PrintSoft or semi-hard tooling and CNC machined cavities are a great solution for non-critical larger parts, but are not ideal for micro molding projects where small tolerances, sharp corners, and micro part features must be achieved. This has always been the struggle with micro-sized parts and larger parts with small critical features.
Many R&D engineers and design engineers have heard the same responses from molding suppliers who utilize soft tooling and machine cavity/core details with CNC milling machines. They often are forced to request adjustments to the part design. There’s a major tradeoff when adjusting part designs to accommodate soft machined prototypes or semi-hard production tooling.
What happens when mold suppliers request adjustments to part design?
Adjusting your part design often results in a functional sacrifice and may increase risk of finished product performance issues caused by the adjusted features. In many cases, OEMs have to adjust their designs to such a degree that the components lose critical features. As companies push more functions into smaller forms, in a growing number of cases these forced design changes have a major effect on final product function. Thin ribs, small hole diameters, and sharp corners on parts are the usual suspects that give molding suppliers a hard time with soft machined tooling. These are often impossible to achieve without hard tool steel mold components and utilizing traditional EDM machining, wire EDM, or Sarix EDM machining processes.
This is why our DFM teams (or in our case, the DfMM team) provides a great degree of upfront engineering support, working hand-in-hand with the manufacturer or OEM development engineering team. It’s also why we’ve put considerable resources into our tooling process and state of the art equipment—we know accommodating micro sized features with great definition is our sweet spot.
Why not use aluminum for micro molds?
As a soft metal, aluminum used to create molds requires looser fitting slides, lifters, and ejector pins because of its tendency to gall around tight fitting moving components. Having to fit these components loosely can cause flash, reduce capability to hold tight tolerances, and make complicated shut-offs nearly impossible.
For production tooling, it is commonplace for molders to use semi-hard steels such as P20 and various grades of Stainless steel for mold cavities/cores. These materials are much more prone to parting line wear and feature damage because of their soft nature. Shut-offs wear quickly, gates wear quickly and lose sharpness, and tight moving component fits are difficult to maintain with the semi-hard tool steels. – When micro feature sizes and tight tolerances matter, hardened steel tooling is critical.
Accumold’s tooling is all manufactured in-house from specialized materials such as stainless steel, A2, S7, Caldie, copper, carbide, and Inconel. All tool steels are hardened to between 45RC and 62RC to provide ideal wear resistance and mold component longevity. Materials are selected specifically for each mold component’s geometry and function. This along with a strict preventative maintenance schedule allows us to run tools for multiple millions of cycles before needing refurbishment. When our customers demand millions of parts on a short timeline, a robust tool build matters.