Hello everyone. I currently have a PM30 mill that has been converted to cnc and am using an omron clone encoder that I have set up 1:1 pulleys off the spindle hooked up to acorn. I have recently upgraded my spindle bearings over to Angular contact bearings from the tapered roller bearings that the factory installed. I will be changing my motor from the factory 90W 2HP DC motor to a 3HP 3Phase AC motor and VFD. With the new pulley combination on motor and spindle I should be pushing close to 14K rpm over the stock motor of 3K. The new motor is encoder ready and I was planning on installing the encoder on the top of the motor where the encoder mount is. What I want to know is the new motor has a top rpm of 5200 at 90hz and the pulley combo I will have a ratio of 2.66 to 1. In the Wizard is there a way to let acorn know this ratio? I thought I found it in the wizard under the spindle settings for high/med & low spindle ratio currently it has a value of 1 in the input box, but I wanted to know if I put the 2.66 ratio in there would that let acorn know my true rpm? I probably can't leave the encoder setup as I have it now with the increased rpms of the spindle. If my changing the ratio won't work, are there any encoders that will work with the high rpms that I will be getting?
Acorn CNC12 wizard spindle window input boxes circled in red
close up of encoder mount on motor
Top cover of new motor with encoder mount
New motor on top of mill
side view with new motor and head spacer block on mill
Your spindle encoder needs to be belted 1:1 to the spindle. You don't give any specs on your encoder, but it's probably only rated for 5-6K rpm max. There's quite a few posts on setting up a spindle encoder and mechanical and bandwidth limitations.
Cheers,
Tom
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Thanks Tom for your reply. I am using a OMRON Rotary Encoder E6B2-CWZ1X . I did find a video of a Tormach 1100 that this encoder was installed on the spindle and I know it does 10K rpm if not a little more. So I guess I will try using my current pulley and belt 1:1 on the spindle.
Tom pretty much covered it.
To use a spindle encoder with Acorn, it must be a line driver/differential encoder. 1000ppr is fine. HOWEVER you need to check the encoder specs as Tom was eluding too. The encoder needs to be rated for the intended RPM both Mechanically (doesn't come flying apart) and electrically capable of reading at a given RPM.
IF the "Omron" encoder you are referring to is purchased from eBay, be aware, its clearly an Omron knock off and I wouldn't hedge my bets that it will last at that RPM.
Also, you really should get your CNC12 software upgraded to the latest revision, 4.50
Your Wizard screen shot is giving away its a REALLY old version of CNC12
Marty
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martyscncgarage wrote: ↑Mon Nov 02, 2020 11:15 pm
Also, you really should get your CNC12 software upgraded to the latest revision, 4.50
Your Wizard screen shot is giving away its a REALLY old version of CNC12
Marty
Marty,
I do have the latest CNC12 software running. I just grabbed a screen shot from an older Centroid video of spindle setup to show the boxes I was referring to. Thanks for chiming in.