Slider Blocks not holding the x-axis rod

[ShinerG 6]

Hi, I'm hoping someone will be able to help me.  I've had 4 failed prints in as many days now.  I've tightened up the pulleys and the short belts onto the stepper motors. I had luckily printed two alignment clips to ensure that the axis rods were aligned.  But the problem is continuing, the slider blocks are not holding the x-axis rod.  The rear one pops out mostly, but they're both not adequately holding the rod.  It's not loose - just that they can release the rod if it knocked against a building print for example, but the prints are fine - until they stop. There's no evidence of the print head knocking against anything.  In Cura I've changed the infill to be 0% and the line number to be 10, to minimise the x-y movements and to fill the interior with just perimeter offsets.  This helps to reduce the jerky movements - but it is not solving the problem.

 

  I don't want to tape, or otherwise hold the rod in place as I'm concerned that this is the safety mechanism to ensure that the motors are not damaged if the axes are not aligned and forced to print skewed. Can these slider blocks' clasping feature wear out and loosen over time - is this a thing?  I've tried to buy the slider blocks and belts from my re-seller, but they're not available in their online shop. TIA.

[gr5 2,265]

You didn't say what kind of printer this is.

 

Is this a UM3 with white blocks?  If so then this is a known problem and contact your reseller and they will send you free replacements.  Or contact igo3d.  The white blocks crack.  UM switched to black blocks that work much better over a year ago.

[ShinerG 6]

Hi Gr5,

  Sorry, I didn't but I'd tagged the UM3.  I've the black ones, so it might be just bad luck. I've gone around the whole unit tightening everything and have another print on at the moment and it looks good - so far.  I was in touch with my re-seller and the slider block plastic parts are only a euro plus VAT and delivery, so I'm going to order 4 with the belts.  I'd prefer to be looking at them instead of for them, when they do need to be replaced.    It's a pain, but I feel relieved to know that they are consumables and do wear out. I was more concerned that it shouldn't be happening or a known problem.

[gr5 2,265]

The black ones shouldn't wear out but the white ones do.  Are there cracks in the blocks?  If so then yes definitely it's a simple fix.

 

[ShinerG 6]

Hi again Gr5,

 There are no cracks, at least visible to the naked eye.  I'd to abort this print too, as the rear end of the y-axis bar popped out again.  I was trying to work out what I changed lately to make it fail - I oiled the printhead's rods - their entire lengths last week.  So I think it's as simple as that (un)fortunately!  I've wiped them down and added a single circumferential-length of Scotch 3M Magic Tape at the point where the rear rod will be gripped by the slider block.  The slippery rods combined with the loose slider could have only one ending.  I hope that this print will work and get me through my customer orders while I wait for the new slider blocks to arrive. 

[gr5 2,265]

Putting on new slider blocks is not easy.  I built a custom tool/jig (out of a block of wood and nails I think) to do it as it was difficult.  Some people do it in place on the printer: pop open the old ones, pop on the new one in place.  It didn't occur to me to do this.  I spoke with someone who does this professionally (changed dozens of printers from white to black blocks) and he said he takes the gantry completely apart and does it the way I did it.  I don't know which is easier though.

 

[ShinerG 6]

Thanks again Gr5,

 

  I came across this great set-by-step tutorial. It's well written, but I'll have to re-read it a few times before I dig into it.  I've become spoilt in the age of YouTube - my skills at extracting the info off the page aren't what they were :) 

 

 https://fbrc8.zendesk.com/hc/en-us/articles/207813353-Replacing-Parts-on-the-X-Y-Axis