Resolution and cut quality
Hi,
I'm trying to calculate a design for a reduction box and trying to get the right balance for speed v resolution using r&p and DMM Technologies 750w servo and mach3.
I see that cncrouterparts have an r&p reduction system which is either 3:1 for nema 23 or 2:1 for nema 34. I was surprised when I saw this ratio as it seems pretty high considering what I've been building machines to in the past. I usually get around .0025mm using a 5mm ball screw and 200x10 stepper. I have used ahrens stuff before (not his r&p) and imagine he's done his homework with acceptable resolution.
I know there's no standard for resolution but I'm trying to minimise the chance of putting myself in a position where I cold end up with any poor quality cuts.
As I'm trying to use the 750w dmm servo I'm trying to design a speedy system around the 1000rpm using there dyn-2 drive as I can't afford the new dyn-3 drive.
My r&p setup will use a 30mm pinion (30x3.142=94.26mm travel/rev) with a 3:1 reduction will give 31.42mm per rev, ultimately giving a resolution of 31.42/2000 = 0.01571mm.
Working with this resolution and a closed servo setup I am wondering if I could run into any problems with cut quality? My experiences have always been based on stepper motors and a lower resolution using ball screws and not sure im heading in the right direction.
Does anyone have any experience cutting at a similar resolution with steppers or servos please? I'm looking for some reassurances if I can as I'm trying to keep as much speed in the positioning of the machine due to the application however there will also be lots of cutting of arcs in and circles the material and industry the machine is being designed for so cut quality especially the curved edges is important.
Any advice would be greatly appreciated.
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The resolution of the encoders on the DMM servos is way higher than on a typical stepper system, so I don't think you'll run into issues with that. You're backlash or flex will probably be higher than the resolution of the encoder. It is 14 bit resolution (16384 ppr), 12 bit accuracy (4096 ppr) so the resolution can be as small as .0019mm and the accuracy .0078mm...
As for cut quality, I think that's more dependant on the stiffness of your machine, the accuracy of your linear rails, and the power of your spindle...
It depends on the material you are cutting and how good a finish you require.Originally Posted by psiron
I run at 0.01mm on my machine (30% finer resolution than yours) and can sometimes see artifacts on curves and especially on very gentle slopes. However my machine is setup for precision (good rigidity, very low backlash and low runout etc) and I also usually cut in plastics like acrylic that will hold extremely fine detail. My next machine will be at 4 times the resolution ie; 0.0025mm steps.
If you material is soft or rough (like wood) then you should probably be fine at 0.015mm as you would not see any features at a size of 0.015mm. Likewise if your machine is not very precise and you have normal levels of slop/flex/runout etc all will likely be larger than 0.015mm so again you would probably not see any detail at a size of 0.015mm (like Louie suggested).
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