Precise stones manufactured in series
De Boer Machines - Netherlands
The de Boer mechanical engineering company checks the moulding boxes of its machines with touch probes and software by m&h. Three months after the intro-duction of the software, the cycle time of production has already been shortened by one week.
Large production machines for the heavy clay industry are the domain of the De Boer Machines Nederland BV company in Wijchen, near the city of Nijmegen. In these large production machines, there is a continuous sha-ping of clay into stones which are then dried and fired. Multiple moulding boxes which rotate on an endless chain are used in the pouring and forming stages.
These moulding boxes in turn contain 8 to 16 adjacent forms, depending on the desired size of the stones. From a large mixing vat located above the forms, the paste-like clay mass is filled and pressed into the moulds. Later, punches are used to push the pre-com-pressed stone mass from the moulds; they then are arranged in rows on the conveyor line for drying.
So far, so good. As usual, the difficulties lie in the details. Not only that for the moulds, the shrinkage of each individual material has to be taken into account, so that they must vary with each type of clay and each stone shape. The moulding boxes are designed as a welded construction, with the individual compart-ments possibly having unpredictable distortions and deformations. But with stones this does not matter, does it? Far from it. There is, after all, the requirement to always produce the same end products having straight edges and the predetermined volume. In ad-dition, the punchers must correspond exactly to any shape in their position, and allow a well-defined gap to the side wall to ensure safe and complete ejection of the moulded mass of stone.
So there are many uncertainties that were previously offset by manual reworking after machine production, but which resulted in a correspondingly long lead time in production. Delivery times these days are more and more decisive to winning contracts. Quite apart from that, shorter lead times mean higher output and in-creased capacity without the need to make additional investments. Which means cash benefits.
Two years ago, De Boer already took a big step to in-crease the efficiency of the operation with a machining centre that is suited for pendulum machining of the mould boxes. The Hedelius BC 100, a touch probe by m&h with infra-red data transmission was also acqui-red. The handling of the new machining centre turned out to be surprisingly simple, and the integration into the manufacturing process went smoothly. With pen-dulum machining, set-up times were possible in par-allel to the machining time since set-up can be done on one side of the machine whilst processing is carried out on the other. This creates additional capacities and reduces lead times. The use of the touch probe further reduces the time required for setting up and creates high accuracy without manual sources of error. „The probe works perfectly, and the handling is easy and simple,“ confirms Jan Brandwijk, head of the mechani-cal department at De Boer. A weighty testimonial, since m&h probes have been valued for longer than those two years. Even on a large Anayak machining centre, an m&h touch probe with wireless data transmission has been employed for many years.
At the Hedelius processing centre, the touch probe is changed in like a standard tool, and its signals are se-curely transmitted to the control via the so-called HDR technology by m&h (High Data Rate). The compact re-ceiver is embedded directly in the spindle head, which ensures that there always is an undisturbed optical connection between the probe diodes and the receiver, guaranteeing optimal reception conditions. Interferen-ce by ambient light is made virtually impossible by the HDR technology anyway. The touch probe itself con-sists of a steel casing and has tempered natural glass as a diode cover, all sealed according to IP68 standard. The robust probe withstands the difficult conditions in the machine tool without any problems. The m&h touch probes and the Hedelius BC 100 have been functioning from day one without any problems.
hree months before our visit to the De Boer plant, the 3D Form Inspect program was bought from m&h. It allows a target-actual comparison of the contours of the workpiece in the machine with the specifications of its CAD drawing. To do this, the machine operator sets the location to be measured and the desired measure-ment function by a mouse-click on a computer in the shop. The program automatically writes the positioning program for the touch probe in the background while simultaneously checking this program for freedom of collisions with the workpiece. An automatic short calibration upstream of the program determines the thermal and load effects in the machine and automati-cally compensates for it in the measurement results: a process patent by m&h.
People can now decide for themselves whether the workpiece is good or not
Now, each moulding box is measured and logged while still being clamped on the machine in all jobs. The insides of the mould boxes are checked at different heights to ensure their straightness. If the toleran-ces are exceeded, not only reworking can be done in the same clamping. Based on the logs, the respective punches can be precisely adjusted to the shape of the mould box. The stamps are precisely matched to the shape of the mould. This ensures that the punch not only fits, but also that it does not drop below the requi-red gap width. Thus, the production of precisely mat-ching stamp is facilitated, just as the times needed for assembly and adjustment of the punches to the mould are reduced. „We have already cut a week off our usual throughput time,“ Jan Brandwijk proudly reports. And his is just the beginning. There should be even more measuring done in the future than has been the case.
The logging of the exact dimensions of the moulding boxes has another advantage. „Based on the number, we now know what any mould box looked like. If the customer needs a repair, we can still deliver exactly the same mould box years later and have much less time-consuming adjustment work,“ Jan Brandwijk is pleased to note. An important point in order to be even faster in the future. Finally, these stone moulds are subject to wear and tear and must be overhauled every two years. By accessing the original data, exactly the same condition of any stamp or mould box can be reproduced again at any time. The logs are archived at De Boer and can be retrieved at any time. This results in more time saving: The workpieces are no longer measured on the measuring machine before they are installed. Time is money, and measuring on the machi-ne creates new capacities everywhere.
For the staff as well, working with the measurement software is an important simplification. Before, they had to individually check the clearances with fee-ler gauges and adjust them individually on assembly. Now each punch is milled directly to the fitting size based on the measurement. „People can now decide for themselves whether the workpiece is good or not,“ Jan Brandwijk says, who is pleased about the relief for everyone. „This small investment paid off immediately.“