Hi there,
I've decided that my next project is going to be a scratch built CNC surface grinder, as this will be extremely useful for a lot of the parts that I want to make in future. I have a few ideas about the machine, but need some help.
Firstly, some ROUGH dimensions. I will probably need about 400 x 300mm of table travel and about 100mm of z-axis travel. It will be used to grind iron, steel and aluminium (possibly other metals too).
I am planning on using ground bar (somewhere around 30mm diameter) with linear bearings to support the table. This is one of the cheaper options and I figured that it would probably be rigid enough for the application. The z-axis with the grinding wheel will probably use a dovetail or a profile rail (I'm not worried about this at the moment though). I am thinking about using a rack and pinion to drive the x-axis, as positioning accuracy is not too important and it will give reasonably high speeds. The y-axis will probably use a trapezoidal screw, as accuracy is not too important here either (but cost is). I think the z-axis (up and down movement) is the most important axis in terms of accuracy, as this determines the amount to be removed by grinding. For this reason, I think investing in a quality, ground ballscrew and good quality slides would be worthwhile.
When it comes to the powered grinding wheel, I have no idea. I don't know what size wheels are available for this application and I don't know what power and RPM I will need to drive the wheel. Any ideas on this?
I am also planning on grinding a fair amount of aluminium. As far as I know, this is not too much of a problem with the correct grinding wheel and RPM, but I don't know how a non-ferrous part can be held down accurately? Does anyone know how this is normally done?
I am obviously looking for the best accuracy possible. I would like the machine to be able to accurately move in increments of about 0.005mm so that I can get the thickness of parts spot-on. This would mean excellent alignment of all parts and zero backlash in the z-axis assembly. I'm not sure how close I can get to this, but that's the aim.
Finally, is a coolant system a good thing to have when grinding? It is useful to know right from the start so that the necessary spray guards/trays etc. can be built into the machine. I would imagine that dust gaurds are also fairly important.
Any thoughts on my thoughts so far?
Regards
Warren