yizhou.he wrote:

I so far have zero experience on high end hardware at all.

Then perhaps you should sit back and be quiet for a change - and maybe learn something from those that DO have the experience.

Just sayin...

It'll be a cold day indeed when that happens.

He literally cannot shut up ever.   

Moving on...   

jwavedog have you eliminated the possibility that you have a bad wire or connection?   Have you checked your drivers?  I've had weird stuff crop up when wires or drivers go bad.   It can be vexing for sure.  I spent a month trying to figure out a print defect only to find a bad wire.   VERY easy to overlook.

I so far have zero experience on high end hardware at all.

Then perhaps you should sit back and be quiet for a change - and maybe learn something from those that DO have the experience.

Just sayin...

You right, the fact that I have been using and building 3d printers since 2008 means nothing. Your outstanding experience is far superior to mine.

Just realize your fix is not the fix for every machine and while it may work to have a rod bound on one machine it may not for others. If the rods are allowing flex due to diameter versus length then that is a poor design and the fix would be to increase the rod diameter.

Not a fix for some of the less technical but still would be the proper fix. Another fix would be to use case hardened rods and not just drill stock. Case hardened rods which is what should be used are much more ridged per given length than drill stock which is the most common used rod in cheaper printers.

Mine are case hardened on my CT'c which why I guess there is no flex in them. You can test them by removing one and using a dremel with a cutoff wheel on the very end you should have a very hard time cutting them if they are case hardened. Again though not something the less technical might want to try.

I think your CTC use thick and short rods, they are lot difficult to bent. The case hardened rod may also contribute to the strength.

Keep in mind that OPS Pxmalion CoreI3 and my MonoPrice Make Select are all low end large size printer (about or under $200), Your CTC are high end mid size printer which target different level of accuracy. I do agree my fix is only for low end machines and most of my fix is cheap fix. I so far have zero experience on high end hardware at all.

carl_m1968 wrote:

That is a bent rod, and it should be replaced plain and simple. Turning it and locking it so the bend is parallel to the screw is just a band aid and band aid repairs with the 3d printers should be really avoided as you are only prolonging and possibly adding to other problem.

When the rod is long and thin, it is impossible to keep it perfect straight, it's own weight in the middle will bent it slightly by gravity. That's how these low end large size machine are designed and unless I determined to replace it with thicker rod with some major mod, I don't think new rod will help. The machine is designed not allow the rod to rotate for a reason.

Even with that hypothetical bent rod, this machine generate amazing print quality. I would love it if it don't generate laud noise. I also have a MonoPrice Maker select plus, the rod design are very similarly locked by a hex screw. It also generate good print quality as well as laud noise.

You're right, the fact that I have been using and building 3d printers since 2008 when they first became home items and only a hobby means nothing. Your outstanding experience is far superior to mine.

All of your machines seem to be low tier sub $500 machines and that would explain the use of rods that are too small for their length and the need to bind them. The binding also prevents them from flexing as easy under their length. My Ct'c not to be confused by the umbrella brand of CTC is an all metal $900 unit that has 10mm rods through out and sealed bearings. It is a very well made but very easy to repair and find parts for machine. I don't know why they stopped making it and went for the cheaper wood frames. It is one of the best machines I have owned next to the D7. It is so quite I have to check to make sure it is operating every now and then.

Just realize your fix is not the fix for every machine and while it may work to have a rod bound on one machine it may not for others. If the rods are allowing flex due to diameter versus length then that is a poor design and the fix would be to increase the rod diameter.

Not a fix for some of the less technical but still would be the proper fix. Another fix would be to use case hardened rods and not just drill stock. Case hardened rods which is what should be used are much more ridged per given length than drill stock which is the most common used rod in cheaper printers.

Mine are case hardened on my CT'c which is why I guess there is no flex in them on the long axis of 300mm You can test them by removing one and using a dremel with a cutoff wheel on the very end you should have a very hard time cutting them if they are case hardened. Again though not something the less technical might want to try.

That is a bent rod, and it should be replaced plain and simple. Turning it and locking it so the bend is parallel to the screw is just a band aid and band aid repairs with the 3d printers should be really avoided as you are only prolonging and possibly adding to other problem.

When the rod is long and thin, it is impossible to keep it perfect straight, it's own weight in the middle will bent it slightly by gravity. That's how these low end large size machine are designed and unless I determined to replace it with thicker rod with some major mod, I don't think new rod will help. The machine is designed not allow the rod to rotate for a reason.

Even with that hypothetical bent rod, this machine generate amazing print quality. I would love it if it don't generate laud noise. I also have a MonoPrice Maker select plus, the rod design are very similarly locked by a hex screw. It also generate good print quality as well as laud noise.

I do agree about the wear. My Y rods are fixed in all dimensions and the bearings are wearing traces in them. I'm actually shopping for replacements now and manually rotated them as a temp fix.

I don't know if this is machine specific, my machine with the issue is MonoPrice Maker select V2, it designed to use a hex screw to prevent the rod from rotating.

https://3dprinterwiki.info/x-axis-rod-a … djustment/

The machine is designed to have the rod fixed and I don't see signs of damage on the rod so far, nor do I see complain on internet about the rod damage. However, if the rod is able to rotate, the print will have wave over z-axis, it is not the z-band we usually see. One wave is about 12mm in cycle less than 1mm tall which I did not bother to measure accurately.

