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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