The last 12 months i spent developing a concept for a small vertical machining center. As it is with any design process, errors were made on the way. Yet, finally most challenges are solved and i am pleased with the results. Very recently, the first real parts have been finished. More about that later. But first, lets have a short look at the machine concept.
The design is a classical column mill with traversing table and BT30 spindel with automatic pneumatic-hydraulic tool changer (the spindle itself is still very much in progress, so expect some posts on this in the following months).
So let´s get into the basic mechanics. Gross weight will be around 300kg. The machine can be easily broken down into parts light enough to be comfortably carried by two average persons. All moving parts are supported by pre-loaded high accuracy 25 mm linear rails. Axes movement will be driven by 20mm ball screws with attached stepper motors (might be swapped with servo drives as needed once budget is available). No use of linear encoders planned. Once completed, however, the machine will be evaluated to see whether encoders are needed for positional accuracy. Possible speeds with steppers are up to 6m/min. Resolution is 1.5 micron, accuracy will be in the range of 0.01 mm.
The main structure is made out of polymer concrete (Rampf systems EPUMENT) with S235Jr steel inlays. The inlays have undergone stress-relief annealing after drilling all holes for lamination anchors. Linear rails and bearing blocks require a perfectly flat and well-defined surface. To create this surface, all functional areas will be machined on a large machining centre in the coming months, then measured. If the surface after machining is good enough, linear components can be mounted and the machine be used.
However, if anything goes wrong, i will either
a) let someone grind the surface (expensive)
b)scrape in all surfaces (extremely time consuming)
Wish me luck!
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