When our mold designer complete a mold design, what is the next step? Do you have a mold design review process?How many times have you come up against issues that are inherent to mold design when trying to resolve a production problem? If the issues are bad enough and the production volumes allow, you make a new mold or modify the existing mold—both of which are expensive solutions. To be proactive and avoid new tooling issues moving forward, the answer is simple: conduct a review of the mold design before cutting the steel.

The mold design review must be properly applied, however. Issues missed in this review often may not be realized until the mold has completed qualification and is in production. Then, weaknesses in the design begin to surface via mold breakages, the need for excessive cleaning or maintenance difficulties. A key aspect of effective mold design review is properly integrating the issues and recommendations identified in the design–for-manufacturing (DFM) and simulation phases, and then ensuring the tool meets the specifications set forth from the review process. In the end, however, a mold’s ultimate performance can only be as good as the part design.

The following sequence is recommended as a best practice for creating a mold design that is an effective manufacturing solution for an injection-molded part.

1. Conduct a DFM review of the part design. A DFM review conducted by an experienced tooling and processing engineer ensures that the part design adheres to common plastic part design “rules” and injection molding process constraints. After a DFM review, it is not unusual for a part’s predicted cycle time to be reduced by 50 percent, and for cosmetic appearance and yield to improve.

2. Perform a flow simulation. Tooling simulations have become more popular as companies continue to push the envelope with ambitious part designs. A flow study based purely on the component geometry enables designers and engineers to strategize best-case gating locations and runner layouts, and optimized water placements. The needed level of simulation depends on the complexity of the component and the tool. It can range from a fill-pack and warp study to full tool-simulation studies. Hot runner systems are also being incorporated into these types of analyses, as are the cost and performance values of conformal cooling and variotherm technologies.

3. Establish mold specifications that define and communicate to the mold designer all necessary requirements for what the mold will do and how it will function, and that are critical for meeting the buyer’s requirements. The mold design review should be completed based upon this document. The mold specification should also address all of the issues identified in the DFM and simulation reviews. Including the relevant output of those reviews within the exact mold specification is most effective.

This preliminary work can influence material selection and tooling requirements; gate location, size and type; cosmetic constraints; ejection requirements and constraints; venting requirements; warpage-risk prediction, and specific core and cavity temperature-control requirements; cycle-time prediction and basic processing-setting sheets.