Uncategorized – UPMOLD

Uncategorized – UPMOLD https://upmold.com Injection molding & mold making custom manufacture | Upmold Sun, 24 Feb 2019 00:34:46 +0000 en-US hourly 1 https://wordpress.org/?v=6.9.1 https://upmold.com/wp-content/uploads/cropped-UP-logo-1-32x32.png Uncategorized – UPMOLD https://upmold.com 32 32 Temp https://upmold.com/temp/ Fri, 26 Oct 2018 02:40:31 +0000 http://upmold.com/?p=9372 Burn Spots on Molded Part Possible Cause Possible Solution Mold is insufficiently vented Make sure vents are clear of obstruction Insure vents are deep Add vents if necessary to assure good operation Injection rate is too high Reduce injection speed Screw RPM is too high Decrease screw RPM Back pressure is too [...]

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Burn Spots on Molded Part

Possible Cause	Possible Solution
Mold is insufficiently vented	Make sure vents are clear of obstruction Insure vents are deep Add vents if necessary to assure good operation
Injection rate is too high	Reduce injection speed
Screw RPM is too high	Decrease screw RPM
Back pressure is too high	Reduce back pressure. Minimum is 0.35MPa (50psi)
Clamp pressure is too high	Reduce clamp pressure

Burn Marks at Gate

Possible Cause	Possible Solution
Melt flow across gate restriction; area causes excess shear heat	Reduce injection speed Decrease nozzle temp Decrease front barrel zone temp Decrease mold temp. in gate area Check for resin contamination

Discolored Streaks or Chunks

Possible Cause	Possible Solution
Additives or colorant have incompatible carriers	Change to an additive or colorant material Never use additive or colorant materials that contain polyvinyl chloride carriers.
Prior runs have contaminated the plastication system	Physically clean the entire system-hopper, barrel, shut-off valve, screw nozzle and mold Purge the system with polyethylene or polypropylene
Melt has insufficient color concentrate blending.	Increase back pressure Increase barrel temp and reduce rear zone temperature Change screw speed Decrease nozzle orifice diameter Replace screw / nozzle with one that has

Distorted Parts

Possible Cause	Possible Solution
Material is oriented during injection process	Decrease injection velocity for slower filling Increase mold temperature Adjust velocity profile to provide homogeneous melt.
There is a difference in packing density	Increase hold pressure Increase injection fill speed to fill mold faster Increase screw RPM.
Material flow into mold is not uniform.	With multi-cavity molds, make sure flow is balanced.
Part is too hot during ejection	Reduce melt temperature Increase cooling time Reduce mold temperature
Molded part has stresses	Increase melt temperature Prevent overpacking at gate by reducing hold pressure or reducing hold time Lengthen cooling time Delay knockout actuation Increase injection forward time Reduce temperature differential in mold.
Knockout is operating improperly	Knockout engaging too fast, slow down ejection Non-uniform operation of pins Bearing area of knockout pins is too small Increase diameter and number of knockout pins Relocate knockout pins to strong area of part With delicate parts change to air blow-off
Part design is incorrect	Make sure part contains no sharp variations in cross sections Correct taper or draft insufficiencies.

Flash On Parting Line

Possible Cause	Possible Solution
Excessive injection pressure causes mold to part	Verify the injection fill time Decrease final injection speed Reduce back pressure Move transfer point back Increase clamp pressure.
Melt temperature is too high	Reduce nozzle temperature Reduce front barrel zone temperature Reduce back pressure Reduce screw RPM’s Decrease mold temperature
Mold function is incorrect	Make sure mold faces are in correct alignment Remove foreign matter from mold faces Decrease size of vents Decrease mold temperature Check platens for square.
Mold release agent causing flash on part	Mold surface lubricant should not be used

Jetting

Possible Cause	Possible Solution
Mold design has insufficient impingement	Relocation of gate to create impingement

Material Drools from Nozzle

Possible Cause	Possible Solution
Pressure build up	Add decompression
Barrel front zone is too hot	Reduce front barrel zone temp
Nozzle is too hot	Reduce nozzle temp

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