Dual extruder installation questions and documentation notes

I started installing the TAZ 3 dual extruder as per the OHAI documentation, and have run into a few issues. First a few that apply to my base TAZ 3 before I installed anything new:

  • The stock heater cable for extruder 0 is extremely tight, which could cause reliability issues in the future. I recommend in the future using slightly longer cable for that. All the others seem fine.
  • The OHAI for the TAZ 3 dual extruder installation has a photo showing the connection of the thermistors. It shows a cable with a pair of yellow wires (heated bed thermistor?) going to the top thermistor connector on the RAMBO, connector number 0, and a cable with a pair of orange wires (extruder 0 thermistor?) going to connector number 2. My TAZ 3 wiring as supplied is the opposite, with orange going to connector 0, and yellow to connector 2. Since my TAZ 3 has been working, it’s hard to believe that it is wired incorrectly. Is the OHAI photo wrong? Or has this changed with newer firmware releases? I’m reluctant to install the dual extruder wiring until I understand why my TAZ 3 doesn’t match the photo.

Other comments about the TAZ 3 dual extruder installation OHAI docs:

  • The supplied wiring harness appears to include cabling for two extruder fans, which is good, but it’s not explicitly covered in the OHAI doc and might confuse people.
  • One of the extruder fan cables in the harness has a blue dot on both ends of the cable, and the other does not. I decided arbitrarily to use the one with the blue dot for an extruder 1 fan, but perhaps the OHAI should state what’s intended so that everyone does it consistently.
  • The wiring polarity, or at least the color scheme, of the extruder fan cables doesn’t match the OHAI photo. In the photo, the red wire is on the left, and the black wire is on the right. The provided cables are the opposite. At the other end, the cables have red on pin 1 (denoted by molded triangle). What is the correct wiring?
  • There is no documentation regarding connecting the ground lug. It’s obvious to me, but should probably be in the documentation.

I’m really looking forward to getting this going. I’ve intended to print with support material from the beginning, but haven’t had the time to build my own dual extruder.

Hello brouhaha,

Thanks for all the feedback! Let me see if I can address some of your questions:

Wiring harness length: If you could post a photo of your printer that would be great. My TAZ3 wiring harness seems to be able to print max volume without want for extra length, so I’d like to take a look at yours to compare.

OHAI thermistor coupler: Yes, my RAMBo is the same with the yellow and orange wires inverted. It may be that the photo was taken of an earlier model. Installation of the second extruder is the same either way.

Fan wiring: Yes, the dual extruder comes with wiring for fans, but inasmuch as the dual extruder does not have fan mounts designed yet, we don’t have instructions for how to install those fans. Several of us in the community are hard at work designing fan mounts for the dual extruder. As to the dots, which extruder you would like to be marked by the dot is up to you. I would guess that convention would have the dotted fan harness fan1, and the undotted fan0.

Grounding: Good point, we should have a step explicitly mentioning that.

If you have any other feedback, please let us know!

It’s not a matter of max print volume. The part of the stock heater cable for the first extruder is too short inside the electronics box. I tried taking a photo, but it’s not obvious from that. There is literally negative slack in that cable, and it’s pulling on the board-mounted connector, which is likely to cause an intermittent or failure at some point in the future. This is an assembly error, as there should be a minimum of a few mm slack in all of the cables inside the box. It’s possible that this only happened to my own unit. I can’t pull more of that cable into the electronics box without cutting all of the cable ties binding the black first extruder wiring harness. I’ll do that the next time I open the box.

OHAI thermistor coupler: Yes, my RAMBo is the same with the yellow and orange wires inverted. It may be that the photo was taken of an earlier model. Installation of the second extruder is the same either way.

I don’t think it’s an older model. I think the photo was staged with an otherwise unwired board to make the picture clear, and it was wired wrong.

Fan wiring: Yes, the dual extruder comes with wiring for fans, but inasmuch as the dual extruder does not have fan mounts designed yet, we don’t have instructions for how to install those fans.

I wasn’t asking for fan installation instructions. The OHAI indicates where to plug those connectors (though not differentiating the blue dot and non blue dot connectors), but either the OHAI photograph shows the polarity (red vs black) wrong, or the supplied wiring harness is wrong.

I would guess that convention would have the dotted fan harness fan1, and the undotted fan0.

That’s what I thought too, but more recently through another forum posting I found the drawing for the cable harness, and it specifies blue dot for fan 0 and no dot for fan 1. Obviously it doesn’t actually matter as long as you are consistent at both ends, but given that the OHAI says to connect both to the RAMBo, it should say which to connect to which connector, so that later when a customer buys an appropriate fan upgrade, the instructions for that can accurately state which cable at the extruder end goes to which fan.

Best regards,
Eric