3D test structures

@Gareth Owen i know this sounds obvious but that looks like the filament is too hot and not issues with over extrusion. Have you checked the thermistor is shoved all the way in the little hole as far as possible.

This was exactly problem i was having with my prints. As soon as i checked this and corrected the location my prints were 100 times better. also my temperature fluctuations have decreased massively now.

Here's my Benchy...

I made the lead-screw cap (with bearing) mod which made things much worse. The bed leveling was all over the place. In the 2cm span of that test structure I had one side high and barely sticking while the other side was digging into the surface mat. Then, after I found a happy medium on the z-offset, it printed the the wave much like the OP, times 10. My macbook went into deep sleep in the middle of the print so it didn't get to finish (usb turned off so pronterface couldnt talk). But, here's what it looks like:

My thinking is that my mod pulled the lead-screw off center and kept it there ... kinda like the tilt of the earth. But which appears as periodic wobbly tower instead of yearly seasons.

@Holger that's a pretty good looking print!

I tried the Z bearing mod but it didn't work for me.

I fitted a 'proper' aluminium Z coupling and that's noticeably helped.

My Z guide made things a lot better.

The adjustable cam guides are garbage - I'm designing a pair of rails (in my head) to replace the X & Y guides completely. I'm wondering if I should incorporate the Z guide.

@Holger Well, mine might be better in the bottom third, but yours is definately better on the rest. I think my gantry might have slipped somewhere around 80mm ... or maybe my z-offset was off a smidge and that's where the nozzle pressing into the layer started to affect the stability of the part. In the upper third I could easily see the part moving with the print head.

I think they used the wrong sort of bending technique to form the "rails". ..or possibly just gave the manufacturers too much allowance in their specifications. It seems to me the lower lip is making it hard (impossible?) to get clean movement across the entire travel area. Most notably in my platform movement. I can see it tilt and shift in the X[0:100] range. If I adjust that out, it skips in the X[200:300] range. Same with the gantry guides, which allows slight rotation in the X and Y axises which in turn causes the screw to wobble or the gantry to stick and jump. Anyways, perhaps with either less allowance in the bend, or a more rounded die to create a "U" shaped rail rather than the simple "V".

At the moment, all I can do is adjust the guides to optimize printing in a smaller region.

I'm pretty good with the building and software side of the printers but am trying to learn the modeling side. I started a 30 day course for using Fusion 360. I was hoping to have enough under my belt to be able to model what I think we need. I might have to get my tablet and pen out and draw it up so someone else can take a wack at it.

That would be great. We should collect a list of parts which have shown improvements to the printer.

I have my printer rotated on the desk so that I watch the x movement coming towards and away from me. Watching it this way I can see the bed move around as it slides. My z-axis also occasionally "pops". I think it's the flexible coupler. Looking at the printer now from the front with the x-axis all to one side it seems to hang down a bit. Tightening things just makes it bind.

I've ordered a new lead screw, brass threaded insert, and all metal coupler to hopefully help with the lead screw wobble. My Ender 3 wobbles but maybe in 2-5mm at most. This thing skates from under the bracket to all the way off the bracket.

I think we all need to get together and redesign the friction blocks that guide the platform and the gantry.

I think it is also connected to the lead-screw-wobble issue

https://www.forum.makertech3d.com/forum/3d-printing/lead-screw-wobble

The top of the lead-screw is rotating dependent on the Z height. This changes the angle between X and Y axis.

With small heights objects it looks like a parallelogram distortion. At high Z displacements there are waves in Z direction.