Mold warranties: Proper care, feeding, and maintenance required

By: 
June 06, 2001

Editor's note: Consultant Bill Tobin of WJT Assoc. is a regular contributor to IMM and offers some advice on warranties for new molds.


When you purchase a car or a computer, you get a card from the manufacturer that starts a clock. This is a guarantee that the product will perform as expected for a specific length of time. After that period the product's performance is no longer the manufacturer's responsibility. With used cars, in many cases you have the right to have it inspected by your own mechanic, but once you buy it, it's yours—defects and all. 

The problem with molds is that they are always custom built. A mold is not a commodity, and therefore the warranty is different. The first and most basic warranty you can expect with a mold is what is jokingly referred to as the Kodak warranty. This concerns materials. Quite like photographic film, if the mold is defective the manufacturer will give you a new roll of film, but will not pay for another honeymoon or vacation. 

Steel and component manufacturers will replace products, but not the labor that went into your mold. An ejector pin manufacturer warrants his pins to be made of a specific alloy with a certain straightness and hardness. He does not guarantee that your part will eject when you use his product. 

When the mold shows wear after six months of continuous use, you enter a very gray area in terms of cause.
When a mold is purchased there is always an implied warranty that the moldbuilder will produce a mold that should produce a part within reasonable, trade-accepted tolerances for a reasonable amount of use. To understand this last sentence we must go back to the Uniform Commercial Code, which has been adopted in most states and attempts to make uniform all laws relating to commercial transactions. If there is a law governing a specific action, it will take precedence. In the absence of a law, you then look to a published accepted industry standard as an authoritative source. Without a published standard, you look for an accepted practice. At the bottom of this food chain is the contract you both signed. 

"Acceptable tolerances" and "reasonable amount of use" are defined by a reasonable (professional) client. You may wish you could hold a part tolerance to +.0001 inch, but that's all it will be—a wish. Machining steel, anticipating the shrinkage, hoping for process repeatability, and then determining how you will measure to that precision is a fool's folly. It is impractical to ask. 

On the other side, if the moldmaker delivers a mold that immediately breaks after 2 hours of operation, an argument could be made about craftsmanship. But when the mold shows signs of premature wear after six months of continuous use, you enter a very gray area. It could be the mold, the material, the process, or the molder. 

Stories abound of sloppy workmanship, bad materials, and molds that should have lasted for a half million cycles wearing out in 50,000. Conversely, aluminum molds are built daily that should last about 100,000 cycles but have life spans of more than a million. How is this done? Actually, it's simple. 

A Fair Approach 
The first step is in the specification. Too many mold buyers still have the mentality of the level playing field. They think that when they ask for a multicavity hot runner tool that every vendor envisions the same type of mold. Thus the discrepancy in price is merely a reflection of the marketplace. With this mentality buyers usually pick the low bidder. 

The mistake here is similar to purchasing cutlery for your kitchen. If you think a chef's knife is a chef's knife, you will always buy the cheap one. However, if you are interested in buying one set, having the knives stay sharp, and lasting your entire life, your decision is no longer affected by price. You will buy quality over price and not have to purchase another set in a year. 

When specifying a tool you must declare your wants. You not only want parts that work (the ultimate definition of "parts to print") but you also want a sustained flow of parts at an economical price for a period of time or volume. This must be articulated in the purchase order. If it is your intent for this mold to produce three million pieces over three years, it does not mean your normal production will be in shipped lots of exactly 125,000 pieces every two weeks. 

At the initial startup the volumes will be small. As the product goes to market, the shipments will be substantially larger. The sustained volumes in a mature market may well be more than the average. However, when the product is retired, the average might hold. Thus, you must inform the molder and moldbuilder of both peak requirements and average requirements. 

Prior to sending out an RFQ, discuss the pros and cons of conventional two-plate molds, three-plate tools, hot runners, or combination tools. Discuss the use of robots and the cost of end-of-arm tooling and other devices that will assist in fully automatic production. Do not waste time by issuing an RFQ with statements like "cost savings input, such as the type of mold and/or additional equipment that might be used to lower the part cost, should be included in your quotation." You are asking for free consulting without offering the job. 

Keep in mind that most suppliers are usually awarded less than 25 percent of the jobs they quote. A lot of time and energy is spent without the reward of getting the job. If you ask for too much, a shop will look at its history with you, calculate the odds of gaining the job, and put a proportionate amount of work into the quote as it sees fit. For no other reason, this should be logic enough not to bid competitively, but simply to pick someone who will work with you through the design phase, and then award the contract to that company. 

You may ask for tooling with an infinite warranty; however, don't think you will get it for free.
The Extent of the Warranty 
The second step in specifying a tool is a cardinal rule to keep in mind: Asking isn't stealing. You may ask for tooling with an infinite warranty; however, don't think you will get it for free. It is reasonable to ask for a warranty against failure of the tool for the first six months of production. But if these are hard months (continuous 24/7 use) you will put on a significant amount of mileage. If the project hasn't launched yet, the clock may time out with little production. It is better to ask for a warranty in terms of mold closures. An inexpensive one-way counter can be purchased and mounted below the ejector plate or on a separate pin. It counts each time the mold closes. 

Books are available on tooling standards that instruct about the construction standards of tools according to their useful life when measured in the number of closures. For instance, never ask for an "Alpha Class" mold unless it has been defined somewhere. Words like "high quality," "high precision," "Class 1," or "Class A" defy definition unless they are accompanied either by your company's standards or an industry standard. 

Once the warranty period is over, so is the honeymoon. You may have put in your PO that the cost of maintenance should be included in the mold. This is a common but naive mistake. If you ask for a preventive maintenance schedule and pay for it each time, you know what you are paying for. If it is buried in the part price, you will pay for it with every part produced. Several studies have shown that the amount charged for maintenance when buried in the part cost is almost triple the cost when paid for as a separate charge. 

Warranties are tricky and require the use of sanity and common sense. Fighting over who pays is silly. One way or the other the customer will always pay. If threats are made, production will be endangered. Since the goal of constructing a mold is solely the production of parts, focus on that goal and act accordingly. 

Contact information
WJT Assoc.
Louisville, CO
Phone: (303) 604-9592
Fax: (303) 604-0319

 

 

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