Hallo again all,
I recently have been rather annoyed by the massive grinding noise of the Z axis and the slow speed of the farmbot moving- It deafens anyone who walks into the greenhouse, and it is agonizingly slow. I know that graphite lubricant can be used on the drive axle, but this helps only substantially. I have recently listened to higher-speed runs of the motors, and surprisingly, it’s a lot quieter. Still, the speed is somewhat slow. I have six NEMA 17 stepper motors with sun gear reduction, encoders and hardware that can be used to modify them. They are a hell of a lot faster and are very quiet. I also have researched using PTFE plastic rods as an alternative to the aluminium Z-axis drive axle since the plastic is oil-treated and has lubricant properties. Does anyone have any ideas? I don’t see that this should be very hard to execute.
Hallo again all,
You can use different motors, The Farmbot runs on alot of the same hardware as 3D printers, if your looking for more information in general I would start there, specifically motor and driver upgrades.
Also what version machine are you working with?
I used https://www.omc-stepperonline.com/nema-17-closed-loop-stepper-motor-56ncm-79-3oz-in-with-magnetic-encoder-1000ppr-4000cpr-17hs19-2004-me1k, for my motors and past the encoders scaling it was plug and play. There are a few factors you will look at, the step degree will effect your movement precision and mm per step, torque and basically size will determine your power usage.
Speed can be adjusted in the settings, and depending on how well your machine is calibrated it can really get up there. 200 mm/s is pretty quick, though my fiance does say it sounds like bagpipes. The z axis is a bit different and inherently slower because it’s not moving as much per step as your x and y because of the lead screw. You could use a screw that has more travel per rotation, but that has it’s trade offs, if its too steep it could cause the gantry to fall from gravity. The x and y could similarly be affected by changing the gears on the motors, and belts, but again this will affect your step distance
The noise from regular movement will depend alot on your steppers drivers, my machine for example, is running A4988 which are notoriously loud, where as the newer express runs TMC2130, the TMC or trynamic drivers are much much quieter, among having other improvements. Other noise is likely going to be coming from vibrations, such as the lead screw you noted, go through the machine and tighten things down and it may help.
Back to stepper drivers, these are going to be important to the motors you can run, too big or too small and the drivers will not be able to power them without overheating, which causes the motors to act up or overheat themselves. You may also be able to increase the power the drivers are putting out which will give your steppers more torque, you’ll just have to find a happy place with cooling. Once you let us know what machine you have I can let you know more.
I went and looked and your running a v1.4 so you are also running A4988 drivers on a ramps board. Someone with a bit more experience with the firmware should be able to tell you if that particular firmware could run any of the other drivers with modifications, if that is possible, a switch to TMC drivers would probably solve a lot of your noise problems. You could also consider upgrading to a Farmdunio, which has integrated tmc drivers, I believe they sell an upgrade kit. There’s some other gimmicky tricks you could try, such as stepper dampeners, and TL Smoothers, a cheap plug and play solution, thats supposed to ‘smooth’ the electrical current or some nonsense, but they did quiet my printers. The configuration your running now though does allow you to adjust your VREF and give your motors more power if you were considering a motor change.
