Injection molding DFM checklist before tooling

Design for manufacturability (DFM) is a review of how a proposed part can be made. Use this checklist to prepare a discussion, not to certify that a design is ready for production. A useful review identifies the affected feature, the concern, the proposed action and who must approve it.

• Identify the part number, CAD and drawing revision, units and mating components. Resolve contradictions between models and drawings.
• State the resin grade if selected, or the performance requirements if it remains open. Identify appearance, operating environment and functional priorities.
• Separate initial quantity, repeat demand and target dates. Mark fixed requirements and features open to change.

For the review service and enquiry inputs, see Cemal’s DFM review and feedback.

Protolabs’ wall-thickness guidance describes how uneven sections can contribute to sink and warpage. Its design essentials explains the roles of draft, radii and ribs. Supplier rules of thumb are starting points; the selected resin, surface, geometry and tooling route determine what is appropriate.

1. Walls and transitions: mark thick intersections and abrupt changes. Ask whether coring or a gradual transition is feasible while preserving the required function.
2. Ribs and bosses: identify attachment and stiffness requirements. Review the material buildup at their junctions and any proposed geometry change.
3. Draft and release: confirm the opening direction and surfaces that must release. Ask how texture, depth and appearance affect the proposed draft.
4. Undercuts and access: mark features that obstruct straight release. Request an explanation of the proposed mechanism or design alternative and its implications for the tool.

Do not apply a single wall thickness, rib ratio or draft angle to every resin and part. Ask the reviewer to document project-specific recommendations.

• Gates, parting lines and ejector contact: ask for proposed locations on an annotated model. Identify visible faces and assembly surfaces where marks need explicit approval.
• Fill and appearance questions: ask which features need further analysis or trial evidence. If flow analysis is proposed, agree its inputs, scope and limitations rather than assuming it is included.
• Critical features: identify dimensions, datums, mating parts and functional checks. Ask whether the proposed measurement method can evaluate the specified requirement.
• Finish and color: provide references and acceptance conditions. Define which areas are cosmetic and which are hidden after assembly.

A manufacturability recommendation may affect fit or function. Have the responsible product designer approve that consequence; do not treat a supplier’s suggested change as automatic design approval.

Use one row per issue in your project record. The following is a blank working structure, not a completed Cemal customer review.

For example, if an attachment boss is flagged, record its location and the assembly requirement before agreeing a change. Close the issue only when the approved revision and required verification are recorded. This is a hypothetical workflow example, not a production result.

Before releasing mold manufacture, confirm the agreed design revision, material assumption, unresolved risks and authorization to proceed. A DFM review does not demonstrate that physical samples meet dimensional, cosmetic or functional requirements.

Plan the sample checks, responsible approvers and correction process separately. Record any accepted deviation and whether it applies to samples only or repeat production. Use the equipment and inspection review questions to discuss measurement evidence.

If supplier evidence is incomplete, use the mold manufacturer selection checklist. For a project review, send a drawing or project notes with estimated quantity; scope and timing are confirmed for the specific enquiry.