My DIY Maestro powered Bed-Slinger (many photos inside)
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@droftarts said in My DIY Maestro powered Bed-Slinger (many photos inside):
... to check the motor status and short the coils if turned off. Did he ever do it?!
yes, works as expected
z motor is not very powerful so with original screw on ender5 it "kinda works" so with the glass off the bed it holds the bed, but barely, if there's a print on the bed it will sometimes slowly start to drop.. maybe glass is too heavy, there are also the big hands stiffening the bed, the precision piezo sensors.. but it holds it from "dropping like a stone" as it did before this mod. I'm now waiting for the new replacement screw (with 1 start compared to 4 starts on original one) and with backlash nut (not required for this use but backlash nut adds additional tension to the screw increasing friction) it will stay still even without this mod and with this mod I believe it will be rock solid. Unfortunately, we had a month of post on strike here so everything is now delayed
I doubt I'll get the new screw this year.. I will also replace original motor with the .9 degree one as I have few of them but they are high impedance so too slow for anything else so why not use it to increase precission even more :D, Z is slow anyhow 
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If all you're worried about is the bed somehow doing some damage when it drops, almost anything can be used including putting a couple springs at the bottom of the Z axis so the bed will make a soft landing.
If you want to absolutely stop bed motion when power is lost so that you can resume a print after a power interruption, you need either a brake, a worm gear drive, or some other solution that locks the bed in position. A high ratio conventional gearbox (or a series of pulleys and belts) may work if the detent torque of the motor multiplied by the gear ratio is greater than the torque created by the potentially falling mass.
If the bed drops and you want to resume a print, you have to have an accurately calibrated Z ordinate for the bottom of the Z axis. Then you can just move the bed back to the previous Z ordinate and resume printing. It might be useful to use a switch at the bottom of the Z axis.
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@smece said in My DIY Maestro powered Bed-Slinger (many photos inside):
backlash nut adds additional tension to the screw increasing friction
I think you'll likely notice the 1 start lead screw is more than enough to stop any automatic downward movement. The backlash nut would likely add enough extra friction in that case to allow for easy binding. At least that's what I found with my 1mm pitch single start lead screws. My bed assembly is very heavy and during a power loss there is no movement whatsoever, even when loaded up with several kilograms of filament on the bed. When I first tested the anti backlash nuts the z axis would bind and stall at the start of long travel moves. I had to reduce the acceleration dramatically to overcome that. I gave up on the anti backlash nuts after that.
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@Phaedrux said in My DIY Maestro powered Bed-Slinger (many photos inside):
The backlash nut would likely add
I'll do the test when the darn thing finally arrives... with a month of strike the amount of backlog our post office now has and the half of January in holidays I'm lucky if I get it during winter
My first experience with Z screws and anti-backlash nuts was some ~10 years ago on RapMan by bitsfrombytes (the duet team surely knows them, they were from uk too, one of the pioneers) and they used plexy + two M8 screws with a spring to create anti-backlash contraption. The first mod for rapman was to remove that spring as a bed that heavy had no need for those springs
and that simple mod made the Z work great (and mind they used nema23 motors, quite power ones) ... so yes I also believe that nut will lose the anti-backlash part ... but .. will know when it arrive -
@mrehorstdmd said in My DIY Maestro powered Bed-Slinger (many photos inside):
If all you're worried about is the bed somehow doing some damage when it drops, almost anything can be used including putting a couple springs at the bottom of the Z axis so the bed will make a soft landing.
It can still generate quite the voltage spike even if the mechanical fall is cushioned; and again - print resume with shorted coils work just fine for the tolerances applicable in consumer 3d printer as proven by Tiertimes design in the Up Mini 2. I can find a flat earther leaflet for you if you wanna keep arguing pointless stuff:P
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Hey all,
thanks for the discussion around keeping the bed, or x-axis beam in my case, steady without enabled steppers. Let's postpone this discussion though, as it seems to get a little pointless without test results from my side.
... I hope to make some progress this weekend.
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@mrehorstdmd said in My DIY Maestro powered Bed-Slinger (many photos inside):
I've broken taps in plates before.
You can use Alum to dissolve a broken drill or steel tap in aluminum.
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First off I have to say that is quite the beautiful build. Do you have it modeled and etc in Fusion 360 or some similar program? Also would you mind sharing your source for black pei? I've been looking for a pei that isn't clear. Is it actually pei or more like buildtak?
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@sonderzug said in My DIY Maestro powered Bed-Slinger (many photos inside):
the obvious disadvantage is that the x-axis drops like a stone when the steppers have no power applied
A geared motor like this one could keep it in place when power goes off.
https://forum.duet3d.com/topic/12942/get3d-free-give-away-free-extruder/17?_=1577063841912
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Hi all,
"next weekend" turned into a few weeks, but with the holidays and everything I only had limited time to work on this project. However, the remodeling is more or less completed.
I announced that I would be ditching the igus linear rails. I did so in favor of used/new old stock THK linear rails that I obtained from ebay. In particular, I bought RSR12 (ZMUU) and RSR9 (WVM - double wide rail) rails, which will help this build achieve a much higher mechanical quality but will also be carried over to future builds (the lenghts allow for a bigger build volume than this has).
The problem with the igus rails was, as mentioned, that I chose the square profile rails which are not tensionable. The round profile drylin W rail has options for setting the tension of the gilder with a screw.For the new rails, I obviously had to account for the missing structural components of the drylin rails. The easiest and most precise thing for me was to have aluminium sheets lasercut for my purpose. So this is what I did.
I further wanted to eliminate the cheap chinese belt idlers, which I replaced with 608zz bearings on which the backsides of the belt run. Obviously there are no flanges to guide the belt, which is a bigger problem than I anticipated, so I will have to replace some of those with flanged bearings.
I opted for genuine Gates GT3 belt, to eliminate further influence from cheap components. So far the print results are way better than before, regarding the quality aspects that can be traced to the mechanics of the printer.
Pictures:
the x-axis plate has mounting options for the rail, idler, motor and optical endstop. The stepper motor is mounted in a seperate printed part that allows it to be pivoted around the lower mounting hole, allowing to tension the belt.
This arrangement is copied for the y-axis. The heatbed will be mounted like before.
assembled and running:
right now the printer is printing some parts for itself, namely the cooling ducts for hotend and part.
A short glimpse under the hood:
Why the board hasn't been mounted with it's edge facing outward to easily connect the ethernet cord, I can't tell
I didn't deem it too important at the time, unfortunately.I still have to tidy up the cabling of the hotend as well; the cables are connected with two 8-pin connectors for which I want to design plug housings and strain reliefs as well.
On the topic of the x-axis falling down when the power is taken off the steppers.... yes it will of course, and unfortunately also when the stepper's coils are shorted. I will design a little lever that the x-axis can run over at the z-max end, which will snap into place to keep the x-axis up after power-off; I have a RC servo lying around which I will use to release it automatically.
I'm overall happy with the rebuild and hope I'll be able to use the printer for railway modelling etc. in the future.
Best regards, Niklas
