text: Precise Mold and Engineering : Engineering Plastics
  Posted by admin in September 28th, 2009
  I have noticed a number of plastic manufacturing sites that offer simple forms which can be submitted for the manufacturing of injection and compression molded plastics. I have even seen a company offering a free 3D graphics tool so that an individual can create and submit their own drawings. Many offer fast turnaround services, speed being the key ingredient to satisfying their customers.
  As a plastics engineer, I know there are instances where we can turn a part and get it produced rapidly and with few exceptions as fast as the next company, but I worry about the implications that the process of molding plastics is easy. Simply filling out a form with the basic dimensions of a component is just the start of the process. And any oversight of a simple detail can create a very expensive mistake. Worse still a simple 3d graphics program like the one offered misses a wide array of features that consider the ramifications of molding plastics, a simple drawing of a part is not enough. Where do support ribs need to be placed, how thin can the plastic be made or thick for that matter. Placing a hole, cutout or bend in the wrong place can reduce structural integrity. Sure you can draw the part, but that is not enough, you need to know the part will work and if multiple parts are expected to interface will the interface work.
  We welcome customers who provide drawings and detailed specifications. For those in-experienced in molding plastics we work with you to complete the specifications. Knowing the general size and shape of the component(s) is a great starting point. Color, application and durability provide additional insight. Engineering considers not only the type of molding process, but pressures, hold times, temperatures both for molding and cooling, and the type of resins that can withstand such processing while creating a resilient cost effective product.
  Because some parts vary in thickness the mold temperature throughout cannot be consistent, but needs varying temperatures for unique areas of the mold. Thicker parts will require higher temperatures.
  The machines that compress or inject plastics for molding are quite expensive and the ability to keep them producing throughout the day (24 hours) helps deversify their cost across their total production run. The more parts a machine can produce in an hour the lower its impact on those parts. Getting parts out of these machines as soon as possible reduces the time in the press, but without the proper care prematurely released parts can sage losing critical dimensions.
  Complicating the process further is the need for stringent environmental controls. The humidity in a well run plastics plant will be well below 30%. Some resins hold moisture and must be dried immediately prior to press time.
  Molds in some cases must be chrome plated or polished to a mirror finish to develop some components. These molds can be marred by a single finger print destroying the finish.
  When looking for flaws clear parts may need to be free of specs from dust or impurities found in inferior resins.
  Knowing a mold expands a millionth of an inch and that a plastic resin may shrink 600ths of a inch are important considerations for the engineer. When you ask to have a part made they need to ask enough questions to ascertain not only the size and color of the part to be made but a greater understanding of is use. From this information they will address the details of humidity, pressures, temperatures, set times, resigns and molds types. Good engineers know how to use the most appropriate materials for the job, they can extend the life of the mold and keep it's performance levels high.
  We provide the best in engineering and production. When other plastic manufactures fail to perform they turn to us. We know how to deal with undercuts, over molds, live hinges and multi-part molds. We have engineers, machinists, operators and the equipment on-site. We have plant engineers that specialize in the maintenance and up keep of the molds and equipment. When a problem needs to be solved the team comes together sharing a breadth of knowledge often not found in other plants.