Anyone out there ever have issues with lead screws for Z axis automatically moving

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(Greg Nutt) #1

Anyone out there ever have issues with lead screws for Z axis automatically moving downward due to the weight of the gantry/carriage? How have you resolved it?

(Kevin Danger Powers) #2

I had that issue with my Anet E10. I just tried not to touch it because if I pushed on it, usually 1 motor would spin more than the other and it would throw my calibration off. The remedy to fix this is to attach a belt to both lead screws to make sure they spin at the same time. This way if the z axis does move down, both sides move together. I ended up just buying an Ender 3 which only has 1 lead screw so I don’t have that issue anymore.

(Michael K Johnson) #3

I solved it in my i3 clone that didn’t have a good route for a belt by switching to single-start (8mm diameter, 2mm pitch, 2mm lead) lead screws instead of the more typical 4-start 8mm lead screws.

(Petr Sedlacek) #4

@mcdanlj Sounds like the best solution. I always wondered why are these 8 mm lead screws used instead of the 2 mm ones - why reduce the Z resolution?

(Kevin Danger Powers) #5

@Petr_Sedlacek maybe it’s because the Z axis is accurate enough and 2mm would make the Z Axis take forever to go up and down?

(Petr Sedlacek) #6

@Kevin_Danger_Powers I really like the Ender 3, thinking about getting one to have better print quality for my (seemingly endless) large delta build. But this single Z screw makes me nervous - I imagine the X gantry must be sloping since it’s only supported on one side :wink: But I suppose it’s not a problem if the X-Z interface is stiff enough.

(Petr Sedlacek) #7

@Kevin_Danger_Powers The only upside I could think of was the speed - but I was thinking who needs to go fast in Z? Also, I’m used to an M8 threaded rod for Z with 1.25 mm pitch :smile:

(Kevin Danger Powers) #8

@Petr_Sedlacek It’s VERY stiff actually. I was worried about that as well but it’s so solid I bet that I could remove the vertical support on the right side and it would still print decent. This is the 3rd printer I’ve owned and it’s by far the nicest.

(Petr Sedlacek) #9

@Kevin_Danger_Powers Good to hear that. It’s really amazing what they can sell at $180 and still make a profit!

(Kevin Danger Powers) #10

@Petr_Sedlacek I was blown away at the price to performance ratio of the Ender 3. It’s far better than expected.

(Michael K Johnson) #11

Even on my custom corexy build I’m doing, where I have one motor and synchronous belt driving two lead screws, I’m using single start 2mm lead screws. I see no reason for fast start screws. Z speed is just not important, resolution and stability are…

(Alex Wiebe) #12

Yup. I was hoping to find a simple firmware setting to keep the Z stepper from de-engergizing, but turns out you have to recompile the firmware from source. Not quite that brave yet.

I ended up putting a second nut on the rod, separated with a spring and held close with a zip-tie. That increased the friction enough to almost eliminate the sagging.

See the comments for a picture:

(Michael K Johnson) #13

zyltech carries single-start T8 lead screw with anti-backlash nuts in the US: http://www.zyltech.com/8mm-t8x2-lead-screw-trapezoidal-acme-w-brass-anti-backlash-nut-kit-pre-cut-lengths-150mm-2000mm/

I haven’t purchased from them only because I learned about them about a week after I bought my most recent T8*2 from china after giving up on finding it in the US… :slight_smile:

(Dave Lawrence) #14

My ball screw does the same when my big router is mounted. Fixed by using some long rubber bands as anti gravity lifts. I can lift over 20 lbs but if the motor goes idle 3lbs would make it drop. This does not add any mad like a counter balance would but I’d very effective. May take a little trial to get it correct, but very chest and easy.