Silicone Mold Calculator
Estimate silicone volume and weight from mold box size, master displacement, wall thickness, density, mix ratio, degassing expansion, and pour waste.
Silicone mold estimate
The calculator treats the mold box as its inside dimensions and subtracts the master displacement before adding degas and waste allowances.
| Mold type | Side wall target | Base/top target | Allowance range |
|---|---|---|---|
| Open-face tray or soap bar | 0.4-0.6 in / 10-15 mm | 0.25-0.5 in / 6-13 mm | 6-10% |
| Block mold for small objects | 0.5-0.75 in / 13-19 mm | 0.4-0.75 in / 10-19 mm | 8-12% |
| Two-part mold with keys | 0.75-1.25 in / 19-32 mm | 0.5-1 in / 13-25 mm | 10-15% |
| Brush-up glove mold | 0.2-0.35 in / 5-9 mm | Mother mold supports shape | 12-18% |
| Mix ratio by weight | Part A share | Part B share | Best check |
|---|---|---|---|
| 1:1 | 50.0% | 50.0% | Equal weights |
| 10:1 | 90.9% | 9.1% | Use gram scale |
| 100:10 | 90.9% | 9.1% | Same as 10:1 |
| 100:5 | 95.2% | 4.8% | Measure carefully |
When you are pouring the silicone into the mold, you might find yourself without more silicone than you poured into the mold before the silicone has completely covered the objects that you are molding. If you do find yourself without more silicone, then there is a chance that the mold will not completely cover the master object and the mold could have thin spots in areas that did not have time to recieve the silicone. In order to avoid running out of silicone, you must calculate the amount of silicone that you need prior to pour it into the mold.
The best way to calculate the amount of silicone that is required to pour into the mold is to use a calculator, which can subtract the volume of the master object from the volume of the mold box. The resulting number represent the amount of volume that the silicone will occupy. In order to calculate the amount of silicone that you will need, you must first understand the concept of displacement.
How to Calculate the Amount of Silicone You Need
Displacement represent the amount of volume that the master object takes up within the mold box that the silicone will fill. In most cases, the master objects is not in the form of rectangular objects. Instead, they may have curves, dips, and undercuts.
In order to account for these variables, mold boxes include a fill factor that you apply to the calculation of the displacement. Additionally, it is also necessary to consider the thickness of the walls of the mold. If the walls of the mold are too thin, they may warp or tear when you remove the molded object from the mold.
If, however, the walls are too thick, you will waste silicone and the silicone will take longer to cure. The walls should of a thickness that will permit the mold to successfully release the object while minimizing waste of the silicone. After calculating the volume of the mold, it is necessary to account for potential material loss.
The tendency of silicone to stick to the mixing bucket, the stir stick, and the pouring cup causes material loss. An allowance for this loss of material should be included in the calculation. For instance, if you use a large mixing bucket, you will lose more silicone than if you used a smaller mixing bucket.
Likewise, if you use small measuring cups to measure the silicone, you will lose a larger percentage of the silicone that you add to the mixing bucket. Additionally, if you use a vacuum chamber to degas the silicone, it is necessary to account for vacuum rise. Vacuum rise is the rise in height of the silicone caused by the removal of air from the silicone when it is degassed in the vacuum chamber.
An allowance for vacuum rise should be added to the amount of silicone that you calculate in order to avoid boiling the silicone over the rim of the mixing container. The last calculation that you must perform is to calculate the proper mix ratio for the silicone. Most silicones have two separate parts (A and B). Each part contain a different ratio of the components of the silicone.
It is important that you dont measure the amount of silicone by volume. Different densities of parts A and B of the silicone could lead to a failure in the curing of the silicone. Instead, you should weigh the silicone out on a gram scale to ensure that each part is mixed in the proper ratio.
Furthermore, the calculator can account for the different mix ratios for parts A and B of the silicone. By calculating the volume of the mold, the waste allowance, the degas allowance, and the mix ratio of parts A and B of the silicone, you can be certain that you have the proper amount of silicone to completely fill the mold box.
