What a Mold DFM Study Should Contain

Why the DFM is the cheapest document in the project

Every change costs more the later it is made. A gate position moved on a drawing costs an email. The same gate moved after the cavity is finished costs a weld insert and a week. The DFM exists to force those decisions into the window where they are still cheap, which is before fabrication starts.

The ten items

A JEC DFM covers basic project and product information (part number and name, steel and resin material, injection machine specification), the injection system with detailed pictures of the gating, the main mold layout with dimensions, the product main parting lines and the split lines of the inserts, draft angle analysis and product thickness study, the ejection layout and concept, the cooling sketch layout, the product surface finish review, and the part and steel tolerance review. Anything else you require is added to the same document.

Read the gating section first

The gating pictures tell you where the weld lines will be. If your part has a visible face, check that the flow fronts meet somewhere you can accept before you look at anything else.

Then read draft and thickness together

Draft angle and wall thickness are the two items that most often come back as a part change rather than a tool change. Reviewing them in the same sitting is how you find the corner that has no draft because the wall was thinned late in the design.

Treat it as a record, not a formality

The DFM is the document both sides refer back to when something is disputed during the build. Comment on it in writing.