Does anyone happen to know the max mm/min of the Acro Lead Screw system? My new build is most similar to an acro lead screw - Nema 23 high torque, lead screws, etc - and I'm adding a laser to it. Before I go and destroy it at some crazy speed, wondering if there was any advice on what the Blackbox X32 was capable of running with lead screws and anti-backlash nuts. Yes, I realize that there is also an acro build with a belt system specifically for lasers, but I'm trying to make a multi-purpose system due to space limitations in my shop. I've seen anywhere from 3,500 mm/min to 5,000 mm/min max recommended speed. Any general rules/guidance out there? Thanks.
3500 is a good starting point. Then tweak upward until you stall out. With the stallpoint known, dial back a 20% margin for reliability Repeat same exercise for acceleration
Would you recommend only testing with the x axis? If it stalls out, you aren't torking the machine. If the y stalls out for one of the motors I would possibly twist the machine at high speed. Would you setup some test pattern or can I test all of this using the jog feature on the interface or inside OBControl?
Long straight moves are best to test stalling (accelerate, get to top speed, slow down - reliably) - to get up to speed you need distance You gotta test Y too, what works for X won't always work for Y: either coming up short and leaving performance on the table, or being on the lighter side (just a plate, not a whole gantry) could be too fast - either way.
So a jog motion from OBControl of say 400mm, down the X. Any suggestions for safely testing Y? Is this a hope and pray exercise? Hold a finger on a limit switch until one motor stalls? There isn't any circuit I could put in-line on the power lines to the y motors that could detect a stall in one of the y motors and stop both simultaneously? That would be handy.
I do not think you need to go 400mm. If your acceleration is too high, you will know it very quickly. If you have an e-stop, you could always use that. I would think 50 to 100mm should be plenty. That is not enough to damage the machine. I have racked mine much worse than that.
Are there any limitations using Interface or OBControl? If I jog the machine, will it go to it's max speed? I've noticed that I can get a cut to run faster than a jog on interface, so there must be something limiting it.
You should read the grbl Wiki, or at least the "Configuration" part. It explains how it all works. You can set the max speed of your motors in the configuration to whatever you want. But that doesn't mean they are capable of achieving that speed. They will try though. Grbl v1.1 Configuration $110, $111 and $112 – [X,Y,Z] Max rate, mm/min are what set this. Acceleration and maximum speed rate are corelated. So if -- for example -- you find your machine will cut at a significantly higher rate than say 3500mm/min, but as soon as you increase acceleration it starts to stall, then you may need to decrease the max feed rate. The reason is because the machine is trying to get up to this maximum rate faster with increased acceleration. The magic is finding the balance that works best for your projects. If your cutting passes are really long, then increase your feed rate but leave acceleration alone. That way you optimize the feed rate. If you are doing a lot of short moves and up and down moves, you will never get to the highest rate you set so then faster acceleration is the way to go. If you want a an example of optimized acceleration compare these two items I cut. This video has 4000mm/min as my feed rate, but I had not yet changed the acceleration. Skip to about the 1 minute mark in both since it is most noticeable in the finishing passes. In this later video, I sped the Z axis max rate up a bit, and dialed in my acceleration. However, I can no longer reliably cut at the higher feed rate (4000mm/min) as in the previous video, so I backed it off to 3500mm/min). But overall, the job gets done way faster with the higher acceleration. . If you put them side by side in two separate windows, you can really see how much faster the slower feed rate/higher acceleration is in getting the job done.`1 `
Speed: X axis topped out at 7,100 mm/min working, anything higher and it loses steps, 20% = ~5,700 Y axis topped out at 5,600 mm/min working, anything higher and it loses steps, 20% = ~4,500 Acceleration: X-axis topped out at 220 mm/sec^2 working, 20% = ~180 mm/sec^2 Y-axis stopped testing at 290mm/sec^2, 20% = ~230 mm/sec^2 Interesting, was not expecting Y to have faster acceleration, seems odd doesn't it? Do these numbers look reasonable? After playing some more, I ended up turning it down even more, as rapid accelerations/decelerations followed by acceleration/deceleration can cause the motor to skip. Landed on: X: ~4,200 Y: ~3,600 Acel X: 180 Acel Y: 180
