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SoliForum - 3D Printing Community → Hacks & Mods → Eliminate banding: 5mm Theaded Rod Fitment Kit
With a normal nut and screw thread you will always have backlash due to the play in the junction.
You need either a lock nut or two nuts to combat this.
As for increased wear, I had to buy the M5 rod in a metre length so I have another four pieces spare.
With a normal nut and screw thread you will always have backlash due to the play in the junction.
You need either a lock nut or two nuts to combat this.
As for increased wear, I had to buy the M5 rod in a metre length so I have another four pieces spare.
That pretty much depends of a few factors.
1. First - grease. Adding grease will reduce the backlash a little, since quite a force is needed to push it away from between threads while moving.
2 The nut height. For minimal backlash theory says the height of the nut should be at least 1.2*rod_diameter. So my 12mm height is quite an overkill.
3. How the rod and the nut was manufactured. This is th main lottery. There are a LOT of variations here, so this is pretty random. For instance, the original threaded rod was definitely at the lower boundary of allowable deviations, since when I tapped the nut, I only used screw tap number I and II out of three. For M8 rods (close to 5/16) I got here tapping only I and II usually will never allow the nut to fit at all.
The nuts from the same shop gave me some backlash I could see, the ones I had gave a little bit different, older soviet aviation-grade 4mm height nuts gave literary none. (I'm lucky to still have a few of these)
In case of M5, the maximum possible backlash is really small. (I don't remember the allowed deviations for these rods and nuts, if someone does post it please), added grease the will be barely noticeable. But still, the lottery applies.
So summing up, my suggestion for whoever tries this mod is the following order of experiments:
1. Try a few different nuts from different stores, preferable 4mm height or more, don't forget the grease and nothing more. If you end up with no backlash - you won the lottery.
2. If still backlash, and making own brass nut sounds like black magic - got for lawsy's 2-nut
3. If you are hardcore enough - go for a custom nut, since this will likely to give you best results possible. Remember, that older, worn-out screw taps result in more tight nuts!
Great post.
Personally in my case, there was noticeable movement when trying to move the platform up and down. I hadn't greased the rod much, however.
Once I added the second nut and the nut hugger, the movement was gone.
Just printed you parts Will tackle next few days.
read the article regarding Z wobble in this magazine.
http://reprapmagazine.com/issues/1/index.html (article starts on page 29, but look at the information regarding Z ribbing on page 30/31)
Darned article! It's the bad penny that keeps coming up. I (and several others) thought it was right myself and I posted about it until I did the math and found out that the frequency of banding we're getting on the Solidoodle (18tpi) can't be related to step error. If microstepping had an effect it would not be spaced matching the thread pitch but at an intermediate one based on the layer height you were using.
I calculated that microstepping ribs would be spaced out every 0.5mm when printing .1mm layers, and another spacing when printing at .3, and none at all when printing at a multiple of .07055mm. And yet on the Solidoodle everyone is seeing ribbing at a constant frequency of 1.411mm no matter what layer height they print at.
Thus, if this sort of microstepping-based ribbing is occurring, it's far too small an effect to notice on the Solidoodle, and is being far eclipsed by the wobble-based ribbing.
Instead, all the tangible success I've seen is using combinations of one or more of the following: flexible coupler, soft motor mount, thin rod, fine-threaded rod, anti-backlash device, and software compensation.
Using a fine-threaded rod is my current favorite; since you're changing the thread pitch, it's the only method that's guaranteed 100% to eliminate the ugly, coarse, 18tpi banding. Even if you still had the worst wobble/backlash in the world, bands at .5mm are hardly noticeable compared to 1.411mm, and going to a fine thread and thin rod automatically reduces backlash and wobble.
tealvince, I don't think that the issue on solidoodle is anyhow related to microstepping. The reason is that the way they attach the threaded rod to the stepper never guarantees them being centered. Even if you take the stock rod, detach it from stepper and reattach with even a poorly printed ABS coupler you'll get MUCH better results.
Well, and the stock nut sucks as well.
Sanity Check.
Most articles Ian included on Wordpress article switched to the thread rod away from the coupler for the banding issue? Is this true? I just printed the 2 ABS blocks from Neromant build for now.
Do not want to do it if it will be worse
tealvince, I don't think that the issue on solidoodle is anyhow related to microstepping. The reason is that the way they attach the threaded rod to the stepper never guarantees them being centered. Even if you take the stock rod, detach it from stepper and reattach with even a poorly printed ABS coupler you'll get MUCH better results.
