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Mach3 always hesitates in arcs and circles
« on: September 11, 2017, 07:49:01 PM »
Hi ,


I have something that has been bothering me for months now.

When I am milling splines and circular movements like helix ramping my spindle always moves kind of like in shocks and not in a smooth movement which leaves marks on the finished parts, also it slows the process time. It is like when he mills splines after every line of g3 code the spindle pauses for half a second to continue the next movement. It drives me crazy.

In settings i have read ahead 200 lines on, so why doesn't he know what the next movement is going to be.

(Servo motors, leadshine drivers, )

I really hope someone has an answer to this, or is this an inherent problem with mach3 that a smooth movement in helix ramping without hesitations isn't possible? Cause than I have to look for another system. But I like mach3 so I hope there is a solutions to this.

Thanks in advance all of you
Re: Mach3 always hesitates in arcs and circles
« Reply #1 on: September 11, 2017, 08:39:03 PM »
Hi,
do you have backlash compensation in operation?

Craig
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Re: Mach3 always hesitates in arcs and circles
« Reply #2 on: September 12, 2017, 05:26:48 AM »
Hi Craig,

Where would I find this? This is a setting I don't know where to find.

Stephane

Offline RICH

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Re: Mach3 always hesitates in arcs and circles
« Reply #3 on: September 12, 2017, 05:50:55 AM »
Stephane,

You will find it in Config>Backlash.That is where you define the backlash, speed , and if you want to  enabled  it.

RICH

Offline ger21

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Re: Mach3 always hesitates in arcs and circles
« Reply #4 on: September 12, 2017, 09:34:12 AM »
And are you in CV mode?

You should be in CV mode, with ALL CV options turned off, except  "Stop CV on angles". Turn off all CV options in General Config, and CV Distance and CV Feedrate on the Settings page.

Make sure you are seeing G64 in the status line when the code is running.
Gerry

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Re: Mach3 always hesitates in arcs and circles
« Reply #5 on: September 12, 2017, 04:30:46 PM »
Hi,

I will be looking at what you guys told me tomorrow morning. I wasn't able to boot up the machine today. To busy, I really hope one of these answers will solve this problem for me. Thanks already, I will update tomorrow
Re: Mach3 always hesitates in arcs and circles
« Reply #6 on: September 12, 2017, 06:08:03 PM »
Hi,
I was thinking that backlash, or at least backlash compensation could cause the problem you describe.
The machine will momentarily halt and 'back up' an axis that reverses direction during an arc say.
Backlash compensation would ideally be off and and of course the acutual backlash should be zero or close
it.

Craig
My wife left with my best friend...
     and I miss him!
Re: Mach3 always hesitates in arcs and circles
« Reply #7 on: September 14, 2017, 06:29:56 PM »
I have tried all of the things mentioned and I got it to jerk a little less. By upping in config -> backlash the speed from 20 to 100% (everything else is on O and backlash enabled is not vinked. Also changed CV for angles to 90 it was on 6 before, all other CV options are off.  But the hesitation is still there in arcs. ( For example milling letters in baroque lettertypes)

What else could be helping out so my machine makes 1 smooth motion and doesn't slow and speeds up at every line of g3 and G2.

Hope you guys have some other suggestions.

Also the backlash compensation mentioned above... Where do I find these settings? Cause haven't found any backlash compensation settings anywhere. 2nd thing. When I activate CV feedrate and set to 100 it makes it jerk more.


Thx
« Last Edit: September 14, 2017, 06:31:56 PM by stephanisk »
Re: Mach3 always hesitates in arcs and circles
« Reply #8 on: September 15, 2017, 02:40:53 AM »
Hi,
turn backlash compensation off. Turn CV on.

From the manual:
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Re: Mach3 always hesitates in arcs and circles
« Reply #9 on: September 15, 2017, 03:14:28 AM »
sorry, misclick, from the manual:
Quote
5.6.3 Configure Backlash
Mach3 will attempt to compensate for
backlash in axis drive mechanisms by
attempting to approach each required
coordinate from the same direction. While
this is useful in applications like drilling or
boring, it cannot overcome problems with the
machine in continuous cutting.

Again from the manual:
Quote
6.2.15.3 CV Mode/Angular Limit
This LED is lit when the system is running in "Constant Velocity" mode. This will give
smoother and faster operation than "Exact stop" mode but may cause some rounding at
sharp corners depending on the speed of the axis drives. Even when the system is in CV
mode a corner with a change of direction more acute than the value given in the Angular
Limit DRO will be performed as if Exact Stop was selected. Full details of this are given
under Constant Velocity in chapter 10.

And Chapter 10 as promised:
Quote
10.1.16 Path Control Modes
The machining system may be put into any one of two path control modes: (1) exact stop
mode, (2) constant velocity mode. In exact stop mode, the machine stops briefly at the end
of each programmed move. In constant velocity mode, sharp corners of the path may be
rounded slightly so that the feed rate may be kept up. These modes are to allow the user to
control the compromise involved in turning corners because a real machine has a finite
acceleration due to the inertia of its mechanism.
Exact stop does what it says. The machine will come to rest at each change of direction and
the tool will therefore precisely follow the commanded path.
Constant velocity will overlap acceleration in the new direction with deceleration in the
current one in order to keep the commanded feedrate. This implies a rounding of any corner
but faster and smoother cutting. This is particularly important in routing and plasma cutting
The lower the acceleration of the machine axes, the greater will be the radius of the rounded
corner.
In Plasma mode (set on Configure Logic dialog) the system attempts to optimise corner
motion for plasma cutting by a proprietary algorithm.
It is also possible to define an limiting angle so that changes in direction of more than this
angle will always be treated as Exact Stop even though Constant Velocity is selected. This
allows gentle corners to be smoother but avoids excessive rounding of sharp corners even
on machines with low acceleration on one or more axes. This feature is enabled in the
Configure Logic dialog and the limiting angle is set by a DRO. This setting will probably
need to be chosen experimentally depending on the characteristics of the machine tool and,
perhaps, the toolpath of an individual job

If you haven't got the manual go to the Artsoft site and get it. Manuals work best when they're read, usually several times!

Craig
My wife left with my best friend...
     and I miss him!