Dual V3 Head Not Ready for Prime Time

BEWARE the Dual V3 head! Thumbs down!
I bought the Dual V3 head for my second Taz 6 and have nothing but regrets. Nozzle 2 has the known thermistor wonky connection problem, so temperatures are reported all over the map, causing wrong temperatures to be generated in the hot end. After 3 days of wondering why prints kept failing and temperature warnings kept halting prints, I finally noticed the reported temps on the LCD were hoping around like crazy, varying from 170º to 250ºC. No wonder the hot end was confused. So after wasting 3 days I decided to send the V3 back for a refund. Then I found out that the return policy at Lulzbot says they charge a 15% “restocking” fee, whatever the hell that means. I’m pissed because that means I will have paid $74.25 (15% of $495) plus insured return shipping of $25.50 for a total of $99.75 just to try out a defective piece of experimental crap that wasted three days of my time. They sent me an empty and worthless apology for their return policy, taking into account NO consideration that their print head was DEFECTIVE from the start. I wouldn’t have the nerve to treat my customers like that, but the difference is I STAND BEHIND MY PRODUCTS 100% and Aleph Objects doesn’t. Instead, they profit from defective returns. $100 down the drain! And three days of wasted time.

I have bought two Taz 6 printers and one Lulzbot Mini. My next printer will not be coming from Lulzbot as a result of their treatment.

It doesn’t make matters any better that Cura 2.6.66 is by far the worst piece of software I’ve ever encountered. The GUI fails to refresh the screen practically every time you make a little change to the settings, that is, when it doesn’t just totally crash.

I should have known better than to buy a newly developed and apparently under-tested piece of hardware before there’s been time to work the bugs out.

We’re sorry your v3 was behaving like that. It’s not normal. We’ve seen some reports of temperature fluctuations, and are looking closely at the thermistor, the thermistor crimping, and even updated firmware settings to drill down to the root cause.
We hope you try us again. Thank you for your understanding and patience, any deviation from our established return policies goes through our department leaders, who typically come in at 7 a.m. Mountain time. We have some good news for you in your inbox.

Thank you for waiving the “restocking” fee after I complained about it a couple times.

I may try a dual head again some time in the future, but after they have been tried and tested and revised a few times. I’m making production parts and really don’t want to spend all my time experimenting with under-developed or defective equipment.

That sucks that it took so long to figure out! It was either better or worse for me. I got mine friday night, worked on it all day yesterday, but all my prints kept failing within 20 minutes or so with the same error. So it was pretty easy for me to figure out that was the problem. Tech support suggested I recrimp the connectors or just squish them with needlenosed pliers. I had thought of stripping and soldering them in a bit better, but there’s not really the length required for that. But pinching them a bit and putting them back in let me get some prints done and move on to the next problems. So I’ve done that.

I’ll have to keep trying with all this to see if I agree with you or not. It seems like knowing the root cause of a problem for a while would let you go run some better quality control on them (I found my issue REALLY fast, and I don’t think it happened in shipping). Then again, they had filament in them when they came so they probably ran a test print, so I don’t know why it wasn’t caught then.

I might just be more willing to put up with the abuse since getting even bad prints with faults going within a day or two is leaps and bounds above the other printers I’ve dealt with.

The thermistor that failed in the unit I had, had some kind of white potting compound (perhaps ceramic) around the leads coming out of the metal cylindrical housing of the thermistor. There was no way to crimp anything, as the thermistor’s leads were potted into the thermistor’s package. If yours was different, my guess would be that this was an attempted fix made prior to shipping the V3 to me. And when I pay $500 for something, I expect it to be in working condition and not have to repair it as the first step.

It would have been nice if they adopted the E3D thermister cartridge with the connectors…

There are connectors. I have some posts on my trials and tribulations with the V3 and thermal irregularity. The connector is in the loom between the sensor and the main head connector. I should have posted pics. I soldered the thermistor leads to the crimp and have had no sensor-related thermal problems since.

I would just like to mention that the dual v3 unit i received about a month ago was finally installed last weekend and has worked great so far with the current FW available in Cura 2.6.69 (which I believe is After calibrating the Z-offset, I was able to print the Impossible Gears demo without issue. I also tried some prints just using the E1 extruder and so far they have come out just as good as my single extruder. I will keep an eye on the temperature fluctuation issue, but so far I have not experienced it.

