Centroid Acorn CNC: Step Rate and Driver Frequency Interactions
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- Опубликовано: 7 июл 2018
- Please Note: These parameters are set outside of the Wizard. Running the Wizard will reset them back to the defaults.
Parameter 968
Value Frequency (Hz)
0 200000
1 1200000
2 600000
3 400000
4 300000
5 240000
6 200000
12 100000
30 40000
60 20000
100 12000
Parameter 39 - Feedrate Override Percentage Limit
This parameter is used for limiting the upper end of the Feedrate Override Knob percentage to a value from 100% to
200%. This parameter can be used to restrict the Feedrate Override Knob effect on machines with maximum rates
over 200 in/min. The Feedrate Override Knob percentage is normally allowed to go to 200%. However, on machines
with high cutting speeds, if the knob is turned up to 200%, it creates overshoots on corners. If this parameter for
example is set at 110, it will stop the Feedrate Override Knob from exceeding 110%, and thus cause the overshoots to
disappear.
Parameter 146 - Feed Hold Threshold for Feed Rate Override
This parameter sets the lowest value permitted as the feed rate override percentage before feed hold is engaged. Feed
hold will be released when the override percentage is greater than this value. 
Наука
Thanks for figuring this out, it was a big help to me.
Thanks for sharing this info. One of my drives was doing the same thing. This fixed it! Much appreciated!
Great video, thanks for taking the time to post this. The oscilloscope pics really drove it home. so the driver never saw the narrow steps to begin with hence it “lost” them.
You got it. The particular driver I was working with needed a longer step duration in order to be "stable". Otherwise, it would miss some of the steps, especially at extremely low feed rates.
Thanks for your effort. Good info!
Thanks very much for this. I have a zillion questions, but if only one, then: would you choose closed loop stepper drivers over servos for a y axis which employs two motors? Does either alternative protect the y axis from going out of whack? That's two, I know, but thanks for your advice.
Hi. Closed loop steppers and servos would (IMO) be equal when it comes to dual motor Y-Axis machines. Both are excellent when it comes to not loosing steps. Personally, I would probably go with closed loop steppers. Servos are "better" in that they are more efficient and capable of higher RPM, but most DIY machines aren't capable of taking advantage of that extra performance. I've been using closed loop stepper systems on my mill and my lathe and I'm extremely pleased. Additionally, I'd say closed loop steppers are easier to configure than a servo system.
@@FrancoCNC thanks very kindly
What drives did you have? Were they leadshine or leadshine copies?
As I recall, they were Leadshine copies but this is a consideration for all drivers.
( Thank you for your help )Hi Franco I have 2HSS86H Leadshine driver copies, does this setting effect the turning of your drives if you move 0.010” at a time? Or does it only effect the steps when you slow the feed rate down really slow? The only documentation I could find about 50μs is in this below where it says below (this product adopts an optical encoder with high speed position sampling feedback of 50μs)
The HSS86H-KH hybrid stepper servo drive system integrates the servo control technology into the digital stepper drive perfectly. And this product adopts an optical encoder with high speed position sampling feedback of 50μs, once the position deviation appears, it will be fixed immediately. This product is compatible the advantages of the stepper drive and the servo drive, such as lower heat, less vibration, fast acceleration, and so on. This kind of servo drive also has an excellent cost performance.
2. Features
Without losing step, High accuracy in positioning
100% rated output torque
Variable current control technology, High current efficiency
Small vibration, Smooth and reliable moving at low speed
Accelerate and decelerate control inside, Great improvement in
smoothness of starting or stopping the motor
User-defined micro steps
Compatible with 1000 and 2500 lines encoder
No adjustment in general applications
Over current, over voltage and over position error protection
Green light means running while red light means protection or
off line
Imagine your Motion Control Unit (Centroid Acorn Board) is talking and the driver is listening. If the MCU is talking too fast, the driver may not hear every single word - it will miss a few. So, if you are going fast, your driver will miss a few steps and fall short of the desired position. If you are going slow, the driver may not even move because the pulse is missed. My suggestion: Set the frequency as low as possible. It won't have any negative impact on slow motion - it will only limit the max velocity.
@@FrancoCNC the way you explain how this works is very clear and very understandable. Thank you again for all your help! I’m now moving into making tool paths in fusion 360 and am goin to try and machine some things I designed. I’ve Machined parts on my imservice 12x12 cnc router ( I Would almost like to put a acorn on that! It has servos) I have 12 3D printers which I sell parts from them. And I have a millwright cnc mega v plasma/router. So hopefully I’ll be able to pick this up! The hardest part I think is the cam part of making tool paths and stock set up! Have a great Christmas. Paul
Is this issue with just stepper motors? Or is it with servos with encoders as well?
Hi. It can be an issue with any drive/motor system configured to accept step/direction inputs. Most of the closed loop systems I've used (steppers with encoder feedback to the drive) are step/direction types of devices.
Hi franco ive just bought some closeloop steppers for a mill i,m building and i was wondering does centurion software work with fusion 360 if could let me know that would be great thanks Rob uk
Hi. Yes, you can run standard g-code on the Centroid control. Here are some videos you may want to check out.
ruclips.net/video/yfGVdfHlDNg/видео.html
ruclips.net/video/zqgEijP4WTQ/видео.html
Great info Franco!
Thanks Marty. I'm glad you liked it.
Nice i am in the process of converting my pm 25 have you figured out a way to incorporate an encoder i was thinking about the same area the rpm sensor is located
Hi. I haven't worked on that just yet. But, I was thinking you could attach something to the top of the motor where the cooling fan is mounted.
Very nice.