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### Author Topic: Mach3 logic help  (Read 6952 times)

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#### lopata

• 9
##### Mach3 logic help
« on: August 30, 2016, 02:27:07 PM »
Hello fellas cnc enthusiasts.

I have build up a High speed machine in last few weeks, and I am having trouble with understanding Mach3 logic.

My machine setup.

Leadshine easy servo motors with drivers, 4Nm.

Max feedrate 10000 mm/min

Acc: 2000mm/s/s goes up to 4000 mm/s/s without problems, but that is insane acceleration.

Ball screw 2505 C3 precision.

All axis are below 0.01 true, with work table max 420x420x100 mm.

Machine does not stutter and shakes. Cutting in pure motion, without any hiccups.

Few problems which occurred.

1. Mach3 does not cut the same paths on the feed rate on 100% (around 30 mm/s) and on 50 %. How can this be, and why is that?

2. Making a part on CV=180 is not the same as CV=1, or ever CV=0.1 -- Can anyone explain a bit on this.

Questions:

1. Is this common issue with Mach3, and should I consider moving to EMc2 or Mach4?

2. What is the lowest CV tolerance that can be set?  Mine is set to 0.1 mm, but I will be going to 0.01 or even less.

I have been making JIGs for my parts, and to tolerances from that CV is affecting my parts significantly. I should be running tolerances around 0.005 mm on 100 mm range, but there are tolerances greater than 0.1 mm.

The parts that has been cut on CV=180 cant fit my JIGS at all, while parts made on CV=1 can fit but with some convincing.

I have read up all the common issues with CV and Mach3, but I just need an answer why does Mach3 cuts differently on different speeds.

Thank you

Marko

#### ger21

• 6,293
##### Re: Mach3 logic help
« Reply #1 on: August 30, 2016, 03:46:06 PM »
The CV Tolerance setting in Mach3 is not a part size tolerance.
You're best bet may be to turn off all CV settings, except "Stop CV on Angles <", and set that to whatever works best for you.
Mach3's trajectory in CV mode is influenced by a lot of factors. IN addition to the CV options, lookahead and acceleration also have an effect on the trajectory.

High speeds tend to show  Mach3's limitations in it's trajectory planner. High acceleration is the best way to avoid these issues.

This might help explain some of the details:
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

#### lopata

• 9
##### Re: Mach3 logic help
« Reply #2 on: August 30, 2016, 04:32:19 PM »
Hey Gerry

My current setup on the acceleration is 2000mm/s2, which is pretty high. Actually, maybe acceleration is extremely high for the hard aluminium.

Regardless of acc, the sharp corners get rounded. When I reduce the CV, its better.

I dont have the problems with CV as much, as all of my parts are rounded, and there are no sharp corners.

My problem is that Mach3 is making shortcuts when applied with different speeds. For example: If I run it with 30 mm, and slow it down to 50 % of feedrate, the mach starts to be more precise. If I return it back to 100%, it will not be precise again, which is disturbing thought.

Also, I am milling a socket which is 6.2 in diameter, with 6 mm end mill, and that sockets are making troubles, not fitting in the JIG. Roughing and finishing passes, but also finish pass is also a bit high speed.

I could be missing something. What I will try, is to make smaller cutter, and make another jig with new setup of CV.

Image will show you.

First two are my products, and last two is machine while being built.

Will also upload the video of milling.

#### ger21

• 6,293
##### Re: Mach3 logic help
« Reply #3 on: August 30, 2016, 07:57:25 PM »
I've never used EMC (now LinuxCNC), and afaik, Mach4 still has no CV control at all. Although I believe that some CV control was being tested.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

#### lopata

• 9
##### Re: Mach3 logic help
« Reply #4 on: August 31, 2016, 07:32:22 PM »
Regarding the issue I am having. Maybe the pictures will explain better.

First picture was made on 100% feedrate, on around 25 mm/s with CV=180, but unchecked.

Second pic shows the same Gcode but on 50% feedrate, reduced in mach3. Also CV=180, and unchecked.

How can this be and why is it happening?

Tomorrow I will do some test on CV settings =0.000001 units (mm) and will run the same Gcode on same speeds.

In backup, I will give it a go on EMC2 to see how it goes.

I know I am doubling my post on cnczone and machforum, but I really need answers.

#### Davek0974

• 2,607
##### Re: Mach3 logic help
« Reply #5 on: September 01, 2016, 02:10:46 AM »
I have noticed odd things happen when increasing feed rate in Mach, done via code its ok but increasing via feed rate override does odd things sometimes.

#### lopata

• 9
##### Re: Mach3 logic help
« Reply #6 on: September 01, 2016, 03:28:21 AM »
Hello Davek

Well, this is the problem. When I leave my feedrate on 100% (normal speed), it get rounded corners, and when I reduce it gets more squared.

25mm/s was initial settings for engraving end mill. I fuess its 2 fast for it.

Mach3 is just not as it should be. Ita very anoying to have that kind of setup which I cant rely on it.

Moving to emc2 in a few days.

#### Tweakie.CNC

• 8,864
• Super Kitty
##### Re: Mach3 logic help
« Reply #7 on: September 01, 2016, 03:44:07 AM »
Just out of curiosity what values do you have set for Velocity and Acceleration for the X and Y axes in the Mach3 Motor Tuning ?
Are you using the Parallel Port or an external motion controller ?

Tweakie.
KEEP SAFE !

#### lopata

• 9
##### Re: Mach3 logic help
« Reply #8 on: September 01, 2016, 03:55:37 AM »
Hey Tweakie

Velocity is 5000 mm/m

Acceleration is 2000 mm/s/s

For now its parallel port, but moving ASAP on some good motion controler.

By elimination, I will remove the weak points, and mach3 seems to be one.

Will do more testing today with different settings and report here.
« Last Edit: September 01, 2016, 03:59:58 AM by lopata »

#### Davek0974

• 2,607
##### Re: Mach3 logic help
« Reply #9 on: September 01, 2016, 03:56:24 AM »
Yep it's not perfect but still damn good;) You just have to know the limitations between software and hardware i think.