Ender 5 plus - How to get a reliable Z

[Jordan Jones]

This is my second 3d printer, first being an Wanhao duplicator i3+ which printed very reliably, but just too limited in built volume. Needed 350x350, so I got an ender 5+.  Initial calibration cube and benchy were spot on but in the last dozen prints my failure rate is well over 50%.   This printer was used, so I thought it probably had issues. Indeed, it does... 

Here are the issues:

- Build plate needs re-levelling on a daily basis, which is a clunky process in this interface (goes through a really slow homing / bltouch check). I'm almost always adjusting Z-axis compensation during the first layer.

- Printer occasionally seems to 'forget' where the Z axis is at the beginning of the print, go off the plate and smack the front left corner (probably the BLTouch too, though I haven't seen it)

- BLTouch doesn't always register (red blinking on startup). Possibly due to damage from the previous issue.

- Z axis seems to 'drop' layers sometimes, leaving a weak or non-existent layer even if the rest of the print is perfect. Not always in the same place. Photos attached.

- Screeching from guide when doing big Z-axis movement.

I have my own ideas, but where would you far more experienced people start?

[Kurt Wendt]

What is the build plate? Glass??

Am not familiar enough w/E5+ , maybe switching build plate may resolve some issues...

-Kurt

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[Jordan Jones]

The ender 5 is a cube-frame cartesian printer. The + has a much bigger build volume, factory BLTouch and dual Z rods. It got a decent glass bed from the factory, which my straightedge says is OK. Bed adhesion isn't great but that can be tweaked.

https://all3dp.com/1/creality-ender-5-plus-review-3d-printer-specs/

[Vishal Pai]

I'll start by getting rid of the BlTouch from Creality. Go for a double Z endstop switch and manual four point leveling and make sure you have strong springs below the bed. 

For the Z steps missing,  check for straightness of the lead screw. If it seems straight bind it with an idler bearing at the top. Make sure you have a backlash nut or double delrin nut driving the Z up and down. 

Oil the Z bearings (sewing machine oil or saw chain oil) and make sure the rods have been trammed properly for smooth motion both at top and bottom.

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[TobyCWood]

Uh…. Strong disagreement on binding the top of a lead screw with a bearing. Bad idea.

If the top of a lead screw wants to wander you let it wander! Forcing it into being straight deforms the threads as well as creates sideways forces both of which will greatly inhibit the z axis movement.

[Vishal Pai]

I beg to differ on this

The do-not-add-bearing-at-the-top philosophy came from i3 style printers that use printed parts to align the Z nut and the Z rod linear bearing. The idea was that if the axis were not exactly parallel after the linear bearing was press fit inside the plastic the free end of the lead screw would move using the give in the spring coupler to accommodate that misalignment and give incremental Z lifts.

But Machined metal/laser cut sheet metal plates do not have this issue if they are cut accurately.

From very simple mechanics,we are converting rotational motion (motor spindle) to translational motion (carriage plate).  

Using a hard and centered spyder coupler (like a CNC axis) and constraining the screw allows more precise Z motion. If the axis are not parallel to the lead screw then you have to tram the rods or fix other manufacturing defects in alignment or fixing the straightness of the Z screw.

Checkout any prosumer well engineered 3d printer. Even professional ones from Desktop Metal and Markforged. They all have constrained Z even with ball screws. 

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[TobyCWood]

WRONG.

The "do-not-add-bearing-at-the-top philosophy" came from some of the most respected bot builders in the community. It was NOT only about Mendel machines. It has to do with using cheap lead screws. I DID see the Mark Forged and I DID talk directly with them about it YEARS ago. The simple reply they gave me was the lead screws they used are qual checked BEFORE they are used. They are NOT stressed into position which is what you are recommending to someone else to do.

Dude... You do whatever the heck you want to do on your machines... but if you are going to make recommendations to people looking for help I suggest NOT shooting from the hip.

[Vishal Pai]

I think you got me wrong there..

I am NOT asking him to stress the lead screws but add a bearing at the top that prevents any kind of wobble without over constraining it.. If the lead screws are bent then they need replacements (which is QC in a way !) because he is having missed layers as well.

Look at any SLA printer and you'll see they have these bearings at the top that keep the lead screw straight. Heck every Ender 3 dual-z upgrade has a bearing on the top because two screws rotating in tandem are going to add forces to the gantry even if one of them has a wobble. His printer also has two screws ! 

The solution to troubleshooting cheap (aka badly engineered !) printers is not to redneck hack the way out and pray they print well. The solution is to engineer them with good components so they become consistent and reliable. 

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[Jordan Jones]

I think, for now, my goal will be to get it printing correctly with the stock design. Any inherent design flaws are not significant enough to prevent most of the ender5+'s out there from printing without skipping layers.

Whether the bed can be made to stay level.. well, that may just be intrinsic and I'm open to the shotgun approach. I hope to have time to disassemble this weekend and see if I can find anything bent.

[Jordan Jones]

In the end it appears it was actually an extrusion issue. My current theory is that it probably had some blockage which caught in the feed assembly occasionally, but dislodged or lodged itself during the layer change. (Although this theory would make more sense if 'retract at layer change' was enabled)

What happened: I had a few prints with major under-extrusion issues which I didn't believe it was related. I took the nozzle/feed system apart. I didn't find any blockage, but I did have to trim a few mm off each end of the bowden tube during disassembly. Upon reassembly I printed a few parts and not only is the under-extrusion issue solved, the layer-skipping issue also disappeared. Still work to do on the bed levelling and Z screeching, but the printer is usable. Will continue to monitor.