I posted Periodic Calibration Loss / Z - axis randomly lost steps in middle of a loooong cut a few days ago about my current carving project: here is an update on what happened next:
It turned out that I was losing steps because the two little nuts that hold the gear head to the top of the z-motor cam had wormed their way lose, and when the cam turned the gear was slipping. Once I figured that out, and go them tightened down, magic was ready to happen again:
I used an 1/8" ball mill for the finishing pass. The model is built in fusion 360, using easel as a gcode sender. The toolpath for the clearing passes was a straight 3d pocket clearing, but for the finishing path it was a morphed spiral. All I can say is WOW! here is another view:
when you are mostly doing flat clearing work, as I have been doing, you do not really get a chance to see the x-carve move in all 3-axis at once while cutting or smoothing a complex shape. Watching it do so, while maintaining the tool contact so precisely, was actually thrilling. It made all of the effort to get to that point worthwhile.
Some lessons learned and things I will be thinking about:
The projects I am working on are weird in that they involve very complex mesh shapes being milled into irregular stock. Just getting the stock defined well enough to generate a toolpath is difficult. Then you have to mount the stock into a table that accommodates very deep-z material so it matches the x/y of the toolpath, which is a bit of an adventure in itself:
here you can see the bit set up for zero: I deliberately set the point on the stock in the single place on the stock that would not be carved and would be left as waste. On the last finishing pass I lost the Zero point, as it snapped off to accommodate the milling head, which ended the milling passes as I no longer had the ability to set zero.
so the thought is to try to set up some other way of defining/recording zero so I can find it again even as I mill the entire surface and lose the physical point. The constraints are that using easel does not allow independent setting of x/y/z: you can only set ‘zero’ once for all three. Also, with a split top table and arbitrary stock placement, a touch plate sort of approach seems like it might not work. I’m literally wondering if I could solve this with a couple of intersecting laser beams. More to follow as I work it out.
As noted, the stock I am cutting into is non-standard. In this case it is literally a piece of firewood. To define it so I could generate a toolpath, I used Autodesk 123d catch to generate a mesh model.
I then had to size the mesh in Fusion 3d so it was the right size to embed the face model into. Turns out I was not too precise in this, but pretty close. There was about 10mm of air cutting happening on either side of the x as the toolpath was written against a stock model that was slightly too big. I did not mind this as it meant that I cut cleanly off the edge of the stock as I had wanted, but it reminded me I need a better tool to generate this mesh model for the stock with and will be looking into that further.
Feeds and Speeds
At one point I had to edit the gcode so I would not have to sit through an hour or two of air cutting to get back to a point where I have been interrupted. It turned out I edited the file down too far: I turned on the mill and watched as it went into the stock and carved a 5 mm deep path straight through part of it at 1500 mm/min. Again, WOW!. I had NO IDEA it could do that: I was still playing with 1mm and 2 mm stepdowns. The notion a high speed pass through the stock like that had never crossed my mind: I thought the x-carve would either stall or snap the bit. So I learned it is stronger than it looks, and more capable than I thought.
so between the model being a first try, the stock being defined very imprecisely, the placement of the stock being somewhat haphazard, and then the multiple passes and technical issues I encountered, the idea I would be at all successful seems very sketchy. The fact it came out as well as it did seems a minor miracle.
some references, just to close this note about this project off:
the message threads that have helped me learn what I needed to know to complete this first project:
Finally: thanks to everyone here for your help in pulling this first project together.
You’ve ALL been really awesome, I’ve learned so much, and I feel like I really graduated from school today because of all your help and support. Thank you so much for everything.