Keith's Electronics Blog

The Voron community comes across as antagonistic about a number of issues, one of which is: If your build surface is perfectly flat, there’s no need for bed mesh leveling!

Well, if your build surface is perfectly flat, good for you.

Even then, it would be more accurate to say that if your Voron 2.4 build surface is perfectly flat, the Voron is intrinsically incapable of using bed mesh leveling to improve it. (The Voron 2.4 levels the gantry to be parallel to the build surface by probing near the four corners. If the plane of the build surface isn’t square to the vertical members of the frame, the Voron has no way of determining that it’s always going to print non-rectangular parallelograms in the X-Z and/or Y-Z planes. But I digress.)

My aluminum heat spreader is not perfectly flat because it came in a kit from Fysetc rather than from a milling machine with a fly cutter; and my Voron 2.4 benefits tremendously from bed mesh leveling. (Above, without; below, with.)

To take my mesh to the next level, it’ll help to get the bed mesh configuration correct. The provided configuration is a useful starting point but can be improved significantly.

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The Voron 2.4 has a Z home switch off the back end of the build plate with a steel pin on top. The hot nozzle tip can press the steel pin without melting anything; so once you calibrate the height offset between the switch’s trigger point and the surface of your build sheet, you have absolute repeatable positioning of the height of the tip above your build surface. As long as you never ever change to a different build surface.

If, on the other hand, the Z pin is positioned further back than the tip of the nozzle can travel and the hotend’s silicone sock is pressing the Z pin, results may vary from minute to minute. Literally.

With the Spider mainboard online and talking to OctoPrint, a cabling issue corrected, and a pinning issue I-thought-dealt-with-but-actually-no, documenting-soon, it was time to work through Voron’s initial startup checks to verify all pinning and basic functionality. The document’s order of operations is fantastic; but too often it says what to do and doesn’t say how to do it. Let’s fill in some gaps.

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With OctoPrint talking to the Klippy host software on the Pi talking to the Klipper firmware on the Spider mainboard and the Voron’s LCD lit up and control panel working, I could see that the firmware was able to read hotend and platform temperatures and I used the printer’s control panel to test each of the two heaters. The heaters worked; but I noticed that when heating the hotend, the part-cooling fan came on and the heat break fan didn’t. Probably the fan connections were swapped?

I’d wired the printer per Fysetc’s diagram for this printer on a later revision of their Spider board because it was the only diagram I could find at the time and I wanted to be able to use a sample configuration file as a starting point rather than do the whole pin configuration from scratch. Tempting though it was to just swap the two fan plugs on the mainboard and be done with it, I went back to the wiring diagram from the Fysetc Spider board GitHub page first for a closer look.

Oh. Oh, I see. I had previously noticed that Fysetc had labeled both of them as 4010 fans; but I hadn’t noticed that they had swapped the labels of which fan served which function. I had originally connected my fans by tracing which function was connected to which Spider port; but with the functions swapped on the diagram, my wiring was swapped on my board. I now changed my wiring to match the Fysetc diagram’s intent (and the sample printer.cfg‘s configuration) and noted the error in the wiring diagram here for later reference. The fans now behaved as they should.

After running the Spider mainboard test firmware as a sanity check of the Spider’s operation and LCD cabling, several paths are available to get Klipper installed onto the Spider. My factors were:

• not feeling like continuing to power the Pi from an external source, even during the firmware process
• not feeling like continuing to re-jumper the Spider board for DFU programming
• my Spider should now have a working 32K bootloader installed

That led me directly to SD-card firmware installation, which was easy-peasey since I have another *nix-ey computer available for one step.

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I still have notes to share about the rest of the mechanical assembly and I have so many thoughts about the wiring; but I just powered up the Voron to test the mainboard and want to record my thoughts while they’re fresh.

No, my Voron won’t run Marlin; but the test firmware does.

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So actually the AB stepper motors need to be installed with their connectors facing each other, toward the center of the back plane of the printer. The 2.4r1 instructions don’t mention this at all; the 2.4r2 instructions mention it clearly.

If you installed them with the connectors facing out the back, especially if you did that based on my earlier and now corrected misinformation, be apprised that you can correct them merely by loosening the AB belt tensioners on the front of the printer, removing the three long M3 screws that go all the way through each of the blocks into the steppers, rotating the steppers in place, and reassembling.

If you know someone who’s a dope and already took the top off of the A or B block, spilling precious towers of bearings and washers, let them know that it’s even easy to recover from that. Remove both AB steppers from their blocks to get lots of slack in both belts; hold long M4 machine screws up from below through the bearing positions and rebuild the towers; nudge the belts out of the way of plastic parts; put the lid back on; and push the M5 machine screws down through the bearing stacks, pushing the temporary M4s out of the way as you go. I mean as they go.

The 2.4r1 assembly manual only shows assembly for the plug_panel_filtered_mains.stl (lower), which is what I printed while waiting for my kit to ship with the power inlet that fits the plug_panel.stl (upper). Don’t be fooled like me.

On the subject of the power inlet … the default configuration puts the power switch oriented with off up and on down, which I cannot abide. A small prying tool on the switch’s latches frees it from the inlet housing to be reinstalled in the One True Orientation. Just take a snapshot of the power wiring on your switch before undertaking such shenanigans.