metal chips

Well, I almost made my first part. Almost.

I bought some cheap 1/8" two flute end mills from Amazon. 10 for $11. I am actually quite happy with them. As you might recall when I was cutting wood, with the 1/4" end mill I had I could cut out the big void in the middle and the perimeter, but the 1/4" end mill was too large to make the bolt holes and socket cap pockets. These end mills do the trick, and I only broke one in the process of making those bolt pockets.

I used adaptive clearing, setting a boundary of the outside of the part, with these settings it was able to clear all the holes with the 1/8" end mill. I omitted the center circle because man, that would take a long time to adaptively clear all that material! Here is the adaptive settings I used for the bolt holes and socket cap pockets:

• Under Linking, section Ramp, set minimum ramp diameter to 1mm. This will allow you to mill out a pocket of (end_mill_diameter + 1) 
• Turn off rest machining and ensure it isn't leaving extra stock
• Change the optimal load to 0.75 (reduces loading, prevent snapping)
• Make depth of roughing cut 1mm
• Set "Order By Area" to ensure it finishes one pocket before moving to the next one - otherwise it will do all pockets at 1mm depth, then all pockets at 2mm depth, etc... 
• Adjust speeds. I chose 250mm/min travel speeds, with my mill running at ~ 2000 RPM. If you have a router going faster, you can travel faster

I then set up a separate adaptive clear for the large center hole, and a 2D perimeter cut with tabs. For these I set up a 1/4" end mill. I managed to snap several of the 1/8" end mills trying to do 2D perimeter tests and gave up on that idea for today. It would successfully make a few passes, then bind and snap. I have some culprits (the Y axis is still sloppy, maybe it lets the bit drift and bind). But I figured sooner or later I'd have to entertain tool changes, why not start practicing now. 

Code set up, I kicked it off with ChiliPeppr. I had a few stumbles (y axis grub screws came loose, y axis end nuts came loose - I locktited them) but once I was cutting reliably in scrap aluminum it was time for a clean sheet.

The four bolt hole with socket cap pockets and the two thru-holes cut excellently. The tool change triggered. This part was nerve wracking but turned out to be no big deal. The steppers lock in place and so long as you drive with the GUI you can raise the head up, do your tool change, and drop it back down no problem. Which I did! Once you drop it back make sure you measure the position of the tool relative to the part. You can drop it to zero, align the tool on top of the surface, and tighten up. Resumed the code - a it did wind up binding up on the second pass - the X axis stumbled a bit and the bit gummed up and I killed it. I should have had the RPMs set higher on the spindle. DAMN. What to do.

Well, I decided to generate new GCode which just has the center adaptive clear and the perimeter cut. Instead of referencing the corner of the part, I referenced to the center of the circle. Using a compass, it is easy to find the center of the circle as the starting point. This went well, clearing out the middle pocket, but then it bound up on the second pass of the perimeter. I was using the same feed and speed as the adaptive clearing, but the adaptive clearing only loads about half the tool, whereas the perimeter cut is loading the entire tool. I should have the spindle going faster, or the tool going slower, or take a shallower cut. 

The other culprit is the slop in the Y axis. As it is going along the channel it can drift back and forth and suck itself laterally while still being driven, and potentially gum up the works because the channel depth of cut is deeper than the direction it is being driven.

So close, and yet so far away....

Next thing I am going to do is fix the Y axis coupler, before trying again. But regardless, videos below: