In our country, manufacturing companies are increasingly focusing on high-mix low-volume to become and stay competitive. For that, that production then needs to be automated, because low-volume with long lead times, afijn. Lean manufacturing offers well thought-out solutions for various parts of the production process. All with the aim of guaranteeing short lead times, keeping stocks low and being able to deliver Just in Time.
An important aspect is the changeover times from one product to another. Many of the methods we are familiar with in lean manufacturing come from the Toyota ranks. Shigeo Shingo devised the SMED, Single Minute Exchange of Dies, a fast and efficient way to change over a production process. Conversion is the set of activities required to switch from one product to another. This concept says that each changeover should take less than 10 minutes. In the case of metal machining, we are then talking about changing moulds, or dies, in the case of plastics machining we should call it SMEM, Single Minute Exchange of Molds.
Development
Harm Nijzink started developing systems that enable such short changeover times more than 30 years ago. "In Japan, companies were working on it, but in Europe it was still completely virgin territory." We speak to Harm Nijzink at the headquarters of the company he ran for many years, EAS Change Systems. He has since retired and still plays a modest role in the background.
"At that time, when I started discussions with VW about a system to clamp moulds, I noticed that there was a clear need. A student at hts who worked with me came up with the idea of making clamps with a wedge function at an angle of 5 degrees, making them self-locking. That idea struck a chord. But we thought about the whole spectrum. Because clamping a mould or a punch is only one part of the changeover procedure. It also involves the actual changeover, the ejectors and, in the case of plastic injection moulding machines, also cooling lines and preheating the mould. Before we had a product, we already had the orders. Our first brochure consisted only of ideas, it didn't have a product yet, but if you look back at that brochure now, you can see that all those ideas have become products."
Mentality Change
What strikes him is that many companies still really need to be convinced about quick change systems or QDC and QMC - Quick Die Change, Quick Mold Change systems. Nijzink: "Companies buy an extra machine while their machine efficiency is at seventy per cent. That can be increased to above ninety per cent with these systems, which then means in many cases that no additional machine is needed. We do say then that people need a Quick Mentality Change," he laughs. "In fact, there are a lot of factors to consider when making such a consideration. And many companies don't even think about calculating an ROI. Because that does involve a few aspects. They assume a priori that it is way too expensive. But not only the purchase of that extra machine might not be necessary, but also expensive inventory is no longer needed. Besides, your mould or jig is an expensive tool. Taking good care of that can very much increase the lifespan, but also the quality of the products. For some industries, the latter is of course just a real must. Moreover, you can decide how automated you want something to be. It can range from very simple to very advanced.
If you imagine that a mould of 40 tonnes is used for a certain product, to take an extreme example: a car bumper, it needs about six to eight hours of changeover time with conventional methods. With a QMC system, that changeover time can be reduced to less than two minutes. We used to change products only once a month, now we can do it several times a day. We have built an exchange system for a very large mould on a hovercraft and this mould can then be driven into a special inspection unit. Maintenance and repair is thus very easy to carry out and the mould provides continuous high-quality products. The bigger the mould, the bigger the time savings."
Further automation
According to Nijzink, companies in the Netherlands will increasingly engage in this. "Automation enables us to produce competitively," he says. What does he see for the future? "We already see moulds equipped with RFID in which cycles are stored. That data is very valuable. Controls for automated change systems are already regularly integrated into machine controls. Furthermore, we will start to see that a robot will be able to change the mould and AGV systems, i.e. self-propelled exchange tables, will ready the moulds at the right machines at the right times. Preheated and all. Thanks to that RFID, the machine recognises the mould and sets the right parameters."
By: Janet Kooren
