Mold Making / Tool Building

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Life Expectancy of an Injection Mold

December 18, 2009 in Injection Molding, Mold Making / Tool Building by brentb | No comments

Of great interest to buyers, accountants, quality managers, toolmakers as well to, of course, molders, is the projected service life of an injection mold for thermoplastics.  Many people in the injection mold industry use the SPI Mold Classifications as guides for estimating the expected life of a mold. The common classifications are:

  • Class 101

For a life in excess of a million cycles, with a hardened mold base (minimum of 28 R/C), hard molding surfaces (minimum of 48 R/C) with other details of hardened steel. Guided ejection is mandated as are other features such as wear plates for slides. Parting line locks are mandated, and corrosion resistance is suggested for cooling channels. This is the highest quality of the SPI classifications, usually accompanied by the highest price.

  • Class 102

This is specified for a lifetime not to exceed 1 million cycles. This features the mold base hardness of class 101, molding surfaces (cavities and cores) also feature the hardness specified in 101, and functional details are heat treated. Parting line locks are recommended. Guided ejection, wear plates, and corrosion resistance of water passages are not mandatory, but dependent on expected total production quantities. If expected cycles approach the maximum, then these features should be specified.

  • Class 103

Aimed at molds intended for under 500,000 cycles. These are molds for low to medium production needs, and corresponding price ranges. Mold bases are at least 8 R/C and cavities and cores in excess of 28 R/C. Any extras must be agreed upon.

  • Class 104

For less than 100,000 cycles and limited production. These are lower priced molds. The base can be aluminum or mild steel. Cavities and cores can be of the same or a metal agreed upon.

  • Class 105

These are for cycles less than 500 (prototyping only) and are very inexpensive. They can be of cast metal or epoxy.

These SPI, or Society of the Plastics Industry (http://www.plasticsindustry.org), classifications should and do take much of the guesswork out of estimating the useful life of an injection mold, but not every class 101 mold is the same, and this is true in all the mold classifications. Classifications indicate, but don’t guarantee quality.

No matter the class of mold, how the molder treats the mold can determine the life of the tool. I have seen and heard of aluminum molds that have lasted for years, indeed decades, and conversely witnessed class 101 tools rapidly turned into junk.  Much of what the molder does, or how he treats the tool will determine the life of the mold.

Never over-clamp (use more than required clamp force) the mold not only will you wear, stress, or deform the steel prematurely, you will peen closed the vents, leading to a viscous circle of more injection pressure being dictated and then even more clamp force.

Don’t neglect preventive maintenance on the tool, devise a schedule or consult generic schedules, or better yet consult a reputable mold builder. Taking the mold down for a day or two for PM can add years of life to a mold. If you don’t have in-house tooling capabilities for this you can contact a mold builder such as Matrix Tooling Inc. A great part of mold PM is disassembly and cleaning and replacing components such as springs, o-rings, and pins. Many molding shops designate a person for these relatively simple but extremely important tasks.

Don’t skimp on mold protection, sometimes called low clamp pressure. You want to be set “fat” enough to stop the mold from clamping well before a possible stuck part is crushed by the mold faces. Your press maker can train you in this if there are any doubts. Many mold protection settings can be defeated by closing the mold too fast. Never slam a mold closed. Where there are slides or other actions and angle pins, you should slow the movement before they engage. The possibility of saving a half second on the cycle here could cost days of lost production while repairing the damage that a defeated mold protection could produce.

Daily cleaning of mold faces and lubing components such as pins and slides will extend the life of any class mold. Use the right lube for the job: FDA and medical grease where required and high temp grease for hot running tools such as those running PEEK, PEI, PPS and PSU, where mold temps can exceed 400°F. Remember it is the film of grease a few thousands of an inch thick that does the job, so don’t goop the grease on. It is counterproductive and can attract dirt.

Again the SPI classifications can give the molder a good idea of the potential lifetime of an injection mold, but not all molds in any one classification are made equally. One should always have their molds designed and built by a reputable mold builder. A mold builder such as Matrix Tooling Inc. will stand behind and care for every mold the build over its extended lifetime.

