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Author Topic: Sherline speeds direction transition  (Read 3934 times)

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Sherline speeds direction transition
« on: February 09, 2014, 09:21:56 PM »
Hello,

I'd like to figure out how to increase the speed on my mill. The purpose is to decrease job times. I'm using the stock steppers and control box from Sherline. I have success with increasing IPM in the CAM software as well as using the feed rate override. I still see a slow down in direction change.

Would i make adjustments in the motor tuning screen?
Increase backlash rate?
Is it possible?

I have included a video i have found on you tube by Neo7cnc. I have asked him about his setup with no reply. Any thoughts you have are appreciated. I have looked at his posted specs. From what i can tell he i using steppers.

http://www.youtube.com/watch?v=7jY-_rR4Yg4&list=PLFc8_pNqVayKjZOWfq7PzxyowhobPZPae&feature=c4-overview-vl

Offline Fastest1

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Re: Sherline speeds direction transition
« Reply #1 on: February 09, 2014, 09:47:39 PM »
Do you run Mach 3 in this machine? (I am guessing so since you are here). Are you familiar with it settings?

The motor tunings will alter quite a few things, distance traveled and the speed and acceleration at which it does so.

Yes you can change the amount of backlash to be compensated for and at which speed it does take this slack up.
« Last Edit: February 09, 2014, 09:51:52 PM by Fastest1 »
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Re: Sherline speeds direction transition
« Reply #2 on: February 09, 2014, 09:52:20 PM »
Fastest1,

I do run Mach 3 on my sherline. I have looked at the settings for the motor tuning. Am i on the right path? I suppose the next step is to make some adjustments and see what happens.

Thank you,

Offline Fastest1

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Re: Sherline speeds direction transition
« Reply #3 on: February 09, 2014, 09:56:40 PM »
I dont understand why you linked this video? That is a CNC router I believe. Maybe a 3020
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Offline Fastest1

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Re: Sherline speeds direction transition
« Reply #4 on: February 09, 2014, 10:03:21 PM »
I thought Sherline used flashcut?

Anyway yes, go into Config/Motor Tuning, only vary the velocity (the max speed you desire the axis to go in a rapid) and accel (how quickly it gets up to that speed). You will hear the difference in the song. As you listen to different machines on YouTube the people with higher accel rates sound entirely different.

Also go to config/general config and check Constant Velocity under the motion mode area. This will keep the machine running a more continuous speed. on the right side of that same page, change the "look ahead" to 100 or more.
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)
Re: Sherline speeds direction transition
« Reply #5 on: February 13, 2014, 07:44:40 PM »
Fastest1,

Router or Mill i don't believe there is much difference in the motion systems. Granted there is belt and rack and pinion. The router in this video is lead screw driven. I looked at his description he is using Mach3 with steppers as opposed to servos and it was the best example i could find. I believe i need to tighten up my backlash up a good bit.

No, Sherlines can be run under number of control software and driver boxes. I have seen Linux based emc2 as well.

Thank you for your input.

Offline Fastest1

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Re: Sherline speeds direction transition
« Reply #6 on: February 13, 2014, 10:51:06 PM »
I have seen Sherlines run everything too, however the cnc packages from Sherline are what I was talking about. Isnt flashcut totally different that Mach? I dont know but I do know how to tune Mach.

Did you mess with your velocity and accel settings and see the difference?
I want to die in my sleep like my grandfather, not like the passengers in the car! :-)
Re: Sherline speeds direction transition
« Reply #7 on: February 14, 2014, 06:46:16 PM »
Oh Flashcut is a CAM program. I thought it was a machine controller; My error. I use SolidCam.

CV Mode is on. Changed the acceleration to 30 in motor tuning. The mill still slows for the backlash comp. It was faster but not what i was looking for. Take a look at the video below. When the circle is being cut i don't see any noticeable change in velocity as the circle is cut.

http://www.youtube.com/watch?v=itqz-7T-24o

Offline RICH

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Re: Sherline speeds direction transition
« Reply #8 on: February 14, 2014, 09:18:49 PM »
Quote
how to increase the speed on my mill

Increase the velocity until it starts to skip. Then back off by say 30%. You can only run the steppers so fast before they won't have have
adequate  torque left to do cutting. It is more important to have reliable machining then the fastest speed.  

Once a velocity is found now start increasing the acceleration and see where it skips. Again leave some headroom on the accel.

The  50-50-50 rule which you may want to consider for backlash is as follows:

50% - The max velocity is 50% of where your steppers will start to skip
50% - Set the shuttle Wheel setting in configuration to .0050  to .050 ( .5 too slow )
50% - Backlash speed

RICH

Re: Sherline speeds direction transition
« Reply #9 on: February 16, 2014, 12:51:16 AM »
Rich,

Thanks for the info. I did have a motor stall while milling some parts which ruined them. Obviously running too fast. I did take out a lot of backlash mechanically. I'm running with backlash comp off with pretty close tolerance. It's nice to see the smooth transitions with minimal slowing while rocketing along. Job times are much faster.

Is there any benefit in adjusting the Gs?

I have a video of the smooth transitions. Pardon the shaky cam effect.

http://www.youtube.com/watch?v=O-l6XndKqus