New Parts and the Y-axis assembly

On my first order one of those U-bolts was missing. The dealer promised to sent a spare one, but now after 3 weeks I still don't have it.

Meanwhile I ordered those bearing mounts made out of aluminium from Aliexpress, and they came in today. They come with the bearings inside. The 1.5mm allen wrench was not included, but you need it to properly align and secure the bearings. The big advantage of those is that if you tighten the U-bolts too much, you might ruin your bearings. This cannot happen with those.

Y axis aluminum Bearing holder  €15.31

As you can see on the image they have a little set screw to secure the bearing in the housing. You need to make sure the ballbearings inside are properly aligned to carry the load of the Y-xarriage. Don't over tighten the set screws as you might either damage the bearings or the threads in the aluminum part.

Now that I do have all parts for the Y-axis I recommend to follow the excellent instructions from Prusa for the assembly. Prusa Y axis assembly As I already put the frame together in an earlier post I can skip the first part. So what we need is the Y-carriage, the bearing with the mounts with 6 M3x10mm screws and the clamp for the timing belt with 2 M3x8mm screws.

We start with the mounts for the bearings. Do not tighten them yet! And as you can see, I made sure I can access the set screws from the side. And the open side of the belt clamp must face towards the side with the two bearings.

Then you need to carefully insert the 330 mm steel rods into the bearing. Don't tilt the rods and try to insert them as straight as possible. Otherwise you might push out some balls from the bearings.

Before we can mount them on the printer we have to remove the aluminum mount for the rods. They are not made for snap-in as the 3D printed parts. Don't even try it, you will just ruin you steel rods. For the it was enough to losen them on only side and remove them completely on the other side.

The you should be able to slide mounts on the steel rods and the steel rods in the mounts on the other side. Again, don't tighten anything yet!

The next step is to align the Y-axis. As you can see on the picture below there is just very little place between the mounts for the bearings and the frame. First, tighten the little set screws in the mounts for the steel rods. Don't use a lot of force and tighten them equally on both sides.
Move the Y-carriage to one side and tighten the mounts for the steel rods. Then move the Y-carriage to the other side and tighten the mounts for the steel rods there as well. The last thing to do is to tighten the mounts for the bearings. Now make sure the bearing mounts to not scratch over the frame when you move the y-axis assembly.

The next step is to install the GT2 timing belt. You need to cut a length of 650mm with some good scissors.

Follow the instructions from Prusa to assembly the belt. I need to make sure I loosen up the belt tensioner. I also needed to loosen those 3 Philips screw on the clamp to get the belt in.

Once the belt was in place I could tighten the screws and use the belt tensioner to adjust the belt tension.

I double checked the tension on the belt by holding the stepper motor with some pliers and trying to move the Y-axis. Again, do not over-tighten the belt as it will pull down the Y-carriage and bend you steel rods.