Hi All,
If anyone has any problems with their hot runners I would be interested if you could take the time to tell me what the make and problem is and what you did to cure it, I have many years experience in hot runners but I have found you never stop learning, I am always looking to further my knowledge. Thanks in advance, Graham.

I interested too.

During all my experience of +/- 40 Year of experience in injection molding. The HR suppliers promised it a lot but on the end effect,the results were below the expectations.

Special in color changes. Can you give me a brand that has the expertize in color change, Also to get a good result in the visual aspect of parts with metal flacks.(silver)
Simon Wolf

Hi Simon, Husky I would recommend they have a good back up service I have found, there are other companies out there such as PSG that are worth a look at, if you are doing colour changes then make sure the nozzle insulator tips are fitted that applies to any and all hot runner brands, if you don’t you will get the molded parts streaking of the old colour and it will take a fair time for it to clear, if you have this then assuming you have a nozzle plate on the hot runner you are using, you will need to strip the nozzle plate off the hot runner and clean it all out, running a cleaning agent through is good but it will not clear out those remnants around the back of the gates/at the point of injection through the gates and into the mold tool, hope this all makes sense, Regards Graham

Hi Simon, Sorry missed out on the ‘Also to get a good result in the visual aspect of parts with metal flacks.(silver)’, not exactly sure what you mean hear, I have found in our wonderful world of molding that different processes have their own terminology, if you could explain a little more I will get back to you. Regards Graham

Hi Simon, Assuming there are no signs of streaking from the material you have purged out of the barrel and this colour streaking is only from the hot runner, if you have cleaned out around the nozzle tips/gates and still have the problem this would indicate that there may well be a dead spot in the hot runner, if this is the case then really you need to be looking at the manifold, the manifold at the design stage should have been designed to be equally balanced and the channels in the manifold should have been honed out with an abrasive paste pumped through to take out the dead spots/hang-ups, the last resort would be to pull the hot runner apart and send the sprue, manifold and nozzle tips to a fluid bed cleaning specialist, then you are back to a hot runner that is totally free of any materials, if the problem persists and you have to do many colour changes then it would not be viable to keep sending parts to the cleaners, it would be best to invest in a new quality hot runner. Regards Graham

Hi Graham,we also met some issues on valve gate system.when we used multipoint valve gate system,and try to control position of the welding line according to apply time delay.and we found the fist opened gate without any problem,other delay gate we always have flash around the valve pin area.(with cooling bushing).if we have not applied time delay.the flash will be better....could you explain for me the reasons?
Best Regards

Hi Steven, I have not come across this and there would be much about your process that I would need to know part size, mold tool specifications etc…, I would look at the melt viscosity and the clamping force generally if you have flash the clamping tonnage is the first port of call after this the melt viscosity and shot size, but as this flash disappears when you remove the delay I think I would rule out the shot size, weight the part does it weigh what it is meant too? See if the clamping force is coming off too early, increasing clamping force and melt viscosity should help, start with no delay and slowly increase the delay and temperature of the melt flow, check out the plastic manufacturers recommended melt temperatures, that is where I would start with this one, hope this is of help. Regards Graham