Well, and the stock nut sucks as well.
I agree; that was the point I was trying to argue. The banding is due to wobbling of the rod, not microstepping, which is why the width of the bands matches whatever thread you are using on your rod. More flexible rod/coupler/motor-mount => less banding, and finer thread => finer (hardly noticeable) banding. Put them together and it's effectively gone.
Incidentally, I also found that my motor shaft itself was bent a bit off-axis.
Sanity Check.
Most articles Ian included on Wordpress article switched to the thread rod away from the coupler for the banding issue? Is this true? I just printed the 2 ABS blocks from Neromant build for now.
Do not want to do it if it will be worse
I don't see any way that can give more precise mount on the stepper, than a coupler. Unless, well, you make the hole for the stepper on the same lathe as the rod.
I think in my case the printed couple was off center, and the direct attachment was centered better. Also I suspect the rods they had might have been better as well. The really bad ribbing seemed to be non-existent until about Oct, and then lots of posts and photos about it started showing up.
With the stock set up, the ABS coupler may not be better, because everything has to be installed just right to get good results. Using the thinner rod, better nut, etc makes the aligment of the motor coupling less critical.
My ribbing developed over time.
The Z stepper had started to lose its grip on the inside of the threaded rod. If I had the second backlash spring too tight, sometimes the stepper would spin with the platform not moving. On a bad day the platform would get stuck, on a good day not all of the the z movements would occur properly, leading to some very dodgy layers.
With the stock set up, the ABS coupler may not be better, because everything has to be installed just right to get good results. Using the thinner rod, better nut, etc makes the aligment of the motor coupling less critical.
That's precisely the conclusion I came to. When I first installed my M3 rod, I mistakenly tightened on the coupler at a slight angle so that it wobbled so much it was kind of comical. When I made a test print this way, however, it still came out perfect, which told me if you you have a thin rod with a fine thread and a snug nut (I used a 1" long threaded brass tube) then wobble becomes an unimportant issue. I did find that a helical spring coupler could introduce a little bit of random (non-periodic) ribbing due to its compressibility and changed out later for a rigid brass coupler.
This is the best mod so far and eliminated all banding completely.
HOWEVER, it's really important that you use a good coupling.
I tried printing several before my china-made aluminium one arrived.
All of my printed couplings generated banding, and I was very disappointed until the production-made arrived.
(I bought one that looked like the one used in the original post)
PS.
I also added a washer / nut fitting on the upper-part of the coupling (if that made any difference I don't know)
Now my prints look astonishing!
This is the best mod so far and eliminated all banding completely.
HOWEVER, it's really important that you use a good coupling.
I tried printing several before my china-made aluminium one arrived.All of my printed couplings generated banding, and I was very disappointed until the production-made arrived.
(I bought one that looked like the one used in the original post)
PS.
I also added a washer / nut fitting on the upper-part of the coupling (if that made any difference I don't know)Now my prints look astonishing!
Those prints look amazing! My coupling is being delivered monday or tuesday. I hope I get the same results.
This is the best mod so far and eliminated all banding completely.
HOWEVER, it's really important that you use a good coupling.
I tried printing several before my china-made aluminium one arrived.All of my printed couplings generated banding, and I was very disappointed until the production-made arrived.
(I bought one that looked like the one used in the original post)
PS.
I also added a washer / nut fitting on the upper-part of the coupling (if that made any difference I don't know)Now my prints look astonishing!
Would this coupler work?
I just finished this mod and thought I would share some pictures of the install process.
You could several larger nuts or anything really to sleeve the 5/16" thread but this is what I used.
You can't see it in the picture but the top of the rod has 2 5/16 nuts jammed together to help keep it from turning. 
It would have been smart to use a flat washer under this tool but I couldn't find one at the time. 
You can see the ring that was scored into the stepper motor from not using the flat washer. The 5/16 rod had red thread lock in it. It still came off remarkably easy. 
Make sure to replace the printed coupler with metal one as soon a possible. This coupler makes me lose 50mm of print height because the screws don't clear my bed.
M5 nut placed in carriage nut holder. 
Make sure to put grease on the rod then run the rod up and down to work in the grease.
Insane results!
That last pic is really great.
I'd like to note that I had a tiny bit of banding creep in again. The rod/nut had worn a fraction, so I tightened the top nut a quarter turn and clipped on the nut hugger again. Banding gone again.
That last pic is really great.
