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Palletizing system: a foundation stone

Palletizing system: a foundation stone

I consider myself a lazy guy, but sometimes being lazy is a good stimulus in finding better solutions for everyday problems. Setting up a job on a milling centre takes a short time or even hours, depending on its complexity. In any case i’ve always found it a bit odd that a machine tool worth tens or more often hundreds thousand euros has to be kept idle while carrying out such operations like job setup, which, although vital, compared to the technically sophisticated machining itself, is basically a little added value  activity. In search of a better way I tried different ideas, like permanent setups on the machine table, with dowels or vises, to have fixed references, or a touch probe for quick and easy alignment. All of them worked well in many situations but lacked overall flexibility, and most of all they had to be repeated every time a new setup was required, especially when the very same workpiece had to be shifted from one machine to another. 

At the beginning there was edm. Edm machining the “old” way is probably one of the most time consuming jobs in a tool shop, it is itself an intrinsically slow  process, and setting up takes many different aligning and measuring activities for both the workpiece and the electrodes. Basically, when edm is required , it is as if you should manufacture milling cutters all the times milling is required on every workpiece.

That would be of course totally nonsense, but in edm is practically unavoidable. At The time when I started making molds I had no means but doing the very old way, milling electrodes on a vise then mounting them on the edm head with all the hassles of The case. I simply could not bear all this!

I almost had a fight with my partner who did not want to invest in a palletizing system…and eventually I decided to do my way. Call me crazy but I started to design a whole new palletizing system on my own.

The advantages that I was expecting from such a system were so relevant that I did not hesitate much. 

I tried to conceive it in a way that could allow a quick and easy manufacture by milling, grinding and maybe wire edm. I came out with a prismatic square pallet 70 x 70 x 18 mm with M6 screw holes and two 10mm dowel pin holes, that fitted on a square base with retaining strips on two adjacent faces and two cup spring loaded washers on the other two faces to ensure proper seating. The first set of 15 pallets were made of 1.2311 steel, hardened and ground on all faces, very accurate and robust and they proved very good and durable.

Immediately after installing the system on two milling centers and the edm machine it became essential, a the point that no one could understand how was possible working without one until then. Of course 15 pieces became soon insufficient for the number of electrodes we needed. I understood that the number of pallets had to grow larger and larger for such a “system” to be really effective. The advantages of a quick setup even after some time the mold was completed, maybe only for some remachining, became clearly evident. 

The only option was to find a way for manufacturing more pallets very quickly, this excluded heat treatment and an “easy” material was desirable. Not without some worries I tried to make them in 7075 aluminum alloy. Keeping my finger crossed then I did several repeatability tests, and,  with a lot of satisfaction, they proved to keep 0.005 mm or better, they also proved very durable despite 7075 is, of course, not as hard as steel. 

The more you get the more you want. After a couple of months all electrodes made in the workshop were fitted to a pallet, and also confidence in machining them increased as well their average number per mold with no overall increase in lead time.

It was clear that such a concept could be extended to mold parts other than electrodes, and being the pallet a square plate, it was suitable for index positioning. Therefore conceiving a pallet base for horizontal fitting was an immediate evolution. At this point the system was capable of 5 faces machining with very high accuracy extending a lot the overall flexibility of machining centres. The last machine to be equipped was the wire edm, then it was possible to quickly and easily machine a workpiece by milling, edm an wire edm with the same setup: a small revolution! In this picture a special pallet for machining thin foils can be used seamlessly on all machines, here on wire edm. In the following pictures the final machine setup is comprised of a magnetic table a double pallet base for vertical placement and a single base for horizontal placement, all mounted on a baseplate with 20 mm precision hole pattern for quick setup, although all fixtures were kept on the table almost all time.xibility of machining centres.