Web Goblin cnc has begun

[Web Goblin]

James,
backlash would look like an uneven cut. The finish edge at the corners would be like a wavey line. This happens when there is play in the mechanics of the machine like a set of cogs not meshing together correctly so that when your turn one cog it moves slighlty before the other one moves. In a profiling machine that drives atart to wobble a bit at a change of direction until the machine sort of balances itself out.
t I have found that the best way the check for backlash is to run your machine at a 45 degree cut so that both x and y axis are travelling at the same time ie cut a square but rotate it to 45 degrees on the bed. The corners should be nice a smooth without any wobble in the cut surface. Cutting at 45 also tells if your speeds are the same in both axis at the same time. If they are not you would have an uneven cut surface all the way along the cut.

Ian

[Jonathan]

Whether or not you get a wavy line/arc depends on the direction of cut (climb/conventional), the cutting force and the friction of the slides. Either way you will get a 'blip' on the corners, or wherever any axis changes direction. Here's an example:




The corners should be smooth, but as you can see each corner has a line/offset portion where the axis changed direction. For that part it doesn't really matter - it's still shiny

That was on my milling machine which currently has more than it's fair share of backlash.

This part was made on my router which has very little backlash, so the corners are smooth with no 'blips':