Any way to reduce G28 feed rate (other than firmware)?

I use G28 homing to 0 on a hard origin (aluminum angle) on my MPCNC. However I don’t care for the homing speed of the first touch, feel like I am going to break a tool.

I have tried M220, but that doesnt seem to effect G28s. You cannot specify a F parameter on a g28 either.

Any other way to do this without a FW flash? I know G38 can take feedrate parameter, but that requires FW flash too. For what its worth, im not afraid of a FW flash, I have done it to my 3D printers many times, just lazy I guess.

Alternatively I suppose I could make a dedicated “probe” (steel cylinder) of known diameter to mount in the router. Just adds a tool change.


Or use a broken mill.
I’m not sure how homing to an angle works. I’m on switches and that’s pretty good.

Can you put a (reasonably strong) spring on the homing target so that the breakage risk is lowered without losing precision on the homing location?

You could change the steps/mm and then change it back. I would be worried about unintended consequences.

The firmware is the right way to fix it though. Is there a reason you’re not willing to do it that way? We get a lot of questions about flashing firmware here on the forums, but I think that’s only the few that have trouble, and most get through it just fine.

No reason. Like I said I have updated FW on both of my 3D printers (Anet clone and Ender 3). On the Ender it was a pain because it didnt ship with a bootloader so I had to use a usbasp to load one first.

I assume that isnt a problem with the mini rambo. I was just looking to avoid dragging my old bulky laptop out there, and to have the flexibility to play with the speeds without multiple flashes.

You could try changing the global feedrate with M220, but I don’t think that would work during homing. Who knows? You could also set the max feedrate with M206. That might work.

Thanks. M220 defintely does not work, tried it last night.

I will however try M206 (edit: just looked it up, I think you mean M203). Wasnt aware of that one. It would be terribly easy for me to implement a G code solution as I use a custom command routine within Octopi to do my homing. I can simply bracket the homing codes in M203’s before and after and it will all still happen at the push of one button. IF it works.

I will try this tonight and if it doesnt work I will flash the firmware.


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Greaat success! M203 worked a charm. My homing routin now looks like this:

G92 Z0
M203 X6 Y6
G28 X R0
G92 X%(rad)s
M203 X50
G0 X15 F2500
G28 Y R0
G92 Y%(rad)s
M203 Y50
G0 Y15 F2500
G0 Z30 F2500

The button in Octoprint shows:

So I just type in the tool (or probe) radius and hit go. As far as I can tell arithmetic is not allowed in the custom control editor in octopi, or else I would type in the tool diameter (and in english units).

The tool touches this:

However I do need to make my gantry squaring procedure more repeatable, and re-shave the aluminum blocks to match the square of the machine. I did have squareness issues on a recent job over a 22" cut. I’d like to see if this can be improved on my big machine. I also need to modify these plates to use a c-sink screw, I believe that clamping material and bumping with the tool has caused them to shift slightly.


As I sit here thinking about it, I probably want to go ahead and make probes. By reducing the speeds, I’ve increased the torque at the steppers. If I forget to place the probe on the tool (it has already happened), rather than crashing and skipping steps, the tool will probably snap. It is probably still worth slowing down, but it would be a shame to break a tool by homing the machine…