Polyram Ram-On Industries Moshav Ram-On, M.P. Megiddo Israel Phone (972) Fax (972) Troubleshooting injection molding for Polytron products is very similar to the troubleshooting for many other thermoplastic compounds. The priority that you place on each possible source of problems is slightly different as the long fibers in the melt affect the flow and fill of the mold. The long fibers also give an anisotropic orientation of fibers in the final part. This also affects the order you should take in problem solving. Polyram is always available to assist you in your problem solving, but many issues can be handled faster by following the simple list of areas to review in your process. These are listed by the type of problem you may find.

FINISH Brittleness Fiber Length Degradation Fiber Length Degradation Delamination Burn Marks Flashing Discoloration Nozzle Problems Poor Dimensional Control Poor Dimensional Control Short Shots, Pit Marks, and Surface Ripples Short Shots, Pit Marks, and Surface Ripples Sinks and Voids Sticking Problems Splay Marks, Silver Streaks, & Splash Marks Splay Marks, Silver Streaks, & Splash Marks Warpage and Part Distortion Warpage and Part Distortion Un-melted Pellets Weld Lines

Fiber length is the key to the properties and performance advantage of Polytron. Evaluation of fiber length retention should be the first priority in evaluation of molding effectiveness with Polytron products. The higher the fiber length retention: the higher the properties and performance of the end part. There are two simple ways to check for fiber length. The first and simplest way is to remove the resin on a molded part by burning it away in a muffle furnace or other high temperature device. A three dimensional matrix of woven fibers should remain when the polymer is burned away. If the glass is a slump of dust, then you have a fiber length retention problem. The second way to check the length is to send a part to Polyram. Our lab can evaluate the average fiberglass length in your part and quickly report the value to you. If you find your parts have degraded fiber length, then you should evaluate the molding machine and tools to determine if there are changes needed to retain the necessary fiber in the finished part.

PROBLEM SOLVING RECOMMENDATIONS: Dry the material. Check for contamination. Reduce material temperature.

PROBLEM SOLVING RECOMMENDATIONS: Decrease injection speed. Decrease booster time. Increase venting in the mold cavity. Alter gate positions. Increase gate size. Check melt temperature.

PROBLEM SOLVING RECOMMENDATIONS: Check for and eliminate any contamination. Raise mold temperature Raise Material temperature. Dry the material. Increase injection speed. Purge the machine.

PROBLEM SOLVING RECOMMENDATIONS: Check screw and barrel temperature. Purge heating cylinder. Reduce material temperature. Lower nozzle temperature. Shorten overall cycle time. Check hopper and feed zone for contamination. Move mold to a press with a smaller shot size. Provide additional vents in the mold.

PROBLEM SOLVING RECOMMENDATIONS: Check mold for obstructions. Decrease injection pressure/speed. Decrease injection hold time/booster time. Reduce material temperature. Check mold closure and clamping. Check parting line of mold for wear. Check press platens for parallelism. Move the mold to a larger press.

PROBLEM SOLVING RECOMMENDATIONS: Set a uniform cycle time. Maintain a uniform feed/cushion from cycle to cycle. Fill the mold as rapidly as possible. Increase the gate size. Balance the layout of the runners, gates, and cavity. Reduce the number of cavities in the mold. Add vents. Check the machine’s hydraulic and electrical systems for erratic performance. Use fixtures if necessary

NOZZLE DROOL NOZZLE FREEZE-OFF

Lower nozzle temperature. Increase decompression time. Reduce material temperature. Reduce back pressure. Decrease mold open time. Dry the material. PROBLEM SOLVING RECOMMENDATIONS: BACK TO NOZZLE PROBLAMS BACK TO NOZZLE PROBLAMS

PROBLEM SOLVING RECOMMENDATIONS: Increase nozzle temperature. Decrease cycle time. Increase mold temperature. Use a nozzle with a larger orifice. BACK TO NOZZLE PROBLAMS BACK TO NOZZLE PROBLAMS

PROBLEM SOLVING RECOMMENDATIONS: Increase injection pressure.(for sinks) Decrease injection speed. (for voids) Increase hold time. Use a booster and a maximum injection speed. Raise mold temperature. (do this only with voids) Lower mold temperature. (do this only with sinks) Decrease the cushion/pad. Increase the size of the sprue/runners/gates. Relocate the gates nearer the heavy sections.

PROBLEM SOLVING RECOMMENDATIONS: Check for a proper cushion and increase/decrease feed if necessary. Increase injection pressure. Increase injection speed. Increase booster time. Increase melt temperature by raising the cylinder temperature(s). Raise mold temperature. Check the cavity vents for blockage (trapped gas prevents the part from being filled). Increase the size of the sprue/runners/gates.

STICKING IN THE CAVITY STICKING ON THE CORE STICKING IN THE SPRUE BUSHING STICKING IN THE SPRUE BUSHING

PROBLEM SOLVING RECOMMENDATIONS: Decrease injection pressure. Decrease injection speed. Decrease booster time. Decrease injection hold time. Increase mold close time. Lower mold temperature. Decrease cylinder and nozzle temperature. Check mold for undercuts and/or insufficient draft. BACK TO STICKING PROBLEMS BACK TO STICKING PROBLEMS

PROBLEM SOLVING RECOMMENDATIONS: Increase injection pressure. Increase booster time. Increase injection speed. Decrease mold close time. Decrease core temperature. Check mold for undercuts and/or insufficient draft. BACK TO STICKING PROBLEMS BACK TO STICKING PROBLEMS

PROBLEM SOLVING RECOMMENDATIONS: Check sizes and alignment of the holes in the nozzle/sprue bushing. Decrease injection pressure. Decrease injection hold time. Increase mold close time. Increase nozzle temperature. Replace or repair sprue puller. Check sprue bushing for wear, undercuts or any abrasions. BACK TO STICKING PROBLEMS BACK TO STICKING PROBLEMS

PROBLEM SOLVING RECOMMENDATIONS: Dry material. Check for contamination. Check for drooling. Lower nozzle temperature. Raise mold temperature. Decrease injection speed. Reduce material temperature. Shorten overall cycle time. Open the gate(s).

PROBLEM SOLVING RECOMMENDATIONS: Increase melt temperature. Dry/preheat the material. Move the mold to a machine with a larger shot capacity.

PROBLEM SOLVING RECOMMENDATIONS: Equalize the temperature in both halves of the mold. (eliminate hot spots) Observe the mold for uniformity (or lack thereof) of part ejection. Check for proper handling of parts after ejection. Increase injection hold time. Increase or decrease the pressure as appropriate. Reduce mold temperature. Increase mold close time. Reduce material temperature. Try differential mold temperatures to counteract warp. Review the part design. Use fixtures

PROBLEM SOLVING RECOMMENDATIONS: Increase mold temperature. Increase material temperature by raising the cylinder temperature settings. Vent the cavity in the weld area. Increase injection pressure. Increase injection hold time. Increase injection speed. Provide an overflow well adjacent to the weld area. Change the gate location to improve the flow pattern.