Building the Dual Extruder

The official subforum for discussion of the installation and use of the official M2 Dual Extruder upgrade.
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Tim
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Building the Dual Extruder

Post by Tim » Fri Aug 15, 2014 5:54 pm

Okay, finally I get to join the fun! I was on vacation when the dual extruder kits started to ship, so I had to have MakerGear delay my shipment until I got back. So I'm a little late out of the starting gate.

Here is my building experience, which is slightly different from others, because I have the vintage December 2013 model M2 with the split power supply, so I had to do both the 24V upgrade and the dual extruder upgrade at the same time.

Generally, the build went very smoothly, the instructions were clear, and all the parts were present.

My main problem is probably a result of the model M2 I have. The instructions indicate that the Fan 0 and Fan 1 wires on the new harness (Harness 1) will not be used. However, as I got the new harness into place, it was clear that my old harness had simple header connectors for the fans that would not connect to the molex connectors used on the new fans. That this issue is specific to the older model M2 is supported by the fact that the 24V upgrade kit came with a fan (which I don't need, since the dual extruder kit also has one) having a molex connector, so apparently MakerGear switched from simple headers to molex connectors on their fans at some point. The solution was to use the Fan 0 and Fan 1 wires from the NEW harness, and leave the fan connectors from the old harness unconnected. Because of this, the terms "Fan 0" and "Fan 1" end up reversed from the instructions. On the new harness, the wire labeled "Fan 1" has a series connector meant to connect to the electronics box fan; because these are connected in series, they would be the two 12V always-on fans. "Fan 0" has its own dedicated connection and is therefore the one connected to the 24V fan. Then the only remaining item was to assemble a 2-pin molex connector for the electronics housing fan. Fortunately, I had bought a bunch of molex connectors for the E3Dv6 hot-end that I bought, so I had the right kind of connector (well, good enough, at least), and with a quick solder/crimp job, I had the connector in place. Which is a lot better than the original, trying to screw bare wire ends into the teminal blocks.

My second issue has been noted by others, that the fitting of the wiring harnesses in the wiring bracket is very tight. I have two complaints here:

(1) The screw holes on the backside of the wiring bracket really need to be vertical slots. The bracket does not necessarily line up exactly with the motors. However, the exact positioning of the bracket is not critical, so a little room for movement in the screw holes would not cause a problem. I found it very difficult to feed the screws into the stepper motors, and there was no room to wiggle it around. I eventually forced the screws to go into place, but ended up stripping the threads in the stepper motor for one of the screws. I should have drilled out the holes in the bracket to a larger diameter, but I didn't think about that until after I had stripped the screw hole.

(2) I could not get the wires from Harness 1 to feed through the four parallel holes at the bottom of the clamp. The two fan wires had a fit that was too loose, and the extruder and thermistor wires wouldn't fit in the holes at all. The fact that the holes are open on the bottom means that the wires may eventually shake loose and come out. Plus, the connectors are impossible to reach if the instructions are followed as written. The better way is to leave the wires out of the holes, assemble all the motors, connect up the wiring, and then, as the last step, press the wires up into the holes (if you can get them to fit). I ended up leaving the extruder and thermistor wires out of the holes and just routing them around the side of the motor, making sure they were held firmly in place with a cable tie or two. Overall, it's not bad, but there must be a better way to hold the ends of the Harness 1 wires.

I was a bit skeptical of aligning the filament drives over the holes in the hot-ends by eye, and then covering over the whole thing with the fan duct so that it is very difficult to go back and realign it. However, the eyeballed alignment seemed to work okay. I guess I could have tested the alignment by doing a cold extrusion of filament down into the top of the hot-end before mounting the fan duct. Might have been a good extra precaution. Fortunately, it wasn't needed.

The short Z-knob collar did not fit well on my Z axis screw. I had a similar problem with the original Z-knob, so it may be some imperfection in the Z axis screw that's making the fit too tight. I resorted to whacking it a few times with a mallet until the top of the Z-knob cleared the extruders when pushed all the way to the left. I don't expect that was very good on the Z axis stepper motor, but it survived. The collar is not physically connected in any way to the knob, which looks like it will make it impossible to do Z axis adjustments during printing by using the knob, as the knob wants to spin freely before it will generate enough torque to overcome the resistance of the stepper motor.

I think that the new right-side filament guide should stick out the back of the chassis, not to the right, and I really wish it would swing freely like the one on the left does. And it would be nice if the filament guide tube would fit down into the filament guide like it does on the left side. Time for a redesign. . .

Really, I liked the original spool holder with the three bearings. It has always worked for me, and I've never needed to change it. The new spool holder seems very inelegant by comparison. Plus, it doesn't fit the old, wider spools that MakerGear used to ship before they changed filament brands. I have not yet checked to see if the new version of the spool holder works better.

The firmware upgrade went very smoothly. I just changed the stepper microstep values from 16 to 8 in Configuration_adv.h due to the older RAMBo that I have, and it downloaded and works perfectly (except some PID tuning is needed, as the temperature control has a severely under-damped response and oscillates for a long time).

Finally, my new 24V heated bed had a thermistor with a flaky wire connection, causing me to get intermittant reads of zero back from the thermistor. Since the thermistors on the 12V and 24V heated beds are the same, I fixed this problem simply by swapping out the thermistor with the one from my old heated bed.

I have not yet attempted to print anything with the new setup. I just wanted to write down my assembly experience and the various thoughts I had while doing it. It may sound like I have a lot of complaints, but in fact, I think the process went relatively smoothly. The new extruder setup looks very sharp, the wiring is a lot cleaner looking than it used to be, and I'm looking forward to giving this thing a good workout.

jsc
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Re: Building the Dual Extruder

Post by jsc » Sat Aug 16, 2014 1:39 am

Regarding the Z axis knob, did you back out the set screw in the caller all the way before attaching?

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Tim
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Re: Building the Dual Extruder

Post by Tim » Sat Aug 16, 2014 2:03 am

Yes, I did. I can remove the set screw completely and the collar still does not fit over the Z screw. On the other hand, the knob pops off the collar easily. Just a bad component?

markb
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Re: Building the Dual Extruder

Post by markb » Sat Aug 16, 2014 5:55 am

That does not sound right mine was not that way at all. Mine tighten right up nicely.

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Tim
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Re: Building the Dual Extruder

Post by Tim » Sat Aug 16, 2014 5:17 pm

Can somebody please take their Z-screw knob off and measure the outer diameter of the Z-screw and the inner diameter of the collar? I figure one of them is not right for me, but I don't know which one. My calipers give a reading of 8.0mm diameter for the Z-screw, and 7.9mm for the inner diameter of the collar. No wonder it's a tight fit.

I should add that it's not even proper to call it a tight fit. . . I got the collar to go down a few mm on the screw, and there it's wedged, far enough that the knob clears the extruder assembly, but it's definitely not seated properly. I suspect that the collar's inner diameter is too small, but I'd like confirmation before I go request a replacement from MakerGear.

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Tim
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Re: Building the Dual Extruder

Post by Tim » Sun Aug 17, 2014 2:31 am

For the record, there being an extra set of unconnected wires (two pairs, actually), I made use of them by taping a short LED strip to the bottom of the extruder fan and wiring to a spare set. LED strips typically run at 12V. While in general, it is not possible to wire LED strips in series, if you have exactly twice the supply voltage (24V), and you use two sets of exactly the same number of LED lights, they can be wired in series, with 12V across each set. Plug them into the same terminal block that drives the always-on extruder fan and electronics case fan.

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