In October 2022 I got a small CNC router. To test it out and push it’s limits I decided to try out Winston Moy’s isogrid coasters.
I designed the coasters in Solidworks – very similar to Winston’s but adapted to the stock I had. I then used Solidwork’s built in CAM tools to generate tool paths. I first tested the paths on some plywood, just to make sure that the feeds and speeds were reasonable and that it wasn’t going to do anything unexpected.
I then moved to the aluminium. An immediate problem I had was chatter. The feeds were too fast for this poor little machine to handle. In addition, the roughing toolpaths that Solidworks generated didn’t play well with the backlash in the axis. The endmill would go straight into the corner of the isogrids and start chattering, pushing them way out of spec. It was unavoidable, even slowed down. Through trial and error I figured out that the adaptive toolpath setting would gently scallop out the corners instead of going straight in, and the finishing toolpath preset would take appropreate passes which didn’t generate too much chatter.
I couldn’t figure out how to fine tune the toolpaths in soldiworks, so I just went with this approach of adaptive and finishing – keeping it well lubricated and cooled. I was halfway through so there wan’t much else i could do.
In the test I did a plunge path round the perimiter to cut it out from the stock, but this generated some pretty bad chatter. Instead I opted to machine away the waste stock since there wasn’t much.
Lot’s learnt… I’d like to try this again and make some functional parts – perhaps out of nylon or delrin. It battled valiantly but I think aluminium is just a too much for this poor little router.
Perhaps if I can fix the backlash I might give aluminium another go.
