Prusa i3 6" Z motor to threaded rod connection prob

Hi all;

New to the forum, forgive if this problem solved somewhere here...

My new Makerfarm Prusa i3 (6" model) worked great first time, but then I noticed one of the threaded rods on the Z axis was working it's way out, then of course the whole carriage went out of step and I can't print. I was really suprized that the connector for the 2 Z axis motor to threaded rods was just a piece of clear tubing. One would think there would be a much better connection than this on such a critical connector. What is happening is that the Z axis, when dropped down to begin a print, was pushing the plastic tubes off the threaded rods. There seems to be no way to avoid this...the carriage can't get low without pushing the tube off every time. I was really suprized to not find that this was a common problem. There are solutions on Thingiverse, but with no printer... (also there is such a tiny space on the threaded rod available).

I was just wondering...did I do something wrong in making his printer, and does anyone else have this same problem? Looks like a real engineering mistake.

Michael Scott
Citizen13
Ottawa, Ontario Canada

Makerfarm has some metal z-axis connectors available in the hardware section if you want to try them, I think it'll be the 5mm-5mm ones. Otherwise you could try to put a zip tie around the plastic tubing to help hold it onto the threaded rod.

---

MakerFarm 8" Prusa i3v
RAMPS 1.4
0.4mm E3D v6 for 1.75mm

I put a ziptie on mine only on the bottom where is attaches to the motor.

I had this issue when I first got the printer but it was fixed with a ziptie and also lubing the z screws. If there is ANY binding on those threaded rods it will pull that hose right off.

Thanks for the advice, guys. I have ordered the metal Z-connectors, and will lube the rods...we tried zip ties but there wasn't much rod to tie to. May also drill out the bottom hole in the carriage to make room.

Mike

Yea unless you drill out that hole on the bottom of the X carriage you cannot put a zip tie on the threaded section because it goes into the wooden section.

I had similar problems when I started testing my axis, on Colin's suggestion I lowered the z-motor to 15 (instead of 30) which helped me a lot in figuring out what else was going wrong, ie; nuts on the threaded rods were not secure in the nut traps on the x-idler and x-motor. I also eventually took 2 zip ties to the plastic tubing connecting the motor and the threaded rods.

What do you mean by "lowered the z-motor to 15"?

---

MakerFarm 8" Prusa i3v
RAMPS 1.4
0.4mm E3D v6 for 1.75mm

In Pronterface

Unfortunately it was only a temporary solution and I'm still having issues with the nut on the x-idler sliding down.

Did the Couplers work?

Yup, the metal couplers work for me, once I learned to not mount them so high they hit the bottom of the X axis, and to tighten the screws beyond what I thought was the bottom of their holes. I like having them attached with screws and not zipties

The only times I've had a problem with the nuts on the threaded rods coming untrapped is when the Z axis tried to move the nozzle through the print bed. The X axis won't move, but the nuts will.

Edited 1 time(s). Last edit at 04/28/2014 09:06PM by AbuMaia.

---

MakerFarm 8" Prusa i3v
RAMPS 1.4
0.4mm E3D v6 for 1.75mm

The metal couplers worked for me too...I had to cut some of the wood away to get down far enough to the build platform. Really, this should be the default coupler, not the lame plastic tubing.

My other problem is as AbuMaia stated...sometimes the nut trap on the threaded rod pops out and stops raising the carriage. Every now and then for some reason the Z stop doesn't click and the nozzle gets driven into the bed, popping out the nut. There is nothing to hold the nut on the bottom, seems to me another weak point of the design.

I haven't had to cut any wood away to use the metal couplers I got from MakerFarm. Just don't try to give the motor shaft and the threaded rod an equal share inside the coupler, and it'll fit. Push the coupler as far onto the shaft as you can, then put two or three millimetres of threaded rod in the top, and tighten it all down. It also helps to have the nozzle as close to the bed (or touching) before you tighten down on the threaded rod, to make sure you have room.

---

MakerFarm 8" Prusa i3v
RAMPS 1.4
0.4mm E3D v6 for 1.75mm

I got couplers today, they seem to slide right on the motor shaft with no problem.

Are the rods supposed to have wiggle room when first inserted into the coupler (before tightening)?

Yeah, the rods are a bit looser than the shafts. When you tighten the screws, you'll feel what seems like the screw "bottoming out". If you leave it there, the threaded rod will be too loose still. Put more torque into it, and really tighten the screws. Be sure to leave a small gap between the end of the threaded rod and the motor shaft, too.

Edited 1 time(s). Last edit at 04/29/2014 09:52PM by AbuMaia.

---

MakerFarm 8" Prusa i3v
RAMPS 1.4
0.4mm E3D v6 for 1.75mm

The threaded rod shouldn't be resting on top of the motor shaft?

Thanks!

how will I know when it's tight enough?

thanks!

No, the threaded rod should not rest on the motor shaft. You'll know when it's tight enough when you can turn the top of the threaded rod (with the printer off) and it turns the motor shaft without slipping. You can hear and feel this.

---

MakerFarm 8" Prusa i3v
RAMPS 1.4
0.4mm E3D v6 for 1.75mm

Thanks!

---

MakerFarm 6" Prusa i3, Kossel Mini in the works

Still having issues getting the couplers on right, am I using the wrong type? [instagram.com]
I got these at my local DIY electronics store, I think they were made by Servocity.com

thanks!

Edited 1 time(s). Last edit at 05/01/2014 08:18AM by BlaiddDrwg.

---

MakerFarm 6" Prusa i3, Kossel Mini in the works

They look similar to mine. Mine, which I purchased from MakerFarm (http://www.makerfarm.com/index.php/hardware/5mm-to-5mm-z-coupler.html), have a split on each end, so that when the screws are tightened, the metal "clamps" around the shaft and rod. It looks like yours just have grub screws to press directly against the shaft and rod to hold them. I don't see any reason why yours would be "wrong", or that they wouldn't hold.

---

MakerFarm 8" Prusa i3v
RAMPS 1.4
0.4mm E3D v6 for 1.75mm

Good to know I'm probably just being super OCD, but I can see how the clamping could be a better.

---

MakerFarm 6" Prusa i3, Kossel Mini in the works

I use aquatic tubing very tight to get on but the flex will compensate any z wobble But my tubing had inner diameter of 4mm had get it over 5mm shaft and threaded rod

---

Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]