Squareing a printer frame

I am right in the middle of installing a dual Z axis (mechanical) on my Ender 3v2 and I decided I should check everything to see if it is all the frame parts are square to each other. So as I found it they are pretty good but placing a precision square on the corners there are some very small gaps. How accurately square do these parts really have to be. These are extrusions, not machined parts and generally very good in size and shape but they will never be perfect along there length. Plus the ends are milled “square” (probably cut to length with a CNC cut off saw and not actually milled, reasonably accurate) but again there is some variances. So far I have been printing fine with them the way they are, even with the single Z axis droop and even though we would all like everything to be perfect do they really need to be “improved”.

P.S. there is also a very tiny difference in the distance between the two vertical frame parts.

It all depends, you night not notice any problems on things that are small, printed on the one spot on the bed where you test everything. If you extend that small tolerance error out can you still get 0.4mm layers to land on each other at the edges of the build area

Is there a preferred method to fix the out-of-squre condition or do I just shim it back to square. It would be VERY thin shims.

hrm, that depends on the joint and why it’s out of square. I have shim stock down to about .0005" but that’s still .01mm. My printer goes out in the Z-axis often because the sheet metal base is … well sheet metal … one the little bump and it’s out enough to allow light between the upright and the base and a square. This to me is not a huge problem except if it’s only one side it pulls the X out of alignment and makes it impossible to level the bed. I don’t often print tall things and the things I did print were just junk that didn’t matter if it had a lean or not. lately, I’ve been using a lot of air cylinders so I have been making some parts with internal threads but they are all close to the bed So as long as my bed is level and my Z is reasonably perpendicular to it then it’s fine for me. This aluminum is a little like spaghetti so to me it’ll never be perfect but it doesn’t need to be on small printers. If I get a 400mm build area printer one day it will have to be made differently than mine is. We used to send apprentices to try and tram the clapped-out old mills, I always imagine the manufacturers of these machines snickering when they ship one. I was that apprentice once, if the machines can’t stay in tune then don’t waste too much time on it. These extrusions (I’ll bet) are cut in bundles. if they are made that way then some are going to be slightly bent near the cut end so it’s a good place to look for a problem.

The real questions are; What are you going to make with it? and What is it realistic to expect from an E3V2?

Keeping in mind that we’re working in plastic, which is, well, “plastic” - that is to say, inherently flexible. So, are your tolerances out by more than you would expect the plastic to deform? Keeping in mind that you would only ever see that much error on a part that uses the full range of whatever axis is out of alignment. If you’re Y-axis is .006mm higher at one end than at the other, a part would have to be the full width of the bed for one end of the part to out that much. If you’re only making parts that are 1/3 the size of the bed, the most deviation you’d get is .002mm. How often do you truly need that much accuracy in plastic?

You can spend a lot of time, money, and effort trying to get perfect results for parts that just don’t care. Also, of course, the more you fiddle, the more you risk getting something else out of alignment in the process.

Then, as I said, there’s the question of what is reasonable to expect from a $400 printer? If it was a $4000 printer, I’d say you should darn well expect near perfection from it, but Enders are designed to be quick and easy to mass produce, not to be precision equipment, so I suspect there’s slop inherent all over the place. Is it reasonable to expect high tolerances from such a product? You wouldn’t be the first person to go down that rabbit hole in pursuit of perfection from an inherently sloppy design.

I agree, that is why I made the statements about the extrusions. Considering the cost and how they are fabricated I think it is actually well made. So good enough is good enough. I have to go back to building my Cadillac now.