Raising / Lowering table while paused

[John Blazy]

I am going to be cutting thermoformed acrylic panels (20" radius - guitar body faces - about 12 x 19, variable height about 2") and would love to pause the laser then raise or lower it back into focus. The cut is not critical, as it is oversized to be flush trimmed to a wood body.

I would rather not bandsaw the panel or jig saw it as to risk scratching it (although I could mask it), or worse - to crack it during the curved cut due to strain, especially around the horns.

Even if I do cut it with bandsaw, I will be lasering out the pickups, the switch and knobs, which will go out of focus, and would love to pause the program, then adjust bed height, then continue cutting.

Does anybodies laser allow this? Wondering if my Rabbit will.

[Kev Williams]

I can program my LS900 to change table heights automatically by color. Works great for engraving multi-level parts trays and titanium bracelets with 4 focus positions :)

but then, it's made in France, not China ;)

My Triumph has a solid table, no help there--

My old ULS had a manual crank table, no help there either--

but all of my other machines have always allowed changing table position anytime with no problem.
As long as you can slew the table up and down manually, I see no reason why you can't change it on the fly with your Rabbit--

[John Blazy]

Might look into rigging up some manual override. Chalk this up to spending real $ for a quality laser. Thanks for your input.

[John Lifer]

I know rdworks allows pause and once paused, I can change power, change speed. I haven't tried changing z axis. It would take several steps on the controller. But I just installed a wireless remote that I bought when I ordered my fiber, (saved shipping charges whoopee:-!)
And All three axis are available at button push. Guess I'll see how it works while lasering and paused. Don't know about your Rabbit as it is different software

[Mike Null]

You can do that with a Trotec. and program by color as well.

[John Noell]

My LOngtai does not allow for automatic control of Z axis but I have done many parts where I changed height in the middle of a job. As long as the table moves straight up and down... (hehe, it is a low-cost Chinese machine).

[Bert Kemp]

John I pause and raise or lower my rabbit all the time. If Im rastering and want it darker I'll pause and lower it..
Shouldn't be a problem :)

[Doug Fisher]

It depends on your controller and z axis transport equipment (e.g. does it have a stepper motor + controller). Some Rabbits come with a Leetro controller. Newer ones can come with a Ruida controller. Call Rabbit and ask them.

Here is an example from a Thunder Laser unit that looks like it has a Ruida controller. Fast forward to the 1:01 mark.

https://www.youtube.com/watch?v=v2An_tVgvBc

[Bert Kemp]

John I haven't read anywhere where your Z is programmable < I'm assuming its manual controlled Like mine by the up down button on the laser. if you have LaserCut 5.3 and Leetro 6535/6565 DSP control system All you have to do is hit the pause button when ever you want to raise or lower the table, press the up or down button to focus it then hit the start button again.

[Rich Harman]

I can change table height on mine while paused, since the cut isn't critical I think it would work pretty well. My table does not move perfectly straight up and down, there is a very slight wobble to it due to the jack screws not being perfect.

[Dave Sheldrake]

The bigger Rabbits etc tend to use a chain drive on a 240 volt motor here , totally seperate from the normal controller so can be moved while the machine is running or paused

[Kev Williams]

That's actually a good feature- My old ULS with the crank table made it easy to make focus adjustments on the fly, and I did that more often than one might think...

[Dave Sheldrake]

Same Kev, just a tap on the up/down can make all the difference on a cutting job and gets used quite a bit :)

[Ray Scott]

Getting your laser to move the Z-axis during a pause status depends on the vintage. The Rabbit models (similar to automobile evolution) have improved throughout the recent 11 years. Small changes have surface each year, but the major differences are directly related to the Z-axis control.

The early models had automatic control of the X and Y axis, but required manual usage of the "up" and "down" buttons to adjust the table height with an AC motor. The next generation (near 2012) of Rabbit Laser machines had a stepper motor to control the Z-axis. This feature allowed the Leetro controller to perform an "auto-focus". The most recent evolution of Rabbit laser machine is the conversion to using the Ruida controller. The software Manual says that the Z-axis can be moved out of focus using the "pen" mode. My current understanding is that there still is not a way to move the Z-axis during a paused status.

I am sure that the stepper amplifiers are using a control circuitry of "open collector" pulses on the STEP and DIRECTION wires. I think that you could build an Arduino project to take over the Step-Direction pins during the paused status. Arduino, wire, two momentary push-buttons, programming. .... YOU can do this for under $20. ... But it would surely cause the laser controller to lose tracking of the Z-axis position.

