DFM stands for Design for Manufacturing, it is a process/document discuss how the manufacturer going to make/manufacture/produce a product. Here discuss a DFM for a injection molding mold, which generally consisted of following elements:

Plastic part design review (2D/3D)

Collect and study the purpose of the plastic part (for appearance or functional of assembly, the match situation with the counter part and other study as below…etc.), it is usually a set of 2 electrical files consisted of a 2d drawing and 3D CAD file.

General/basic information of subject plastic part

Gather/arrange following information of the subject plastic part design and discuss with sales/engineering team for further detail. It shall be at least but not limited to following items.

  • Project Name
  • Mold Number
  • Part Name
  • Part size
  • Raw material data sheet
  • Shrinkage
  • Color (If more then 1 color)
  • Cavity no.
  • Runner system
  • Appearance surface finish
  • Texture Code (if available)
  • Equipment Standards
  • IMM spec. (Ton)
  • Design Cycle Time
  • …etc.

Feasibility of making mold

Study the plastic part design and see if it is feasible to be produced by injection molding process. Any unsolved undercut/ straight/no draft angle area…etc. need to be raised before mold design started/ taking the mold order. Software such as Solidwork/ Creo/ UG…etc. can cover the study with pretty high accuracy.

Mold flow analysis (with suggested gate location)

Study the mold-ability of the plastic part design, how the material flow run inside mold cavity during production. Generate the analysis/simulation according to the suggested gate location (it could come from mold manufacturer or customer). At least but not limited to following items shall be simulated in the analysis report.

  • Filling balance
  • Pressure drop
  • Air trap
  • Welding line
  • Possible short shot area
  • PVT/Shear rate change during injection
  • Plastic part size and volume
  • Injection pressure drop
  • Clamping force

Discuss with customer if the results fulfill the plastic part purpose before mold design starts. This could be analysis and demonstrated by software (Moldflow/ Moldex…etc.)

Parting line

Discuss with customer and demonstrate the parting line location on plastic part 3D design. Parting line location could affect the mold layout as well as the mold cost.

Mold layout

Demonstrate the mold layout, it includes mold size, general specification…etc. At the meantime, the specification of expected IMM for production at customer side shall also be considered.

Potential issues from previous experience/mass production

  1. Gate location
    • If gate can only be applied at non-appearance area, instead of most suitable area according to mold flow analysis.
      How warpage may happen??
    • If use side gate
      Is the gate blush acceptable??
      What is the acceptance criteria??
    • If use submarine gate
      Is the gate blush acceptable??
      What is the acceptance criteria??
    • If gate on the appearance area
      What is the acceptance criteria of gate residue and stringiness??
  2. Appearance
    • Is draft angle for texture area enough??
      If not, plastic part scratch during molding process acceptable??
    • Are ribs/ structure thickness too much??
      If yes, what is the acceptance criteria of sink mark??
    • Is the mating area having enough space/ tolerance??
  3. Dimension
    • Is linear tolerance reasonable??
    • Is geometric tolerance reasonable??
  4. Raw material
    • Is the shrinkage too big to lead to unacceptable warpage??
  5. Profile
    • Is the thickness variation too big to lead to unacceptable warpage??
      Is the overall thickness too thin to lead to unacceptable warpage??
    • Is the part size too big to lead to unacceptable warpage??

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