Tinyg Parameter Questions

Discussion of tinyG control platform
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psppb
Posts: 38
Joined: Tue Jun 17, 2014 7:57 pm
Location: Mlwaukee, WI

Tinyg Parameter Questions

Post by psppb » Mon Dec 22, 2014 4:00 am

I am working my way through the tinyg config files that tgfx uses and for the most part I can figure out what is going on but there are a number of settings I am not familiar with.
I have a dual y axis machine with nema 23 motors except for the z axis because I could not get the kit last fall. The work envelope is 780mm by 550mm. I can jog the machine and run
demo but the machine can crash.
I have decided I am going to use the metric system to simplify things.

Here is a line out of the .cfg file can someone explain what some of the settings are for?

Code: Select all

{"y":{"am":1,"vm":16000,"fr":16000,"tn":0.000,"tm":301.000,"jm":5000,"jh":20,"jd":0.0500,"sn":0,"sx":0,"sv":-1000,"lv":100,"lb":2.000,"zb":1.000}}
What does fr, tn, tm, jm, jh,sn,sx,sv,lv,lb, and zb stand for?

Further into tgfx I find these settings

Current Settings:
Junction Acceleration 2000000.0
Chordial Tolerance 163.8706
Motor Idle Timeout 2.0 Seconds
Inches

ZAxis:
Velocity Maximum 630.0 // Should this change along with the feedrate?
Feedrate Maximum 630.0
Travel Maximum 11.732
Travel Min 0.0

I have no idea what these are. Through physics I know the jerk is the 3rd derivative of a postion polynomial. Could someone explain the rest?
Maximum Jerk 197.000
Junction Deviation 0.002
Jerk Homing 1.0
Search Velocity -39.4
Latch Velocity 4.0 Latch Backoff 0.079
Zero Backoff = 0.039

Thank you very much!
Bill

22" x 32" Shapeoko NEMA 23, ACME screw upgrade, DW660 Spindle with TinyG controller

AlBorland
Posts: 75
Joined: Mon Jun 23, 2014 5:26 pm
Location: Austria

Re: Tinyg Parameter Questions

Post by AlBorland » Mon Dec 22, 2014 5:46 am

psppb wrote: Here is a line out of the .cfg file can someone explain what some of the settings are for?

Code: Select all

{"y":{"am":1,"vm":16000,"fr":16000,"tn":0.000,"tm":301.000,"jm":5000,"jh":20,"jd":0.0500,"sn":0,"sx":0,"sv":-1000,"lv":100,"lb":2.000,"zb":1.000}}
What does fr, tn, tm, jm, jh,sn,sx,sv,lv,lb, and zb stand for?
Tgfx just uses the tinyg config values and groups them by axis, "fr" above corresponds to $yfr in tinyg. Here is a good overview on what is available.
psppb wrote:Further into tgfx I find these settings

Current Settings:
Junction Acceleration 2000000.0
Chordial Tolerance 163.8706
Motor Idle Timeout 2.0 Seconds
Inches
The meaning of junction acceleration, junction deviation and chordal tolerance is described in the link I gave above. Most people leave them at default.
Motor idle timeout switches off the power to the motors after they have not been moving for X seconds (depends on the power mode of each motor $1pm $2pm etc). When the motors are not powered, you can move the axes by hand, but the machine will not notice the change and thinks the axes are still at the old position.
psppb wrote:ZAxis:
Velocity Maximum 630.0 // Should this change along with the feedrate?
Feedrate Maximum 630.0
Travel Maximum 11.732
Travel Min 0.0

I have no idea what these are. Through physics I know the jerk is the 3rd derivative of a postion polynomial. Could someone explain the rest?
Maximum Jerk 197.000
Junction Deviation 0.002
Jerk Homing 1.0
Search Velocity -39.4
Latch Velocity 4.0 Latch Backoff 0.079
Zero Backoff = 0.039
Velocity maximum is used for fast traverses with the G0 command when the machine is not milling (feeding). Good to start low (~400 for screw-driven axes, ~2000 for belt-driven) and when the machine is running stable, tune it up.
While "feeding" (cutter engaged) with gcode commands G1/G2/G3, the machine uses the feedrate that is specified in the gcode file, but it will not allow it to go higher than the feedrate maximum specified for each axis.
[Minimum/maximum travel] is currently not used by tinyg itself, but is used by tgfx to size the tracker area.
[Maximum jerk] takes the place of accelleration, higher values = more accelleration.
The rest is used for a homing cycle if you have limit/homing switches. For example, if you have a minimum limit switch on the X axis, G28.2 X0 will initiate a homing cycle for the X axis:
First, tinyg will move left with the [search velocity] until the limit switch is engaged. Then it will decelerate with [jerk homing], and move X to the right with latch velocity until the limit switch is disengaged again. Finally, from that point it moves to the right for [zero backoff] distance and sets this position to the 0 position for the X axis.
In other words: [Latch velocity] should be very low, [jerk homing] very high (as long as the motors do not lose steps while accelerating/decelerating), [search velocity] also low (so that the machine does not crash into the limit switch or physical endstop).

Hope that helps, and have a lot of fun with tinyg and the Shapeoko!
Shapeoko2, 4xNEMA23, tinyg, Kress 1050, various Z axis modifications

psppb
Posts: 38
Joined: Tue Jun 17, 2014 7:57 pm
Location: Mlwaukee, WI

Re: Tinyg Parameter Questions

Post by psppb » Mon Dec 22, 2014 11:59 pm

You are awesome. Kamra abides
Bill

22" x 32" Shapeoko NEMA 23, ACME screw upgrade, DW660 Spindle with TinyG controller

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