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Layer lines visible - tips for a VERY large print?

Posted: Fri Jan 06, 2017 12:01 pm
by Mulanzo
Hi all. I've just received my Taz 6 and love it.... but it's been a challenge dialing it in. My rocktopus printed fine and my first print went alright as well in Ngen, however now I'm printing a life size trex skull (estimated over 30kg of filament) and I'm getting heavy banding in the z axis. I did have one failed first print that resulted in a HUGE tangle of filament and that caused the z axis things to bind up as well as the y axis belt to loosen but i tightened it up and relevelled the axis and thing I have that sorted out. I'm just getting heavy banding with PLA (maybe other filament as well but haven't tried) and it's super ugly.
IMG_6443.JPG
Any thoughts on what I can do to fix? Thanks and I'll be on this forum a whole heck of a lot! Looks like a helpful place... much better than my previous 3D printer's forum.

Re: Layer lines visible - tips for a VERY large print?

Posted: Fri Jan 06, 2017 1:03 pm
by piercet
There isn't an anti wobble that will fit a Taz 6 yet. There is a bit of a space limitation in the Z axis design that makes fitting one problematic without a redesign. You can try the "clock one of the leadscrews over 1/4 turn and see if that fixes it"

Re: Layer lines visible - tips for a VERY large print?

Posted: Fri Jan 06, 2017 1:49 pm
by Mulanzo
Oh that's sounds easy enough. Is there an instruction on how to go about it? Does that mean unscrewing the z screw nut and turning 1/4 then screwing back in?

Re: Layer lines visible - tips for a VERY large print?

Posted: Fri Jan 06, 2017 1:55 pm
by piercet
Not so complicated as that. You basically just power the machine off and unplug the motor, then deliberatly turn the leadscrew a bit just so the thread pattern is slightly offset, using the auto leveling to compensate. It can work, it may do absolutly nothing for you through too.

Re: Layer lines visible - tips for a VERY large print?

Posted: Wed Jan 11, 2017 10:00 pm
by suntorn
piercet wrote:There isn't an anti wobble that will fit a Taz 6 yet. There is a bit of a space limitation in the Z axis design that makes fitting one problematic without a redesign. You can try the "clock one of the leadscrews over 1/4 turn and see if that fixes it"
Please elaborate... What is an anti wobble? Also your telling me that turning the lead screw on z axis will fix this? Which screw left, or right? And how does this translate into cleaner layer lines?? Thanx in advance

Re: Layer lines visible - tips for a VERY large print?

Posted: Wed Jan 11, 2017 10:50 pm
by piercet
I did a video about it a while back that might be give you more details
http://youtu.be/yokdL-T7lW4

Basically an anti wobble device divorces the x and y motion of the leadscrew from influencing the carriage position, while preserving the exact z axis position the carriage should be at. Each time you turn a leadscrew, the leadscrew nut tends to want to shift slightly to one side due to the angle of the threads in contact and gravity due to the tiny amount of play present between the nut threads and the leadscrew threads, and in thevery case of the Taz 5, flex in the x end plate. A bent or malformed leadscrew will increase the presence of wobble.

Two contra rotating leads crews would help combat the issue, but they are somewhat rare. De syncing the leadscrew rotations so that the thread positions are slightly different can sometimes also help. It doesn't always. It also doesn't matter which screw. The downside is that doing do places the bed slightly off level.

How this all translates into cleaner layer lines is related to whether your printer is experiencing wobble or not. To tell if you have wobble, print something, preferably a cube or a cylendar, then hold it up next to your leadscrew. If there is a layer offset pattern that matches the leadscrew thread spacing, you have z wobble. If it doesn't match it's a different issue. If wobble is present, the anti wobble just prevents the offset force from trying to move the print head, leading to no layer offset.

A sticking or improperly set up anti wobble can also make wobble worse.

For the Taz 6, you would need to lose a good 22mm worth of print travel to fit one in, which is the main reason there isn't one yet. That or rebuild the x ends. The 6 generally doesn't have wobble because the z rods are better placed than they are on the Taz 5. Where it is present, there isn't a good permanent fix for it.

Re: Layer lines visible - tips for a VERY large print?

Posted: Thu Jan 12, 2017 7:13 am
by suntorn
Totally understand now. Thank you for the breakdown piercet! I have the taz4, and do have slight z banding and would love to try your anti wobble device. Did this eliminate all z wobble, it seems like the other lead screw would still cause wobble? What If you did the same Genius idea by the way! Also I have been printing my new printer parts with PET, I believe it is much better than abs. What are your thoughts on which materials would work better than abs for printer parts... Have you tried amphora? I know nylon910 is to flexible for most parts.

Re: Layer lines visible - tips for a VERY large print?

Posted: Thu Jan 12, 2017 11:40 am
by piercet
suntorn wrote:Totally understand now. Thank you for the breakdown piercet! I have the taz4, and do have slight z banding and would love to try your anti wobble device. Did this eliminate all z wobble, it seems like the other lead screw would still cause wobble? What If you did the same Genius idea by the way! Also I have been printing my new printer parts with PET, I believe it is much better than abs. What are your thoughts on which materials would work better than abs for printer parts... Have you tried amphora? I know nylon910 is to flexible for most parts.
Thanks!

It does eliminate all Z wobble, though not necessarily all Z printing artifacts. For example if you have inconsistant extrusion, due to an improperly tensioned idler for example, that can show up as pulsed layers, usually intermittant where every 3-4 layers one will be slightly smaller than others. The trick is that z wobble is additive. http://www.thingiverse.com/thing:1089626 You would normally have one of those anti wobble setups on both leadscrews. I've actually ran for an extended period of time with just one installed though as a test. Having one anti wobble and one hard mount leadscrew in the system reduces apperent wobble by quite a bit, nearly half. The remaining hard mounted leadscrew can still influence carriage position, but not with as much force as when it is both leadscrews.

PET is a nice material. I like printing with ABS becasue it works very well with my machine and has slightly higher printing temperatures, which means it has slightly more heat resistance, but PET is a fine material and once you get the temperatures dialed in, is much easier to print consistantly than ABS. I haven't personally tried Amphora yet, but I hear good things about it.

Re: Layer lines visible - tips for a VERY large print?

Posted: Thu Jan 12, 2017 11:39 pm
by suntorn
The thing I like about pet, and amphora is they have 100% layer bonding. Something I can never achieve with abs, although I've come close. Parts printed in abs when stressed, always break along layer lines, but pet and amphora break against layer lines, like a solid piece. The lower tg of pet never gave me trouble, even using it to hold in my e3d hot end, with a part I made that clamps it to extruder. Esun pet is really as good as the more expensive ones like madesolid petg. It sucks to the bed with one layer of glue stick and never lifts, yet easy to remove. It has become my favorite material, and it's cheap. Amphora is expensive but prints beautiful and is very strong. Both filaments are not as flexible as abs, which can be a good thing or bad, depending on the part.
Also pro tip, when printing with pet set your nozzle height so a piece of paper barely rubs when slid under nozzle, for .50 mm. That's the most important thing with pet, you have to set the start height insanely higher than any other material.