Manifold volume

[back4more]

My question is concerning the amount of plastic a hot-runner manifold should contain versus the part weight. I am involved in the building of a 2 cav mold valve gated into a subrunner. The parts weigh about 1/2 pound each, for a total of 1+ lb shot weight.
Is there a rule of thumb about how many shots the hot-runner manifolds should contain? The resin is Ultramid A3WGM53, a 40% glass filled 66 nylon.
Any suggestions appreciated.

[Suhas]

Hi,
There is no rule for number of shots in the manifold. All you need to make sure of is that: Total residence time = (Res Time in the barrel + Res time in Manifold) is always less than the recommended residence time for that material.
Having said that, do keep in mind that the more the number of shots in the manifold, the lower is the shot to shot consistency. Plastic melt is compressible and so if you have 10 shots in the manifold, then you are compressing 9 shots to get one out. This is nothing to do with the residence time.
Hope this helps.
Suhas