I think this wave will not be visible if the rod is perfectly straight. However, the longer and thinner the rod is, it is less possible to keep it perfectly straight. When it rotate during printing, tinny bent will generate small inconsistency over time and produce weak waves over z-axis. I think those machine that allow rod to rotate must have rod that is >10mm in diameter and have limited length <220 mm. 

I don't think rod rotate can cause the OPS issue, but if the rod are allowed to move can cause the backlash symptom. I do agree loosing belt related issue is the most common cause, if he can not identify issue from the belt angle (which I think your reply already got it covered), it doesn't hurt to check if the rod are mobile.

P.S. I can not open the image linked in original post

That is a bent rod, and it should be replaced plain and simple. Turning it and locking it so the bend is parallel to the screw is just a band aid and band aid repairs with the 3d printers should be really avoided as you are only prolonging and possibly adding to other problem.

Carl, Can you explain how it would be possible for the x carriage rods to be able to rotate but not to slip in the x dimension when using the Lawsy carriage design? I think he even built in a hole for a lock screw to hold them in place. This also prevents rotation of the rods when used.

I see this thread is about a different printer design so maybe this is not applicable here.

Rods that slip along their axis is fine and prevents no issue as long as the slippage is only along their axis and so much that they can be pulled from their mounts. The only time I can see a rod slipping in its own axis being an issue is if the home or max end stop was mounted directly to the rod. Then that slippage would allow for the end stop positions to change and this would cause dimensional issues.

My Ct'c dual head has rods that move along their axis by about 1mm total. They do not have any play in any other direction though and they do spin. I can print perfect circles and boxes with it at all times. I know this machine is reliable and trust it to all my jobs.

So again rotation and small play along it's axis should not cause issue with a rod and a print. Again the exception is if the endstops are hard mounted to the rod and not the rod mounts.

https://3dprinterwiki.info/x-axis-rod-a … djustment/

The machine is designed to have the rod fixed and I don't see signs of damage on the rod so far, nor do I see complain on internet about the rod damage. However, if the rod is able to rotate, the print will have wave over z-axis, it is not the z-band we usually see. One wave is about 12mm in cycle less than 1mm tall which I did not bother to measure accurately.

I think this wave will not be visible if the rod is perfectly straight. However, the longer and thinner the rod is, it is less possible to keep it perfectly straight. When it rotate during printing, tinny bent will generate small inconsistency over time and produce weak waves over z-axis. I think those machine that allow rod to rotate must have rod that is >10mm in diameter and have limited length <220 mm. 

I don't think rod rotate can cause the OPS issue, but if the rod are allowed to move can cause the backlash symptom. I do agree loosing belt related issue is the most common cause, if he can not identify issue from the belt angle (which I think Carl's reply already got it covered), it doesn't hurt to check if the rod are mobile.

P.S. I can not open the image linked in original post

I see this thread is about a different printer design so maybe this is not applicable here.

My experience with one of my printer is the rod that x-axis carriage or Y-axis print bed slides on is not fixed can also cause this problem. If you can rotate or even move any of the rod, find ways to fix them.

Rods that can rotate are fine. In fact in most printer designs the rods are not fixed to allow rotation. They are allowed to rotate as this prevents wear from occurring from the bearings running in the exact same spot over and over. I have never seen a printer where the rods where not allowed to rotate. The reason is that in most cases the balls in the bearings are harder than the rod and they will score the rod if they are allowed to run on the same surface.

The main thing to assure is that rods are straight, parallel, and not allowed to move on their opposite axis. For example you do not want a Y rod to be able to move at either end in the X axis. Like wise with the X versus Y. Rods that rotate are the easiest to find if they are bent or not. Just place the head over the bed, rotate the rod by hand and note if you see the head move any. If you do then that rod is bent. That is also another reason rods are allowed to turn.

The shop I used to work in even had rods that would turn on their large CNC machines. By binding the rod where it can't turn you are doing more damage than good.

We are trying to remove issues here, not create more. When you have an issue like the OPS, you have to focus on the mechanics and physics that can cause the issue. A rod that can rotate as long as it is straight will not and cannot contribute to the OPs issue.

While you think this may have been an issue for you in the past it was probably something else you did while messing with the rod that fixed your issue.

I'm using a variant of the Prusia i3 (Pxmalion CoreI3), and it consistently prints circles with these two "corners". It's the same every single time too.

https://s9.postimg.org/oh3ey08kf/20180307_041358.jpg

You can see how they come off the bed here.

https://s9.postimg.org/hqmxolvpb/20180306_214746.jpg

Up and down is Y, left and right is X.

The belts feel just about as tight as each other. Everything seems to be moving freely. It prints cubes just fine. I'm not sure what's wrong.

The manufacturer says to: print a square to help in troubleshooting problems of XY axis and backlash. (https://www.thingiverse.com/thing:795967) The shorter belts in most case can cause backlash that is the primary cause of circles being not so circular. Make sure all belts are securely tight and check all pulleys have their set-screws tight, and aren't slipping.

I've done that. Everything's tight. everything feels fine. What do I do?