Z-Axis a bit tight

[R4fuksake]

Hi, I have messaged tech support 3 times and not had a response...!!!!
I have assembled the i3 Pro-C and find that the Z-Axis smooth rods and bearings are not allowing free movement, ( I have disconnected the belt), they seem a little tight. I can move it by hand but I can feel the tension. This is bound to cause strain on the stepper motor and will no doubt lead to failure. I would like some sort of response and or a solution to this, I haven't even turned the printer on yet.
As this is the 4th time I have made an effort to get a response, if I can't get any help out of Geeetech, I will be sending it back.

[Soadyheid]

Can you please clarify... The Z_axis is the up and down one driven by the threaded rods. The X-axis is the one which drives the extruder head left/right, I assume this is the axis you're having trouble with, not Z?

If so... Have you checked the rods straightness? First thing you need is straight guide rods. My printer had one rod with a 0.020mm deviation which I managed to reduce to 0.0035mm before building. No noticeable tightness and it prints fine.

When you move the extruder from one end to the other is there any particular place it feels tight or is it all the way from left to right?
If one (or both) are slightly bent you may feel tightness at certain parts of the travel. Try rotating one of the rods in it's frame and check again, does it stick somewhere else along its length? if so, suspect bent. You can remove the rod and roll it on a flat surface with a light behind it, look where the rod and surface meet, if it's bent, you'll see it. Biggest amount of light between rod and surface - mark the top of the rod at this point with a permanent marker pen and try (gently!) bending it straight. Recheck as required. Careful! Bend it too much and it's junk though!

You can also use some lithium grease in the linear bearings and on the rods to help free off. I don't know what "a little tight" means. Just noticeable? - the grease may do the job without any other actions.

anyway...
My two cents.
Play Bonny!

Soadyheid

[R4fuksake]

Ooops....sorry.
Its the hot bed axis, thats the Y axis?
Yes, it is the Y axis I should have said.

[R4fuksake]

In relation to your diagmostic checking, the bed travel seems consistantly tight, no free or loose travel t any point.

[Soadyheid]

Yup! That's the Y_axis. OK, There's a possibility that your frame is off the square causing the bearings to bind on the straight rods.

I'm assuming the only difference you have from me (I've got a single extruder B model) is the second extruder.


Can you slide one of the straight rods out of the back of the printer so the Y bed is only supported by the other one. Move it back and forwards. Does it still feel stiff? If it does, you'll have to check each bearing on that side independently which unfortunately means snipping the ty-wrap/zip fastener.
However... If it's fine and free with one side disconnected, check it with the other rod replaced and the first one removed.

At this point you've possibly found a bad bearing or that each side on its own is free.

If each side is free but you get binding when both straight rods are fitted, I'd reckon the base of the printer; front plates, back plates M10 screwed rods and straight rods are not square.
Can you measure the distance between the Y straight rods at the front and back of the printer? Because you say it's tight all the way, the measurement should be the same. Can you check the distance between the associated linear bearings (left one to right one, front and back. i.e. are they aligned properly.)

If the back and front plates aren't at 90 degrees to the M10 screwed rods, the distance between straight rods would be reduced enough to "pinch" the associated linear bearings on the Y carriage bed. Can you check this? I just used a steel ruler to check the distance from the M10 screwed rod end to the end plate was the same,which seemed to work. If there was an appreciable difference you'd be off square. Better idea. - Maybe you can find a kid's geometry set-square to check for 90 degrees between the rods and end plates?

All that's left that I can think of is the alignment of the four bearings in the Y bed carriage, but you'd have found something wrong earlier in the tests probably.

Anyway... Check that little lot and report back.

Good luck!

Play Bonny!

Soadyheid

[R4fuksake]

I did a glass table test with the rods and sure enough they are all bent to some degree, the Y rods being the worst.

[William]

As to the bend Y rod,you can contact your seller about it.

[R4fuksake]

As to the bend Y rod,you can contact your seller about it.

Geeetech are the seller...!

[Soadyheid]

Hi R4fuksake,

I did a glass table test with the rods and sure enough they are all bent to some degree, the Y rods being the worst.

So are both Y rods bent? Can you tell if the bend is in the middle? (which is easier to fix) I found a YouTube video showing the glass table test which may be of interest to anyone reading this Thread with a similar problem:

https://www.youtube.com/watch?v=alWesY-0t1E

You'll note that the guy's attempt to get replacements ended up with a second couple of bent rods. I'd reckon it's odds on that you're more likely to get replacements with bends than straight ones due to the handling inconsistencies of the mail service!

However... I also found a pretty neat way to straighten them as well! I used an arrow straightener to "tune" my rods to something I felt was useable (0.0035mm deviation worst case.) Like I said previously, the printer works fine, no tight spots. But... It's a lot easier to bend an aluminium tube than an 8mm steel rod though!! I reckon I could have damaged the arrow straightener if I'd used too much force.

I found this video of a heavy duty home made straightener which looks much better fitted to the job using a few cheap parts:

https://www.youtube.com/watch?v=mRtIxG2co5w Thanks Robonza!

Hard bits to source may be the skateboard wheels and L-beam, The DTI with mag base is only about £20.00 on Amazon

https://www.amazon.co.uk/s/ref=nb_sb_ss ... AGMKP4AMX3

Just think of the kudos you'd have among your 3D printing mates if you had one of these! Rods straightened while you wait!

Play Bonny!

Soadyheid

[William]

Hi R4fuksake,

I did a glass table test with the rods and sure enough they are all bent to some degree, the Y rods being the worst.

So are both Y rods bent? Can you tell if the bend is in the middle? (which is easier to fix) I found a YouTube video showing the glass table test which may be of interest to anyone reading this Thread with a similar problem:

https://www.youtube.com/watch?v=alWesY-0t1E

You'll note that the guy's attempt to get replacements ended up with a second couple of bent rods. I'd reckon it's odds on that you're more likely to get replacements with bends than straight ones due to the handling inconsistencies of the mail service!

However... I also found a pretty neat way to straighten them as well! I used an arrow straightener to "tune" my rods to something I felt was useable (0.0035mm deviation worst case.) Like I said previously, the printer works fine, no tight spots. But... It's a lot easier to bend an aluminium tube than an 8mm steel rod though!! I reckon I could have damaged the arrow straightener if I'd used too much force.

I found this video of a heavy duty home made straightener which looks much better fitted to the job using a few cheap parts:

https://www.youtube.com/watch?v=mRtIxG2co5w Thanks Robonza!

Hard bits to source may be the skateboard wheels and L-beam, The DTI with mag base is only about £20.00 on Amazon

https://www.amazon.co.uk/s/ref=nb_sb_ss ... AGMKP4AMX3

Just think of the kudos you'd have among your 3D printing mates if you had one of these! Rods straightened while you wait!

Play Bonny!

Soadyheid

Wow,thanks for your sharing,it will be very useful for someone who need it.