Ever since I got a MakerBot Thing-O-Matic, the build platform has been an issue. The belt was uneven. This weekend, I took it apart and reassembled it with a new belt – and resolved the issue at the cost of two nuts.
Comparing the illustration on the MakerBot assembly instructions wiki, I realized that their belt is much more narrow than the ones I’ve got.
The result of this is that the silicone nozzle wiper sits on top of the belt, causing friction. Pulling on one side of the belt means that it warps and becomes uneven.
The obvious solution to this would be to cut the new belt, so that the wiper fits next to it, but this would be at the cost of printing area. Instead, I decided to place a nut under the wiper, to lift it off the belt. This way, I get a wider printable area, while avoiding a wobbly printing bed, so that I can print without a raft.
You can see the end-result to the right. Actually, it contains two nuts, as the length of the M3 bolts shipped with the kit fits in this configuration. The GCODE initialization places the nozzle just over the head of the bolt while it heats up, so I did not change it. The wiper also touches the wood during the first few layers when printing. However, this did not seem like an issue to me. The machine is strong enough to handle the increased friction.