[Mountaincraft]

How do you know if you're losing steps?...

Is there a way to test for this?

Thanks,
Mark

[ger21]

The machine's not where it's supposed to be at any given time.

Depending on how bad it is, it can be hard to test for. I ran my machine for months cutting 2D parts with no problems, but as soon as I started doing 3D carving, the Z axis would very noticeably lose steps.

What you can do, is set up a dial indicator, move into it until it's zeroed, than rapid away and back and see if it goes back to zero. Try it for each axis, in both directions.

[Mountaincraft]

Cut 2d type stuff 'usually' ends up like it's supposed to.. esepcially if I slow the feedrate down..

But the V Carving stuff I'm doing is pretty bad..

Homing afterwards can be 1/2" to an inch from where it's supposed to be... The longer and more involved, the worse it is..

What are the causes and remedies? Splitting the project up and resetting the home in between each phase? Slowing the feedrate way down?

[ger21]

What are the causes

Trying to go faster than your motors are capable of is the usual culprit. Although many other issues can cause it, like programs running in the background on your PC.

Either slow the feedrate or the acceleration, or both. Cutting the acceleration in half can help to pinpoint it.

[woffler]

Gerry is right measure with a indicator and see what you get,also you need to determine how much backlash you have in your machine and you can try and compensate with the backlash setup in mach . I assume your running a router as you seem to be running cut 2d. If you could describe your set up and your motor setting and what size motors you are running and if there are any belts and pulleys involved .We need more info to help.

[louieatienza]

You can also disconnect the motors for each axis and check that each axis slides evenly with no tight spots. Even just slowing the accel may help.

You're at a bit of a catch-22 since you need the faster speeds due to your fixed spindle speed, at least for now.

[Mountaincraft]

It might have a lot to do with the file I'm trying to run... It includes a couple vectorized bitmaps of carnations on the stem with leaves.. Probably 6-8 flowers plus a couple smaller flowers.. That seems to be where everything goes haywire..

I just tried it running the job in several parts, saving those for last.. that's when things go screwy..

Currently have
x velocity @500, accel @ 15..
y velocity @ 400, accel @ 15..

running a feedrate of 30 IPM, DOC @ 0.125"
CV 'on' (default setting).. all other CV stuff off...

I need to work through the rest of the V Carve tutorial videos.. Have hardly touched the machining ones yet... Maybe there's an 'ah ha' in there...

It's obvious I'm not gonna get this done in time for saturday... Oh well..
Gonna take a bit...

What does "IJ mode>absolute" do? I tried that last night and thought I saved it with it set to 'inc', but it was set to absolute this morning, and I turned it back to inc and tried cutting a couple simple mirrored rectangles with holes in each corner, and they lined up nice and square.. so I don't know if that's the problem I was having last night or not.. as I also reduced the accel this morning...

[sirkossorg]

I recently had a file I was trying to carve, and it was off zero in x and y by about a quarter inch by the end of the job. Usually, my machine runs quite well and reliably (if not a little slower than I'd like). After going through my mechanicals and finding nothing amiss, I decided to recut a file that I had recently done. I even sped it way up to try and force a failure. Ran fine.

What I found in the gcode was that the file I was having trouble with had a bunch of little micro-arcs where there should have been long straight lines. Now if my machine was perfect, it probably wouldn't matter, but I think I was getting a bunch of micro-stalls that added up.

The root of the problem was with my DxF conversion. I reconverted the file using Inkscape with the Big Blue Saw DxF output plugin, and after that everything was golden. Same exact picture, no issues.

Probably not your problem, but maybe something to consider.

[Mountaincraft]

I recently had a file I was trying to carve, and it was off zero in x and y by about a quarter inch by the end of the job. Usually, my machine runs quite well and reliably (if not a little slower than I'd like). After going through my mechanicals and finding nothing amiss, I decided to recut a file that I had recently done. I even sped it way up to try and force a failure. Ran fine.

What I found in the gcode was that the file I was having trouble with had a bunch of little micro-arcs where there should have been long straight lines. Now if my machine was perfect, it probably wouldn't matter, but I think I was getting a bunch of micro-stalls that added up.

The root of the problem was with my DxF conversion. I reconverted the file using Inkscape with the Big Blue Saw DxF output plugin, and after that everything was golden. Same exact picture, no issues.

Probably not your problem, but maybe something to consider.

It very well could be.. This file has a kazillion little arcs in it... I'm new to the PC world.. If I knew how to zip the file in Windows XP, I'd upload it an have you guys take a look at it... and see what you find..

[ger21]

A file that causes lost steps on one machine may run perfectly fine on others. Every machine is different. Unless you're having a problem with one specific file, it sounds like you need to reduce speeds.

I'd probably try cutting the velocities in half first. If it still does it, then it's probably the acceleration. Cut that in half, and if it cuts OK, slowly increase it until it loses steps again, then reduce it by 25%.

Of course there could be many other issues which make the speed reduction necessary.

[Mountaincraft]

A file that causes lost steps on one machine may run perfectly fine on others. Every machine is different. Unless you're having a problem with one specific file, it sounds like you need to reduce speeds.

I'd probably try cutting the velocities in half first. If it still does it, then it's probably the acceleration. Cut that in half, and if it cuts OK, slowly increase it until it loses steps again, then reduce it by 25%.

Of course there could be many other issues which make the speed reduction necessary.

