Welcome! Log In Create A New Profile

Advanced

Hot end Carriage shifting

Posted by mrmuffin 
Forum List Message List New Topic
mrmuffin
Hot end Carriage shifting
August 23, 2015 03:27PM
I recently started a project on my kossel mini when I noticed that some of the cylinders I was printing did not come out circular. There was a difference of about 1mm on either side of the cylinder. I decided to print a cube to test this further and found the same thing. One side was 1mm longer than the other. The weird thing was that no matter the size it was always 1mm off. I sat and watched my printer and noticed that the carriage where the hot end is attached wobbled from left to right when the printer moved in the y-axis. My belts are tight and as far as I know the printer is calibrated so that the head moves parallel to the bed. I think there is some sort of backlash happening but im not sure what to tighten or what to check.

Here is my printer






The hot end tilts like this one only the head is picking up when it shouldn't


Reply Quote
dc42
Re: Hot end Carriage shifting
August 23, 2015 04:14PM
Do you have exactly the same spacing between the bearings at both ends of each pair of diagonal rods? If not, that would explain the problem.


Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Reply Quote
dougal1957
Re: Hot end Carriage shifting
August 23, 2015 04:25PM
Quote
mrmuffin
I recently started a project on my kossel mini when I noticed that some of the cylinders I was printing did not come out circular. There was a difference of about 1mm on either side of the cylinder. I decided to print a cube to test this further and found the same thing. One side was 1mm longer than the other. The weird thing was that no matter the size it was always 1mm off. I sat and watched my printer and noticed that the carriage where the hot end is attached wobbled from left to right when the printer moved in the y-axis. My belts are tight and as far as I know the printer is calibrated so that the head moves parallel to the bed. I think there is some sort of backlash happening but im not sure what to tighten or what to check.

Here is my printer
[attachment 60585 20150715_215237.jpg]


[attachment 60587 20150715_215257.jpg]


The hot end tilts like this one only the head is picking up when it shouldn't

[attachment 60588 thisone.jpg]

Looking at your photos it appear's that your rods are not parallel ie your effector may be installed rotated by 120 degrees that would cause all sorts of weird effects the rods MUST be parallel for the thing to work correctly.

Doug
Reply Quote
dc42
Re: Hot end Carriage shifting
August 23, 2015 04:52PM
Quote
dougal1957
Looking at your photos it appear's that your rods are not parallel ie your effector may be installed rotated by 120 degrees that would cause all sorts of weird effects the rods MUST be parallel for the thing to work correctly.

Doug

I think you mean 60 degrees, but otherwise I agree.


Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Reply Quote
mrmuffin
Re: Hot end Carriage shifting
August 24, 2015 12:05AM
Sorry this is an old picture when I had exactly that problem. Right now the arms are attached properly and parallel on the effector. The one thing i'm really unsure of is the carriage's wheels. when I watch the printer the carriages wobble on the rails. Almost as if the wheels are not holding onto the rail firmly enough. I have tried tightening the wheels as best I can but the problem still persists. If anyone has any experience with this type of movement system I would like to know the best way to secure the carriages.
Reply Quote
nebbian
Re: Hot end Carriage shifting
August 24, 2015 12:19AM
Check that the bearings inside the rollers themselves aren't completely shot. I'm running into exactly this issue on a new build (different manufacturer, same idea). It seems that some of the bearings are really loose, leading to the slop you're seeing. Try grabbing the effector and trying to tilt it in every direction. You'll see the bad wheels slopping around.

If anyone knows where to get reasonable quality V rollers delivered to Australia then I'm all ears...

Edited 1 time(s). Last edit at 08/24/2015 12:20AM by nebbian.
Reply Quote
o_lampe
Re: Hot end Carriage shifting
August 24, 2015 02:18AM
The problem is the design of the carrier itself. A single ballbearing isn´t meant to give radial stability.
We would need two more rollers ( or a needle roller ) on the back of the extrusion to take the sideload.

The good news is, we have 3d printers to create a stabilizing cage to combine it with the existing carrier.
-Olaf
PS: Just found an interesting roller, that would provide axial and radial stability ( the small black one )



Edited 1 time(s). Last edit at 08/24/2015 02:24AM by o_lampe.
Reply Quote
dougal1957
Re: Hot end Carriage shifting
August 24, 2015 02:35AM
Quote
dc42
Quote
dougal1957
Looking at your photos it appear's that your rods are not parallel ie your effector may be installed rotated by 120 degrees that would cause all sorts of weird effects the rods MUST be parallel for the thing to work correctly.

Doug

I think you mean 60 degrees, but otherwise I agree.

Yep one of those Blonde moments there Dave bit of tiredness induced Brain Fade (Been on call at work and been out most of the weekend around 34 hour's overtime and counting so will be able to afford a Duet 0.8.5 at the end of the month).

Doug

Edited 1 time(s). Last edit at 08/24/2015 02:40AM by dougal1957.
Reply Quote
dc42
Re: Hot end Carriage shifting
August 24, 2015 02:57AM
Quote
o_lampe
PS: Just found an interesting roller, that would provide axial and radial stability ( the small black one )

Those are the ones I use. Searching for "delrin v-roller" brings up a number of suppliers. Each one needs two 623ZZ bearings.

Edited 1 time(s). Last edit at 08/24/2015 02:57AM by dc42.


Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Reply Quote
o_lampe
Re: Hot end Carriage shifting
August 24, 2015 03:16AM
Thanks David,
am I right, these rollers roll on the face of the extrusion? Did you print your own carrier to match the smaller diameter?
I only have standard t-slot extrusions, I´m afraid their v-center section won´t fit there.
-Olaf
Reply Quote
dc42
Re: Hot end Carriage shifting
August 24, 2015 03:25AM
Quote
o_lampe
Thanks David,
am I right, these rollers roll on the face of the extrusion? Did you print your own carrier to match the smaller diameter?
I only have standard t-slot extrusions, I´m afraid their v-center section won´t fit there.
-Olaf

Yes. They work nicely on my Motedis I-profile 2020 T-slot extrusion, and on Mitsumu 1515 extrusions. The maximum slot width they would work with for T-slot extrusion is about 6mm. My remixed carriage truck design is here [www.thingiverse.com].

Openbuilds has a wider selection of rollers.


Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Reply Quote
Newer Topic Older Topic
Sorry, only registered users may post in this forum.

Click here to login