Sorry for the delay in my promised reply Mr. Kaplan. But as promised here is a bit more info on my tool paths. I hope I do not bore anyone to tears! As a side note guys, I am on a bumpy flight home from Detroit to Houston so please forgive any minor typos.
The mount needs 3 end mills and 7 or 8 tool paths to make. I use a 3mm 3 flute Destiny Tool end mill for the heavy cutting, a 1.58mm 2 flute end mill for the notch and the boring of the tap holes for the inner screws, I finish off with a 3mm 45 degree 4 flute Chamfer mill.
I first clamp down and mill a scrap spoil board flat with a 2 flute 3mm fishtail end mill. This makes sure the stock is 100% flat in relation to the mill. I use wide double stick tape to attach the Alca 5 tool plate 5083 aluminum to the freshly milled flat spoil board. I then load the 1.58mm end mill and attach a lead to it and one to the aluminum stock then perform a g28.2 Gcode command on the TinyG controller. This drives the end mill down to touch the surface and connect the leads whihh stops the Z axis on contact (almost). The controller stops the spindle, but not before dropping a TINY bit more then it should for true 0. So I send a g28.3 Z0 command to ZERO out the Z Axis, then send a G0 Z.375 followed by a G28.3 Z0 command. This raises the end mill up .375mm to allow for the “over run” fof the spindle dropping a fraction of a MM after making contact( I arrived at this number by testing and found it to “start” the cut at a true 0 for my setup). I then raise the Z axis to Z5 and start the first tool path for cutting the pass through on the mount. This is tool path is done in HSMXpress as a 2d contour with runs at .15mm DOC, 75MM/M feed rate and a 2 degree ramp in starting at .25mm above the surface. As each .15mm layer is cut down, it plunges the next .15mm down at 15mm/mm then makes the cut at 75mm/m. Then 2 finishing passes of .05 mm are run at full depth of cut at 75mm feed rate. then a third and final finishign pass is run at 45mm/mm.
Next the 1.58mm end mill runs a boring tool path to cut the holes on the inner lock ring screw holes for an M3 tap. This is run as a spiral bore path at .15mm down cut at 75mm/m feedrate. This is a rather fast bore so I might suggest starting out slower.
Next the end mill is changed to a 3 flute 3mm Destiny Tools VIPER end mill. The smae zeroing out process as above is used to reach a TRUE 0 above the work.
The next tool path cuts the main outer screw recesses. It is a bore tool path at .2mm DOC and run at 75mm/m. It again runs a spiral cut at .2mm DOC. Thhis produces a shallow recess in each of the three screw locations to hide the screw heads.
Next the same end mill is used with the same type of .2mm spiral bore cut to mill the screw holes to M3 pass through specs. This tool path STARTS just above the surfacce of the recess, but below the level of main stock to reduce air cut time and speed the tool paths along. care must be taken to make sure clearance height is allowed above stock level when moving from one recess to the next. The spindle is then moved to Z50 X0 Y75 to allow for tool change.
A 4 flute 45 degree 3mm chamfer end mill is inserted and zeroed out in the above method. Then a chamfer tool path is run at 55m/m then followed by 2 finshing passes at full speed then a third one at .45mm/m for a final smooth finish. Then the spindle moves again to Z50 X0 Y75 and Small #2 wood screws with custom milled washers are installed in the holes of each mount to lock them in place for all tool paths to follow. The 3mm end mill is placed back in and then zeroed out again.
Then the hotend recess bore tool path is run with same 3mm end mill. This is again a spiral bore tool path. But it is run at .2mm at 135mm/m. This is a faster cut due to larger size of the 16mm bore being milled. This cuts a 16mm 3mm wide recess in the stock. This will produce the needed space to hold the E3d heat sink for the mount. Again 2 finish passes are run at full speed and then a third run at .75mm/m.
Then the main cutout 2d contour tool path is run at .2mm DOC and 150mm/m feed rate. This frees the mount from the stock which is held in place by the #2 wood screws. The cut passes .2mm below the bottom of the stock. This tool path has 2 finishing passes of .05mm each at full depth run at full feed rate, then a third at .75mm/m for a smooth finish. The spindle then moves to Z50 X0 Y75 for a tool change to the Chamfer end mill.
The main outline Chamfer is run at 55mm/m then has a final finsihing pass of 40mm/m for a nice smooth finish. The chamfer tool paths are by far the hardest to program and cut. Even the slighest shift in the work will ruin a chamfer toolpath and your piece. It is for this reason that I run them after the last step of each tool path which i wish to Chamfer innstead of runnig all the Chamfers at the end in one tool path. The belts drive system of the Shapeoko just does not tend to produce a fine enough finish if a chamfer toolpath from several steps in run only at the end. I have found much better results by running the Chamfering tool path after each toolpath which i desire a Chamfer on.
Overall that sums up the toolpaths used to make my mounts. All my 2d contours are run without lead ins out lead outs and most have a ramp into them from .4mm above the surface to be milled. All the bore tool paths are spiral boring paths at a given DOC down cut. Care must be taken in reducing feed rates for smaller (narrower) end mills and tighter bores. Too deep of a DOC at too high of a feedrate might cut without breaking on a Shapeoko, but you tend to get a slight oval shape instead of a desired circle. While the same tool path at a slower feedrate wih give a “true” ciircle. Calibrate the Shapeoko often if it mills deep DOCs or higher feedrates in Aluminum. The belts so slightly drift a bit over time and need adjustment and watching to keep things where they belong and help you produce the same results week to week in aluminum. This is done with a dial indicator mounted to the spoil board and measured off the spindle shaft with it off. Command the spindle to move 1/2" towards the dial after zeroing it out on the spindle shaft. Adjust the belt tension and controller settings to make sure you get a TRUE 1/2" on the X and Y Axis… Removing the spindle and mounting the dial to the Z Axis will allow you to do the same for it which is VERY important for milling aluminum since DOC are so very shallow in aluminum milling on the Shapeoko… Also always mill a scrap spoil board for aluminum milling to make sure your stock is flat to the spindle plane. This one step alone along with getting a TRUE zero after each tool change will mak aluminum milling much easier for anyone wishing to give it a try on the Shapeoko.