Originally Posted by
datac
I just wanted to comment more on the question of using belts rather than direct drive.
The nature of home brew CNC machines is such that the builder more often than not simply does not have the engineering experience necessary to really come to an overwhelming successful conclusion. People have got very lucky at times.
Seriously, there is an awful lot of mathematical calculation necessary to even come close to arriving at perfection. Actually sitting down and attempting to calculate all of the specifics related to the goals of the machine.... weights, inertia, loads, temperatures.....
Then add in the fact that many home brew machines are built with a few parts gathered here, a few gathered there..... often parts not initially desired but purchased because they got them cheap. Nothing wrong with that !
Now enter in the cogged belt and pulleys. One poster mentioned that it was easier to "adjust". This is where they are a benefit. If by chance you get your machine completed with perhaps screws that were not your first choice on available pitch, with a few pulley changes and a new belt, you might have a chance at squeaking out a little better performance, be it faster speeds or the other way, finer resolutions.
One final aspect of using belts is that the machine can often be made a little more "compact". Even some OEM machines over the years left a motor or two sticking out annoyingly past the footprint of the machine or work area. YUCK !!!
Any comments about belts reducing accuracy on a machine typically discussed and used in this forum is slightly misleading. indeed, there is going to be a "measurable" amount of added slop for lack of a better word in a machine. However, that measurable amount is so MINIMAL when using a decent pulley and belt brand its almost silly to even mention it, again, with the typical Router, Engraver or Milling machine discussed here. If your really a NASA engineer probing for ideas on a new telescope lens grinder, then you might have a concern.