Scheduling and running production of injection molded parts is an important operation of any molding company.
Most molding companies usually have several sizes of injection molding machines which are categorized by the shot size and also the tonnage. Shot size means the amount of plastic which can be molded during one cycle. For example, an 8 ounce machine or a 30 ounce machine. Tonnage refers to the size of the injection molding machine and the largest mold it will accept and mold properly without the part flashing. This is determined by figuring out the square inches of the actual molded part and using this information in a formula to determine the minimum size injection molding machine needed.
Once your company has received an order from a customer, several thing s must happen. First, is what size machine will be needed to be able to accommodate the existing size mold (tonnage) and material (shot size) for this particular part. A contributing factor to this would also be how many cavities are contained in this mold. Secondly, if this part would be made of a clear or natural material you would tend to use an existing machine which you have been molding clear resin as this would keep production material from being contaminated from other colors or black. Another factor for determining your production would be how many shifts the company has in place. One shift (8 hours) two shifts (16 hours) or three shifts (24 hours). Also, depending on material such as Nylon, Polypro, or Santoprene for example, auxiliary equipment may be needed. This may include mold temperature controllers, hopper dryers, and/or robots for removing parts from the mold.
Another issue is if the mold can run automatic or semi- automatic. Semi-automatic means that a machine operator is needed to open the machine door and remove the parts from the mold. Automatic means that the machine door does not need to be opened. Either the parts drop down to a chute or a robot removes the part from the mold. Once the parts have been molded, the operator must inspect each part visually for acceptability making sure that there are no flaws such as short shots, flashing, gas burns, etc. The operator will then remove the runner from the part using cutters, if needed. Depending on the part, secondary operations may be performed, if required. These might include placing parts on a shrink fixture, trimming flash or material over flows, unscrewing hand-loaded threaded cores or other cores and inserts from the molded parts. Sometimes the operator may have to apply labels if requested or add a screw or nut to the part. Once completed the parts are placed usually in a cardboard box for shipping.
For additional information regarding injection molding please contact Toth Mold/Die, Inc.