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Part 02 - Y Axis

Next step is the sliding bed assembly. I started off by mounting the linear bearings into their printed holders - man what an effort that was! As you can see from the picture, I took the safe route in the end, and only pressed them in up to the end of the holder - the instructions specify that they should be pushed all the way through, with an equal amount of bearing protruding from each end, and I tried every trick I could think of to get them into this position, including kettle steam, a hot air gun and brute force - on the first one I tried I came close to splitting the plastic whilst pushing down on the heated holder with an open spanner...and decided that rather than risk breaking it with no replacement to hand, I'd play it safe. Once I get the RepRap up and running I'll likely upgrade these to something like this design to make them easier to work with, or at least print off a couple of spares of the original before I start hacking them about again.

edit: I needed to have another go at the linear bearings as I couldn't get the bed mounts fitted between the inward facing bearings. Originally, my intention was to spin them around, so the protuding bearings faced outwards instead of inwards as in the picture. In a moment of madness, I decided to try to position them properly again using the open spanner resting on the PLA and hammer trick - this time it worked, and I was able to get all four bearings correctly positioned in the mounts! I guess I must have loosened them previously....

Once the mounts where finally screwed onto
 the delightfully named "frog", I 
was able to feed the two guide rails through the bearings, and place these loosely into the U shaped retainers on the frame separator bars. This is where the vernier caliper was very useful, as I could move the U brackets to within a 10th of a millimeter to ensurer that that the assembly was completely central on the frame. Once the U clamps were tightened off, the bed was able to move freely up and down the rails, even under it's own weight - win!!

One of the instruction points before mounting the frog fully, is to drill a small hole in the edge of the laser cut frog, and to insert a screw which acts as a pusher for the end stop switch to be fitted later. Now, I'm not good with the combination of drills and thin surfaces, and had also read on the forums about people splitting the wood - again with no spares to hand, I opted for a safer, albeit temporary workaround, until I can print out the great modified part here

My solution was pretty simple - a cut off cable clip, the kind used to nail cables to a wall - seems to work a treat! 

I simply removed the nail, clipped off the excess plastic so that the clip would sit flat on the belt mount, and ran a needle file through the hole so that it was M3 sized.

The clip screwed down onto the existing M3 belt holder bolt - It seems fairly stable, and operated the switch perfectly, but I'll put blob of hot glue on the top to ensure that it doesn't move around.

I've kinda jumped ahead a bit in this section and missed the motor mounts fitting - this is deliberate, as if anybody is following this alongside the eMaker instructions, I wanted to emphasize the importance of setting the switch assembly before the belts etc are fully installed, as this will be a royal pain for you to get the switch pusher in otherwise, particularly if you go the drill/screw method as recommended. My solution above doesn't even require the Y axis motor or idler brackets to be in place, although it's a good idea to loose fit the idler bracket and switch, just to check that your pusher makes contact with the switch. A further modification I'm likely to make, would be to trim the trailing edge of the clip, so that it lines up nicely over the belt. This is purely aesthetic though. 

Next step is the Y axis motor and idler brackets. The motor bracket went together very well and didn't require too much fine tuning even with the belt installed. The idler end...well that's another story! 

One thing to remember about both of these brackets - don't over tighten the bottom bolts (the ones that sit either side of the 626 bearings) - these will grip the bearings and I found that with the nuts even finger tight, they would stop the bearing from moving, creating an unnecessary drag on the belt, which won't help the motors. So, make sure when you've finished adjusting the brackets, that the bearings still move with the belt!

As I said, the motor bracket went together nicely and fitted well. The belt threaded through with no issues, and runs true on the 626 bearing at the bottom, and only moves by about 1mm on the motor gear whilst running the frog the full length of the bed. The motor sits nice and secure with no movement. As I mentioned above, the only issue really was with the bottom 626 bearing which was binding on the mount due to me over tightening the restraining nuts, but that was easily resolved.

The problems for me on this part all came with the idler end. Firstly, the thing didn't want to go together properly - as with the motor end, its assembled in two parts, one thick, which houses the 623 bearing and a couple of washers, all held together with one M3 bolt and nut. The first problem was the thinner part of the bracket was slightly warped, meaning it wouldn't sit flush when assembled. A hot air stream and some careful pressing sorted this issue...eventually. 

Next issue was getting the belt to run smoothly over the 623 bearing - I needed to file away a lot of PLA on the thicker part of the bracket to even get it in, let alone running smoothly. Once I was (barely) satisfied with this, I mounted it up and ran the belt though, securing to the frog as per instructions. 

At first the frog wouldn't slide at all as the belt was binding so badly on the idler. I'd pretty much expected this, and adjusted the idler accordingly along the separator bars until it would allow the frog to move. I'd read in the forum that it was sometimes necessary to tip the idler over in order 
to allow the belt to run true without jamming up against the PLA in the brackets - this was certainly true with my build. I did, after a lot of fiddling get it to run without snagging, but the amount of pressure I now need to exert on the frog (compared with it moving under it's own weight prior to the belt being fitted) to get it moving is considerably more than I would have hoped for - I can only hope that the motor is up to the job. Time will tell I guess, but I have a feeling that I will be returning to this during the commissioning phase.