Feeds pushed to the limit. How fast can the X-Carve move?

X-Carve
1

Hi there,

We’ve got a set of 3 500mm X-Carves (2 original, 1 new one with the X-Controller) and we’e been running them pretty hard for the past year. They’re amazing machines and they’ve hardly ever let us down.
I’ve had the feed rates in our toolpath generator (ASPIRE) set to 8000mm/min on the X&Y and 500mm/min on the Z axis.
We cut really soft material so in theory we can be cutting much faster than this (25-50% faster). The forms we’re cutting fits in a 45x45x25mm envelope and we run a 3D finishing pass over them which take on average 5 minutes. The real limit to improving cut-time seems to be the speed on the Z-Axis as it rises/ plunges over the contours of the form.

I chose to do some testing on the newer X-Carve we have as it has the Nema 23 motors and more powerful drivers.
The grbl limits in the firmware are set to 8000mm/min maximum and 500mm/min for the X&Y and Z axes, so I changed these in universal g-code sender to 10000mm/min and 800mm/min. All good - an improvement of about 30% in speed. Amazing how quickly it can move!
When I increased it further to 12000mm/min and 1000mm/min the X and Y axes could cope but the Z Axis motor couldn’t keep up. If you moved it 30mm up, it would shoot up about 20mm then do a high pitched whine/ power down noise, so in fact it would only move about 22-25mm.
I noticed that you can also change acceleration rates for the axes to adjusted these but still sometimes get a kind of run-off situation from the Z motor.

As the motors I’ve got are the standard 140oz NEMA23, I’m wondering if I can get a better result from putting on a larger 262oz motor on, since we’d have more torque to work with. I’d have to raise the Z axis up 25mm to accomodate for the larger motor but if it gives us more speed we’d be keen to try. We’re a business so faster speeds = higher output and lower operating cost.
I also assume electronically it’s compatible with the X-Controller.

Now to the question:
Does anyone else have experience / stories with pushing the speeds of the X-Carve to the limit? Does anyone have an idea how fast it can move? And has anyone had the same runoff noise from a stepper motor?
Note I’m asking about feed-rate, not rapid movements

Thanks !

Chris

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Hi Phil,

All great suggestions -Thanks! Indeed I know that for most of the movements the motion doesn’t even get near enough to top speed as they’re so short, so as you say we hit acceleration limits.
Does the 269oz motor fit for the z-axis by just moving it up or did it require further work to fit?
I’ll keep this test on the X-Controller machine.
A new lead screw with a bigger pitch is also a great idea - and I’m sure I’d need the bigger motor for that.
Having bigger pulleys is a good shout too - what would I need to do in the firmware if I had a pulley that was say 50% larger than stock? Just a change in steps per mm?

Also out of curiosity what were your reasons for your changes in z-axis pitch and new belts? faster movement or because you’re milling some tougher material?

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The max rpm for a stepper motor is 3000 rpm, so for real high speeds you might need bigger pulleys. Sadly bigger pulleys reduce the torque. Double number of tooth on the pulley = half the steps per mm.

Also motor torque degrades quickly with the number of microsteps. If you want to move faster on the belts you might reduce the number of microsteps and adjust your settings too. Accuracy will be less too, it is a trade off.

The ACME rod seems to have a speed limit of 500 mm/min, I tried faster but that was not a success. I just completed a re-design, 8mm dia 2mm pitch ballscrew and NEMA 17, 2,2A motors, did some testing today and at 1000 mm/min accuracy is still very good.

It is not the speed that is the limiting factor, the accelleration multiplied with the weight is the power you need to put into the machine. So choose the lightest spindle that will do the job.

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Just wanted to share my data for a similar setup as I have ACME T8 rods for all axis.
Single X-axis motor (Nema23 @2,6A (rated 269oz@2.8A)
Dual Y-axis motor (Nema23 @2,6A (rated at 140oz @2.8A)
Single Z-axis motor (Nema23 @2,6A (rated 269oz@2.8A)

My max feed rates are 3000mm/min for X&Y and 1500mm/min on Z.
Acceleration is 200 (GRBL value) for X/Y and 100 for Z.
Running half step on all.

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