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Graphite Plugged Bushings for R2

Discussion in 'Projects' started by adikted2astro, Dec 24, 2019.

  1. adikted2astro

    adikted2astro Active Member

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    The following is a written description of how I upgraded the bushings on my R2 for the 8mm X/Y axis rods. I need to point out again that this is written only. I did not take pictures while I did this, but someone requested I do a write-up about it anyway. I apologize in advance because some of these steps will seem a bit vague. So here goes.........

    First of all, there are a couple of options when getting the bushings. These are what I bought a couple of years ago and only recently installed: https://www.robotdigg.com/product/175/Selfgraphite-ID8*OD12-Linear-Bearing.
    However, these are only 30mm long and the original bronze bushings are actually about 36mm long. You will see that the difference doesn't really matter (at least not for my machine). However, recently, another member showed me these: https://www.ebay.com/itm/153552765087?ul_noapp=true. They are 35mm long and if I had seen these when I bought the other ones, I would've gotten them instead. Regardless, I am more than pleased with the performance of the 30mm bushings. These 'Ultimaker' bushings also come in 6mm x 12mm x 35mm size, which is perfect for the X/Y axis guide rods that go through the print head. They are a replacement for the LM6UU linear bearings in the print head. I bought a set and plan on upgrading to them soon.

    There is something else you will need and you can get them here: https://www.partsbuilt.com/bushing-block-r2c2-robo-3d/. You will need 4 of them because taking apart the original bushing blocks without destroying them is near impoissible. I was only able to save one half of one of the blocks. I don't believe they were designed to come apart once snapped together.

    Okay, step one of course is to remove the entire gantry, which consists of 10 screws; 8 of them are on the upper part of the gantry, under the 8mm rods (23 on each side), the other two are near the rods on the back that guide the bed. Do NOT forget to unplug the wires that go to the X and Y limit switches, and of course unplug the wires on the X and Y stepper motors. Also don't forget the wire bundle that plugs into the print head on the top. Once the gantry is out, put it on a table or bench and make sure you have plenty of room to work.

    The next step is to remove the print head. In order to do that, you need to remove the X/Y guide rods (6mm diameter) from the bushing blocks. They are snap-fit into the blocks, so the best way is to rotate the blocks away from the rods. Or, place your thumb on the block, then grasp one of the rods and poull upward while your thuimb pushes down on the block. It will take some force to remove them, but they will come out. Once all of those have been removed from the blocks, slowly and carefully rotate the entire assembly and remove it.

    Now comes probably the most important part. If you look at each corner of each 8mm rod, there will be one or more gears attached and of course the belts attached to those gears. You will also see black spacers between the gears, and between the gears and the frame. These are extremely important because they are how everything is aligned properly. The gears are all identical and can be exchanged, but those spacers are ALL DIFFERENT. Each one is a different length and have to be put back in the same spot, or you will have serious problems aligning everything. You can take pictures of each one, but honestly the best way is to mark them as you remove everything. So, I believe you need either a 2mm or 2.5mm allen wrench to remove the set screws in each of the gears. Start on one rod, loosen the set screws on each gear (two screws on each one) so that it spins freely. I cannot remember exactly how I did this, but I do know I did it very carefully. Once you loosen the screws on the gears for one rod, the rod can basically just be pulled out. As you start removing the rods and gears, mark the spacers (and gears if you want) so you know which one goes where. I made simple markings on mine; LB, LT, RB, RT. The stand for Left Bottom, Left Top, Right Bottom, Right Top. So the left and right would correspond to the rod on the left side of the gantry, and top and bottom mean they came from a rod that was near the top of the gantry, or one near the bottom. If you look at the picture below, this rod would be considered top, because it's near the top of the frame. I labeled the gears and spacers here as BT (on a rod near the top, rear of the bed). Sorry if this is confusing. The point is, label them, take some pics if you need to, do whatever you need to do to make sure you replace them in the same spot they were before. The rods themselves are like the gears, they are all interchangeable, but I put everything back in the spot it was in before. Note: I also labeled each of the rubber belts either left, right, front, or back, so they could be put back in the same location.

    rods.jpg

    Be a bit careful when taking out the gears for the stepper motors, it's not hard, but be careful. You will also see two shoulder bearings on each rod that hold it centered in the frame (arrow above). Once everything is apart, then you can start on the bushing blocks. I used a couple small flat head screwdrivers to pry off the tabs on each block. To be honest, if you have new blocks, just break off those tabs and pull the block apart (much quicker). Remove the springs and drive belts from each block. To remove the springs, use a small screwdriver and just pry it up from the bottom until it pops off.

