The Business of Molding, #5

Editor's note: This series of articles on business relationships between custom molders and their customers is from Bill Tobin, of WJT Assoc., a consultant in injection molding who believes in looking at the molding business in the most practical way.

This is an interesting question that almost everyone asks when someone either complains about the quality of the parts or the molder wants to send a bill to repair a badly worn tool.

Let's draw an analogy: Remember the first apartment you had? If it was like mine, it was a dump. The landlord wanted the first and last month's rent plus a cleaning deposit the size of my roommate's trust fund. There were holes in the walls, cockroaches in the kitchen, and the shower was filthy. Fortunately, I owned a Polaroid camera and photographed everything we saw. I had the landlord sign the pictures so that when we moved out we wouldn't get charged for fixing what we didn't break.

When, upon our departure, the new management company wanted us to pay to restore it to like new, I pulled out my old photographs and got a full refund (with interest) for our deposit. The argument all revolved around the issue of normal use vs. unreasonable wear and tear.

The lesson here also applies to molds: Molds, quite like apartments, are subject to wear as they are used. With periodic maintenance, though, the mold should last the life of the part. However, the amount of maintenance is affected by certain factors that should be agreed to before production begins.

Let's look at each one separately and try to sort out who pays for what.

1. How well is the mold made and what material is it made of?

The first priority is to build a mold to make parts. However, a very close second should be to design the mold to minimize the cost of maintenance. This means a mold should be designed and built with spare components that are front loaded so that they can be easily replaced with a minimum of work.

No one can make good parts from a mold that is worn out, poorly constructed, or simply junk. This is the bane of the molder who accepts a tool that has been pulled from another molder. Usually, the reasons for pulling tools have been poor quality, rushed delivery, or too many mold smashes. Taking this kind of mold will almost always require a high maintenance bill to be paid for by the customer.

If the mold was constructed to standards that were designed for 100,000 closures and you are now in the 250,000-closure range, the mold is probably tired and worn. Maintenance and/or replacement is the burden of the customer, not the molder.

2. What material is running in the mold?

In a perfect world, all molds would run nothing but high-melt-index, low-density polyethylene. However, the world isn't perfect. Many designers have fallen in love with 30 percent mica-filled PEEK. Mica is extremely abrasive, and PEEK processes at temperatures where some steels begin to become soft. The combination of these two will cause the tooling to wear out fast.

It is the responsibility of the molder to inform the customer that abrasive materials will wear out tooling faster than normal. Thus, higher maintenance bills should be expected, and earlier. It is important to communicate this early in the project before the production contract is signed. This kind of service is all part of your Early Supplier Involvement program.

3. How professional is the molder running the mold?

This is a major sticking point between the molder and the buyer of the parts. As a molder, if you believe the way to get rid of flash is to increase the clamp pressure, you put in vents with a hand grinder, and "If it ain't broke, don't pay it no never-mind," you'll get everything you deserve. The same applies if, as a buyer, you believe that trimming parts and burying the cost in the part price is cheaper than paying for maintenance.

As a customer, think of choosing a molder with the same care you'd take choosing a doctor to do a cardiac bypass on your spouse. Your molder is holding a significant asset of your company (the mold). The parts he produces are the source of your income. Keep in mind that paychecks only come from the sale of good products. These products come from your molders. Therefore, take care of the people who take care of you.

It is the industry's common practice for the molder to do inspection and routine maintenance. This means he looks for and cleans clogged vents, makes sure everything that moves is moving properly, that is, well lubricated and not worn out. Periodically the tool is taken apart, cleaned, reinspected for wear, put back together, relubricated and put back on the shelf ready for production. This cost is buried in the piece price and is transparent to the customer.

Occasionally the mold crashes. This creates a problem. It is the molder's responsibility to pay for these repairs. However, it is the customer's responsibility to be sure the repairs are done properly. If there is welding or retexturing to be done, there must be a welding procedure in place that includes heat soaking and normalizing of the inserts before the job is let to the contractor.

If the mold crashes frequently, this means there is a lot of weld on the cavity surface. No matter what the metal suppliers tell you, weld is never as strong as parent metal. The more weld, the weaker the cavity. You'll have to find some middle ground to agree on either the repair or replacement of the cavity if the damage is severe enough. If damage caused by the molder affects the inspection dimensions of the part, the molder should pay for the requalification of the part or cavities affected. This is even more complicated when a perfectly good tool has a lot of engineering changes in it that have been welds.

The truly professional customer will have a General Maintenance and Major Maintenance program in place with his molders.

4. What part accuracy or precision is required of the mold?

I've met designers who take almost impish delight in specifying impossible tolerances, or almost unachievable quality standards on tricky parting lines that are prone to flash. There is a simple mathematical relationship between precision and the cost of maintenance. One is almost the square of the other. Put simply, the more you demand of the part, the more you'll pay in maintenance to keep the original precision of the approved parts. Molds can and do wear with use. If there is no room in the design tolerance for this wear, it is the customer's financial responsibility to pay for the maintenance.

5. How complex is the mold?

Most molds are simple open-and-close molds. Others look like machines that literally unzip/unscrew/ unlock/dismantle themselves with each opening. Mechanisms and the cost of maintenance are almost geometrically related to each other. The more mechanisms and the more complex they are, the more they must be maintained and the higher the cost. Since this was designed into the mold, it is the customer's responsibility to pay for it. This is the quintessential argument of elegantly simple part and mold designs.

The Cost of Maintenance

Predicting maintenance and its cost is still part of voodoo engineering. The cost of maintenance of each tool will be a function of the agreement between the molder and customer based on the items above. This can be further articulated through the use of a set of tooling standards where maintenance procedures are spelled out and therefore can be quoted in advance.

How do you get these procedures? Here are three of the most common ways:

As a buyer of parts, don't think you're paying for the same real estate twice if your molder asks for money for maintenance. As a molder, don't think your customer is willing to pay for your abuse of his tool. Professionalism is the watchword in this kind of relationship. It must be based on trust and the agreement that paying for maintenance on tooling is always cheaper than trying to whittle parts with flash knives and accepting a part price increase.

It must be acknowledged that trying to stretch the life of a tool beyond its intended capability should only be done with both parties understanding the risks and costs. While it may seem superficially foolish, running the many "last-lifetime runs" from a single cavity (either new or stolen from the old multicavity tooling) is smarter than trying to make the old multicavity tool produce good parts.

Look at your own tools based on what's been said above. This should give an indication if your maintenance will be relatively small or large. Make sure what you want is documented and clear to both parties as far ahead of time as possible. This will make the tool produce quality parts as long as possible.