09-02-2014 05:34 AM
I have a brand new 12 CV mold from Germany and one cavity got cracked due to a double shot. material leaked to HR maniflod & burned the entire HR wiring. Is this acceptable for a expensive mold
Mold cavity got cracked due to a double shot
09-02-2014 07:54 AM
Which hot runner you are using
09-02-2014 10:03 AM
Thilian, first question that comes to my mind is; where is/was the crack? Near the hot runner gate? Was the gate a thermal gate or valve gate (tapered/cylindrical shutoff)? What wiring on the HR that is burned are you referring to? Is it the nozzle/drop heater wiring on the external faces of the HR or internal wiring as well?
09-02-2014 12:17 PM
Near HR thermal gate and internal wiring as well. Molten PP has pass through the manifold to internal wiring
09-02-2014 03:07 PM
When a hot runner is designed, it has a gate well. This gate well is cut into the cavity. At the time of the tool design, the mold designer is aware of how much steel there is between the cavity and the gate well. I start at a minimum of 3/8" or 9mm of steel. Also, what steel is used and its heat treat? Worst condition is putting a hot runner nozzle into the inside of a test tube. The hot runner needs a large gate well for flow and insulation while the inside diameter of the test tube forces a small gate well.
09-02-2014 05:45 PM
Thilian, you did not explain the product. But if the product is cap with gate inside this kind of risk is potential if you have double clamping. Because for this kind product often we don't have enought space to put steel thickness. I believe your moltem pp did not flow imside directly after your double clamping/inject insiden. I suggest to do detail checking for critical mold every time we have insiden and put additional safety device. Last time we put camera sensor to our mold to prevent double clamping/inject.
09-02-2014 08:33 PM
Hi Roelly , It's thread cone mold
09-02-2014 11:04 PM
Thilian, If it's thread cone mold, I think the mold maker want to optimize temperature to obtain good and stable product. But sometimes it has consequent in several part will be thin. Usually expensive mold for this kind of product use berillium copper for good temperature condition with optimal mold material thickness. We must consider that berrilium copper is not as strong as steel. Double clamping can make the mold damage. Thread cone mold especially with PP material usualy tall but thin. I am sure your doule clamping is not one time or after double clamping you keep runing for several hours.