| ... | @@ -42,7 +42,7 @@ You can find all the safety and processing recommendations for Mold Star 15 Slow |
... | @@ -42,7 +42,7 @@ You can find all the safety and processing recommendations for Mold Star 15 Slow |
|
|
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 quite well in equal ratio by mass and since it is easier, that is this last way we will use here.
|
|
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 quite well 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 pour a certain mass of part B:
|
|
|
|
|
|
|
|
|
|
|
|
|
You add the same mass of part A:
|
|
You add the same mass of part A:
|
|
|
|
|
|
| ... | @@ -89,7 +89,7 @@ If you want to slightly color the sample for imaging purpose, you should use [So |
... | @@ -89,7 +89,7 @@ If you want to slightly color the sample for imaging purpose, you should use [So |
|
|
Casting method
|
|
Casting method
|
|
|
--------------
|
|
--------------
|
|
|
|
|
|
|
|
Once you have chosen the good stiffness, the next step consists in making urethane rubber and pouring it in the silicone mold. This once is the tricky part...
|
|
Once you have chosen the good stiffness, the next step consists in making urethane rubber and pouring it in the silicone mold. This one is the tricky part...
|
|
|
|
|
|
|
|
Everything you need for this step is:
|
|
Everything you need for this step is:
|
|
|
* A and B parts of the Clair Flex.
|
|
* A and B parts of the Clair Flex.
|
| ... | @@ -111,7 +111,7 @@ You need first to mix parts A and B in equal ratio to make the urethane. Recomme |
... | @@ -111,7 +111,7 @@ You need first to mix parts A and B in equal ratio to make the urethane. Recomme |
|
|
You pour a certain mass $`M`$ of part B:
|
|
You pour a certain mass $`M`$ of part B:
|
|
|
|
|
|
|
|
|
|
|
|
|
If you want to color the urethane that is now! First remember that the dye is called 'So Strong'... So if you want to keep the transparency of your sample just add very few.
|
|
If you want to color the urethane do it now! First remember that the dye is called 'So Strong'... So if you want to keep the transparency of your sample just add very few.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| ... | @@ -127,7 +127,7 @@ Depending on how strong you want the color to be, you can add more. |
... | @@ -127,7 +127,7 @@ Depending on how strong you want the color to be, you can add more. |
|
|
Then you add $`M/2`$ of part A:
|
|
Then you add $`M/2`$ of part A:
|
|
|
|
|
|
|
|
|
|
|
|
|
Note that you can use any elongated tool to conveniently guide the liquid flow out of the bottle. Also note that it is very important to carefully clean the A part bottle before closing if you do not want the crosslinker to permanently seal the bottle. You will see what I am talking about the next time you will make a sample...
|
|
Note that you can use any elongated tool to conveniently guide the liquid flow out of the bottle. Also note that it is very important to carefully clean the A part bottle before closing, if you do not want the crosslinker to permanently seal the bottle. You will see what I am talking about the next time you will make a sample...
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| ... | @@ -152,7 +152,7 @@ When degassing you will see more and more bubbles, then less and less: |
... | @@ -152,7 +152,7 @@ When degassing you will see more and more bubbles, then less and less: |
|
|
After 2-3 minutes when just few small bubbles are remaining you can pull the cup out of the vacuum chamber. You should get something like this:
|
|
After 2-3 minutes when just few small bubbles are remaining you can pull the cup out of the vacuum chamber. You should get something like this:
|
|
|
|
|
|
|
|
|
|
|
|
|
It is now time to pour the urethane in the mold. This is the most sensitive part. You need first not to add bubbles by pouring or by sucking up into the syringe. And you also need to pour the exact quantity to fill the mold... plus a little bit more! Indeed you want your geometry to be the exact one but the Clear Flex will retract when curing. So imagine that the top of your sample corresponds with the top of the mold, if you add exactly the right volume of liquid, you will get a flat surface before curing and something convex after. Which is definitely not what you want for an accurate photoelasticity. Instead if you add a little bit more than the mold volume, you will get something flat after curing. Because the liquid is viscous you can forget using anything to carefully add the right volume (especially for small quantities), it will not be accurate and, most likely, you will add bubbles in the liquid. Last problem... you need to be fast because the liquid will be more en more viscous very rapidly (we come back on this point a bit farther).
|
|
It is now time to pour the urethane in the mold. This is the most sensitive part. You need first not to add bubbles by pouring or by sucking up into the syringe. And you also need to pour the exact quantity to fill the mold... plus a little bit more! Indeed you want your geometry to be the exact one but the Clear Flex will retract when curing. So imagine that the top of your sample corresponds with the top of the mold, if you add exactly the right volume of liquid, you will get a flat surface before curing and something convex after. Which is definitely not what you want for an accurate photoelasticity. Instead if you add a little bit more than the mold volume, you will get something flat after curing. Because the liquid is viscous you can forget using anything to carefully add the right volume (especially for small quantities), it will not be accurate and, most likely, you will add bubbles in the liquid. Last problem... you need to be fast because the liquid will be more en more viscous very rapidly (we come back on this point a bit further).
|
|
|
|
|
|
|
|
So to fill the mold taking all these points into account, here is a suggestion. First, use a syringe. This is the most convenient way to manipulate urethane without adding bubbles (still you need to be careful). Choose a syringe with a convenient volume: if small you will be accurate when pouring but if the sample is large it will take time to fill it (and you need to be fast); if big it will go faster but it will be less convenient (or even impossible) to add the right quantity. You can also use different syringes: a large one to fill in the mold rapidly and a smaller one to add the exact quantity. Also try different syringe mechanisms because some can have stick-slip behaviors when you push on them which make the accurate filling impossible to get.
|
|
So to fill the mold taking all these points into account, here is a suggestion. First, use a syringe. This is the most convenient way to manipulate urethane without adding bubbles (still you need to be careful). Choose a syringe with a convenient volume: if small you will be accurate when pouring but if the sample is large it will take time to fill it (and you need to be fast); if big it will go faster but it will be less convenient (or even impossible) to add the right quantity. You can also use different syringes: a large one to fill in the mold rapidly and a smaller one to add the exact quantity. Also try different syringe mechanisms because some can have stick-slip behaviors when you push on them which make the accurate filling impossible to get.
|
|
|
|
|
|
| ... | @@ -194,7 +194,7 @@ You get a very sticky material. To finish the curing, put it in an oven at 100C |
... | @@ -194,7 +194,7 @@ You get a very sticky material. To finish the curing, put it in an oven at 100C |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
The sample will be let sticky. If you want something even less sticky, you can slightly add a little bit of talk on top of it. You will somehow loose the transparency but it will not be sticky any more.
|
|
The sample will be less sticky. If you want something even less sticky, you can slightly add a little bit of talk on top of it. You will somehow loose the transparency but it will not be sticky any more.
|
|
|
|
|
|
|
|
Finally here is an example of what you can get if you pour too much urethane:
|
|
Finally here is an example of what you can get if you pour too much urethane:
|
|
|
|
|
|
| ... | | ... | |
