Print bed leveling and quality problems

3d-help
(Dave Hartburn) #1

Can anyone advise on a couple of problems that are driving me to insanity?

I have a Wanhao i3 v2.1 with a glass bed held firmly in place with bulldog clips. It has been fine until a few months ago and now the print quality is rubbish. Flat layers feel rough and the first layer has ripples in it, which seems typical of bed leveling problems. No matter how hard I try now, I can not get the bed level.

If I start with all four thumb wheels turned down tight, it leaves a even space of 3-4mm between the bed and the extruder. I have tried a number of methods from here, but the one I am currently using is:

  1. Move the extruder to the back middle and turn the two back wheels together until I can just see a small gap between the extruder and the bed.
  2. Move the extruder to the back left corner then the back right making sure the distance is fairly consistent.
  3. Move the extruder to the front middle and turn the two front wheels together until I can just see a small gap between the extruder and the bed
  4. As before, do the left corner then the right by eye until it looks close.
  5. Move the extruder round each corner making sure nothing is way out or touching the bed. Usually so far so good at this stage.
  6. Home the extruder to the front left, and using the slight friction on paper method adjust the corner until it feels right.
  7. Do the same going back right, front right, back left, then home again. (I used to go just anti-clockwise round the corners but had the same problems)

What I am finding is I go round and round and round but I can never get consistent leveling. By the time I have been round a few times, the front left and back right corners end up screwed down as tight as they will go. The front right and back left become so slack, the spring is no longer able to push the bed up to the extruder and the wheel spins freely.

I have checked the printer is on a level base and that it does not rock back and forth. It seems stable. Using a try-square, I did find the frame was a few degrees out, so I have straightened that up and it seems true. I printed off some x-axis calibration bars, which I put between the y and the x rods to make sure the X was level. Finally I printed some spring corner holders to make sure the bed springs stayed in a nice and stable position.

I don’t understand why I can’t get the bed level anymore. I’ve spent hours on this and I’m at a complete loss.

(Michael K Johnson) #2

Other than doing the bed tramming with the bed and nozzle at printing temperature… Have you checked to make sure your nozzle is clear? Replaced the nozzle? First time I had a partially-blocked nozzle I thought the bed was out of tram. :slight_smile:

(Dave Hartburn) #3

Yes, after posting I remembered I had a spare nozzle, but alas no difference.

(Michael K Johnson) #4

I don’t know whether beds warp more over time. I found that I had to switch to cast aluminum bed in my i3 clone. The bed wasn’t flat, and screwing it down tighter wasn’t helping that any.

There’s a general problem with having four adjustments to tram a bed: three points define a plane and four points for tramming the bed is over-constrained. Every time you adjust one point, you are tweaking a complex system. This is not impossible — ask any machinist who has leveled a lathe with four, six, or more feet — but to tighten one corner will also pull the adjacent corners down a bit, as a class 2 lever, with the effort being at the screw you are tightening, the load being between the adjacent corners, and the fulcrum being the opposite corner. Depending on the relative tightness of the two adjacent corners, the effect may not be symmetric. So you have to keep the whole system in mind while making any adjustment.

However, having alternating loose and tight corners as you describe sounds like the bed is warped like a potato chip. Glass is flexible. If you clip glass to a warped bed, the glass warps.

(Phil Trick) #5

I’ve found I could never get the original bed level, so got a new thicker aluminium bed, much better but still almost impossible to level with the glass clipped down, I now just have the glass resting on the bed and have had no problems since.

1 Like
(Dave Hartburn) #6

Thanks for the suggestions. I found a few things that might be causing the issue and a few other posts that had not shown up on previous searches.

My y carriage (plate below the bed) was warped, particularly in one corner that was one of the ones I have been having problems with slack screws. I have straightened it with pliers but a number of people advised a thicker replacement. They are fairly cheap but only seem to come from China so I have a few weeks to wait on that.

The glass bed was warping. Without any clips I put the side of a metal ruler on it and checked it seemed straight in all angles. I then clipped it and leveled, where I could see a small bend in it, I didn’t think the glass could warp like that. I’m going to print some holders from thingiverse that stop it sliding from side to side, but not from lifting up. I did have a large silicone pad holding it on but took that off (and it tore lots!) when I noticed that one corner was sticking up higher than the bed.

While doing all this at eye level, I did notice the extruder was not straight either, it was off by a few degrees. I can not find anything about anyone having a wonkey extruder causing problems, but it did mean the two bearings on the x rods were a bit offset. It certainly can’t help.

I’m not going to have time to do any test prints for a few days, but hopefully this will resolve the majority of problems. If not, I’ll be back begging for help!

1 Like