Dolly in need of help

Hi my first post here …
I stumbled upon Tom building the Dolly and decided to make one also. The build went well with no difficulties (extruder assembly is fiddly) and then came the setup
Arduino mega 2560 and RAMS 1.6 with full graphic smart display: having never tackled Marlin before it was a but scary but perserverance paid off and Dolly started to breathe.
Marlin version 1.1.9
Bed size 220 x 220
All was going well until i got to homing y axis wouldnt home…end stop would not activate but soon fixed that.
I am now completely stuck at auto bed levelling Im hoping that some kind soul can help me as i cannot get it to work.

Following the dolly build videos p5 and 6 and trying to set bilinear levelling i notice that the code Tom sets is different to what i see when setting grid max points

When i compile and run the extruder rises and travels to approx x170 y10 and performs levelling then fails

Can anyone assist me on this …i have spent 2 days trying to work this out
Code extract available…
Many thanks

Hi and welcome.
Can you upload your





Good morning thank you for your reply I have tried to upload as requested in zip format but the forum will not allow me to upload as im a new user


should now work

many thanks please find uploaded configuration.h and configuration_adv.h as a (45.9 KB)

Hi i had some time to look into the config it look’s ok.

Maybe an issue with the probe.

what say’s ?


maybe you have to invert the logic for the z probe …

Thank you for taking th time to review
M119 reports open when clear of the bed, triggered when metallic object placed below it so it appears to be functioning correctly.
The issue with that config was that it allowed the head to run off the back of the bed when performing G29.

I downloaded the dolly firmware as a stop gap and had some success but printing has failed each and everytime for the following reasons:

Bed thermal runaway - most common failure
Extrusion stops - cured this in slic3r( different temperatures set for 1st laers and following layers)
Print catches on the Inductive probe - this is the second most common failure and unsure of the way forward
Print becomes unstuck from bed

Any suggestions to these issues

Best regards

Bed thermal runaway 

do pid tuning

Print catches on the Inductive probe

Maybe over extrusion which accumulate each layer.

Print becomes unstuck from bed

If you have a aluminium heated bed buy a pei sheet from prusa / or energetic on aliexpress and put it on it.

Thank you
I will address PID tuning again…1st attempt seemed to throw temp readings out wildly

Any thoughts on the the extruder over running the back of the heat bed in G29 with the config you reviewed?