5 axes. But maybe I will get some promising results.



PocketNC is a 5-axis milling machine for the desk. It can be used to mill wood, wax and soft metals.

Spindle Speed 2,000-10,000RPM
Tool Diameters Up to ¼” (6.35mm)
Spindle Runout 0.0005 in (12.7 µm)

First, I disunited a casting mold in fusion. This took me some time until I knew what had to be cut away and what should remain.
Then I wanted to do my first test freshening. I found out that I ordered the wrong wax, it was much too soft and melted during the milling process.After I cleaned the milling cutter I did some research and ordered new wax. I will now make my first tests with wood and as soon as the wax is there I will make the forms.
This has also given me the opportunity to work my desein more times over until I was satisfied with the goods as it is put together.

Milling Maschine setup

Now I have to send the file to the milling machine. To do this I connect it via usb cable and first of all I install the driver. Afterwards I can reach the milling machine under the ip address

Wood form

As above, I have done my first experiments with wood. That was good as I first had to learn how to use the machine and which settings are best for which surface. Enough wood rests in the right size we had in our box.

Wax form

The wax is there.Before I milled the form I reworked it because the pins in the middle don't work very well to bring the forms together so I made one of them bigger to put the other one in. Hopefully I will get more precise results now and have no more wood spiliter in my silicone. I ordered the casting wax from hear.

Silikon Casting

Now we come to the second step of the Selikon form.
I have ordered 2 Verschiednen silicone crosslinkers. One has a drying time of 2h the other one of 24. The one that takes longer to cure is stronger and more resistant.
I ordered the Silikon and the rong wax from hear.

Cast resin

The last step is now with the silicone form my workpiece to cast. For this I use the casting ahrz of the company Toolcraft which I purchased hear.

Cast aluminium

Since half a year we have an open fablab with which you can melt aluminium. I wanted to try it out imma but unfortunately I didn't have the time. The theme of this week gives me the chance to try it out. I haven't really thought about what I want to do yet, so I'll only do some demonstration pieces to understand the process. The process is a little bit different than the process I planned for this week so I just added it.

Now of course the mould must be prepared.


3D Part:

3D Part for aluminium cast: