Wednesday, July 29, 2015

CNC Machining Learning

Much of what I am learning is stuff I needed to know with my manual mill.  I have discovered that along with the Chia pet fur from cutting acetal, aluminum is a struggle.  It appears by unpleasant experimentation that I can mill .030" of 6061 aluminum with my fine 3/8" end mill; more and it grabs the workpiece out of the vise.  But it produces a gorgeous mirror like finish.  The rough mill is the next experiment.


Will said...

Either the vise is not strong (stiff) enough, or you have insufficient surface engagement of the block. You can crank pretty hard on alum. You may want to look into getting a selection of hold-down tooling. That would be various clamps and associated spacers and bolts, essentially.

Oh, another possible cause of this would be a lack of sufficient stiffness in your mill's vertical track, and/or the head sliding mount. The cutting bit must be held very ridgedly, or getting precise cuts gets problematic. That, and depth of cut and/or engagement has to be very limited to avoid damage to the part. Also hard on the milling bits and head bearings.

Check the mounting area of the vertical to the base. It may not be of sufficient mass to avoid warping. It's possible you may be able to beef things up by adding judicial amounts of stiffening. The problem is doing so without impeding movement of the head.

Or, it could also be that the table has the same limitations on stiffness. And, it could very well be a combination of the two.

Frankly, it is too small, I suspect. There are three factors that you have to work within with mills. Power, work size, and inherent stiffness of the design. That sort of hobby mill is intended for making very small parts, without time constraints. They have severe limitations, as you are now encountering.

After you get comfortable with the CNC system, I would strongly recommend stepping up to a more full size mill. Check Craigslist and ebay for this. Having more machining capability than you need now is always a good thing. Using equipment that is maxed out regularly is not a good situation. That leads to frustration, damage, and injuries.

I strongly suggest checking this site for info on all your machining questions. Lots of helpful people, and a depth of knowledge that can't be matched. Their archives are very useful.

Clayton Cramer said...

No question the Sherline is not a large professional mill. But the days when you could buy used Bridgeports for next to nothing have passed. Al of these bargains have moved to China.