Unreliable connections for UTM

I have had constant issues with the connections between the water head and the UTM.

If the tool head is loaded by the load tool sequence, which is very gentle in the load, the connection is not detected. (About 50% of the time). I have confirmed this numerous times and used the ‘verify’ button to confirm.

If, I manually load the head, which is not so gentle, the connection works reliably.

It is driving my bonkers as it is not reliable. Any ideas anyone?


We overcame that exact issue by upgrading the magnets to the thicker more powerful magnets. These magnets :point_down: are the ones that are used on the rotary tool, but they solve the reliability issue because they press harder on the UTM pins.

Also, here is the troubleshooting page for UTM problems:

This is what I was thinking. Upgrade the magnets but I wanted to know if I was alone on this. A firm click, and the connection is made. A very gentle programmed ‘touch’ and extract and it does not make the connection.

It is a shame that it is unreliable, as unreliable things drive me crazy.
I need reliability and consistency over everything else.

I ran through the UTM debug list but it made no difference.

My two unreliable things are this and a constant Z-axis stall (which is also driving me mad)

No you’re not. We have the same problem and the unreliability of the tool mounting is the single reason why we have not further progressed with our Farmbot usage. Surprised the stronger magnets are not supplied as standard but we will try these.

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This is a little bit worrying. I did see that someone came up with a permanently watering head that wraps around the UTM. This solves one of the issues of needing to change heads just to water. I kind of like that solution as it is elegant - but it needs to work.

I totally enjoyed the build experience. It was fun. However, I want (Need) something that works every time. I am going to continue with FB for now but if required I may redesign they UTM head and use an optical encoder for the detection - but if Magnets work - that would a whole heap less work.

FB - It appear that there are issues of reliability that need to be address.

@captainsemtex - Have you had issues with Z-Stalls? I lubed my Z axis and not it cannot hold itself up without always being power which appear to cause overheating and motor stalls.

Fortunately no. We have lubricated the Z-axis but we used dry graphite powder and that seems to have worked well for us. No Z-axis issues.


You can also eliminate tool switching for the watering tool by using this simple 3D printed part as a permanent water nozzle. Because watering is such a common activity it is best to make it a permanent tool like the camera. The part STL is available on thingverse.



My two unreliable things are this and a constant Z-axis stall (which is also driving me mad)

For the Z-Axis Stalls, check your motor current setting and change it from the default of 58% to 100%. Also you can spray your leadscrew with graphite lubricant like Jig-a-loo Graphite Extreme.

Change them all to 100%.

Here is the product that you want to use on the leadscrew. Just don’t spray the top 6 inches or where it connects into the Z-Axis Motor shaft coupler.

Same issue here, mounting the tool with alternative movement sequence. Tilted the toolmount a bit backwards (1 to 2 mm over the 50mm distance the tools slide (really) in), prevents the tools from falling out. When moving the UTM above the tool it clicks the tool in and pulls it up.
BTW the sequences first Home to 0, then Find Home to have a reliable start for mounting.

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Yes. I have tried that. Even when performing a watering sequence where there is no Z-axis requirement except to ‘hold’ in place I am getting Z-axis drops which triggers a Z-Axis stall. The motor (or driver) is giving up dropping the Z-axis, detecting the fault then recovering.

When the Z-Axis was stiffer, before lubrication, Z-axis was not powered all the time so I think it had enough thermal headroom (or whatever it is) to cope with moves. Now it is powered all the time, it runs hot and Z drops.

And yes on the lube I used/ Same stuff.

This is a good work around and to be honest, as watering is the majority of the FB work, it makes sense to implement it. I think I will go down this route.

Part of me needs to solve the unreliable UTM connection as I expect things I buy just to work. [I know this is not a consumer product. I get that but it is not a first generation product] Unreliable things I tend to throw away as they are a constant source of frustration and life is too short to deal with annoying things on a constant basis. I don’t know how reliable the other tool heads are so I think I am going to play with loading and unloading other tool heads and experiment with the stronger magnets to see if that also helps. In the end, we all want (need) reliability as that was the point [well for me at least] of making a robot to grow things for me. Yes it is a hobby, but I would be prefer to experiment and grow and expand the system rather than having to constantly check on it to see if it is still working.

I want FB to be successful as I want FB to be around forever, as it is good for everyone. If FB gets a bad reputation for not being reliable, it could kill the business then we are all stuffed.

At the moment, I have two reliability issues. UTM and a Z-axis that drops at random intervals. (like the motor just turns off then recovers most of the time with a Z-axis stall). I don’t know the answers but I am going to keep pushing to get solutions as that is good for everyone in the long run. If a simple magnet change on the tool head solves that problem, then FB need to upgrade their product offering accordingly to the feedback. I have already recommended a second power setting for a ‘hold’ for X,Y and Z axis which is likely to remove the load from the motors as they can be at a less power rating when ‘holding’ and can step up the power when a ‘move’ is required. It makes sense as it is good design principles. Why would you run something at 100% of load when it is not required? I am hoping the recommendation is adopted but I understand FB have a backlog of ideas and limited programming resources - So I will probably have to wait. :sunglasses:

Just printed the part. Will mount it as soon as the weird channel nuts come from FB.

Thanks to the person who suggested adding some washers under the B & C pins. I added 2 x 3mm washers under each screw and it appears to have made the difference. I think it is too early to tell for certain, but initial indications are very positive.

If this tiny fix works, I hope FB implements it on future ‘Water heads’ and recommend the upgrade to other people suffering from this unreliable connection.

If the washers don’t work, I am going to look at doubling up the magnets which will increase the force and the pressure…