RE:
Instructions:
Calibrate Z.
Use the display to raise Z to around 50-60 mm and take your measurements.
(See image)
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
Instructions:
Calibrate Z.
Use the display to raise Z to around 50-60 mm and take your measurements.
The comment in the image, "gap will increase as you go higher", is important. There may also be a fixed left vs. right difference due to tolerances in the frame and chassis. To separate it from the effect of unmatched thread pitch, I would do this measurement twice, at two different heights of the bed, say 10 mm and 110 mm below the nozzle. Then the change in the left vs. right discrepancy over 100 mm travel can be determined.
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
That approach is good for the front 2, but not any good for the rear leadscrew.
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
There is another common and related complaint that seems to fit this thread. That is loud and scarry rubbing and vibrational sounds the core one produces when tranvsersing the full range of the Z-axis.
In my case, I was attempting to groom my mk4s to coreone+ upgrade to eleminate those noises when I noticed the front lead screws were tiled backwards with the bed at the bottom and tilted frontwards when at the top. I didn't attempt to measure the lead screw pitchs, but it was visually obvious that the bed tilt changed over the full range of Z travel. My bed is tilting along the y axis, not the x.
To me the most likely explainatations that fit both of these observations is that the lead screws are rotating at differnet speeds, one or more of them are slipping poles, or the lead screw pitchs are not the same. In any case this definely a design or manufacturing flaw that prusa needs to address.
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
That approach is good for the front 2, but not any good for the rear leadscrew.
In that case the best is a digital clinometer
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
[...] I noticed the front lead screws were tiled backwards with the bed at the bottom and tilted frontwards when at the top. I didn't attempt to measure the lead screw pitchs, but it was visually obvious that the bed tilt changed over the full range of Z travel. My bed is tilting along the y axis, not the x.
To me the most likely explainatations that fit both of these observations is that the lead screws are rotating at differnet speeds, one or more of them are slipping poles, or the lead screw pitchs are not the same. In any case this definely a design or manufacturing flaw that prusa needs to address.
I think you are misinterpreting this. The tilting lead screws are due to lateral forces which the black trapezoidal nuts exert on the screws. This is a common alignment issue in the Core One, because the assembly instructions do not ensure that the lateral position of the nuts agrees with the position defined by the smooth vertical rods that guide the heatbed. But it is easily fixed:
- Drive the heatbed all the way down.
- Loosen the six M3 screws which attach the three trapezoidal nuts to the heatbed (two per nut). This lets the nuts find lateral positions that are in agreement with the smooth rods.
- Probably the lead screws will already have straightened and centered when you loosened the M3 screws. If they are still a bit slanted, center each top end with your fingers while you fasten the corresponding M3 screws again. Do not overtighten the M3 screws; the nuts are plastic (POM).
This should give you smooth Z movement without lateral strain and push on the lead screws. If the Z drive still "groans" during longer moves, it needs to be lubricated. Apply a bit of the lubricant that came with the kit to the lead screws.
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
That approach is good for the front 2, but not any good for the rear leadscrew.
In that case the best is a digital clinometer
Agreed 100% 👍
What was the outcome with yours? Did you contact Prusa?
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
If the Z drive still "groans" during longer moves, it needs to be lubricated. Apply a bit of the lubricant that came with the kit to the lead screws.
Although this is the best approach, I hate the fact that soon after lubrication the screws are then a magnet for dust and other airborne contaminates.
RE:
Frankly, I don't see why anybody would want to use an inclinometer. It needs to be absurdly precise to show small errors, e.g. better than o.o5 degrees for 200 µm offset over the spindle spacing (that is, pi/180*atan2(0.02, 300)). Having two digits after the decimal point is still a long way from being accurate ... The only advantage I can think of, it doesn't distract the user with needless worry about "small" errors that may be "totally negligible - really", still clash inconveniently with marketing language. Do your own math 🙂
To confirm the relative alignment between the three screws,
- home and move the print bed up to Z=0
- move the print head near each of the spindles and turn it manually (against the resistance of the Z motors) until the print bed is perfectly parallel, relative to the head plane. A playing- or business card serves as ad-hoc feeler gauge between print bed and nozzle to set consistent distance at all three spindles, within +/- 0.5 motor step if working accurately.
