I've been thinking about adding the double-nut-and-spring anti-backlash thing to the z-axis on mendelmax

I’ve been thinking about adding the double-nut-and-spring anti-backlash thing to the z-axis on mendelmax 1.6, but I can’t seem to find any information about what springs are suitable dimensions/force, anyone with recommendation or even better ebay link ?

If gravity won’t bring the X axis down, you’re binding on the Z axis rods. Fix that instead, probably for free.

I don’t think that is the problem, I believe the force trough the filament up to the roll is slightly lifting it when rapidly moving along the x axis.

I’m a little surprised you’re not missing steps on X then. Perhaps you have good enough cooling to turn the current up on the driver. I still want to put a fan on my RAMPS, but it’s working now and I always have something else I’d rather get done when the printer has my attention.

Anyhow, I’d still suggest fixing a problem rather than adding complexity to cover it up. People stopped putting these springs on Mendel variants close to 2 years ago because they found them to be unnecessary. If your X axis is tugging on the filament, I think rerouting it or adding a guide is the thing to do. My MakerGear Prusa came with some tubing for experimenting with a Bowden setup. Instead, I used it as a flexible guide for the filament so the X axis never pulls on it.

What @Dale_Dunn said. The slop in the leadscrew nut is just one of several present on the Z plane. There is also some slight axial deflection in the cheaper flexible couplers, deflection of the X rods, loose clamps, bendy plastic parts etc etc. Backlash is a problem on X and Y due to the rapid directional changes incurred, as long as your Z movement isnt bananas fast, gravity should be enough.

Tubing is a good idea, but a little bit more work to implement.

Actually I’m not sure this is a real problem. I just wanted to give it a try. Yesterday I started a print with the filament tangled up on the roll. What I could see (I caught it at the end of the first layer) was that the nozzle/extruder was lifted further from the build plate the the further from the center (x) of the build plate I got (my filament spool is mounted top center) and I didn’t loose any x-steps.
Then I just got to think that this force is probably normally there, increasing with higher speeds. Since I’m using ordinary M8-rods there is an obvious gap lifting the extruder (and x-axis)

Tubing is probably the correct solution, but springs seems simple.

@Tim_Rastall Thanks for your input, I’m not fighting backlash caused by z-axis movement, but from the force through the filament when moving along X. Leading the filament trough a tube is probably a good solution for this, but I havn’t seen that on any medels before. Anyway, with your arguments (more sources for z-backlash) tubing is an even more attractive option.

Look at the Mendel 90 design - fed from a similar situation, and little to no impact on the x-carriage…