The new belt mounts, with heat-set inserts attached
3D Printing

Why I Buy Open Source Printers

I recently replaced the belts on my Lulzbot Mini. What started off as a simple bit of work ballooned into somewhat more serious work because of a few mistakes I made. The Lulzbot Mini being open source – along with Lulzbot’s excellent documenation – made the repairs possible.

It all started when I noticed that a box-and-lid print I’d designed wasn’t fitting together: the lid was too small for the box. Measuring, I found the nominally 2 mm thick sides of the box and lid were well over that, which is why the lid didn’t fit.

Digging around the net I found one possible reason for the too-thick sides: loose belts. Since the belts hadn’t been replaced since I bought the printer new in 2016, I decided to replace the belts rather than just adjusting the belt tension.

Lucky for me, Lulzbot has published detailed instructions for assembling my Lulzbot Mini V1.0.3. Using those instructions, I had no trouble removing the old belts and inserting the new ones.

The Lulzbot Mini Y axis belt, underneath the print bed
The Lulzbot Mini Y axis belt, underneath the print bed
Removing the X axis belt, which is behind the print head
Removing the X axis belt, which is behind the print head

When I say “no trouble”, I tell a lie: In replacing the Y axis belt, as I was using a screwdriver to pry the belt mount apart enough to insert the new belt, I heard the dreadful “plink” of the belt mount cracking. I ignored it, convincing myself that it was just a hairline crack, and once the belt mount screws were in, the cracked part would hold.

I heard the dreadful "plink" of a 3D printed part cracking
I heard the dreadful “plink” of a 3D printed part cracking

Unrepentant, I managed to do the same thing when replacing the X axis belt: I pried the belt mount too far. This time the part cracked and a bit flopped loose – I couldn’t ignore this problem. The belt mount might hold for a while, but eventually it would give up completely.

The broken X axis belt mount
The broken X axis belt mount

Now is where an open source printer shines: Lulzbot has placed the .STL 3D model files for all the printed parts of their printers online, along with the BOM (Bill of Materials) for all the other hardware the printer requires.

I visited the Lulzbot site and downloaded the X axis belt mount part (the X and Y are the same), and printed two copies in PETG on my Prusa i3 MK3 – it’s handy to have two printers, so you can always print parts for a broken one.

I then followed the assembly instructions – in reverse – to remove the broken X and Y axis belt mounts. The Y axis was easy: I only had to remove the print bed to get to the bolts that held the belt mount in place. The X axis was a bit harder, but straightforward based on the instructions: I had to remove the print head to get to the bolts that held the belt mount in place.

After removing the print bed I could easy unscrew the bolts that held the Y axis belt mount in place
After removing the print bed I could easy unscrew the bolts that held the Y axis belt mount in place
After removing the print head I could unscrew the bolts that held the X axis belt mount in place
After removing the print head I could unscrew the bolts that held the X axis belt mount in place

Looking at the old belt mounts I remembered that each one has 5 heat-set inserts in it. Attaching those inserts is another story (See “Adding Heat-Set Inserts to your 3D Printed Parts“), which again, wasn’t hard because of the excellent Lulzbot documentation and online help.

The new belt mounts, with heat-set inserts attached
The new belt mounts, with heat-set inserts attached

From there it was easy to follow the assembly instructions to install the new belt mounts, and to – carefully this time – insert and tension the new belts.

The new Y axis belt, mounted on the new belt mount, tensioned and trimmed
The new Y axis belt, mounted on the new belt mount, tensioned and trimmed

So, the Lulzbot Mini being open source means that I didn’t have to send the printer to the factory to repair it, and didn’t even have to order new belt mounts from the factory. Using the onllne .STL files, Bill of Materials, and assembly instructions, I was able to do the repairs myself.

References