I bought a new printer - the Creality Ender 3, and for a $200 printer it looks impressive. I just assembled it today and ran into a few problems but none as difficult as the assembly issues with the Kossel. The Ender 3 is a 222x220x250 Cartesian style printer which uses belts to drive the X and Y with a single screw for the Z. Probably the biggest plus is that it runs on 24V which should mean faster heating. I watched a couple review videos and read a bit on forums before buying it, and it has a pretty good reputation so when I found it on sale I bought it.
It is about 70% assembled when it arrives but there is still a good bit to do to get the printer working out of the box. It is the standard 2020 extrusion frame and every hole was spot on and the threads looked good where they were needed. The only issues I had were with the extrusions themselves and the Z endstop mount.
The 2020 extrusions are not perfectly flat on top, appears that with both the base frame parts, the center of the extrusion is just about a perfect 40mm, but the sides are 0.16-0.3mm shorter. I ended up shimming these but made a bit of an error which seems to have not mattered in the end. I had seen a video where somebody ran into the same issue and used some paper to shim, and others where people had to widen holes on the top cross frame due to the same problem. Widening the holes though seemed like an extreme way to handle it, and would not correct the geometry that is off (the verticals tilt inward - or possibly outward, due to the higher center on the 2020 base rails). I found that when I got it shimmed so the distance between the inside edges of the vertical frames was 25cm at the top and bottom (that is, they were parallel), the screw holes lined up on the top frame which indicates that it was manufactured correctly. The problem is that the vertical rails won't be parallel without shims, or a lot of luck. I also ended up shimming more on the inside edges of the frames since there was still a tilt to the inside after the initial round of shimming. Below is a pic of the problem:
It is about 70% assembled when it arrives but there is still a good bit to do to get the printer working out of the box. It is the standard 2020 extrusion frame and every hole was spot on and the threads looked good where they were needed. The only issues I had were with the extrusions themselves and the Z endstop mount.
The 2020 extrusions are not perfectly flat on top, appears that with both the base frame parts, the center of the extrusion is just about a perfect 40mm, but the sides are 0.16-0.3mm shorter. I ended up shimming these but made a bit of an error which seems to have not mattered in the end. I had seen a video where somebody ran into the same issue and used some paper to shim, and others where people had to widen holes on the top cross frame due to the same problem. Widening the holes though seemed like an extreme way to handle it, and would not correct the geometry that is off (the verticals tilt inward - or possibly outward, due to the higher center on the 2020 base rails). I found that when I got it shimmed so the distance between the inside edges of the vertical frames was 25cm at the top and bottom (that is, they were parallel), the screw holes lined up on the top frame which indicates that it was manufactured correctly. The problem is that the vertical rails won't be parallel without shims, or a lot of luck. I also ended up shimming more on the inside edges of the frames since there was still a tilt to the inside after the initial round of shimming. Below is a pic of the problem:
I found that the amount of shims needed was different between the sides so here is what I ended up up:
Now here is where I messed up, I should have divided the amount of difference measured between the heights of the sides and middles of the base 2020 extrusions by 2 and then used that as the starting point, but instead I used the whole value. As it ended up however it seems to be fine and the screw holes in the top cross frame line up (I actually over shimmed a bit on the inside edges since I had to put some inward pressure to get the screws to line up). However I see a slight (under 1mm) skew to the right as would be expected since the left side is now shimmed higher than the right side - I will probably need to go back and fix this by removing some shims from the left side, likely around 0.1mm from each side of the left side.
Below are some pics of the shims and how I measured the 2020 base rails to get the sizes I needed (to start with):
Below are some pics of the shims and how I measured the 2020 base rails to get the sizes I needed (to start with):
The second problem was that the z-endstop is too high. I'm not sure why I couldn't find anyone else reporting this problem but I acknowledge that I may just be missing something stupid. There is a small indexing catch on the z-endstop mount plate that does not allow it to be moved lower (without cutting the tab off). The manual indicates that there should be about 32mm from the bottom of the base 2020 extrusions to the bottom of the z-endstop mount but mine is closer to 36mm. This means the z-endstop will trigger before the extruder nozzle is still a few mm from touching the bed - and that is with the bed screws all the way out. I am printing a new mount now, but this just seems like a strange oversight (again could be me doing something stupid too).
And below are some other pics I took during the assembly, for reference primarily:
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