Any success with the Dual Metal TAZ (Dual V2)?

General LulzBot TAZ
1

I have spent about 15 hours in total calibrating and attempting to print with the new V2 Dual Extruder. I can’t get consistent results. Anything larger than the size of a quarter fails catastrophically. The first print that I tried with support material ended with a solid block of ColorFabb nGen surrounding both extruders. I have leveled and re-leveled my bed countless times, checking all 4 corners for exact distances before and after leveling the extruder head assembly with the screw at the front. I have had my bed so level that both extruders were dragging over printed layers. Each print that I have tried has had major issues with the exception of one small keychain widget. Tech support can’t seem to provide me with any solutions other than re-leveling my bed and making sure that the extruders are level. To redo that once more at this point would substantiate the definition of insanity.

Primary issues:

“Dragging” of extruders causing delamination, imperfections on side walls of prints, catastrophic stringing, and layer separation.

Ooze. Even with Ooze shield and wipe & prime tower, the ooze coming from high end filaments like co-polyester at lower than usual temperatures comprimises the quality of the prints.

The combination of the two issues resulting in birds nests of filament forming around extruders and destroying prints.

I am nearing my 30 day anniversary of ordering this tool head and I need to make the decision whether to keep it or return it. I really can’t afford to spend any more time calibrating this thing without results, but it is a shame to even consider returning it after so much anticipation and implied possibilities.

So what I’m asking for is success stories. Is there anyone in the community that has had good, consistent results with their Dual V2 printing large, high detail parts? Did you experience similar issues? What solutions did you implement to overcome the issues?

Thanks to any and all that can provide some insight.

2

I am about a month and a half into a Dual V2. I have had my share of heartache, but have learned a lot.

Leveling in the corners is of course necessary, but I think it is crucial to follow that up by going to the center of the platform and re-homing the Z axis there. Why? Because there is quite a bit of weight cantilevered forward from the X-axis guide rails due to the larger head, and I believe that it sags downward in the middle of the X-axis travel. I am certain other people have measured and reported this.

Picture the print bed as being slightly convex, that is the effect. Particularly, if you are attempting (as I was) to print with PVA or some other flexible filament from the front head, you could see some problems. PVA is very flexible, and there’s about three inches of travel between the feed bolt and the extruder head, where the filament is essentially unsupported. Slight back pressure caused by the head being too close to the print bed (see above) was wreaking havoc for me with the PVA, it was just wadding up below the bolt.

I actually kinda bias the front head up a little bit when I am doing the leveling, i.e. paper dragging on the rear head, only very slightly dragging on the front head. It eases the flow for the PVA, and doesn’t seem to negatively affect the print (and it is, after all, only my support material).

The second most important discovery for me was the wonders of a glue stick. I was having so much trouble getting PVA to stick, I tried a bunch of different things and was about to give up, but then I tried a glue stick and it worked perfectly. Too good in a few cases. My experience was that on large prints the PVA would curl up on the corners, but not so much in the middle, so my new M.O. is to just apply the stick around the perimeter to hold the edges down.

I am doing large prints using Cura, with Verbatim PLA at 205 in the rear head, and LulzBot (eSun) PVA at 195 in the front head, with a 60 degree build plate. Most of the stuff I am doing I am using 0.25mm layer thickness. It is going really well and I am getting high-quality parts with some build times going over 30 hours (I think speed will be the next thing I start working on).

Your issue with all of the oozing and “birds nests”… Do you have retraction enabled? That might help. I can’t comment much more on that because I do not have that specific problem, although I will say that PVA is just really “oozy”, it just seems to keep dribbling out. Fortunately the mess that it causes dissolves in the water.

If you have specific questions or problems post them here and I will help if I can.

3

Thanks for your response!

I did actually notice the same thing with the front extruder dipping in the middle of the X axis.

I didn’t have an issue with PVA when I printed it. I’m not using the eSun PVA, I don’t remember which brand my PVA is. The PVA support material seemed to print just fine for the most part, and I was OK with any imperfections. The nGen was where the problems really started on that print. It didn’t seem to stick to the PVA at all. Which I could troubleshoot more, or just use a different filament.

But the major issues for me are around printing with two colors of the same types of filaments. I have mostly been experimenting with nGen since that has yielded the best and most consistent results in single extrusion prints for me, yet I can’t get anything to print without failures. I do have retraction enabled with some very robust settings which should compensate for any possible oozing, yet it still occurs. I’ve also taken print temperatures as low as 205 for the nGen materials and had the same results, with potentially compromised layer adhesion.

4

Anyone running into the rod sag issue, I reccommend either hardened rod replacements, or this:
http://www.thingiverse.com/thing:866604
Also this:
http://www.thingiverse.com/thing:949082

5

Have you played with the “Dual Extrusion Overlap” setting in Cura? I am using 0.15mm with good results, I think that is the default. I wonder if too low or too high a setting in this field could cause adhesion issues between colors/layers?

6

Very nice mods, thanks for the suggestions, and for doing all of the heavy lifting. I may have to look into doing these.

7

I’d recommend the hardened rods or openbeam for the X-axis also… the dual extruder v2 is heavy. Its probably the reason for the delay in releasing the all-metal dual extruder and why LB is going to 12mm rods for the next version.

I’ll also add that when bed leveling, adjusting one corner will affect another corner… it will drive you insane. :slight_smile: I’ve had better luck using two dial gauges measuring both corners simultaneously…

8

Yes, I’ve noticed that. I go back and measure each corner repeatedly when I level my bed.

Unfortunately, I’ve decided to return my Dual Extruder and take the hit on the 15% restocking fee. I may entertain the idea of designing and developing my own, but I’m not sure how to go about the software end of it.

9

Hmm… that’s unfortunate.

If you do decide to go with a new design, the software should be fairly straight forward… it usually involves telling the slicing software the distance between the primary and secondary nozzle in X and Y directions.

Before the Dual Extruder V2 came out, I contemplated a side-by-side direct drive variant. Since the X-axis would support the weight of the side-by-side extruders, the Y-axis adjustment wouldn’t be necessary… at least in theory. :slight_smile: Regardless, the project isn’t completely dead in my mind. I’ll give this one a shot.

10

I don’t think that the extruders should exist on the same Z plane while only one is printing at once. I’ve seen commercial grade printers that rotate the assembly that the extruders are mounted to to change the heights and leave the one that is printing lower than the idle extruder. Building an assembly that could do this should be fairly easy, but I wouldn’t know where to begin with the software that would run that sort of thing.