    The drive belt will stay attached to the spring, so don't worry too much about it. Now, take on side of a new block like this one:
    block.jpg

    To put the spring back, just grab one side with your left hand, the other with your right, then pull away slightly to open the spring a bit, then try to slide it onto the post (arrow) in the new block, in the same orientation it was before (with the 'legs' pointing towards the location of the bushing). Also, make sure the drive belt goes through the slots on each side of the block. After I placed the spring back on the post, I used a clamp to push it all the way down the post.

    Then, take your new bushing, and place it centered in the block, where the old one used to be. Once that's done, you can take the other side of the block and snap it back together. When it is snapped together, the bushing will be secured inside and will not rotate (mine didn't), or slide from one side to the other. Do the same for the other bushing blocks and drive belts.

    Granted, this is all probably already too confusing, but once you start doing this, you will see what I'm talking about. Now I am going to confuse you more because it took me a while to put everything back together. I placed the gears, spacers, and bushing blocks back on one of the rods, in the correct order of course, then I reinstalled each rod into the frame. At this point, don't worry about the alignment of the blocks, because you can realign them later. But, leave the gears free spinning, or only slightly secure them until you get everything back together (also make sure your gears are put back in the correct orientation). I apologize I don't have a step-by-step on this, but trust me, if I can figure it out, so can you. Just make sure everything goes back in the correct order and make sure the belts are on the gears properly.

    Once it's all basically back together, you now have to align the bushing blocks to each other so those 6mm guide rods fits in properly. The way I did it was I secured the gears corresponding to one of the blocks (push everything to the side, up against the edge and secure the set screws) and pushed the block all the way to one edge. One the other side, I let the gears spin freely on the rod and pulled on the block until it was aligned with the other block on the opposite side. You can use the 6mm guide rods to help with the alignment (install them on one side, then move the other block until the 6mm rods could snap in place. The good thing about moving these blocks all to one side of the frame is that you can eyeball and/or measure the distance each block is away from the edge of the frame.Trust me, it helps. Again, I apologize this is so vague. I wish now that I had recorded everything I did. However, if I had, you would've heard me cussing every ten seconds and I have a mouth that would make a sailor blush :).

    Okay, now that all the 8mm rods, gears, blocks, and belts are back together and secured in the frame, you have to put the print head and 6mm guide rods back. This is a bit tricky, but I found that if you rotate the entire assembly 45 degrees, put it into the gantry, then rotate back, the 6mm guide rods should be aligned with the nothes in the blocks. Then, just push down and snap them all back into place. Then you are basically done and can put the gantry back onto the printer.

    I will say that I decided to put some blue locktite on each of the set screws in the gears to make sure they wouldn't loosen up later on. But, only do this when you are certain you have everything aligned. If you want to double-check your alignment, then you can follow the instructions Robo provides here: https://help.robo3d.com/hc/en-us/articles/115001792512-Gantry-alignment

    I can also say that my printer is performing much, much better than it was before. Movements are so much smoother, it's astonishing. I am so pleased with this upgrade that I recommend it for everyone. If you could see how well my prints are coming out now, you wouldn't hesitate. If you want to, you can also replace the linear bearings in the print head with graphite plugged bushings while you have everything apart. That way you don't have to remove the gantry later, which is what I have to do.\

    If anyone needs help, or has questions about this, you can PM me, or reply here on this thread. I'll help however I can. When I replace the LM6UU bearings in the print head, I'll make sure to take pics and hopefully, some video, and then post it all here.

    p.s. another thing I did was when I took out the spacers and marked each one, I also measured the lengths of each using calipers and wrote them down. This can help quite a bit if you are at all unsure about their placement.
     

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