Technology

Questions and answers

Question: I am getting breakage during ejection of my products, I run on horizontal with three plate mold.
Answer: It would be helpful to know the kind of part you are molding, in any case we believe the rubber is too fragile due to high temperature so we suggest to reduce the temperature of the platens and if it is allowed add some natural rubber.

 

Question: I am a compression molder, can I start molding rubber soles by injection, is it economic?
Answer: Yes of course, we have dedicated injection machines to mold rubber soles. Our Sole Jet machine is specifically designes to mold rubber soles by injection and to change compound color very quickly.

 

Question: I am experiencing troubles in molding a new type of bellow my customer ordered, which I am prototyping right now. My major problem is ejection: the bellow breaks easily during blowing off, and due to the cost of the production tool, I may refuse the order.
Answer: We can offer you a patented technology in which the stripping is very easy and mold price is reasonable. If you can provide us with a sample we will be back to you with our proposal shortly.

 

Question: I am injection molding, and I would like to know how to divide the percentage of the injection quantity into 1s/2s/3s. I would also like to know what is the unit on the base of the figure, and how to transform it with the actual ones.
Answer: If you are running a RUTIL injection machine it would be helpful to know the serial number in order to give a more complete explanation. In any case, indipendently from the brand, you can calculate the maximum shot available then divide the shot by the stroke of the injection plunger and get the CC. per stroke.
During the first phase of filling it is very important to control the injection speed of material as this can determine the formation of air bubbles and other molding defects, such as, the overheating of the compound can lead to prescorching.
In order to reduce the duration of the cycle and to heat the mix more effectively, the fastest possible speed is the best option to be selected. An initial speed of 95% of the machine capability is used for the first shot phase which then passes to a definitive speed of 85% in the second.
Obviously, this should be checked after the first injection in order to verify that the speed is not excessive and has not caused pre-curing and/or any air inside the molded parts. If this happens then the speed should be gradually reduced, 10% at a time, until the best speed is determined. The temperature of the mold would also have to be considered. It should be kept in mind that only a small part of the injection pressure used for filling is present in the cavities untill all of them are completely full.
If the mold has been set up correctly, in terms of the layout of the runners and dimensions according to the operations suggested earlier, then it is certain that up to the injection of about 30% of the material required no undesiderable pressure will form inside the mold. For the first phase of injection a stroke of 5% is set and 25% for the second (total 30%). At this point we enter into the most delicate setting phase which is related to the injection pressure defined as PP (packing pressure), in RUTIL machines.