August 26, 2010
At Matrix Tooling & Matrix Plastic Products, we design and build injection molds for a wide variety of advanced materials and processes, including metal injection molding (MIM.) While it is possible to build a very accurate injection mold, getting the actual molded part to meet the print specifications often requires more.
Resins with predictable shrinkage rates allow you to confidently machine details to a specific size without having to invest additional time "sneaking up" on them after processing. However, when working with MIM tools, not only are the shrinkage rates significantly higher (often representing a large percentage of the part size) but they are also less predictable. Subjecting the molded MIM pieces to the next required stage of heat treating further complicates things. Re-compounding the feedstock to adjust the "green" part is a common method used to achieve the required shrinkage and physical properties. But because each round of sampling entails the secondary processes of debinding and sintering, qualifying a MIM part can be time consuming.
While our industry's conscious efforts to reduce lead times have benefited the development of medical devices, certain parts are proving more difficult to qualify quickly. MIM parts seem to be among them. In order to address this challenge, Matrix has worked with our customers to develop "breadboard" parts: small quantities of machined finished parts, made to the database using conventional machining technologies, and made from the same raw material. This approach has numerous benefits. Since the initial test launch of a device may require as few as 3-6 units, machining breadboard parts is a more timely way to sample components that are destined to be produced using MIM. Any problems that crop up during the testing of the breadboard prototypes can be remedied prior to cutting any steel in the MIM tool, saving both time and money. Being able to prove out the concept more quickly and inexpensively with breadboard parts results in a faster release of MIM tooling for production and a smoother debugging and qualification process.
July 2, 2008
A thermoplastic injection mold is like most anything you buy in life; you get what you pay for. If you want a throwaway mold with a limited life expectancy that produces simple parts and allows for generous dimensional and flash tolerances (and may require post-molding defect corrections like flash trimming), then by all means purchase inexpensive tooling from a low-cost supplier. But if factors like part consistency, uptime, conforming to quality standards, on-time delivery, low maintenance costs, long mold life, and fewer headaches are important to you, you’ll likely want to consider buying a quality mold upfront.
An injection mold is not a small purchase to be taken lightly, even for a tiny plastic part produced by a large corporation. It should be viewed as an investment, with each running cycle giving back a portion of your ROI.
For many of the molded parts of bygone years, an inexpensive mold might have been sufficient. Times have changed though and products have become more demanding. Their geometries and resins have demanded a more complex, precise and robust mold. An inexpensive mold won’t be able to give you these parts, at least not for long. What good is a cheap mold that breaks down in the middle of a production run, fails to make in-tolerance parts, or runs slower than the calculated cycle when the customer needs a steady stream of good parts promptly and consistently?
There will always be a place for simple and cheap molds in certain applications, but if there is any complexity to the part or tool, it would be foolish to build and design based on price alone. Overseas low-cost providers are an option, but that opens up potential issues with communication. Not only due to language problems, but time zones, local customs, and general business practices can add on top of that. Logistic issues and rising transportation costs should also be considered.
Reputable mold builders stake their reputations on every mold they build. They want a robust mold, built correctly with the best materials, that doesn’t come back for repair or adjustment. They want the customer to be there if at all possible for design reviews and samplings. All the teleconferencing in the world can’t take the place of personal meetings at times. These personal meetings are with the mold maker’s technical staff and design specialists, not some sales rep or consultant for a cheap offshore mold builder.
Often, time to market is critical, and control of the project timeline is not always possible with an offshore supplier. When a cheap mold is late, produces out of tolerance parts, or breaks down, its low purchase price suddenly becomes very expensive. Many times a cheap mold that doesn’t perform like it should can end up being more costly to correct than a more expensive North American mold would have been in the first place. Losses in time and productivity are often just as costly and are even harder to recoup.
When the whole picture is looked at, you can see that in the purchase of an injection mold the old adage of “you get what you pay for” holds so true.