Y Axis Bearing Alternative

This is a replacement / upgrade to the Robo3D R1 and the LM8UU linear bearings used to guide the Y Axis of the moveable bed. This model uses self-aligning self-lubricating sintered bronze bushings instead of ball bearings. Advantages are operation with less mess and little or no lubrication is needed along the rails. Quieter operation from the solid bronze bearings. No possibility of gouging the rails in the event of a bad or dry ball bearing.

This pillow block uses 7Z41MPSB08M bearings available in the US from Ultibots.com




Designed to be printed laying flat. When doing so support will assist the center hole stay round but is not absolutely necessary. Can also be printed from either end with no support.

Please print this with ABS or other filament with a higher Tg (Glass Transition Temperature) because of the close proximity of the top of the pillow block to the bottom of the bed heater. Alternatively, insulating the bottom of the heater pad may also provide satisfactory results.

There are a few significant differences between these blocks and the OEM Robo3D blocks.

1. They are one single piece. Instead of using two pieces like the Robo, it is designed to hold the bearing without artificially compressing them while fastening the block to the printer.
2. The holes for the bolts are recessed. To allow for more room under the bed, the screws are recessed and can use readily available socket head cap screws which allow for easier installation over phillips head screws.
3. Uses self-aligning/lubricating bearings over LM8UU. Bronze bushings provide longer life, less maintenance and quieter operation over ball-bearings.
4. As a result of bearing design and placement, the effective support length is actually increased without increasing the size of the block itself.

The model as well as 3D solid source files, in a variety of formats, can be found on Thingiverse. Autodesk Fusion 360 was used to create this model.

X Axis bearing replacement thread located here.

 

Installation notes:

In order for these larger in diameter bearings to fit within the pillow blocks, there were a few things you should make note of during assembly. This model raises your bed approximately 1 to 1.5 mm. You need to make sure that your Y Axis belt runs straight with no binding. This gave me an opportunity to adjust things properly. Please note that the Chinese man or woman who assembled your Robo3D only cares about how many they can put together during a shift. You on the other hand, as a Robo3D R1 owner care much more about reliability and print quality. Here are some things to look for when substituting these bearings.

1. The two idler bearings under the bed will likely need an additional washer under the bearing to move the bearings up. Most 8 mm washers are 1.2 to 2.0 mm thick so one should suffice, alternatively you could pre-print a 1.5 mm spacer.
2. The Y stepper GT-2 gear will also likely need to be raised on the motor shaft.
3. The Y Axis Belt Tensioner (you know the part that sometimes comes broken in the box) can be swapped around so the the solid edge is up, this will lower the belt approximately 1 mm. You need to have these five items aligned for smooth operation.
4. There will be a break-in period for these bearings so things will get smoother with use as the bearing deposits a micron level layer of material on your rods through use. Tim Rastall has a video that in part shows how to speed up the break in process:
5. Your bed will need re-leveling, please follow the guides on this site for doing the paper level.
6. Z Offset will likely change, you are moving the bed in relation to where the stepper motor thinks that full steps are, this will change the relationship between actual height and desired height of the extruder (Z Offset).

 

Testing:

Here is a video of the bed moving after final assembly. Most of the noise you hear is Fan and Motor noise:


Here are a couple of pictures. Excuse the quality and white balance, these were cell phone pictures:

 

You can get smoother and quieter linear bearings, they just cost more.
Even so they will not be as quiet as these

 

Cool upgrade. I'm looking at doing something similar.
I bought some IGUS bearings that were advertised as LM8UUs. Of course I now find that IGUS doesn't actually make LM8UUs and the details of the listing said that they aren't actually quite the same size and don't fit in the stock bearing blocks. Anyone know if someone else has already designed a mount I can just print?

 

The problem with the Igus bearings is that they are designed to be compressed, so they are oversized, I am not a fan of the split pillow blocks with plastic bearings either. They have a tendency to squash the bearings into an oval shape, That is why I like these better. LM8UU are 15 mm OD, these are 15.9 mm OD. I don't remember what the nominal (compressed) OD of the IGUS are.

@Printed Solid, you could still download my pillow block design as I included STEP, IGES, SAT, SMT as well as Fusion 360 files along with the STL, easy enough to modify.

 

@danzca6 I am in the process of doing the same for X, but after printing out a few carriages and not really liking the results, here is what I ended up with:

1. Took the X Carriage completely apart, including removing the old LM8UU bearings.
2. Walked to my drill press, chucked up a HSS 5/8" bit and drilled out the holes (5/8" is something like 15.82... mm, close enough)
3. Used Acetone to clean up the holes and smooth them a bit.
4. Press fit the new bearings and did the break-in procedure in the video above.

Still not up and running as I broke my thermistor and one of the wires into the E Stepper in the process and I need to solder a couple of leads.

PS - In case anyone wants to know, the steppers use a JST-PH 6-pin connector.

 

Go ahead and add it to this thread. I probably won't do this upgrade but others could be interested. My Robo is now good enough for my own personal use with 8 mm rails but 10 mm will make it just a little bit more rigid.

 

40% rectilinear

 

Exactly how I printed one set. Two at once on end.