11. Molding and casting¶
This week we worked on reviewing the safety data sheets for each of our molding and casting materials, then making and comparing test casts with each of them.
Safety first¶
| Material name | Manufacturer | MSDS |
|---|---|---|
| Mold Max 60 | Smooth-On | 823A-231B |
| PMC-121/30 | Smooth-On | 642A_1-642B_1 |
| Oomoo 25 | Smooth-On | Oomoo |
| Smooth Cast 300 | Polyurethane rubber compound | Smooth-On |
Materials available at the lab¶
| Material name | Material type | Manufacturer | Technical bulletin | Mix Ratio | Mixed viscosity | Pot Life | Cure time | Color | Useful temp. range | Dielectric strength | Thermal conductivity |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Mold Max 60 | High heat resistant silicone rubber compound | Smooth-On | 823A-231B | 100A:3B by weight | 20,000 cps | 40 min | 24 hrs | Red | -53°C to 294°C | >500 V/mm | 0.347 W/M.K |
| PMC-121/30 | Polyurethane rubber compound | Smooth-On | PMC-121 series | 1A:1B by weight or volume | 1,800 cps | 30 min | 16 hrs | Clear amber | |||
| Oomoo 25 | Silicone rubber | Smooth-On | Oomoo | 1A:1B by volume, 100A:130B by weight | 4,250 cps | 15 min | 75 min | Light Blue | -53°C to 205°C | 357 V/mm | 0.37 W/M.K |
| Smooth Cast 300 | Polyurethane rubber compound | Smooth-On | Smooth-Cast 300 | 1A:1B by volume, 100A:90B by weight | 80 cps | 3 min | 10 min | White |
Of the molding and casting materials available at the lab, the only one that hadn’t dried up, its cover had not stuck, and its both parts A and B were available was Mold Max 60, which had the highest curing time (24 hours).
How to cast with Mold Max 60¶
Pre-mixing should be performed. This means that the bottle for part B must be shaken well, and part A should be stirred well with a tongue depressor before mixing. Then it should be measured out in a 100A:3B ratio by weight and mixed using the tongue depressor in a horizontal manner, without scooping, while once a while scraping the walls for 2 minutes.
Then the mixture should be placed in a vacuum until the vacuum reaches about 53 torr(-28 inHg). The mixture will ‘bubble out’ in the vacuum and lose some volume.
Then the mixture should be poured in a narrow bead from one corner of the mold. It dries and can be de-molded in 24 hours.