Move gantry manually

I have the new YoraHome 6550-PRO and want to know if I can manually move the gantry SLOWLY to position it exactly where I want to start a project. I could do that with my 6550 with no ill affects. However, the PRO seems to lock the X & Y steppers. Is there a way to unlock them or was the machine built that way so the gantry could not be moved manually?? I used the x-rail and a small framing square to square up the work piece to the gantry.

By manually you mean by hand?

The GRBL config may have the steppers always engaged.

Can you run $$ in Console and return results?

Yes, by hand.

By chance can you give me the $ number(s) to check. I won’t be back in my shop till tomorrow morning.

Just heard back from YoraHome and I won’t be moving the gantry manually. But thank you for your help.

What did they say?

Take a look at the value of $1. This represents the idle time in ms before the steppers will be disabled. If this is set to 255 the motors will be on permanently.

All kinds of bad things could happen.

Jim_YoraHomeTeam

13h

Couple of things to keep in mind here:

Moving the older 6550 manually could have always had ill effects - as the stepper motors will generate AC voltage when they are spinning (I measured 3-4VAC just “flicking” the motor shaft with my fingers) - so you always want to take that into account. We will NEVER recommend moving the gantry manually; rather, use the jog functions to move it where you want. Since the Pro will home on startup, you can always use the starting location to define where you want the laser to start at.

The $1 configuration setting in the GRBL configuration is defaulted to a value of 255 on the 6550 Pro - this means that the motors will stay energized (or locked). Changing that value to a 0 will mean they never lock, and values between 1-254 will be the number of milliseconds before it releases.

Keep in mind this info from the GRBL config wiki - removing the idle delay can result in lost steps, so use this with caution.
#### $1 - Step idle delay, milliseconds

Every time your steppers complete a motion and come to a stop, Grbl will delay disabling the steppers by this value. OR, you can always keep your axes enabled (powered so as to hold position) by setting this value to the maximum 255 milliseconds. Again, just to repeat, you can keep all axes always enabled by setting $1=255.

The stepper idle lock time is the time length Grbl will keep the steppers locked before disabling. Depending on the system, you can set this to zero and disable it. On others, you may need 25-50 milliseconds to make sure your axes come to a complete stop before disabling. This is to help account for machine motors that do not like to be left on for long periods of time without doing something. Also, keep in mind that some stepper drivers don’t remember which micro step they stopped on, so when you re-enable, you may witness some ‘lost’ steps due to this. In this case, just keep your steppers enabled via $1=255.

Note that the dangers of backfeeding current from the steppers is not unique to that machine. This is true for all machines with these motors.

This can lead to problems like blowing out laser modules if they lack adequate protections from this.

So there’s certainly value in being aware of this and avoiding unnecessary movement. However, there’s a false security that disabling idle delay is somehow a fix for this. For example, if the laser is off entirely the laser head is free to move around and is likely to do so during transport or maintenance.

Typically you’d disable the delay in situations where there’s a static load on the motors that would otherwise cause unwanted motion. Imagine a 3D printer with auto bed leveling. Typically the Z-axis motors stay engaged otherwise the bed will go out of level due to gravity.

I don’t think there’s particular harm in this other than higher load on the steppers and drivers but something to be aware of in terms of rationale and impact.