Reducing injection molding cycle times is a good thing, right? Not necessarily

Solutions to an existing problem often create a new problem

Finding solutions to the various problems that plague manufacturing is not easy. Often a solution for one manufacturer creates a new challenge for someone else. For example, everyone is always talking about ways to shave seconds, or even tenths of a second, off the cycle times of molds. That certainly sounds like a winner! But when we look at it more closely, we find that there are many reasons some do not find this to be a good thing.

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Image courtesy Stuart Miles/
freedigitalphotos.net.

The moldmaker can do a lot when designing a mold to make it run faster cycles—hot runner systems, conformal cooling, components to eject the parts faster and so forth—but what is the advantage to the molder? After all, the molder sells machine time, and part cost is based in part on cycle time. If the molder runs a fast-cycling mold, it means that the molder can complete a production run faster and have more time to run other parts. The advantage to the molder is that he gets additional machine time. That’s good unless the molder doesn’t have anything to put into the press when a run is completed, which means that saving cycle time can be a negative. When they’re busy, it’s good. When things slow down, it’s not.

One molder told me that saving cycle time on one particular mold gave him the equivalent of having two additional presses. That’s great, but the machinery manufacturer isn’t happy about that. The machinery makers want to sell more machines and if molders run molds with technology to reduce cycle times and gain more press time without having to buy a press, they’re unhappy.

Faster cycle times also mean cost savings for the molder, and they’re happy about that. But what about the OEMs? Automotive OEMs, in particular, won’t be quite as happy because now the molder is making money and the automotive OEMs don’t like that. They want a piece of that savings so they ask for rebates on their part pricing. Now you have three people in the supply chain unhappy about reduced cycle times in molds: The molder, machinery maker and OEM customer. Each one tries to find a way to deny the others the benefits of reduced cycle times.

What about technologies for lightweighting and thin walling? Those technologies save OEMs money in the part price because less material is required. So, automotive OEMs are happy because they are under a mandate to meet CAFE standards and reduce fuel consumption, and lighter weight vehicles help them do that. The materials people are unhappy, however, because now they can’t sell as much material. The states aren’t happy because lighter weight vehicles use less gas, so they are losing out on gas taxes which go to pay for new roads and highway repairs. Now the states are trying to come up with schemes to tax something else—the number of miles you drive, road use via tolls and just flat out raising the gas tax at the pump to make up for the big savings everyone else is happy about.

It’s one more example of the law of unintended consequences: We keep trying to come up with solutions to problems that, at the end of the day, create new problems. But hey, it keeps us all busy!

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