I am in the process of building a new large format CNC. I have use plywood to model all the parts for position, size, cutouts, drilling, etc. I am at the stage where I will be able to cut the parts out of aluminum plate in 1/2" and 3/4" thickness. Since most of the processes centre on hole drilling, enlargement, or elongation I was going to peck-drill all the parts first to remove waste using a 1/4" drill bit and then follow that with an end mill to cut to the final shapes. For through holes larger than 1/4" I would do a final drilling on a drill press to the required diameter (using the pre-drilled holes as a guide. Having broken one end mill already, can someone advise on the best router speed, feed depth and feed rate. I am not in a hurry to mill the pieces and so I have estimated that shallow cuts in the order of .5mm would serve me best. However I will yield to the the more experienced to provide their suggestions.
Instead of pecking, you can interpolate (circular ramp) holes slightly undersize, then follow up with a finishing pass. When you do this, you can use the same end mill that you use for cutting, which means less intervention. Another reason is due to the fact that drilling sucks when you don't have torque (sub 5000rpm). You're not going to be able to drill a 1/4" hole in 1/2" aluminum in one shot without plenty of cooling and chip evacuation. If you are making pockets: To better make use of your tool, focus on going deeper with a shallower step over. A 4mm deep pass with a 1mm stepover has the same MRR (material removal rate) as a 1mm deep pass with a 4mm stepover. The difference is that you just wore the endmill down 4 times as much due to only using a small edge. Do not use these numbers. It is just an example. You need to know what tools you are using, rpm range, spindle power, and frame size. For perimeter cuts, you can still use the above method, but it's not efficient. Here is where a shallow DOC (depth of cut) works out. Using an O-flute ("Oh" not zero) works perfectly. IT doesn't have the same surface finish as say a variable flute , but it excels at chip evacuation. You can run a 3mm easily at 500mm/min at a .5mm DOC. I kinda rambled there. What tools are you using?
I am using 6061aluminum. I have a workbee 1510 with a 1/4" router. I am using it to fabricate the parts using a 3 flute carbide upcut bit. Needless to say, all parts have multiple holes - hence the idea of drilling the holes first for chip clearance and then doing the final dressing. I also have air and vacuum to assist in chip clearance. Top
