jerky movement when in the g code view.

[cnckeith]

yep definitely need a new PC with better single core thread count so you can run Centroid's G code Smoothing feature.

and if you want to make it even better...

are the axis motors direct driving a rack pinion with no reduction?

the turns ratio in the report show very low overall turns ratio of .637 turns of the axis motor yields one inch. this is out of the cnc router "happy zone" of 1.5 to 2.5 turns per inch which yields the best performance, the mechanical happy zone for a router is at 1.5 to 2.5 turns per inch which yields both good speed and accuracy. (keep in mind these are physical constants, mach really did a dis-service to the diy cnc community by combining steps per rev and overall turns ratio, see this piece. viewtopic.php?f=63&t=1801 )

[avp]

Hi Keith,
Thank you for your reply. New PC is on the way. So I completely understand how the steps per rev. and the overall turns ratio works in this software. I like that approach much better than mach, I agree. So the .637 may seen low but that is how I had to set it since that is the turns ratio of the pinion that is contacting the rack. The motor is driving that pinion with a 2-1 reduction with a timing belt. Unless I am missing something the motor at that point is turning 1.274 times to move one inch. However if I put that number into the overall turns ratio commanded distance is not correct. At the .637 the measurements are right on. I am using Leadshine EM-806 drives set at 3200 microsteps with that 3200 number in my steps per rev.
Bill

[Gary Campbell]

avp...
You are missing something. The correct math formula. I'm guessing you have a 20* PA 20 tooth pinion. I get 0.636620 turns per inch with 2:1 reduction. Much too low for good operation, unless you have a no load need like a plasma, and even then performance may not be smooth.

[avp]

It’s weird. I do have a 20 deg. Pa 20 tooth. I don’t see how it could be any other number. The operation is very smooth with those settings it’s just when I switch to g code view. I’m getting the issue. 3D tabs are a little jerky as well all other motion seems fine.

[cnckeith]

yes most all of the jerky movement is the PC is underpowered.

the turns ratio is secondary, view it as icing on the cake, to make things even better after you get the new PC up and running.

if the leadshine drives are set to 3200 then you must set the Acorn Wizard steps per rev to 3200. the report you provided shows them set to 6400.

once you set the steps per rev properly, then go set the overall turns ratio.
1.274 would be a good starting rough in..then do the measurement commanded vs. actual and adjust according to the instructions.

the machine is close to the "happy zone" at 1.274, would be even better if you could squeeze in a 3:1 reduction to the pinion someday.

[cnckeith]

be sure to set up the new pc according to the instructions to prep it for CNC use.

[avp]

Will do. Yeah the 6400 you see in the report was a temporary change I made. I went back to 3200 but when I sent the report it was still set at 6400.

I will report back when the new pc is up. I may decide to go with a 3-1 reduction but that would also limit my rapid movement some.

Thank you for your help.
Bill

[cnckeith]

at 1.5 turns per inch the machine will fly! how fast do you want to go?

[avp]

It’s a 5x8 machine so I usually like to have my rapids set at at least 1500ipm. Just want to clarify that with the new PC that I won’t have any problems with the acorn software license. Do I just do it the same as I did the first time?
Thank you
Bill

[Dave_C]

It’s a 5x8 machine so I usually like to have my rapids set at at least 1500ipm. Just want to clarify that with the new PC that I won’t have any problems with the acorn software license. Do I just do it the same as I did the first time?
Thank you
Bill

The licenses is tied to the Acorn board itself and not to any PC, so yes, just follow the install directions like the first time with one difference. You can run a report, save it to a thumb drive and once you have the new PC up and the Acorn software installed you can restore the report which will copy over all the settings from your first install. Then install your licenses or you can do it before you restore the report.

Dave C.