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8. System performance
The following variables may influence the accuracy and repeatability of the system:
1. Material properties. Easy flowing, non-sticky and non-static material that comes in the form of
small regular shaped granules or powder can be dosed very accurate and regular.
2. Periodical cleaning of the dosing cylinder and seals is necessary for proper operation.
3. Extreme vibrations and shocks can have negative influence on system performance.
4. An unstable relay signal has a negative influence on the repeatability.
5. With injection molding the shot to shot accuracy depends, besides the variables mentioned so
far, on the shot time in combination with granule size and weight. If relatively big and heavy
granules have to be dosed in a very short time, it will influence the shot accuracy and
repeatability, because if only a few granules are dosed during the shot, one granule more or
less makes a big difference on the total shot weight.
6. Vacuum or overpressure in the neckpiece caused by driers or hopper loaders.
7. Bridging or rat holing of the material inside the hopper can happen if the material is not free
flowing.
8. Bridging or rat holing of the material inside the hopper can happen if the material is extremely
static.
9. Extremely static material can contaminate the dosing cylinder.
10. In case of water cooled neckpiece, check if there is material build up around the dosing
cylinder and the water cooled pipe. Check also the water supply to the neckpiece.
