Anet A8 Y-axis bed movement "grumbles"
April 30, 2018 01:06PM
I recently built an Anet A8, and it works pretty well right off the bat, but it can be better, and so, in the great spirit of "reprap-ing", I am hacking it to improve it.
So far I have...
Put on a Z-axis end-stop enhancement
Got a single-piece bed plate and put on a three-point leveling system.
Put tower stabilizers on the top of my Z-axis towers
Added front and back "stiffeners"
Added a better part cooler
Put on a X-axis belt tensioner, so I can easily remove that belt

The Creeper in the upper left is my Octopi print server. smiling smiley
I find that my dimensional accuracy is quite good in X and Y, and under 1% off in Z, not bad, need to adjust steps on Z a bit. However I have some waviness in the sides that I suspect comes from by bed movement. Two things that I notice here is that the Y-bed stepper pulley, bed belt clamps and front belt pulley are not all in the same plane. There is a pronounced "arc" in the belt as it rises from the pulley to the bed clamps. That can't be good. Another thing I note is that the bed "grumbles" as it moves forward and back. I am pretty sure that this vibration is adversely affecting the print and could be what is giving me the "waviness" in my sides.

I suspect cheap linear bearings for the vibration, and REALLY want to put all the pulleys and the bed belt clamps in the same plane. What I wonder is, are the cheap bearings the issue, or is the poor pulley/bed-clamp alignment that largest contributor to the vibration.

I am soliciting inputs to determine my next course of action.


Edited 2 time(s). Last edit at 04/30/2018 01:08PM by dlc60.
Re: Anet A8 Y-axis bed movement "grumbles"
April 30, 2018 02:00PM
My bed made the same noise. I pulled one rod at a time and added lube into the bearings. She runs smooth now. Can't remember what I did with the belt, but I do know what you are talking about.
Re: Anet A8 Y-axis bed movement "grumbles"
April 30, 2018 02:54PM
My bed made the same noise. I pulled one rod at a time and added lube into the bearings. She runs smooth now. Can't remember what I did with the belt, but I do know what you are talking about.

Tried that. When I put the frame stiffeners on the base I pulled both rods and oiled them. If anything, now it may actually feel worse... Nothing is binding, the rods are parallel and the bed moves freely. It just, "grumbles".

Oh, one more thing that I did at the time I put the base upgrades on, I replaced both of the GT2 belts with the "softer", more flexible ones that everyone else in the universe but Anet (apparently) uses.

Re: Anet A8 Y-axis bed movement "grumbles"
May 25, 2018 11:23PM
Well, I bit the bullet and installed the drylin plastic bearings. These things are SUPER smooth. Time will tell how long they last.
My "gronching" and grumbling Y motion is gone. But not all was rainbows and unicorns! One side's pair lined up perfectly for an exceptionally smooth motion. The other side, not so much. No matter what I did, that other side would bind. The drylin bearings do not tolerate any mis-alignment, I had heard, and can now attest to. So... A wise reprap'er once wrote, "Three points define a plane, four points define a potato chip". When I built this machine I bought a replacement Y carriage because the one the kit comes with is so flimsy. This carriage had holes for two linear bearings on one side, and holes for three on the other. The third one was centered. This was all the hint that I needed. I pulled one of the linear bearings and mounted only a single on the troublesome side. Everything sits fine, levels fine and works fine. Now, it works very quietly.

Gronching is now a thing of the past and since this grumbling occured near the center of the bed, my prints are much nicer as well. Between the time when I started this thread and now though, I have installed a better Y carriage holder for the belt that drops the belt down so that the belt is now straight between the stepper, the bed and the front bearing. That has to improve linearity at the extremes of the bed movement. I have also made a major change in the hot end. I now have a clone E3Dv6 being direct fed by an "itty bitty belted extruder"(see Thingiverse). This assembly is probably a bit more than just half of the mass of the original kit, and since it is a geared extruder, about four times more precise. I also use Marlin firmware instead of the stock stuff so I could add that extruder and give the machine a safer firmware (one that does heater overrun checks.) This was super easy as the Anet A8 configuration.h files are included with tghe 1.1.8 Marlin release.

The drylin bearings are not very expensive and work like a charm. I recommend them (so far).


Edited 1 time(s). Last edit at 05/25/2018 11:34PM by dlc60.
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