Z axis feed problems

[scaddesign 0]

It seems that we have a problem with a sticking Z axis feed. Occasionally the feed stick and then dropped drops a double space causing a bad layer and a weakness in the print. If you zoom in on the attached image you can see particularly on the infill ribs the bad layer.

When moving the table up and down manually, their is a crunching sounds as though there may be some plastic caught up in the lead screw or drive. I'm not sure if I can easily access the lead screw nut on the table by removing the white cover at the back of the table to see if there is anything caught in there.

I would appriceate any help/guidance in this issue.

Thanks.

[gr5 2,271]

This machine is meant to come apart easily. But that crunching sound is probably normal - those are the ball bearings in the 2 vertical linear bearings for those 2 8mm rods.

Did you actually see it fall? This is actually common but also common is underextrusion for a layer or 3 due to a tangle.

Anyway you are probably right. It's usually related to some recent boards that are more susceptible to overheating I think maybe due to too much current to the Z axis. There are 2 solutions out on the forums - sometimes you have to do both solutions. One solution is to remove the bottom cover and tilt the machine a bit and put a fan - like a window fan - blowing on the circuit board. You can print sideways or even upside-down - it doesn't affect the print.

The other fix is to lower the Z current with a gcode - add it into your existing gcode file - it only changes current temprarily until you power cycle (or maybe the next print? I think power cycle):

M907 Z1000

sets to 1000ma max - I think the default might be 1300ma.

[scaddesign 0]

This machine is meant to come apart easily.  But that crunching sound is probably normal - those are the ball bearings in the 2 vertical linear bearings for those 2 8mm rods.

Did you actually see it fall?  This is actually common but also common is underextrusion for a layer or 3 due to a tangle.

Anyway you are probably right.  It's usually related to some recent boards that are more susceptible to overheating I think maybe due to too much current to the Z axis.  There are 2 solutions out on the forums - sometimes you have to do both solutions.  One solution is to remove the bottom cover and tilt the machine a bit and put a fan - like a window fan - blowing on the circuit board.  You can print sideways or even upside-down - it doesn't affect the print.

The other fix is to lower the Z current with a gcode - add it into your existing gcode file - it only changes current temprarily until you power cycle (or maybe the next print? I think power cycle):

M907 Z1000

sets to 1000ma max - I think the default might be 1300ma.

Yes, I have managed to remove the cover and check for anything causing the table to catch and yes I did see the table drop.

I'm not sure that it's a board issue and more a mechanical issue. Particularly as it tends to happen at the same level each time.

I've manually slid the table up and down and it did feel like it's catching but after doing this repeatedly, It's seemed to free up and the last test print had a perfect continuous external surface finish with no faults. It just concerns me that I have found a particular reason. I believe it's been a problem ever since we received the machine new.

I'll see how the next print goes.

I feel that

[gr5 2,271]

Actually you can set the lower current in the regular menu. It often happens the same spot because that's how long it takes to overheat the Z driver. But you could be right of course - it might be mechanical. If you can prove it then you can get some parts replaced. Probably the Z rods and/or the Z bearings.

[JohnFox 25]

I would suspect the Z bearings if you saw the bed drop. I think the balls locked up in the raceway, then suddenly released again. It's a bit involved but if you can undo the bearings, try sliding them up and down the pillars. They should move smoothly but mine had frequent lockups. Changing the bearings solved the problem.

[scaddesign 0]

I would suspect the Z bearings if you saw the bed drop. I think the balls locked up in the raceway, then suddenly released again. It's a bit involved but if you can undo the bearings, try sliding them up and down the pillars. They should move smoothly but mine had frequent lockups. Changing the bearings solved the problem.

JohnFox - After some more investigation, I have found that this is exactly the problem. They move freely for the first 10mm then lock up as you say, when the balls reach the end of the race.

Did you change to a different bearing from what Ultimaker provides or the same bearing without that fault? I'm very keen to find out.

Thanks.

[mmcgraw74 1]

I'm having a very similar issue on my Ultimaker 2 that I purchased this month.

I have a support ticket open - I even pulled the vertical bars and linear bearings off mine last night.

I could easily pull the bearing up the bar, but it would 'hang' going down if I pulled the bearing near the top of the bar. Same thing for the second bearing and bar.

I swapped the bars end for end and swapped the bearings between bars - same symptom.

I put the printer back together (following the installation guide I found on github) and thought it might be a little better - but tried printing a 2 inch tall cylinder with walls about 0.2" thick and once again heard the "thunk" as the buildplate dropped - causing that layer to not stick to the previous layer. Since I was printing layers at 0.15mm thickness, a couple of layers later the filament began to stick - but this error results in the part having no strength at the bad layers.

Here is my photo of the bad cylinder on the left. The other two parts are shorter and were fine.

scaddesign - did you get your issue resolved?

Monty

[scaddesign 0]

I'm having a very similar issue on my Ultimaker 2 that I purchased this month.

I have a support ticket open - I even pulled the vertical bars and linear bearings off mine last night.  

I could easily pull the bearing up the bar, but it would 'hang' going down if I pulled the bearing near the top of the bar.  Same thing for the second bearing and bar.

I swapped the bars end for end and swapped the bearings between bars - same symptom.

