New 3018 Pro problems

[RadioBeamer]

Hi All,

Firstly, thank you to all you chaps who provide such useful advice here.

I recently bought a 3018 pro from ebay. You would not think you could go wrong for £140. As an electronics engineer I wanted the machine to make rapid prototype PCBs.

There are three problems with the machine from the off. Two are electronics related so I feel they are fixable easily enough. The third is mechanical.

Problem 1 is that a surface mount fuse on the controller PCB has blown. No idea why it blew, but the controller is completely dead. I can temporarily solder a very fine wire across the fuse and I can power the machine up using a lab supply with a settable current limit as a stop-gap solution. I'll order some replacement fuses as soon as I've figured out the correct rating.

Problem 2 is that one of the three small stepper driver PCBs is faulty. Initially I thought the problem was with a stiff axis because it was stalling and missing steps. However, it is clear that the motor torque when using the faulty driver module is way down compared to when the other driver modules are being used. The module is based on the A4988 driver device. I have already ordered some replacements from ebay.

Problem 3 is more difficult (in my head, at least) as my mechanical skills, experience and resources are not great. The "loose" end of the Y axis lead screw fits into a small bearing fitted to the front rail of the machine, which is made from bakelite. The bearing has not been pressed squarely into the rail so the lead screw does not marry up with the stepper motor on the back rail of the machine. The mis-alignment is enough to prevent the lead screw from rotating if it is forced into place. I am thinking that I might be able to get the bearing out if I can rig up a rudimentary press using maybe a vice, a small 1/4" square drive socket to push, and some plywood to support the rail, with a hole drilled in the plywood to accept the bearing.

However, i'm worried that I may break the bearing or the rail. The screw is 8mm diameter, the bearing is 16mm OD but the hole I need to use for access to push the bearing is only 10mm diameter. So I could only press against the inner half of the bearing and I worry it would just break.

I'm also wondering if it is worthwhile to try and use a vice to press the bearing properly home instead.

Any thoughts or advice would be very welcome.

Many thanks,

Paul