Homing: am I using it wrong?

X-Carve
1

I have the homing & z-probe kit. I thought the advantage there was that I wouldn’t need to reset these things in between carves, even when I had manually moved the gantry, because the machine would re-home itself to know its location, then move itself to the 0x0 position on the wasteboard, at the appropriate height based on the material thickness.

Instead, homing doesn’t seem to get me anything at all. At the beginning of each carve, I still have to carefully eyeball to router bit to the 0x0 point on the wasteboard, and run the full z-probe process.

In easel I see the options “save x/y” and “use last x/y” but neither of these do anything: the machine doesn’t move to old point if choose “use last” and so it doesn’t seem like much has been saved either. I figure I’m missing something, since the zprobe is still useful but the homing doesn’t get me anywhere except a gantry moved slower than I could move it by hand.

3

Not trying to offend, but you need to learn more about your machine to understand the usefulness of homing.

It can save you a lot of time and inconvenience.

There are many threads on this forum that talk about homing and how you can use it to your advantage.

Also, if you don’t consider homing an advantage you can use your machine without homing. You will just need to do some things manually.

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4

Homing / Machine “Zero” => Having the machine “locked” to a fixed location, a reference point. This may not be machine zero because the switches can be left/right etc, hence the brackets.
Work Zero aka Home Position => X0Y0Z0 of your material.

The 0x0 point on the waste board => ignore that because Work Zero / Home position can be anywhere.

You can home the machine, jog it to its intended Work Zero/Home position (or even the waste board 0x0), and hit “G28.1” in the Machine panel. This saves a set of coordinates to the command “g28”, with Machine “Zero” as reference. These values are stored.
If for some reason the carve fails and you need to restart, you re-home the machine ($H) and hit send “g28” and you are at the same point you used as Work Zero/Home Position again.

This is one way, but not the only way.

NOTE - With G28 (and G30) the machine will move in one continuously direct line between its start position and G28/G30 stored value. The Z will not retract before moving in X/Y. So make sure there are no obstacles in the path.

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7

Thanks Bob, if only I’d read you’re reply sooner though. I don’t think I did any lasting damage to my… well, best not mention what. But it’s a good thing I didn’t have the spindle on at the time :wink:

8

Thanks, extremely useful. Exactly the sort of thing I was looking for.

9

I am confused, I thought if the machine was off you can move it by hand slowly?

11

Thanks Phil… I was never aware of that.

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12

Harold hit the nail on the head. Homing the machine when you first turn it on is what makes offsets & soft limits possible. When you turn the machine off at the end of the night it forgets it’s current position in the work area(your table). When you hit the on switch the next time. It “assumes” that’s machine zero. And all of your offsets and soft limits are in a positive direction from that point. Then you have a problem if you expect it to stop itself before a crash. So when you turn it on and send it the home command ($H) if finds the actual machine home position. So if you set an offset fixture at x100 y100 you can always find the x,y of your work surface with the click of a button. I recommend always zeroing your Z. It’s a good habit to be in.

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13

I like to say that homing your machine synchronizes the hardware with the software.

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14

If moving the machine by hand is such a risk, I wonder why there is no cautionary note in the assembly instructions. In trying to diagnose & resolve the X-axis alignment issue I have, I have moved the gantry “a ton”. What should I expect to happen???

15

If you are lucky nothing will happen.

If you are not lucky you will destroy the stepper motor drivers chips.

Certain types of motors when rotated become electrical generators (stepper motors do this). A generator produces a voltage and if it is in a closed circuit current is also generated. If the voltage or current generated exceeds the ratings of the driver chip, then the driver will be destroyed.

gShield users can see this in action as the motor LEDs will flash as you move the motors manually (with or without power applied to the gShield).

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