I am running a stock v1.4 XL with Farmduino and standard drivers- no modifications. A linear rail and FDM printer-style belts would eliminate noise, but would be complicated to set up and have possible missed steps due to tension, belt placement, and other factors. I am going to try to remove the drive axle and spray the living heck out of it with graphite lubricant, then lubricate the spin block. I looked at the Nema 17 modded steppers that you linked and I think I need those exact ones- the ones I have been salvaged from a 3d printer, and use magnetic encoders, but don’t have the right axle. The ones you suggested appear to have the same design as the existing ones. Has anyone tried this yet? Any improvements? Also, I am working on revising the design of the x axis belt driver, since it doesn’t make very much sense that the motors run the belts all the way up the extrusion (torque maybe?) so I have an idea of moving the motors much further down, then adding a tensioner on the gantry. I believe precision movements are really only needed for planting and tool docking- I think using reduction gearing on a PG RS775-125 FRC motor should be fine, with a 3/1 gearing. This should make the farmbot move at an insane speed. Tell me what you think- I have almost every motor and every electronic you can think of
I use the motors I linked but can’t tell you if they are an improvement, the produce a little more torque, but are probably just a side-grade. I don’t know how fast you are trying to get the machine, but standard steppers can get to some pretty impressive speeds, as for the shaft issue you can find gears that fit both D and rounded shafts. I thought about the z axis noise and compared it to my printers the only real difference is the block, printers tend to use brass lead screw nuts, perhaps finding a way to use one of those instead of the block may help, I’m sure that would be a fairly simple mod. As for the x motor position, I think it’s for stability, it sort of tensions the top of the gantry to the frame. Any loss in precision or movement will add up and require more homing, which kinda defeats the purpose of using encoders at all. I would like to stress again though, your steppers drivers are causing a lot of your noise, your actually hearing them cause your steppers to resonate. The z axis in particular is noisy because you’ve got a 800 mm rod, resonating from its motor with nothing else other than the block holding it. I don’t particularly see a motor change doing much for you compared to a driver change. Look at the creality K1, that thing whips around on standard 1.8 degree nema 17s and does so quietly.
The linkage between the shaft and the motor seems to be rattly as hell whenever the Z-axis is moving at slow speeds. I have looked at the drive axle of lower-end printers like the Zortrax m200, and it seems that the motor and the driver are not the problem, it’s just that the vibrations from the shaft have nowhere to go, since the entire assembly is bolted to straight metal. On Monday when I get back to the greenhouse I will try to see if graphite will do the trick, and if it doesn’t, I will try to remove different sections to isolate the point source. I can also send you photos and an audio clip of the differences if you’d like. I found a suggestion on Thingiverse called Silent Blocks for Z-Axis, but it seems to help only substantially. If you would like, please directly message me on the Forum, and I can send you my contact information to communicate more effectively. Also, do read my idea on the DIY section- Absolutely stupid yet insane idea for fully automating growing, you have been very helpful to us and we like to here your idea on this concept. Thank you again!
Side note, the linkage between the motor and the shaft seems to be a straight metal and a double-stack adaptor with tension screws. I suspect the rattling is from the two cylinders not tightened enough- I need to double-check this, but I don’t think the black drive block and the shaft are the problem as much as the coupler.
I will check it out, while digging into the silencing blocks, I stumbled onto this Z Axis - Managed to reduce noise a bit seems it does help. I wonder if adding some small o rings or something between the block and cross slide plate could help in a similar fashion. There are also a couple different styles of z couplers, I personally prefer the screw styled ones because they have a bit more give to them and are in general more forgiving, perhaps using those as well could help with the vibrations. Amazon.com
That link you attached is exactly what I’m talking about. I suspect it’s less of what they think it is- they think it’s the connection between the leadscrew and the block, I think that a rubber bushing around the screws that attach the leadscrew block to the gantry is the most effective at dampening the noise. Again, a theory, but I will be able to test it out soon and get back to you.
Also, after reading the instructions on assembly and looking at both my and your farmbot images, it seems we forgot to leave a larger gap between the motor mount and the coupler- this might result in more vibration running through the farmbot.
As long as the coupler doesn’t touch the plate, and your z rod doesn’t touch your z motors shaft I don’t see how. This is something to check for by the way, the rod is supposed to kinda “float” in a machine like this.
No problem, let me know how it goes, my machine is down already, I tried to use a spring tensioner on the x axis instead of cable chains, and had a nasty snag. So until I finish converting and repairing it, I’m living vicariously through this forum.
@Schmitz @NHSFarmbot that mention of ‘spring tensioner’ just now has me wondering . .
One could reduce the vertical pull-down force on the Z-axis screw with a long axial spring (or 2) ?
With correct lubrication the noise might be reduced somewhat also ?
(I don’t have a fully built bot to play with yet)
I believe it depends on how the spring is mounted. The axial pull is only affected when retracting to home- meaning the downforce rests on the driveblock mounted. This isn’t as much of a problem as dampening the vibration, since lubrication itself seems to not make a very big difference.
I posted an idea earlier on in the thread for making the Z-axis more quiet. Mind you, this only really applies to the farmbot Genesis series, since the Express line has a different design and a quiet mode.
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