Maslow Home Maslow Community Garden Newsletter

Calibration question

is there and easier or shorter way to re-calibrate, (especially the chain length between motors routine) or do I have to go through the same process all over again even when I have all the measurements from the last calibration which I was very happy with. I believe I read a post about marking the sprocket, can someone explain how that is done?
like always thanks


Pronominal question!

In version 1.11 which was just released there are two new options which might help.

First, there is now a manual calibration option which just lets you enter all of your measurements by hand. You can access it by clicking Actions -> Manual Calibration


Second, if you want to refine your measurements again without going through the entire process you can now skip the rest of the calibration process and just run the test pattern by clicking Actions -> Advanced ->Run Triangular Test Cut Pattern


I’m a little unsure if I answered the right question. Did I answer what you were asking?


thanks @bar, I’m pretty sure that will, I’m just scared to update, had many problems with downloading GC the first time, if it wasn’t for @bee and others helping me I would have given up.
thanks again


once you finish your calibration, while you still have a sprocket point stright
up (before you move to the home location), mark the link of the chain that is at
the top of the sprocket.

Then you can use these marks and go to the ‘automatic chain length’ step and
rotate the motors to have a point stright up, hook these marked links over this
point, and tell the system that you have done so and that the lengths of the
chains are now known.

1 Like

so your saying I have to re-calibrate first and not use the manual calibration as bar mentioned.

You can use the manual calibration without the automatic calibration if you make some measurements yourself. I used a metric tape measure and a partner’s patient hands to help.

Manual calibration is getting known measurements into the system

the full calibration calculates what some of those measurements really are.

Chain Sag is not something you are going to figure out manually, but you can run
through calibration once and record the value so that you can set it again
without doing the cuts.

with the chain lengths, you have three options for getting them right.

  1. move the sprocket to 12 o’clock, hook the chain to it and feed out the chain.

  2. measure from the middle of the link closest to the sled to the 12 o’clock
    position on the sprocket (doesn’t matter if there is a pin there or not) and
    enter that value

  3. mark a link that has a known length fed out, and use that mark (and a 12
    o’clock pin) to be able to re-create that exact length in the future.


Our Maslow was working great, but now seems a little out of alignment.

When I last calibrated it I drew around the sled, so I know precisely where the sled should be when the machine is commanded to go to (0,0). Now when I send it to (0,0) it’s a few centimetres off.

I did not mark the sprockets or chain.

Given that I know where the sled should be for (0,0) how can I move the sled there and reset the zero position so that the Arduino’s idea of (0,0) matches reality. I’d like to not have to recalibrate the whole thing again.

Thanks in advance.

This probably means that the chain has skipped on the sprockets.

you need to move the sled to the center (left/right) , get the sprockets at the
12 o’clock position, and then tell the machine how long the chains are

the 0,0 position will probably not be at 12 o’clock on the sprockets.

in the settings, you can tell it the chain length to use when manually resetting
the chain length that the machine thinks it’s at, by default it’s 1650 or 1651mm
(it needs to be a multiple of 6.35mm)

you can try to measure the chain with a tape measure and use that.

start by going to the mark for the real 0,0 position and see how close the
sprockets are to 12 o’clock, try tweaking them to get them right at 12 o’clock,
measure the chains, and try setting that. (once you get it right, you really
want to mark the chains so you can reset easily)

David Lang

Thanks for that. I’ve never delved into the calibration settings, and it’s not very detailed in the wiki.

I don’t think we’ve skipped a link. I think what’s happened is we’ve lost connection to the Arduino (i happens) and then reset it without waiting a few seconds for it to store its actual position in EEPROM.

I’m also not sure it is necessary to set the sprockets to 12 o’clock. The internal pulse generator in the motor has no relation to the position of any given sprocket tooth. Would it not be possible to mark the chain and the sprocket, i.e. put a paint line across both so you can see when the chain and the sprockets are in a known position? Then, tell the firmware that it’s at some known position (ideally (0,0)) and then carry on from there?

you tell the system that the chains are at length X and it goes from there.

it’s not just lining up a line on the sprocket with a line on the chain, you
also need to get the sprocket into a known position.

You could have one line on the sprocket and line it up, but it’s easier to be
ble to line up any tooth rather than having to line up one specific tooth.

Matching lines is not going to be easy, as you are looking to position the tooth
to a very close accuracy (1/4mm or better. error in position can be 2x chain
error, and we are working towards 1/2mm accuracy)

David Lang

Ok, before I press the button, can someone tell me (or show me a wiki entry) about setting the chain lengths automatically or manually?

Our Maslow was calibrated properly and working well, but now, as I said, its idea of (0,0) has drifted. I know this because I drew a circle around the sled just after the calibration. The drift could be from skipping a tooth to not writing the last position to the EEPROM after an aborted cut. Or something.

I did not mark the chains or the sprocket after calibrating.

What I want to do is leave the calibration alone, but restore the (0,0) position to the position I drew. Is this possible, and what are the minutely detailed steps to do it please?


Well, I pressed the button, and some partial success was enjoyed.

I clicked on “Set chain length- Automatic” and lo and behold- lovely pictures and helpful text. This needs to be more visible somewhere else.

I disconnected the sled, set the sprockets to 12 o’clock, put the end of the chain on the sprocket and allowed the machine to feed out a known length of chain for left and right.

Unfortunately, and this is probably what our problem is, the chain is gunked up with sawdust (mostly) and doesn’t bend properly. Occasionally it jumps a link!! Who knew?

So, we’re going to clean the chain and try again.

I can see what this procedure is trying to do, and I can see it should work, so I’m hoping a good soak in diesel will fix everything. Thanks all.


Ok. Back in business. Cutting pretty accurately again. Chain is free, and we know to watch out for it getting dirty.