| ... | ... | @@ -14,27 +14,49 @@ Making a backing mold for the mold of the sample |
|
|
|
|
|
|
|
The backing mold is nothing but the positive of your sample. You need it to cast the silicon mold that you will use to cast the urethane. Unfortunately, the urethane strongly sticks to almost everything (but the silicone we will use) so you definitely need this silicone mold. This means you need its backing mold. You cannot directly machine the urethane mold.
|
|
|
|
|
|
|
|
You have different way to make this backing mold. The simplest is to glue something that have the same shape as your final sample in the bottom of a cup but just like in the examples below, you can also 3D print it of machine it
|
|
|
|
You have different way to make this backing mold. The simplest is to glue something that have the same shape as your final sample in the bottom of a cup but just like in the examples below, you can also 3D print it of machine it. Here the material you will use does not really matter since the silicone we will cast does not sticks at all.
|
|
|
|
* 3D printed small cylinders backing mold:
|
|
|
|
|
|
|
|
* Machined diabolo-shaped particle backing mold:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Making a mold of the sample
|
|
|
|
---------------------------
|
|
|
|
[Mold Star silicone](https://www.smooth-on.com/product-line/mold-star/)
|
|
|
|
[this one](https://www.smooth-on.com/products/mold-star-15-slow/) fits for most of the cases
|
|
|
|
|
|
|
|
Once we have got the backing mold, we can cast the mold. This one is made of [Mold Star silicones](https://www.smooth-on.com/product-line/mold-star/): 'cure to soft, strong rubbers which are tear resistant and exhibit very low long term shrinkage'. They are different sort depending on what you are casting and how fast you want to go. In the following example we use
|
|
|
|
[Mold Star 15 Slow](https://www.smooth-on.com/products/mold-star-15-slow/) which fits for most of the cases.
|
|
|
|
|
|
|
|
Everything you need at this step is:
|
|
|
|
* A and B components of the Mold Star silicone.
|
|
|
|
* a cup and a fork to mix the silicone. You can use something more professional but this woks
|
|
|
|
* your baking mold
|
|
|
|
* protection gloves
|
|
|
|
* scale. You can also use anything to measure volume.
|
|
|
|
You can find all the safety recommendations for Mold Star 15 Slow and how to use it [here](https://www.smooth-on.com/tb/files/MOLD_STAR_15_16_30_TB.pdf). Remember to check it first.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
You need first to mix parts A and B in equal ratio to make the silicone. Recommendations are to mix it in equal ratio by volume but it also works in equal ratio by mass and since it is easier, that is this last way we will use here.
|
|
|
|
|
|
|
|
You pour a certain mass of part B:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
You you add the same mass of part A:
|
|
|
|
|
|
|
|
|
|
|
|
And you strongly mix it with the fork taking care of scratching the edges of the cup:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Once casted, this mold can be reused a lot of times (~100) until it gets a bit sticky. Also, remember that it can be easier to duplicate this casting step instead of duplicating the backing mold or making a bigger one.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| ... | ... | |