Brent Borgerson
Senior Process Engineer (Older Molder)

Transfer Tooling Programs: Streamlining Existing Molding Projects

May 13, 2009 in Injection Molding, Mold Making / Tool Building by paul | 1 comment

Several years ago, a customer we had limited dealings with contacted us to help supply product that was arriving sporadically from their off-shore partner. Numerous quality issues with the molded parts caused a high scrap rate, and the lure of low cost tooling and production wore thin when product was regularly delayed entering the USA. Matrix quickly built low-cavity tooling to keep a stream of parts flowing, allowing time for the transfer of six tools to the States. Once the tools arrived, the molds were disassembled, damage was repaired and mold modifications were performed to enhance their performance. For the next two years, we ran production using the refurbished off-shore tools. In the meantime, customer demand was increasing and production was ramping up so high-cavitation hot runner tooling proposals were submitted. Part of our proposal to the customer was financial justification calculations, including amortizing a portion of the tool cost into each part. Payback to the customer was rapid, in most cases less than 15 months, and with the faster hot runner tools, part prices dropped dramatically. In addition, quality problems went away, and with Matrix covering the tool maintenance for the life of the program, the cost to the customer was predictable and affordable. For more information on our transfer tooling capabilities please visit our main website.

Written By:

Paul Ziegenhorn
President

The True Cost of Cheap Molds

July 1, 2008 in Design, Manufacturing Industry, Mold Making / Tool Building by brentb | No comments

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.

Written By:

Brent Borgerson
Senior Process Engineer (Older Molder)

Successful Mold Building: Technology or Art?

May 22, 2008 in Manufacturing Technology, Mold Making / Tool Building by brentb | 2 comments

Back in the early days of moldmaking, the product was the result more of craftsmanship than technology. A crusty old moldmaker with thick glasses, clad in a denim apron would take the project from a block of steel all the way to a finely-fit, fully-functional injection mold. The mold was his masterpiece. He took his time hand-fitting the components, and each mold, even for similar products, was often unique. Some tools took the moldmaker the better part of a year to produce.

Times have changed though, and the necessity of quick time to market and short product lives have shrunk lead time, while demanding resins and complex part geometries have dictated that robust and precise molds be built in much less time than in the past.

These shortened lead times are where technology has really stepped in to help. The crusty moldmaker has been replaced by a technologically savvy leadman, and each stage of the mold building operation is done under the control of specialized operators who are completely versed in the technology of their stage of the operation.

All steps of the mold building operation (design, steel milling, electrode cutting, wire and sinker EDM operation, turning, and grinding) are Computer Numerically Controlled and connected via a local area network. Many of these operations are palletized and robot attended, enabling lights-out operation to further reduce time to delivery of the finished mold. Direct access to 3D design models is available to every operator at every phase of operation. Time-tested standards like prints and setup worksheets are becoming a thing of the past. Even the progress of jobs and tracking records are maintained electronically.

Matrix Tooling, Inc. is now thirty years old. Having seen the mold shops of even twenty years ago, it would have been hard to imagine that today’s machining centers with their brightly colored computer displays, robotic arms, and servo motors have any relationship with the mold shops of the “old days” where craftsmanship was king.

But there’s no doubt craftsmanship still has its place. We’ve spent the last thirty years blending the best aspects of traditional mold making with state-of-the-art technology to produce a precise, top quality and robust injection mold as quickly and economically as possible. The first paragraph of the Matrix Tooling quality policy reflects this: “Matrix Tooling, Inc.’s mission is to combine traditional craftsmanship with state-of-the-art technology in designing and producing the highest quality injection tooling and molded products.”

Our team members have found the key to successful mold building and we take great pride in combining the latest technology with old-time craftsmanship into every build. Though the mold building business has evolved each team member takes the same pride in our end product as the crusty old mold maker with the denim apron.

Written by:

Brent G. Borgerson
Senior Process Engineer (Older Molder)