Maximum Inches per minute?

I am trying to determine the max speed the XC can move the spindle in the X/Y axis

Does anyone know the max RPM the Grbl is capable of driving the steppers at?
Or how many steps/sec the Grbl can generate?

Starting to juggle after 338 IPM.

Wow, have you really seen it move that fast, was it cutting anything or were just dry testing it?

Nooo I didn’t cut, just the speed test.

And nothing came flying off?

No. It’s just humming after 338 or 340. Even after tweaking the pods.

My opinion is, top speed for cutting ; MDF 200, Plywood 100, Hardwood 70, Plastics 70. That’s my figures. Depths per cycle depends on bit diameter and chip loads.

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Good to know, thanks for pushing the limit. I don’t think I am brave enough to test mine moving at those speeds.

I did cut pine at 140 ipm with a 6mm endmill with a DOC of 2mm and it actually cut very well. Now that I understand the chip load/feedrate and spindle speed relationships I have realized that slow feed rates are really bad since the Dewalt does not have a “slow” speed setting.

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Yep, sometimes you have to run from fire. I never use any speed dial over 4. Mostly between 1 and 3. But feed rate you need to keep your bit cool enough. You may do several extra turn, no big deal. Don’t rush it. Shallower depth + fast feed rate = clean cut.

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It would be fun to see a video of an XC moving in circles (not cutting) at 300 inches/min.

Seems like Inventables should make that video to show how great the machine is.

This is 300 IPM

That is not even scary. It looks like it should be able to MDF at that speed.

I am also impressed with how clean your machine is. Reminds me that I need to clean out all the crud from my vwheels

This one is 350 IPM. No fail. Don’t want to go higher.

Here’s a video that demonstrates the ShapeOko 2 running at 35,000 mm/min or about 1380 in/min. I made this a while ago to demonstrate how fast Grbl v0.9 could go. I would highly recommend never running your machine this fast. I had to loosen the eccentric nuts to minimize the friction and crank up the amps on the motor driver shield to its maximum.

In practice, 5,000 mm/min(200 in/min) is plenty fast and gives you enough time to react to a problem for a small 500mm machine. At 1000mm, a little faster will probably be ok.

And, here’s a experimental video of a Shapeoko2 cutting pine at 15,000mm/min (590ipm) with a special high-speed machining(HSM) toolpath. Don’t try this without HSM or you’ll break bits or something else expensive.


Thanks. That far exceeds what I thought Grbl and the steppers were capable of doing. What frequency is the Grbl running at in order to send that many steps per minute?

About 23.3 kHz step frequency with 1/8th micro stepping on all axes at 40 steps/mm. Grbl could technically go faster, up to 30kHz, if the machine would allow it.

I have new respect for the mighty Grbl. That is very impressive.

Does the Grbl have limits for the acceleration allowed on each axis. For example if I send gcode that tries to move the X axis 20 inches left at 600 inches per minute, does the grbl try to go from 0 to 600ipm instantly or does it limit accelerations to … say 190 inches/sec^2 (half g) ?

Hmm. I haven’t explicitly tested this, so I’m not 100% sure what would happen if you cranked up the accelerations. However, the video did show 4000 mm/sec^2 (157 in/sec^2) accelerations. Grbl generates steps as constant velocity segments about every 8ms. If an acceleration from 0 to 600 ipm is less than 8ms, Grbl should go instantly from 0 to 600 ipm.

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Has anyone actually calculated the perimeter of a toolpath with the time it takes to run to verifying it’s actually running at the set feedrate?

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