Author Topic: Laser rapid speed limit?  (Read 1267 times)

denmark219

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Laser rapid speed limit?
« on: September 05, 2017, 06:22:46 AM »
All, I modified my banggood A3 to be ~36"x36". I was curious if anyone has tested the limits of how fast the rapid speed can be set to? I'm currently running my rapid at 4500, but that seems pretty conservative. Anyone tried 10,000?  Would like to crank up the rapid to speed up the lasering.


ThothLoki

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Re: Laser rapid speed limit?
« Reply #1 on: September 05, 2017, 06:40:14 AM »
Depending on how dialed in your system is, that may be pushing the limit. T2L has the default max speed set at 8000.
Remember, the faster you go, the more likely your machine will slide or skip steps.

I am very conservative and usually keep my rapid rate to around 2000, but that is probably because my first machine was a piece of crap when it came to speed.
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denmark219

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Re: Laser rapid speed limit?
« Reply #2 on: September 05, 2017, 07:02:27 AM »
I just finished 2, 14 hour panel jobs and I was set to 4500 and had no issues. Because I built a larger machine, I was concerned the added weight of the gantry being larger, I would have issues driving it, but it went fine. I'm going to try a 7000 rapid and see what happens. The resistance on my gantry is almost nothing because I was able to dial it in.

ThothLoki

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Re: Laser rapid speed limit?
« Reply #3 on: September 05, 2017, 07:46:53 AM »
lucky you. I would say about 90% of the issues posted on this forum all relate back to dialing in the gantry and belts.

When you go at a higher speed, keep in mind the acceleration and deceleration settings. If it stops too fast, your axis has the potential to "slide" and end up being 1-2mm off from what you might think "home" should be.
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Lob0426

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Re: Laser rapid speed limit?
« Reply #4 on: September 05, 2017, 10:39:25 AM »
I have run it as fast as 20,000. Someone else ran it at 25,000. The controller maxs at 32,000 I believe.

The limit is the wheels and bearings. At around 12,500 I started hearing grinding noises. This was from the wheels. You can oil them and get them to run quiet at higher speeds. The "But" here is that your machine will walk all over the table at these speeds. So you can only really use real high speeds if you bolt the machine down. Then you still have to contend with the inertia of those parts moving. Accuracy suffers from the vibration. And you really only achieve those speeds when on long runs as the accel/decel settings ramp up movement and ramp down movement.

I found the 8,000 setting was a good compromise. But most set to 6,000.

There are several discussion about speed in the forum.
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ggallant571

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Re: Laser rapid speed limit?
« Reply #5 on: September 05, 2017, 02:19:41 PM »
I suspect the poor Arduino Nano gives out long before that. It has to generate the pulse train for the steppers. Also believe that the motors have an upper limit which is much less.
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denmark219

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Re: Laser rapid speed limit?
« Reply #6 on: September 05, 2017, 02:28:10 PM »
I would be happy with 8,000. I was worried about the momentum as well. I'll run a couple tests and see. 4500 was pretty slow and the machine had no issues handling that.

Zax

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Re: Laser rapid speed limit?
« Reply #7 on: September 05, 2017, 02:54:58 PM »
Are your sizes accurate, meaning you have the steps per mm set correctly?

What controller are you using?

If you change the microstepping you would get much faster motion, the trade off being resolution.

Lob0426

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Re: Laser rapid speed limit?
« Reply #8 on: September 05, 2017, 07:12:19 PM »
I would be happy with 8,000. I was worried about the momentum as well. I'll run a couple tests and see. 4500 was pretty slow and the machine had no issues handling that.

Ggallant571;
I was surprised by homing operations at the high speeds. I did not encounter any stuttering on a single axis at 20,000. I do not remember any with dual axis movement either. BUT, on an A5 machine I suspect I never reached anywhere near the max setting due to ramp up/ramp down under acceleration management. Just not enough room. It was hauling along. But my homing operations are separated per axis, X then Y. I did test returning to 0,0 and moving to the opposite corner with both axis simultaneously. Due to wheel chatter I only tested this below 12,000. Also it should be noted that I run my belt tension tighter than either Zax or Ralph recommend! This was only axis movement No laser.

If you have homing switches;
I did encounter the homing switches being jammed by the X and Y axis slamming into them too fast. The Y axis At 10,000 I had the homing switches jammed about 40% of the runs. At 12,000 it was 100%. And increasing homing pull off did not help. End result is my machines homes properly between 6,500 and 8,000, reliably, depending the machine. The X axis can move faster and work well without jamming up. Mine worked 100% at 10,000 if I remember correctly. I just have not bothered setting them separately.
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laser_cutter

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Re: Laser rapid speed limit?
« Reply #9 on: September 05, 2017, 07:42:15 PM »
3500mm per min
175 laser power

makes for a nice carmel carmel color on craft plywood

ggallant571

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Re: Laser rapid speed limit?
« Reply #10 on: September 05, 2017, 10:07:28 PM »
I do homing X/Y at 150. Suspect it could be faster especially if it did a little dance at the switch trip point.

Burning a square with sides of 30mm at a speed of 1200 mm/min should take about 6 seconds.
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