I've slowed it down to 30IPM with accel of 10... and still have the problems... It's mainly this one file... It has a lot of very small moves and direction changes...

I think.. What makes this all difficult is having to load and secure another piece of wood to try it out after a change...

After a while, you lose track of what is happening...

It seemed to be a lot more accurate before I got rid of the backlash in the X movement though... (except for when it jumped teeth.. then of course it was way off)..

Now the pinion has hardly any play against the rack gear.. but now I'm having all these issues...

Could pulling the pinion 'too' tight against the rack cause this?

[stk2008]

Hey.

Did you mechanically remove the back lash or have you done so VIA MACH3 software compensation?.

[ger21]

I've slowed it down to 30IPM with accel of 10... and still have the problems

Is the feedrate 30, or the velocity in motor tuning? If the feedrate is 30, it's still going 400-500 during rapids.

[Mountaincraft]

I think I took it down to 200 during rapids at one point..

Currently I think I have the velocity set to 500 on the x, 400 on the y, and 200 on the Z...

I didn't think that losing steps during rapids could be a problem, since there are no direction changes or whatever.. But now you have me wondering...

What 'should' I set the motors velocity, accel, and the work feedrate for testing and trouble shooting purposes?

[ger21]

There are no hard and fast rules. All machines are different. It's really a matter of trial and error.

[Mountaincraft]

Now we're getting somewhere..

Although it took forever to move the gantry across the table and ref home it all, I set all three axis to a velocity of 75, an accel of 15, and fed the troublesome file at 50ipm..

it seems to have cut everything as expected.. however, when I hit go to zero, it was off considerably.. I had made an 'X' in the workpiece on the x and y axis before running the program, so that I could see where it was at afterwards..

But, I forgot to check it until I had jogged the router considerably out of the way.. so perhaps it got off then...

This is too slow for this router rpm.. I could see that the wood was darkening from overheat on the deeper cuts...

So I'll try a velocity of 100 next and see what happens.. I may leave the Z at this velocity though... The 'grindy' noise on rapids towards the table isn't as bad at this speed...

Once I find the maximum speed I can rapid at now, I guess then it's a matter of trying different things to gradually get it faster... Obviously, the key is to make small and gradual changes.. changing only one thing at a time between tests...

I might not be able to get things 'that' much faster until I do the rebuild though...

And obviously, certain types of projects will be more forgiving than others...

Thanks Gerry!
:cheers:

[Mountaincraft]

Just found 'another' issue too.. And this one was probably responsible for the "out of square" problem.. and in fact could be contributing to the other problem too..

The gantry was a good 3/8" out of square... I'm almost sure that all the 'tooth jumping' caused it to be racked far enough to knock it all out of whack..

This is why in the early tries on this file, it was 'much' closer to being on the money than it was later, after all the tooth jumping and the subsequent solution..

So, I loosened up all the gantry support to bearing carriages, and moved the gantry all the way against the hard stops at the far end, where I know it would be square to the rails, then I let the motors drop down off the racks, pulled them back up and re-tightened them, then checked that the gantry was now sitting square and re-tightened the gantry support to carriage bolts..

Now it's all square..

I expect things to get better from here... Now I know something to monitor on the table and check that it's always adjusted right...

I think that later, when I do the rebuild, I'll build some large rigid steel 'jigs' to hold everything as it should be when being tightened.. Then I can periodically check and realign everything consistently...

Man, it's gonna be a while before I can start making things for profit at this rate...

I also want to make a custom screen for Mach 3 in the near future that allows me to have all the things I use a lot all on one page. so that I don't have to switch back and forth between screens all the time.. for instance, I want buttons to switch between offsets on the main page, as well as a manual data enter field..

I need to make a zeroing assistant soon for the Z axis too.. as this gets a bit old the way I'm doing it now...

[Treischl]

A couple of things you can do that might help:

1. Dry run your machine without any material in place and the router off and listen to what is going on. You can usually hear a machine when it is missing steps. Sounds awful.

2. When you do that, run a program that does not give you trouble and listen to it, then run the one that is a problem, and listen to the difference.

3. I stopped using programs that "convert" bitmaps a long time ago. Frankly, most of them do a lousy job and I don't give a rat's butt about opinions to the contrary. They are usually full of short line segments and jaggies. If you do one and then do a hand redraw of the same image, you will find out very quickly that the hand traced one runs FASTER and LOOKS BETTER than the one that was automatically converted. And then there are the days like you are having today....where all the "saved time" goes up in smoke as you try to figure out what the heck is happening and why. I have a hard time "saving" an hour of drawing time and then sending out a product that does not look as good as it could or cut slower because I was lazy. Top notch work takes some effort.

[Treischl]

In reference to you last post about getting things to be easier in Mach3?

I know from reading your posts that you are watching your expenditures carefully starting up your business and all. But if you find a $20 bill laying around somewhere, I can strongly recommend you spend it on Ger21's screenset. That will make your life considerably easier.

I have not read your build log, so I do not know if you are using an automatic zero plate. If you are not, and you have a Gecko 540 (others will work too) it is really easy to do, Gerry's stuff has the buttons on the main screen so you can use it. I just installed it the other day and feel like an idiot that I did not do it sooner.

[Mountaincraft]

But if you find a $20 bill laying around somewhere, I can strongly recommend you spend it on Ger21's screenset. That will make your life considerably easier.

Link to his screen set?

I'd definitely like to take a look at them...