Squiggly lines- acceleration related?

[Kevin Braat]

So the control computer on my Turnkey 1290 failed and I have since replaced it with another computer. I have reinstalled the software and reapplied my configuration files supplied when first purchased. Something still seems to be wrong with the acceleration settings on cutting lines and I'm hoping one of you sees this and knows exactly what the simple fix is.

1. I did not have this issue before the computer failure.
2. I have verified that the pulley's and belts are tight.
3. The lines having the issue were created using only one node on each end.
4. I reviewed the manual and the only factor out of place I could see was under 'Machine options' - 'Work mode' - 'Cut' - 'Corner acc' was set to 3500 and the manual shows 200. Adjusting to 200 did not fix the problem.
5. The line set is a repeatable decaying asymptote. Rerunning the file gives the same cut pattern each time (see attached picture). The lower line is cut first, then the upper line with the 'squiggle' starting the second lines cut.

Any help would be appreciated.

Kevin Braat

278465

[Bert Kemp]

Could the cartridge wheels become loose.

[Kevin Braat]

Burt,

I'm not sure what you mean by the cartridge wheels. The system runs on some linear slides driven by belts connected to the motors with pulleys.

Kevin Braat

[Kev Williams]

There's a phenomenon I've experienced dozens of times in my life, don't know what you call it, but it's the thing where something develops a problem (like your laser system's computer) immediately followed by another problem (like your laser system's laser making squgglly lines), and we believe that problem #2 is caused by problem #1-- The phenomenon is, in my experience problem #2 is completely unrelated to problem #1 more often than being caused by problem #1!

You may have an issue caused by the computer, but this sounds more mechanical to me...

The lower line cuts first-- does it cut from right to left, and the squiggly line cut from left to right? or?

You need to experiment:

What happens if you pause before the second line has a chance to cut, THEN cut the second line? Does the squiggle still happen?

What happens if you move the lines closer together? Farther apart? Does the squiggle still happen, but change shapes?

If these experiments change or eliminate the squiggles, then you may have a mechanical issue. Like something loose, causing the laser head to wobble from the shock as it stops abruptly before moving to the right...

[Bert Kemp]

ok must be different then mine. My laser head is mounted on wheels , its also belt driven, but what Im basically asking could something have loosened up on the rail, I need a picture. LOL I looked on Turnkey site but I don't see your model .m There website really doesn't show much as far as I can see.

[Dave Sheldrake]

4. I reviewed the manual and the only factor out of place I could see was under 'Machine options' - 'Work mode' - 'Cut' - 'Corner acc' was set to 3500 and the manual shows 200. Adjusting to 200 did not fix the problem.

Did you select "Download CFG" after changing the setting? if not then the firmware in the machine will still be using the old value.

cheers

Dave

[Dan Hintz]

1. I did not have this issue before the computer failure.


There's a phenomenon I've experienced dozens of times in my life, don't know what you call it, but it's the thing where something develops a problem (like your laser system's computer) immediately followed by another problem (like your laser system's laser making squgglly lines), and we believe that problem #2 is caused by problem #1-- The phenomenon is, in my experience problem #2 is completely unrelated to problem #1 more often than being caused by problem #1!

You may have an issue caused by the computer, but this sounds more mechanical to me...

I agree with Kev, though I will go so far as to say it's actually related. It's quite likely your old values prevented heavy acceleration, which hid a mechanical issue. Now that the machine in accelerating more heavily, the previously hidden mechanical issue is rearing its ugly head. My guess is there is some amount of slop in the head track, and once the first line is done, the head is (quickly) brought into line for the next pass... this heavy acceleration/deceleration in the Y-direction is causing the head to rotate (wobble) about the gantry rail.

[Dave Sheldrake]

Dan's right,

After re-reading it's "corner wobble" when the machine shifts in the Y axis to the next line the head is trying to relocate and over adjusting, the same can be seen when you try to turn sharp corners at high speed. Bit like trying to corner in a car at 80 instead of 30, you tend to lose the back end and snake around.

Set your corner accl in machine options / cut to 120.000 Download the CFG to reset the firmware and it should be fine.

cheers

Dave

[David Somers]

Dan and Dave,

Is there likely to be a way to adjust out that sloppiness in the head track and go to the root of the problem? Just curious. Although changing the accl setting is expedient it offends my sense of balance in the world to ignore the cause and fix something like this by changing settings. Of course, the reality is I fudge a fix as much or more as the next person. I just remain offended by the lack of balance in the world as a result! <grin>

Dave

[Dave Sheldrake]

Hiya Dave :)

Yes and no, the steppers on Chinese machines aren't the best in the world but do a pretty fair job, the lack of real power like a servo drive means they will often struggle to keep up with quick direction changes and the weight of the heads often adds to the problem. Chuck in weighty gantries and it all goes a bit pear shaped.

I can do 175mm per second on the smaller machines without losing corner definition but on the bigger flatbeds anything over 75mm per second starts to cause issues (a huge tube mounted in the gantry doesn't help) it all comes down to basic physics really, weight and movement vs energy required to change directions. It's one of the reasons huge tubes aren't always a great idea, even if the tube can cut thick card at 400mm per second the machine just can't supply that speed reliably.

Ball screws and servos seem to be the way to go but by then the savings on a Chinese machine evaporate pretty quickly.

If I need to go really quick I'll use the Galvo's but in general not much I do goes over 60mm per second anyways.

I'm gonna speak to Chris at HPC Lasers over here in the new year and see about getting a servo / ball screw machine to give it a run out and see how it fairs.(that and my Tax return being due Feb means I better buy some machines or my Tax bill is going to be pretty big) :)

cheers

Dave

[Kevin Braat]

So it appears that the Download CFG was the major culprit. The mechanical issue is minor one. Dropping the acceleration to 120 and updating the configuration file returned the straightness to my lines, but looking closer I can see a minor 'squiggle' at the start of lines.

I'll search for the mechanical issue next, but at least I can roll out the prototypes for a model train building I was working on.

Thank you for the assistance everyone.

Kevin Braat

[Dave Sheldrake]

No probs Kev,

Some white lithium grease will help with rail damping and should remove the last of the squiggles :) also check your linear acceleration values as they may be a bit high making the problem more noticeable.

cheers

Dave

[David Somers]

Dave,

When you refer to "the smaller machines" what size range are you including in that. I am guessing a big flatbed is 1500xsomething? Would a 900 x 600 or 1200x900 still fit in your "smaller machines" category?

I ask because I am looking at the 900x600 size. There is almost no cost difference between that and the larger 1200x900, but yeeks! The 1200x900 is large enough for small families to live in.

Dave

[Dave Sheldrake]

I tend to look at anything 1400 x 1200 or smaller as a smaller machine Dave,(Mostly cabinet machines)

The flatbeds go from 2,000 x 1,200 to 7,000 x 3,000 but the common size is 2,500 x 1,500 :)

cheers

Dave