I put the printer back together (following the installation guide I found on github) and thought it might be a little better - but tried printing a 2 inch tall cylinder with walls about 0.2" thick and once again heard the "thunk" as the buildplate dropped - causing that layer to not stick to the previous layer.  Since I was printing layers at 0.15mm thickness, a couple of layers later the filament began to stick - but this error results in the part having no strength at the bad layers.

Here is my photo of the bad cylinder on the left.  The other two parts are shorter and were fine.

scaddesign - did you get your issue resolved?

Monty

 

Not yet. I'm talking to my reseller here at the moment but you have described the exact problem.

[SandervG 1,521]

Maybe this thread and link will be of help

[JohnFox 25]

I got some new ones from Ulitmaker, ( under warranty ).

Very obvious that they slid up and down cleanly.

 

 

I would suspect the Z bearings if you saw the bed drop. I think the balls locked up in the raceway, then suddenly released again. It's a bit involved but if you can undo the bearings, try sliding them up and down the pillars. They should move smoothly but mine had frequent lockups. Changing the bearings solved the problem.

 

JohnFox - After some more investigation, I have found that this is exactly the problem. They move freely for the first 10mm then lock up as you say, when the balls reach the end of the race.

Did you change to a different bearing from what Ultimaker provides or the same bearing without that fault? I'm very keen to find out.

Thanks.

 

[scaddesign 0]

Must be a bad batch.

Good to know there is a solution.

 

I got some new ones from Ulitmaker, ( under warranty ).

Very obvious that they slid up and down cleanly.

 

 

I would suspect the Z bearings if you saw the bed drop. I think the balls locked up in the raceway, then suddenly released again. It's a bit involved but if you can undo the bearings, try sliding them up and down the pillars. They should move smoothly but mine had frequent lockups. Changing the bearings solved the problem.

 

JohnFox - After some more investigation, I have found that this is exactly the problem. They move freely for the first 10mm then lock up as you say, when the balls reach the end of the race.

Did you change to a different bearing from what Ultimaker provides or the same bearing without that fault? I'm very keen to find out.

Thanks.

 

 

[JohnFox 25]

Don't oil the pillars, that seems to be part of the problem. If they are oiled, the balls in the bearings tend to slide rather than roll and make them more prone to jamming.

[scaddesign 0]

New bearings from the re seller seams to have solved the problem (fingers crossed).

[JohnFox 25]

I think the oil on the pillars is the real culprit, the bearings hardly get a lot of use, they only go up and down once in a print.

 

New bearings from the re seller seams to have solved the problem (fingers crossed).

 

[mmcgraw74 1]

I put in my replacement bearings - much smoother action on the vertical shafts.

I also took the opportunity to carefully clean the z-axis screw with a paper towel, turning the screw with my other hand. There are a couple of different tracks to clean. Then I regreased the z-axis screw with the package of grease that was included with the printer.

I've been printing for a couple of days without the missing layer issue - fingers crossed

Monty

[mmcgraw74 1]

Hopefully the final update on my z-axis problems.

My dropped layer issue returned after a couple of days. I contacted support again - they sent a replacement lead screw with attached servo. As I disassembled the leadscrew, I also removed the two vertical shafts and noticed oil on those shafts again. It appears when I put oil on those shafts some of it made its way down to the hole in the base and removing the shaft put more oil on it :(

I tried to remove oil from the hole, sprayed both vertical shafts with brake cleaner spray (which really removes all the oil and any grease) and reassembled.

In performing the vertical bearing alignment - I decided to try raising the buildplate to about half way up the vertical shafts and performing the alignment there instead of at the bottom of the printer. My theory was the shafts may be slightly further apart at the top of the printer, so trying the alignment in the middle might help.

After tightening the bolts on the bearings I raised the bed and lowered it manually and found it was much easier to move the bed up and down at the top of the printer - and it was a little more difficult to push the bed to the bottom of the printer manually.

I've been printing for a week and my z-axis issues have not returned.

Here is an example of printing four ABS models yesterday - about 4 inches tall.

Monty

[JohnFox 25]

You should be OK now.

I give the two pillars a wipe with a kleenex every two weeks or so, this removes any build up of oil from the ball races and keeps the friction between the balls and the pillars high.

Hopefully the final update on my z-axis problems.

My dropped layer issue returned after a couple of days.  I contacted support again - they sent a replacement lead screw with attached servo.  As I disassembled the leadscrew, I also removed the two vertical shafts and noticed oil on those shafts again.  It appears when I put oil on those shafts some of it made its way down to the hole in the base and removing the shaft put more oil on it :(

I tried to remove oil from the hole, sprayed both vertical shafts with brake cleaner spray (which really removes all the oil and any grease) and reassembled.

In performing the vertical bearing alignment - I decided to try raising the buildplate to about half way up the vertical shafts and performing the alignment there instead of at the bottom of the printer.  My theory  was the shafts may be slightly further apart at the top of the printer, so trying the alignment in the middle might help.

After tightening the bolts on the bearings I raised the bed and lowered it manually and found it was much easier to move the bed up and down at the top of the printer - and it was a little more difficult to push the bed to the bottom of the printer manually.

I've been printing for a week and my z-axis issues have not returned.

Here is an example of printing four ABS models yesterday - about 4 inches tall.

Monty