Casting process with variable index

A casting method, comprising:

• providing a mold;
• providing a mixer,
• providing a first material for dispensing into the mixer;
• providing a second material for dispensing into the mixer;
• dispensing a first pour from the mixer into the mold;
• dispensing a second pour from the mixer into the mold, wherein the first pour has different proportions of the first and second materials than the second pour, wherein the first pour forms a first layer of a molded part and wherein the second pour forms a second layer of the molded part;
• providing a third material for dispensing into the mixer;
• providing a fourth material for dispensing into the mixer;
• wherein the mass of the second material, the third material, and the fourth material are the same as in the first pour as the second pour but the proportions are different as the first material is absent from the second pour;
• wherein:
• the first material is curative;
• the second material is prepoly;
• the third material is a catalyst diluted in curative;
• the fourth material is colorant;
• the first pour is dispensed before the second pour;
• and
• only two layers are formed in the molded part such that the first layer has a higher proportion of prepoly, catalyst diluted in curative and colorant than the second layer, wherein the first layer has a smaller proportion of the curative than the second layer and exhibits higher adhesion properties than the second layer, wherein the second layer has a higher proportion of the curative than the first layer and exhibits higher crack propagation resistance than the first layer.

A casting method, comprising:

• providing a mold;
• providing a mixer,
• providing a first material for dispensing into the mixer;
• providing a second material for dispensing into the mixer;
• dispensing a first pour from the mixer into the mold;
• dispensing a second pour from the mixer into the mold, wherein the first pour has different proportions of the first and second materials than the second pour, wherein the first pour forms a first layer of a molded part and wherein the second pour forms a second layer of the molded part;
• providing a third material for dispensing into the mixer;
• providing a fourth material for dispensing into the mixer;
• wherein the mass of the second material, the third material, and the fourth material are the same as in the first pour as the second pour but the proportions are different as the first material is absent from the second pour;
• dispensing a third pour from the mixer into the mold, wherein the third pour forms a third layer of the molded part;
• dispensing a fourth pour from the mixer into the mold, wherein the fourth pour forms a fourth layer of the molded part;
• wherein:
• the first pour is dispensed before the second pour;
• the second pour is dispensed before the third pour;
• the third pour is dispensed before the fourth pour;
• the fourth pour is dispensed after the first pour, the second pour, and the third pour;
• the first material is curative;
• the second material is prepoly;
• the third material is a catalyst diluted in curative;
• the fourth material is colorant;
• only four layers are formed in the molded part such that the first layer and third layers have a higher proportion of prepoly, catalyst diluted in curative and colorant than the second layer and the fourth layer, wherein the first layer and the third layer have a smaller proportion of the curative than the second layer and the fourth layer and exhibit higher adhesion properties than the second layer and the fourth layer, wherein the second layer and the fourth layer have a higher proportion of the curative than the first layer and the third layer and exhibit higher crack propagation resistance than the first layer and the third layer.

A casting method, comprising:

• providing a mold;
• providing a mixer,
• providing a first material for dispensing into the mixer;
• providing a second material for dispensing into the mixer;
• dispensing a first pour from the mixer into the mold;
• dispensing a second pour from the mixer into the mold, wherein the first pour has different proportions of the first and second materials than the second pour, wherein the first pour forms a first layer of a molded part and wherein the second pour forms a second layer of the molded part;
• wherein a pump creates pressure in the first material and the second material to urge the first and second materials to the mixer such that pressure of the pump is maintained even when an amount of the first material dispensed to the mixer is decreased by way of closing a valve to shut off the flow of the first material to the mixer.