I decided to make an improvement to the Buildplate and Y Carriage on our machines here after coming to the conclusion that the recent updates to the D9's firmware and auto-leveling feature should now be able to make use of the changes I've made. Once you reset your Z, auto leveling will be easier since you are now basically giving it a level bed to start with and can rely on the software. The tension spring system is now, legacy and outdated in my opinion.
Some background on it; I have been using printers with similar features for years now. I've never been a fan of constant, and eventual (still) periodic adjustment to bed leveling for that sought after first layer goodness, not when we have already had the means to do away with that system altogether. I'm used to having my printers tuned to set it and forget it. I haven't had to adjust level or even Live Z tweak for over a year on my machines so I stand by proof of concept there.
To date I've tested this change for well over 50 (and counting) prints and in between purposely reset and thrown the X and Z off to require running through the auto leveling procedures without any problems over the last couple weeks after implementing it.
Onward, with a disclaimer:
If you decide you want to give this a go keep in mind that while it's not exactly an advanced modification, it still IS a modification, and with any modification, done wrong can lead to problems, damage, and even voiding your warranty. Proceed at your own risk.
We simply exchange the current screw and spring leveling components for solid standoffs and allow the auto leveling system to do its job with a better initial starting point. Most of the grief I see users dealing with is specifically at the point in printer tuning is leveling and first layer refinement. This modification simplifies the process and makes it far easier to get to printing. Thats the idea right? The below images are pretty self explanatory, and the things you'll need are pretty common and inexpensive.
(4) M3 20mm Brass Male and Female Ended Standoffs. You could use other metal variations but I do not recommend plastic or nylon because of the heat we can experience when printing higher temperature filaments and needed bed temperatures. Just dont do it. I happened to have a few different kits laying around and the standoffs can be purchased individually or in various packages, I prefer keeping stocked up and places like Amazon are great for these. Another advantage to the kit packages is you dont have to rummage around for nuts or screws. Keep that in mind too. I used the included screws in the kit because they were low profile button type and the right length.
Current Firmware: D9 300 V0.164b
Currently only testing on the D9 300.
You'll use the stock insulating washers already on your machine. Do NOT try to substitute these for metal or leave them out completely, they are important for insulating the heat bed from the rest of the machine in the event of electrical malfunction. You'll also use the stock knobs optionally, or M3 nuts for the bottom as shown in the drawing and images. I secured them from vibration with silicone washers I make myself from high temperature gasket and punches. You can buy them as well, or use any similar type as long as they do the job of keeping the knobs from coming loose easily during printing.
Assemble as shown below:
When finished, you'll have something like this:
After its all together:
Once assembled, you will have to go through the auto leveling process as normal. I highly recommend making sure your sensor is triggering properly, and homing Z a couple times to make sure. In the event your current stored Z settings are way off, be prepared to shut the printer down during homing or auto leveling if the extruder begins crashing into the bed. Resetting the Z home fixes that and on a couple tested machines it took a couple times to make it stick, and with additional testing and purposely crashing the extruder I found even though we are making the bed and carriage rigid, there is enough play in the wheel system to keep you from really damaging anything IF you catch it right away. In other words, and I will be plain here: Dont be stupid and let the extruder try to grind itself into the bed, simple as that.
In conclusion and for further testing:
I'd consider the changes a success and improvement. Moving forward, additional changes to further refine this would be as shown below:
We already improved by using the stock points 1-4, but on the 300 series I'll be adding A, B and C. 400/500 series will probably need the addition of D and E. It cant hurt to use all 9 on the 300 as well, but at the start Ill go the approach as I mentioned above.
And finally, a secondary Z-Stop limit switch to limit going below -0.15 or so to failsafe for the people who enjoy hearing the extruder crash below its intended safe zone with this modification. There appears to be a open connection on the motherboard for this, Im looking into this as well.
Look for additional updates soon...