Best way to get rid of z-wobble? (Page 1 of 2)

The finer the pitch, the more precise the movement.

Is there any appreciable results between the m3 .5 pitch and the m5 .8 pitch.  I hear many talk about flexibility of the m3, does the m5 also have enough flexibility then?

After seeing pictures of results people are getting from making the upgrade I am already disassembling my z rod and getting ready to order:)

I'd prefer to keep my z axis moving as fast as possible...but that really isn't that big of a deal I suppose as far as printing goes.

So then I suppose the question is which is an easier upgrade, and or is a flexible rod important, or does a flexible coupler achieve the same purpose as the m3? 

My thoughts are that the benefits to going with an m5 is that is matches the shaft diameter of the stepper. Easier to find couplers perhaps. Also it will have more contact surface area between rod and nut (less likely to strip.) So I can't see a huge reason to go with the m3 other then if it's increased flexibility adds a significant quality improvement in prints.

I think it may have been the same post, but if it wasn't in the post I read they fixed that problem by pushing the motor shaft and bottom of the Z-rod until they touched each other.  This eliminated any vertical flex but still allowed for x-y flex. 

I have decided to go with the M5 size too which I believe isn't nearly as flexible as the M3 mod.  I think I will still get great relative band free results but won't have to drive my z-axis stepper as fast.  And also I actually can pick up the M5 here in town for $5 for a meter. So I can do the mod today. Also I have a heavy piece of granite on my bed, I'm worried about m3 being too whimsy for the weight added by my granite.

I will lathe myself up a coupler, and figure something out to adapt the M5 to my aluminum bed's 5/16 nut.  Hopefully I'll post some print pictures tonight:)

Assuming you never want to use z lift on complex models or have upwards motion the same as downwards motion

Oh, and yes, M5 .8 works fine... thats what I have on my SD3

Hey, call me old fashion - but I like my linear motion to be symmetrical

Symmetrical motion is for those that can't divide by 0.

Got the mod done, and am moderately pleased with the results despite the hack job Aluminum coupling I whipped out.  But I have an actual precision machined one on it's way that will eliminate the banding you're seeing.  I didn't take much time to align my stepper motor, and I can see it wiggling way too much, plus I rushed the coupler, and the drill went off center as it progressed down the piece so it really is atrocious. 

I did however take lots of care to machine two 5/16" x 1/2" Allen head bolts so that I could leave the Aluminum bed nut in place, and reutilize my favorite backlash tool the trusty well nut/expansion nut. 

Anyhow with no hysteresis or z-wobble fix turned on my .3mm prints looks promising! My .1mm not so much, but I think that comes back to my very very horribly machined aluminum coupling.  When the new one arrives in the mail I'll post follow up pictures.

Successfully changed frequency, now if I could just machine a proper coupler...

I have seen a few people remark about the rod being drilled off center.  Are you sure you're not seeing an illusion?  Because of how the thread tapers off at the end of any threaded rod, a center hole will always appear to be off center.
Just wondering..

I'd be surprised if they took the time with a lathe and four jaw chuck to get it within +/- 0.05mm of center. Ok maybe more effort then they are willing to go through.  But why they don't just switch over to a rigid coupler I really don't know. They could have them spin dead center every time for $1-$2 materials increase.  They might even save money due to not having to bore out those 5/16" jobbers.  And why they don't just change over the stupid lead screw to a metric with a .5 pitch...

I love it, but sometimes certain upgrades make you wonder what is going on over there.

All very well said.  I think solidoodle could do a lot more to improve their quality control, and manufacturing tolerances for a relatively minor price per unit increase. And in the big picture view save gobs of money. 

Often as you reduce cost in manufacturing, mfg processes, and materials at the compromise of quality control you increase your customer service, lost customer, returned and replacement costs which can easily out pace your savings in manufacturing cost reduction. I think especially for a company that is relatively new they're reputation is the most valuable asset they own.  And there is nothing like poor QC and corner cutting that can tank a reputation. Ya know. 

I actually have designed a few manufacturing processes for short run manufacturing in the realm of two to five hundred units a week per assembly line.  But not necessarily the know-all of it by any means.

Anyhow I think solidoodle has great opportunity to really compete. It's just odd to me that they don't pick a finer pitched lead screw when it would really help hide some major deficiencies in their design/quality control process.

Thanks for the excellent info. 

Ironically I meant to say a .8 pitch above... That is what I put on mine, and I am certain it is more then enough to make banding a non issue when properly aligned, backlash removed, etc. 

But I side with your views anyhow. 

I've always thought the errant plus or minus 1 micro step "controversy" that I have seen on the forums is a bit funny. at least for the solidoodle Z axis.  Even on a stock machine a tolerance of +/- .0004mm per layer is the least of your precision/accuracy concerns.  Even if you multiply that across all 200mm of z height that is at the worst  case scenario (where the errant step is always in the same direction and miss stepping at .1mm layer heights) something around .8mm tops... The chances of that happening are in my mind pretty slim.  Most likely its in the .1 to .2 range at full height.... Which to me... Well that is a non issue for these machines. But for the most part I think anyone hardly maxes out their z height on a regular basis. 

It's sort of like the numbers games in computers. Where most people look at two maybe three variables when buying a computer for speed. Processor ghz, ram, and maybe your video card.... Now of course I know we are all too savvy around here to make that mistake.  But the irony is of course pretty much any computer you purchase new these days will be blistering fast for the average user.  Sometimes seems like more of an ego game. "Guess the size of my computer's ram processing liquid!?!"

Right let me know when anyone cares kind of a thing.

@Adrian -  well said, and I don't disagree with your analysis of microstepping or the need for an m3 versus and m5, only that all things being equal, I found little reason not to go to an m3, and going to a finer rod has some probable additional benefits (less backlash, flexibility, etc) with little downside.  Also, IMHO, finer banding looks better than coarser banding even at the same amplitude, at least for banding that is tied to the thread pitch (more on that below)

As far as microstepping-based banding, I agree it can be one cause of banding-like symptoms, but I am skeptical that it is the *primary* on the solidoodle cause for two reasons:

1) Many people have tried changing the layer height to one that will result in no microstepping.  A few have claimed "some" improvement, but only one AFAIK on the solidoodle has found total success, and he may not have had the typical banding most of us have seen.  It did not work for me.  Yet, I think you'll agree that if banding were due to microstepping, and you set the layer height to one of these full-step values (1/200th thread pitch) that one should see *no* banding at all, since no microstepping is occurring at these values.

2) The banding most everyone else describes is sinusoidal in amplitude with a period exactly equal to the thread pitch, regardless of layer height.  I can't see how microstepping-based banding could exhibit this profile, as a graph of the attempted microstep values shows a repeated function with a higher frequency than the thread pitch that also varies depending on the layer height.  Instead, I'd expect to see any banding to have a more chaotic profile with a higher frequency than the thread pitch.   If the microstepping behavior were more random as you describe, then of course the profile would be even less sinusoidal than observed.

However, I think everybody who has changed z-rods has gone to an m8 or smaller metric zrod, which tells us very little about the actual cause of any improvement they see, in terms of metric versus imperial, coarse vs. fine, or low-quality vs. a high quality rod.  My suspicion is that changing to *any* other z-rod (including a higher quality 5/16-18 rod) would probably yield significant improvement.  The choice of how fine to go is probably much less important than making any change at all.