I have run prints via USB through CURA on my PC and through the current version Octoprint with this setup. Not that it really matters for the issue discussed above, but just to point out that the current state of things are working stable for me that I have to disagree with the statement “Not ready for Prime Time”.

Between the loading difficulty (I may drill the top plastic piece of mine out to be a straight vertical load), issue with needing to feed before retracting filament, firmware issues weve seen to date, as well as the manufacturing QC issues, its fairly safe to say it was rushed to market to be on sale before the holidays. Things are getting better now, but those of us who got on board early still feel the pain of it.

For the loading, I have found that if you gently bend the last 8" or so of filament so that you reverse the natural curl (so that the curl aligns with the tool head path to the hot end), cut the tip at an angle (as they suggest), and walk the filament in with the tensioner released and the screw backed out a turn or so from the guide setting, it works its way right into place without a struggle.

It did get better at that after I enlarged the original hole. I think it wasnt quite aligned right with where it fed to the hobb.

Funny… I just ran into the thermistor problem after 2-3mo of good use. Using pliers to squeeze the crimps on the thermistor pins seemed to have solved my issues for the time being… a bit of solder might be more reliable, but I remember some tidbit about not soldering the thermistor wires…

Probably not the best place to put this guide, but a quick guide on getting to the pins:

  • Turn-off machine, disconnect main toolhead connector.
  • Cut the zip-tie and remove the wire loom
  • Disconnect the thermistor connector (molex)
  • Use a pin / dental pick to press in the the silver dot in the middle of connector housing
  • Slide out 1st pin
  • Use pliers to squeeze the sides of the second set of crimps (the first tiny crimps are to grip the insulation). Give it a second squeeze for a better chance at making good contact.
  • Insert the pin into housing. Give it a little tug to make sure the pin is securely in the housing.
  • If it doesn’t stay in the connector, remove the pin and give the little metal tab (between crimp and pin) a slight lift. Use pliers and a pin or dental pick to push the pin into the connector housing until the tab reseats.
  • Repeat above for the 2nd pin.
  • Reconnect to the extruder wiring, zip tie the loom back up, and connect toolhead.

    The thermistors look to be different from the E3D cartridge versions… so hoping this holds up until they get more thermistors into the store. Might consider modifying firmware for the E3D thermistor cartridge which looks easier to source.

So you’re saying the problem you had was due to the crimp terminals on the print head connector. On mine, I could make the reported temperature jump around over about a 100 degree range by just barely touching the leads where they come out of the thermistor (at the hot end) with a toothpick. The problem was at the thermistor, not the crimps in the connector on the unit I had.

The problem for me was the thermistor leads to crimp connection. The thermistor leads are a single, small solid conductor and the connectors are 2 pin, inside the loom between the thermistors and the main connectors for the print head. All of the crimps to the thicker, stranded wire tested OK. Again, apologies for no photos.

Ya, mine was the terminal connections. It sounds like you have a much different problem than the common mode failure that has affected several others (including me). That’s either a plus or a minus for their QC depending on the viewpoint since it’s a different failure. But obviously you know your machine better than us as bystanders - so we’re probably just commenting wrong thinking it’s similar when it’s really a very different issue.

Sucks that there’s any issues.

I just know that I’m STILL fighting with Cura, and I HATE it. Like slamming a hammer on gophers, something else pops up elsewhere right after I look somewhere else!

Just a note on soldering crimps in general: You want to avoid soldering crimps if possible because the solder may wick up the wire and create a weak point. If you do solder a crimp, you must apply strain relieve past the wicked solder part to avoid the wire breaking. This is especially important on anything that moves, ie. 3D printer tool heads.

Here is an excellent page on connectors and crimping which has a diagram on why to avoid soldering crimps:

There are holy wars on the internet on crimping versus soldering and soldering crimps, so YMMV.

Thanks for the article. The problem connection is with a single conductor and it’s not in a position subject to movement, so soldering is relatively safe. Without wiggling my blame finger because I am too lazy to look up the connector specs and mic the conductor, I suspect that the conductor is too small for the connector, so soldering is probably the best field hack for this case.

Well, I bit the bullet and decided to try the V3 again, in hopes they’ve fixed the thermistor/thermistor crimp problems.