This approach to moving the Z-axis would be beneficial to all laser machines that use Step-Direction control. It sounds like a fun project. You might even be able to get a technician from Rabbit to help you.

Thank You,

[John Lifer]

I meant to post update on this also, on the Ruidas the remote control will operate my z axis while running. I didn't realize this till I tried he other day, can be a good feature if you have motor controlled z axis. I don't use the autofocus much, except on big flat sheets, don't trust it enough. This will speed thing up a lot. Only one key to press

[John Blazy]

I'm Jealous of all of you that can change Z on the fly. I am cutting thermoformed guitar blanks and am currently lifting the edges manually with my fingers while it cuts. Gonna use a bandsaw next time.
Thanks, Bert, for giving me hope, but no, my rabbit still won't allow Z movement while in the middle of a job. Will have to call rabbit to see if I can bypass somethng in the wiring.

[John Lifer]

Yeah, I was surprised, but I shouldn't have been. Z is separate motor.... But this goes to my post on these Chinese companies not understanding marketing in he US! Moving this axis during cutting could be potential great to customer, they don't market nor even offered​ it to me! I just noticed in another post and had to dig for information!

[Brian Lamb]

Why don't you write multiple programs? These cuts at your base Z height... everything that would cut at the highest point of the guitar body. Then raise to your middle level and laser what you can there, then raise to the lowest cut and finish it. My ULS laser will hold multiple jobs in memory, so it would be as simple as run program 1, 2 and then 3, manually raising the table to be in focus after each pass.

[John Lifer]

More of a pain, where is your start and stop point, you can have the laser not return to origin, just end cut and probably next one start at that point, but much more difficult to make happen in reality

[Bert Kemp]

sorry John mine does it thought yours would too

I'm Jealous of all of you that can change Z on the fly. I am cutting thermoformed guitar blanks and am currently lifting the edges manually with my fingers while it cuts. Gonna use a bandsaw next time.
Thanks, Bert, for giving me hope, but no, my rabbit still won't allow Z movement while in the middle of a job. Will have to call rabbit to see if I can bypass somethng in the wiring.

[John Blazy]

I think I might take you up on this offer, Ray. When I have some spare time, which appears like . . . next year. The more I think about how useful this Z-axis-change-while-paused feature is for me, especially when I cut warpy curvy stuff all the time and edge quality isn't always an issue, I may be happy to pay you to build this Arduino contraption and send it to me. Will call when ready.

Here is a pic of the part needed to cut with obvious variable focusing.

358425



Getting your laser to move the Z-axis during a pause status depends on the vintage. The Rabbit models (similar to automobile evolution) have improved throughout the recent 11 years. Small changes have surface each year, but the major differences are directly related to the Z-axis control.

The early models had automatic control of the X and Y axis, but required manual usage of the "up" and "down" buttons to adjust the table height with an AC motor. The next generation (near 2012) of Rabbit Laser machines had a stepper motor to control the Z-axis. This feature allowed the Leetro controller to perform an "auto-focus". The most recent evolution of Rabbit laser machine is the conversion to using the Ruida controller. The software Manual says that the Z-axis can be moved out of focus using the "pen" mode. My current understanding is that there still is not a way to move the Z-axis during a paused status.

I am sure that the stepper amplifiers are using a control circuitry of "open collector" pulses on the STEP and DIRECTION wires. I think that you could build an Arduino project to take over the Step-Direction pins during the paused status. Arduino, wire, two momentary push-buttons, programming. .... YOU can do this for under $20. ... But it would surely cause the laser controller to lose tracking of the Z-axis position.

This approach to moving the Z-axis would be beneficial to all laser machines that use Step-Direction control. It sounds like a fun project. You might even be able to get a technician from Rabbit to help you.

Thank You,

[Bill George]

My PlasmaCam CNC plasma cutter used torch height control (THC) years ago when I owned one. The circuit was separate from the cutting program and just used feedback from the plasma cutter for controlling the torch distance above the work.

On a laser machine it could be the same thing only using some sort of proximity or IR distance sensor. Just jog the head over the work, set the distance with arrow keys and lock in that setting. As the head moves it measures that preset distance and adjusts the height. On the plasma cutter since it was much slower than the laser it was easy to do, on a laser time would be a factor. I might add the THC did not need to pause the machine to adjust the height it was done on the fly as it had nothing to do with the cutting program.

The Arduino has the ability to control stepper motors, if you can do the rest. I use one on my blue light diode laser engraver to control the X - Y movement using gcode.