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Thermoforming vs. Injection Molding - Which Best Meets Your Needs?

Plastics is a huge industry that employs hundreds of thousands of people and generates billions of dollars of revenue each year. According to recent statistics compiled by the U.S. Bureau of Labor Statistics and the Plastic Industry Trade Association, plastics employed over 900,000 Americans in 2012 alone, has over 16,000 facilities in the United States (with that number growing each year), and manufactured over 107 billion pounds of plastics and resins in 2013.

For these and many other reasons, it’s imperative that plastics companies stay on the cutting edge of technology to manufacture high quality products in less time and, ideally, for less money. In order to do that, managers and executives have to make crucial decisions about which manufacturing processes are most efficient for producing the goods its company makes, and the only way to make the right decisions is to have all of the facts necessary to make informed choices.

Thermoforming or Injection Molding?

Weighing the advantages and disadvantages of thermoforming and injection molding is something all plastics companies must do to maximize productivity and minimize cost. The thermoforming process (also referred to as “vacuum processing”) has many advantages including:

  • Fast prototyping and production times
  • Allows for the creation of large pieces up to 48’ x 96’
  • Ideal for repetitive jobs
  • Small and medium runs offer good price point

There are disadvantages, however, to the thermoforming process including:

  • Parts cannot have the extent of intricate details as injection molded products
  • Clear pieces may exhibit mark-off
  • Consistent wall thickness is not possible
  • Cannot handle large production quantities like injection molding can
  • Only one piece of material can be made at a time
  • Costly and labor intensive to finish many products

Injection molding, while a much more expensive process, has many advantages:

  • High production rates
  • Able to produce intricacies and details that thermoforming cannot
  • Requires very little post-production work-parts come out of molding looking “finished”
  • No waste because all scrap can be re-used
  • Lower cost per part
  • Full automation is possible

Some of the disadvantages of injection molding:

  • Very expensive to start up
  • Requires a large amount of engineering time (more costs)
  • Much lengthier amount of time required to produce

As with all industries, when deciding which production method is best for your product, you have a lot to take into consideration. Start-up costs and other budgetary concerns, design and engineering requirements, production speed and manpower needs are just a few of the factors you’ll need to consider before deciding whether to use the thermoforming process or injection molding.


Benefits of DFM in Injection Molding

DFM 101

When it comes to the manufacturing business, DFM (Design for Manufacturing) can mean the difference between manageable costs (even low costs) and costs that far exceed a budget. Because design has such an enormous effect on the cost of manufacturing, it’s absolutely imperative to identify potential problems of a product, part or assembly in the design phase, which is the least expensive phase in which to fix a problem.

There are three issues that DFM will help to prevent:

  • Product designs that are simple to assemble but that require complex and expensive components
  • Designs that have simple components but a complex manufacturing process
  • Designs that are simple and inexpensive to get rolling but are complex and/or expensive to service and support

Now let’s take a look at how DFM is applied to the plastics industry.

DFM and Injection Molding

For injection molding, DFM follows the same basic principles as with any manufacturing process. DFM helps to ensure the manufacturing plan is problem free, and if problems do exist, they are identified in the design phase. For injection molding design for manufacturing to work, you’d apply basic DFM principles to assess and minimize manufacturing costs of the process.

Why should a Mold DFM Analysis be done and how can it shorten lead time? Mold DFM Analysis is an excellent process to evaluate whether a plastic product is suitable for injection molding. DFM analysis will also let you know the riskiness of injection molding; knowing the riskiness of injection molding ahead of time will help to reduce waste cost.

In injection molding, DFM would be used to assess the manufacturability of the following components:

  • Sprue-Ensure sprues are as short as possible to minimize material usage and cycle time; make sure the sprue puller opens seamlessly
  • Cold Material Trap-Ensure all runner intersections have a cold, solid slug well to aid the flow of material into the cavity
  • Runner Design-Ensure the manufacturability of the main and secondary runners; runner size; hydraulic diameter and flow resistance; branching and balancing of the runners; and balancing of lateral forces
  • Gate Design-Gates should be of the right size to ensure easy separation of the runner and part but large enough to prevent early freeze off of polymer flow; check tunnel gate, pinpoint gate, edge gate, tab gate, sprue gate, flash gate, external ring gate, internal ring gate and wall thickness
  • Adjoining Walls-Ensure the proper connection point between the molded surfaces
  • Ribs Bosses-Ensure proper rib thickness
  • Bosses and Gussets-Ensure proper connection
  • Cooling Design-Ensure development of low-shrinkage, warp-free parts
  • Venting Design-Ensure there is no over- or under-venting

DFM analysis for injection molding can save money, speed production and reduce waste.

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