- run the print bed down near (but not touching) the bottom and use a suitable object e.g. a capped bottle to confirm that the distance is still consistent near all three spindles.
RE:
Frankly, I don't see why anybody would want to use an inclinometer. It needs to be absurdly precise to show small errors, e.g. better than o.o5 degrees for 200 µm offset over the spindle spacing (that is, pi/180*atan2(0.02, 300)). Having two digits after the decimal point is still a long way from being accurate ... The only advantage I can think of, it doesn't distract the user with needless worry about "small" errors that may be "totally negligible - really", still clash inconveniently with marketing language. Do your own math 🙂
To confirm the relative alignment between the three screws,
- home and move the print bed up to Z=0
- move the print head near each of the spindles and turn it manually (against the resistance of the Z motors) until the print bed is perfectly parallel, relative to the head plane. A playing- or business card serves as ad-hoc feeler gauge between print bed and nozzle to set consistent distance at all three spindles, within +/- 0.5 motor step if working accurately.
- run the print bed down near (but not touching) the bottom and use a suitable object e.g. a capped bottle to confirm that the distance is still consistent near all three spindles.
Using the nozzle just throws in another variable (whether the gantry is sitting perfectly flat) so I don't think that's a good method at all.
Using an inclinometer in this application is over the entire length of the screws, where Z is calibrated, and somewhere close to the top...showing around 0.3 degree tilt where a within tolerance leadscrew is compared to an out of tolerance leadscrew.
It's a quick test that shows repeatable results.
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
Posted by: @ Jürgen
I think you are misinterpreting this. The tilting lead screws are due to lateral forces which the black trapezoidal nuts exert on the screws. This is a common alignment issue in the Core One, because the assembly instructions do not ensure that the lateral position of the nuts agrees with the position defined by the smooth vertical rods that guide the heatbed. But it is easily fixed:
You might be correct about the bending forces caused by the trapezoidal nuts, I thought of this as well and in fact spent nearly 2 hours trying to get the T-nuts, the build plate's front mounting brackets, and the motor mounts to settle into a non-binding position. I even lubricated the rods with dry PFTE lubricant. I finally gave up because I couldn't change the noise generation, nor have I been able to keep the bed parallel with the carriage.
On my printer after several prints I will start to get a visually obvious tilt to the print bed. Doing the z-calibration routine will drive the bed against the T- nut screws, but usually I have to rotate the back lead screw an additional turn or two so to bottom out the back of the plate. After this intervention, the print bed appears parallel. But the noises remain. In my case, all the vibration is being transmitted up the right front lead screw. I have been able to very effectively dampen the noise by folding a piece of felt around the top of the screw to absorb the vibration, but I haven't made this permanent yet.
But keeping the bed parallel is by biggest concern.
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
Using the nozzle just throws in another variable (whether the gantry is sitting perfectly flat)
Err... I would argue exactly the other way. Print height (/distortion) is bed-to-nozzle distance so measure it directly.
It's as simple as it gets, arguably with the smallest number of contributing error terms.
RE: Different Z lead screw travel between MK4S upgrade screws and Core One kit — 2 mm mismatch
Using the nozzle just throws in another variable (whether the gantry is sitting perfectly flat)
Err... I would argue exactly the other way. Print height (/distortion) is bed-to-nozzle distance so measure it directly.
It's as simple as it gets, arguably with the smallest number of contributing error terms.
An inclinometer is as simple as it gets.
Calibrate Z.
Zero Inclinometer
Raise Bed
Check inclinometer.
You're overthinking it mate.