Working in the plastics industry is not an easy task if you are a processor. It takes many years to learn the ins and outs of the industry. I have been working in plastics for 19 years and I am still learning. From start to finish, it takes a lot of knowledge to be able to make a part. From the design stage, to the mold build, all the way through the finished product it can take up to a year or more sometimes. As I keep learning and polishing my skill set, I am preparing for a new stage in my career. Hopefully with the steps I have taken and knowledge I have and continue to learn I will be in a position to help myself, others and most importantly my family. 

Hopefully after viewing my blog and reading the posts I have entertained you and given you some insight into the plastics world. Though you still may not understand what you read, there are millions of google searches that can be done to answer any questions you may have.

Feel free to comment on any post and I will answer any questions. Until next time my friends always seek the knowledge you deserve. 

After molding plastic parts some need a little more attention. There are parts that can be ultrasonic welded together. Parts also can be assembled together to make a function assembly. Depending on the application the parts will be used for depends on how many steps it takes to complete the part. The more steps used to complete the part the more the part will cost. Parts that take more than one step to complete are called value added. This means the cost of producing the final parts will cost more money.


 If it is a simple shoot and ship part (no secondary applications) then the part could cost as little as .02 cents to make. Think of a model car kit. When you open the box and take out the pieces they are all attached as one. You have to break these pieces off separately, this is due to no other assembly being done at the molder. A simple product molded and packed in a box then shipped out the door.

  


If the part involves assembly and ultrasonic welding with other added parts, then they could cost as much as $20 to make.



Welding basics.....

Just as important as getting a good consistent part, it is also important to not get molding defects. These will happen from time to time. Good preventive measures can help prevent most molding defects. Defects will arise and have to be dealt with. There are a number of types of defects, but the most common are:


Quick overview of molding defects



Contamination is in my mind the number one molding defect. It can be caused by mixed materials, degraded material or grease from the mold itself.

 

Flash is a defect that appears when parting lines get damaged or the plastic pressure is too much for the clamping pressure to with stand and material leaks into the parting lines. Though correctable, flash is difficult to content with.











Short shots or underloads as they are sometimes called are places on the part that do not fill in completely. These can be caused by gases from the plastic being trapped in the cavity or the full shot of material didn't get injected into the mold creating a nozzle leak. The process may not be developed correctly causing an unbalanced fill between cavities.

Producing and maintaining plastic parts to a tolerance is quit difficult. To ensure parts are consistently good the parts are measured periodically. Measuring plastic parts are done with various tools. Smaller parts can be measured by hand using calipers. Calipers are used to measure from one point to another and can measure to within .0001" These are used by hand so accuracy can sometimes be off.






Another measuring device is the CMM or Coordinate Measuring Machine is used to measure a tight tolerance on the part. It can also give surface readings and the dimensions inside of parts. The CMM is programmed by a trained CMM programmer to set points that need be inspected. CMM machines use these precise data points to give critical read outs of the part dimensions. These can find fractional molding errors and the potential to stop the release of bad product.










CMM in action......