How to: replace/upgrade gearboxes

Last week I was performing a pre-check and noticed one side of the gantry had too much free play after I connected to the controller. Upon further inspection I found the gearbox output shaft had sheared off. Must have happened near the end of my last cut the day before. When I bought my table (used TMX) there was an extra gearbox in a parts box that was also sheared off, so appears this was the second one to go and the previous owner had already upgraded the gearbox on the single motor axis. I decided to go ahead and upgrade both gearboxes on the ends of the gantry.

Thought I'd post some pics of the swap. I got all the parts from LECS.

Here's the sheared shaft



Old box on the right, new box and gear on the left. Notice the height difference between the old and new. The new box is considerably shorter. This requires one of the mounting plates to be swapped out to compensate. Also, the new box has a flat side on the output shaft. I'm sure this will greatly decrease the notorious loose spur-gear/set screw issues.



One new mounting plate and one original plate per side. This pic is of the two new plates.



The new boxes come with a pinch collar that is for a larger motor output shaft than my motors, so I had to replace the collar with a smaller id to fit my 1/4" shaft motors. My motor is on top along with the new collar, new gearbox on left, old gearbox on right.






Here's the new box with the new collar.




Now to remove the old mounting plates from the old gearbox. This really isn't necessary since you only need one old mounting plate for each side, but I didn't want to trash the extra plates along with the old gearboxes. Here's the trick I used to get the nuts off. These were extremely tight and did not want to come off easily. Since the gearbox was trash anyway, I used a propane torch to put some heat to it. I still had to wrestle with it and almost stripped the machine screw head on a couple of them.



Now to install the new gearbox and plates. Here's where I encountered a small issue. My original lock nuts were too big for the new gearboxes. I had to go to the local Bolt and Screw and get some small profile nuts and lock washers.



Old on left. New on right. The new mounting plate is top right. Original plate bottom right. New plate has to go in between motor and gearbox, original plate has to go on bottom.



All done.



My last concern was whether or not the gear ratios would be exactly the same as the old boxes. Which translates to incorrect part measurements. My first test cut was a 4" square with a 1" circle. It was dead on. I cut a full 4x10 sheet after this with no issues.

 

My test cut.

 

Keep after it Jason. make an old warhorse great again

 

The image of the new Micron gear box and coupler adapter, where the two slots line up with each other, you will want to rotate the outer slot so that it will form a cross with the inner coupler. Excellent write up, thank you.

 

Good call out. I turned it before I installed it but neglected to get a pic of it that way.

Thanks!