I'd like to note that I had a tiny bit of banding creep in again. The rod/nut had worn a fraction, so I tightened the top nut a quarter turn and clipped on the nut hugger again. Banding gone again.
Thanks, I am getting some of the best prints to date on this machine right now. Thank you for putting up the files. Currently printing YSBs Black Swan with his .2mm settings. I am curious if I get as good of results.
My banding just started in the last few prints. The bands go all the way around the part, and they protrude. And my rod does not wobble. I think the problem is pitch inconsistencies in the roll die used to make threaded rods, and/or poorly made nuts. This would explain the recurring banding patterns all the way around the part. Backlash could be a part of it too, but I've held the bed down and it makes no difference.
My guess is that a rod with perfectly spaced threads (pitch) would produce no banding.
So, I will start buying parts for my new 5mm rod retrofit!
Thanks Lawsy, Necromant, Tealvince and all the other soliusers for your hard work on solving this problem. At the end of the day, solutions trump theories.
My banding just started in the last few prints. The bands go all the way around the part, and they protrude. And my rod does not wobble. I think the problem is pitch inconsistencies in the roll die used to make threaded rods, and/or poorly made nuts. This would explain the recurring banding patterns all the way around the part. Backlash could be a part of it too, but I've held the bed down and it makes no difference.
My guess is that a rod with perfectly spaced threads (pitch) would produce no banding.
So, I will start buying parts for my new 5mm rod retrofit!
Thanks Lawsy, Necromant, Tealvince and all the other soliusers for your hard work on solving this problem. At the end of the day, solutions trump theories.
You are right about the threaded rod not being even on the thread pitch, just has to do with how the rod is made... cost vs. time thing... one other thing to check on is have you calibrated the PID's yet for the hot end? this has caused me some banding(thermal) when I was first up and running, while not as noticeable as some of the examples of peoples z wobble banding it can also add to it.
Great suggestion Ronsii. If anybody is reading this and has not done this, I highly recommend it as well. I did get thermal banding right out of the starting gate, until i did PID autotune.
BTW, I wrapped the top of my heat block with insulation and kapton, and reran PID. Now my temps don't even vary by more than a couple tenth of a degree or so. The reason I added more insulation was so my 25mm side fan (to keep barrel cool) was sometimes cooling the temps of the hot end down too much.
Could someone provide a link to instructions on how to calibrate the z steps/min for this mod? I have searched and cant find an answer. I know where to di it in repeater host. But I dont know the formula to figure what value I should change it to. Any help would be much appreciated.
Jonathan,
The steps per mm for this mod is 4000. Here is how we figure that out.
I am going to use m5 rod with .8 pitch or 1.25 rotations per mm. I the Z motor is 1.8 degree/step or 200 steps per rotation. 1.25x200 = 250 steps/mm But we use 16x microstepping so 250 x 16 = 4000
For M3: 400 steps/mm x16 = 6400
Could someone provide a link to instructions on how to calibrate the z steps/min for this mod? I have searched and cant find an answer. I know where to di it in repeater host. But I dont know the formula to figure what value I should change it to. Any help would be much appreciated.
The stepper motor has a resolution of 3200 steps/mm, so for thread pitches of:
Stock rod (1/18"): 3200/1.411 = 2268
M5 x .8 (coarse thread): 3200/0.8 = 4000
M5 x .5 (fine thread): 3200/0.5 = 6400
M3 x .5 (coarse thread): 3200/0.5 = 6400
Jonathan wrote:Could someone provide a link to instructions on how to calibrate the z steps/min for this mod? I have searched and cant find an answer. I know where to di it in repeater host. But I dont know the formula to figure what value I should change it to. Any help would be much appreciated.
The stepper motor has a resolution of 3200 steps/mm, so for thread pitches of:
Stock rod (1/18"): 3200/1.411 = 2268
M5 x .8 (coarse thread): 3200/0.8 = 4000
M5 x .5 (fine thread): 3200/0.5 = 6400
M3 x .5 (coarse thread): 3200/0.5 = 6400
Thanks guys I was real confused on this part. Also if anybody has any tips on how to remove the old sd pressed rod. Im all ears lol. I worked on it for 2 hours last night and couldn't get it to budge. I think I might have even hurt the stepper motor pulling on it. 
Does and one have a link on where to buy a stepper motor that doesnt have the sd rod pressed onto it?
SoliForum - 3D Printing Community → Hacks & Mods → Eliminate banding: 5mm Theaded Rod Fitment Kit
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