How to Eliminate Black Specs from Transparent Molding
You may have noticed black specs and carbon buildup in molding products. There are various causes for such buildup. If we have a look, the reasons may sum up as follows.
● The presence of a negative flow zone or still spots in the cylinder, nozzle, or die
● Presence of a hotspot in the machine
● If there is leftover additive, fillers, and color pigments from the delivery system
● If excessive heat, shear force, or barrel dwell time led to polymer degradation
● Unstable resin held in the machine for a considerable time
● Not following regular maintenance schedule
Other than these, the presence of contamination in raw materials can also be the cause of black specs. So again, it would be best if you talked with your supplier to have the best quality raw materials and increase your quality testing of raw materials.