Rapids on a xcarve 1000 with easel

Is is possible to increase or set the speed of the rapids on an xcare 1000 with the new X controller in order to shorten the project cut time?

The speed for rapids is controlled by grbl paramters $110 through $112

$110, $111 and $112 – [X,Y,Z] Max rate, mm/min

This sets the maximum rate each axis can move. Whenever Grbl plans a move, it checks whether or not the move causes any one of these individual axes to exceed their max rate. If so, it’ll slow down the motion to ensure none of the axes exceed their max rate limits. This means that each axis has its own independent speed, which is extremely useful for limiting the typically slower Z-axis.

The simplest way to determine these values is to test each axis one at a time by slowly increasing max rate settings and moving it. For example, to test the X-axis, send Grbl something like G0 X50 with enough travel distance so that the axis accelerates to its max speed. You’ll know you’ve hit the max rate threshold when your steppers stall. It’ll make a bit of noise, but shouldn’t hurt your motors. Enter a setting a 10-20% below this value, so you can account for wear, friction, and the mass of your workpiece/tool. Then, repeat for your other axes.

NOTE: This max rate setting also sets the G0 seek rates.

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Thanks Larry, I guess that I need to read-up more about how grbl controls each axis. I’ll give this a try and see what happens. I learn something new with every project that I cut on my xcarve! I’ve see videos of cnc machines running unbelievably fast rapids. Is this because they are not using a grbl controller? Since the x axis is usually the one controlled by splitting the signal and reversing the polarity, what type of controller would be necessary to run 4 truly independent axis? Thanks for letting me pick your brain!

The limit on speed for the X-carve appears to be the mechanics of the X-carve. You can raise the speeds up to where the X-carve frame just can’t handle it unless you have heavily modified the machine. That just moves the limit up, doesn’t eliminate it.

Grbl is limited to 3 axis of motion at this time. The lead programmer has said that he would like to move to 4 axes in the future.

I’m not sure, but I think that you could move to something like Mach3 to get true 4 axes support. That program is in a different class of motion control options and doesn’t use something like grbl to interface with the hardware.

GRBL isnt the main factor here.

You have two types of motors found in CNC’s :

  • Stepper motors (typical multipole, 200step/rev)
  • Servo motors (regular brush/brushless motor design)

Stepper motors have steps which act as a reference point to it can “count”, they are cheap, reliable and strong. They are however speed limited, typical 1200rpm/min. Torque at speed also reduced so the stepper may stall before ever hitting max rpm.

For a 5mm/turn linear screw = 5mm x 1200rpm = 6000mm/min max.

For a belt machine the mm/turn is higher => higher rapid potensial.

Servo motors require encoder to provide “step” but are not limited 1200rpm, they can go way faster and dont loose torque at speed like steppers. They are more costly though.

To indcrease speed on steppers you need more torque and/or more input voltage. The Xcarve PSU is 24V, if one where to use a 48V system on the same steppers/CNC one would in theory achive 2x rapids.

The stepper drivers for the Xcarve dont support 48V though, but a 36V may be viable.