A short shot is when a mold cavity is not completely filled and results in an incomplete part. Short shots are one of the most frustrating defects that injection molders face. Fortunately, there a
1.) Check Your Heats
Your heats on your tool or screw and barrel can be a major cause of short shots. This is likely due to a thermocouple breaking off or not reading the proper temperature. Double check your heats before making any processing changes.
2.) Check Your Tool & Vents
Verify there is no build-up in your vents. Build-up creates pressure in the tool. You can also look for burns or marks on the tool if the vent is not easily visible.
You should look and see how the material is filling the tool. If a balance tool is creating unequal short shots, make sure drops and tips are not contaminated from a previous run. A purge compound can be a great solution before pulling the tool.
3.) Check Your Machine
Don't forget to take a step back and take a look at what's going on with your injection molding machine as a whole. Is there enough material in your hopper? Are there any restrictions in your feed throat? This could be elevated feed throat temperatures or a slide gate getting closed. Another potential cause is if the machine is undersized for the part. Often I see the frame and tool fit but the material can’t be injected at the speed it requires. Trying to force a situation like this work often leads to other processing issues.
If you are struggling with short shots or any other processing issues, request a free consultation and we will try to help you solve your problems--purging related, or otherwise. Our Technical Sales Representatives are experienced processors who love to work through challenging process issues.
Ready to reduce your production downtime to protect your profits? Learn more about how purging compounds and process efficiency work in tandem.