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X-carve linux cnc upgrade tuning

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13 May 2016 15:35 #74606 by mrbishop
Greetings all, i'm new to the forums but not totally new to the hobby CnC world. I have had my X-Carve for a little over a year now and with the advise of my friends have moved from an Arduino motion controller configuration to LinuxCNC. I have afew things left to get fully functional but i am currently trying to tune the machine. all the steppers are jogging (more or less**) e-stop works, touch off probe is wired properly but haven't tested it in EMC.

here's where i'm running into issues.

when jogging at low speeds (ie. 10ipm) my machine sounds like a jack hammer, more on Y as there are 2 stepper motors. when i was using the Arduino setup this was not the case. i understand i'm using more amps now and this is an entirely different beast by comparison. but i dont think this sound or behavior is correct. i could be wrong but its making the machine jerk and shake which will equate to pore cut quality long term.


i will have to get my machine config and upload it when i get home in afew hours.


Machine configuration physical:
X-carve
acme screw Z
GT2 pulleys belts X-Y
Stepper Driver kit with BOB


Documentation
Stepper driver kit docs




i am also getting some help from friends online elsewhere i will use this as a repository for information and update as regularly as i can in hopes any help or success i have will aid others.

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13 May 2016 17:41 #74613 by andypugh

when jogging at low speeds (ie. 10ipm) my machine sounds like a jack hammer,


Are you jogging with a jogwheel?

A jogwheel sends (in effect) square-wave position commands. These can be a bit harsh on a machine with high accelerations.
You could try reducing the accelleration, or you could pass the jogwheel counts through the ilowpass HAL component (which is intended for this)

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13 May 2016 17:50 #74615 by mrbishop
not using a wheel. just the keyboard and G1 commands.

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13 May 2016 18:04 #74618 by andypugh

not using a wheel. just the keyboard and G1 commands.


That uses up my easy explanation.

What accelleration settings are you using? Is this a parallel port machine or are you using a step generator?

As a simple experiment, make the step-times 5 x longer. Then if that doesn't work make the accelleration 10s lower. You probably don't want to leave either setting that way, but it might help eliminate two possible sources of the problem.

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13 May 2016 18:06 #74619 by mrbishop
its a parallel port card. all DB25. i posted a link to the exact kit i have in the OP.
I will be posting my config in afew hours when i'm home at my machine. and i will try your suggestion as well :)

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13 May 2016 21:04 #74626 by mrbishop
config attached

File Attachment:

File Name: my-mill.ini
File Size:2 KB
Attachments:

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13 May 2016 22:05 - 13 May 2016 22:05 #74627 by PCW
1. Your X and Y acceleration are likely way too quick (you have 200 IPS^2 which is greater than 1/2G)
this means you get to full speed in about 1/250 of a second! Thats starting off with a bang!
I would start initial acceleration at no more than 10 times the maximum velocity

2. Your base thread is quite slow (16 KHz or so) this is liable to make step generation a bit crunchy
I would see if you can improve your PCs latency so you can raise the base thread rate
Last edit: 13 May 2016 22:05 by PCW.

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13 May 2016 23:48 #74632 by mrbishop
i'm basing my base jitter around the maximum wich is about 50k. this is the best PC i have to throw at this thing at the moment. but if there are things i can do to help reduce my lag i'd love to hear them :)

thanks in advance.

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14 May 2016 02:59 #74636 by geoffs
Based on your configuration and the advice here, I need to do a LOT of tuning on my X-Carve :)

(Gecko G540)

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14 May 2016 03:19 #74638 by mrbishop
more info.
steppers are set for 1/8 th inch 3 amps

i'm learning alot about how all this stuff works the more i dig into this project.

the sooner i get this dialed in the happier i'll be and i can get back to business :)


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