Monthly Archives: February 2014

Notes on Marlin – Auto Bed Levelling

Upon enabling the auto bed levelling feature of the Marlin firmware I learned a thing or two through trial and error and wished it had been better documented so I’ll try and let you know what I’ve learned.

Here are links to some useful information that all helped me get setup:

Firmware setup
Hardware setup
PrintrBoard setup

In the Marlin firmware, where you set the left, right, back and front positions for probing, do not set the left and front positions below 10.  I tried 5 (assuming the bigger the test area the better results you would get) and wondered why moving the nozzle back to X0 Y0 after homing resulted in the nozzle crashing both X & Y in to the min endstops.  I quickly noticed that at the start of the probing both the nozzle did not move in either X or Y so they were both then 5mm out when homing after the probing.  I now use 20 for left and front.

I also found that if you just move X & Y to home before probing and your nozzle is quite high in relation to the bed then the bed probe would stop way before it even touched the bed.  I thought I’d fix this by homing the Z before probing but you need to make sure that the probe is within your bed probing co-ordinates (i.e. the middle of the bed, or at least more than you’ve set for left and front).

So here is my start G-Code* that I’ve put in to Slic3r:

G28 X0 Y0 ;home X & Y
G1 X100 Y100 F5000 ;move nozzle to centre of bed
G28 Z0 ;home Z
G29 ;probe bed
G90; set absolute coordinates
G92 E0; reset extruder distance
G1 Z5 F300 ;move nozzle up 5mm for safe homing
G1 X0 Y0 Z0 F5000; move nozzle to home

*If you’re going to use this code then please set your own bed centre and move velocities appropriate to your printer.

If I discover anything more on this topic then I’ll update this post.

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Marlin – Auto Bed Levelling

A great feature was added to the Marlin firmware last year and I’ve finally gotten round to implementing it on my printer.

There were quite a few hurdles to over-come including designing some new parts to make it work.

I wanted to re-design the whole X – axis for my Mendel-Max as the clamps for holding the X – axis rods were poor and the belt being outside of the 2 rods meant there was a considerable amount of turning force on the parts, especially if you wanted tight belts.

So with the belt now between the 2 rods I had to completely re-design the carriage not only because the belt clamps had to be moved but I wanted to move to a direct-drive extruder on top of designing the probe arm to probe the bed!

With all of the new designs complete there were plenty of adjustments to be made to the firmware.  Moving to a direct-drive extruder meant new E – step / acceleration / speed settings. Enabling the bed levelling, setting up the servo including finding out which pin to assign to the servo for my PrintrBoard.  The biggest hurdle was discovering that by enabling the bed levelling filled the RAM on the PrintrBoard! To make the firmware fit I had to remove parts of the LCD menu.

After you have everything is working you need to set the distance from the hot-end to the micro-switch on your probe arm. Spend some time getting this as accurate as possible makes for the best result and only needs to be done once.

Has it been worth it? YES!

It’s great not having to adjust the bed manually, you can fine tune the distance between the nozzle and the bed in the LCD menu which is far more stable that any screw adjustments.

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Slic3r 1.0.0 RC3

So Slic3r is almost at an official version 1!!

The latest release is less about features and more about but fixes.

As always, a very big thank you goes out to Alessandro Ranellucci and everyone else who has contributed to the application.  Especially in keeping it FREE!

The ONE bug I hope gets fixed before the final version 1 gets released is hole diameters.

It’s quite well documented on the Slic3r forums that the holes generated by Slic3r are smaller than designed.  Fingers crossed for version 1.

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