week 8 moulding and casting

For this assignment, we (Ashris Choudhury and myself) chose to cast an Arebic pattern. Base pattern (2D drawing) was downloaded from internet. 2D drawing was simply extruded 10mm. This model was then taken to AutoDesk 123D Catch to make horizontal sections for laser cutting. 1.5mm MDF was cut in the same pattern and stuck. Entire mould was then soaked in machine oil for 2 hours. To hold material edge frame of 20mm depth with press fit construction were made. This was also dipped in oil for 20mins before casting. Once the mould was completely ready, we mixed primex (POP based material) and water in ratio 1:4. The semi-solid made was then poured in the mould. While pouring, it was constantly vibrated. We left it to settle over night. Next day we tried to remove and we could only remove the edge frame. Entire mould is tightly embeded in the cast!

Screen shot of model (Sketch up)

Layers being laser cut

Laser cut pieces

First complete frame

Two moulds ready

Mould soaked in oil

Mould on base with edge frame

Pouring primex

Vibrating final pour

Removing seal (which was made using Fevicol)

Removing entire cast from base

Removing edge frame

Cast with embaded mould
First trial failed. So we made another mould exactly half the size and tried to experiment with Liquid Rubber compound. UPDATES yet to come. At this point we feared that we didn't have enough rubber compound so we decided to use exactly half of the pattern. We again laser cut various layers, stuck them and tried pouring rubber compound.

Measuring compund in equal proportion

Rushing with process never helps. Here we didn't soak MDF mould in oil for required time and tried to use a short cut. We just poured oil in the mould and within few minutes we poured rubber compund in the oily mould.

Started baking at 175 degrees. We baked it for 5 long hours and still it never solidified. Possible reason for failure is oil in the mould. This did not let rubber compound settle.

Unsuccessful mould. After this we decided to mill the same pattern in wax and cast negative mould. Used .png to .rml using 1/8 in. drill bit 10mm deep mould was cast

Having done first 10mm negative mould, we milled another 10mm positive pattern without realizing that we had to pour rubber compound in negative pattern milled.

Screen shot of positive pattern to be milled.

Mixing and pouring rubber compound.

Final pour. This was then baked for 1 hour 30 mins at 175 degrees. This was fist successful cast for mould.

Removing settled cast from the wax mould.

First successful mould in terms of making. Then we realized that we made a mistake. Mould finally made is ready to cast negative of desired pattern. that means pieces. And we start all over again.

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