6 Ohm?
Is 7 Ohm about 6 Ohm or should I cut the wire?
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This is the discussion related to the wiki page Plastruder MK4 Assembly.
7 Ohm is almost 20% off. Would you pay 20% more for gas? If your resistance is too high, the plastruder will heat up much slower and possibly not even reach the desired temperature. If it is too low, you will burn out the electronics. So try to get it right within 5%.
Which reminds me of a joke:
Teacher: 50% of pupils in this class have no clue about calculating percentages!
Pupil: Haha, that can't be true, we are only 36 kids in the class!
Should the recommendation of a double idler wheel be mentioned at all in this page? It seems not to be the right way to do things anymore.
One way to keep the knowledge of the experiment is to keep it in when things go wrong. And to make remark here that is is imperative to offset the idler wheel with spacers.
Since I haven't received my makerbot yet this is a remark borne out of the current documentation and not from practice.
I can only speak for a MK3 with MK4 bearing upgrade applied, but I haven't had any issues with the idler cracking or shifting since moving to the double idler wheel.
It's still working smoothly after many months of operation. The superglue never held very long for me when using a single.
I've got about 11" of wire and my multimeter is still reading 10 ohms. Should I be worried? Google tells me 300mm of wire should be about 11.8 inches… I hate to continue to cut it down based on these readings.
yes, the length of the nichrome doesn't matter as much as the resistance. the correct length of the wire is anywhere between 7 and 12 inches.
Don't forget to subtract out your multimeter's self-resistance. Touch the probes together to find out what that is.
Also, take multiple readings so you get an idea of what the average is.
Turns out I did cut my wire down too much. I borrowed a super accurate Fluke multimeter and it's too low. Where can you buy a new wire from?
While building the MK4 that was part of my batch #11 cupcake I noticed the following:
- the picture captioned "custom bits and motor" has exactly the same bits in it as the "nuts and bolts" picture. Since I have already cut nichrome i'm not able to reshoot a picture of the unmodified custom bits and motor. Can someone else provide a new picture?
I also have the MK4 kit -
My motor Plate only has three holes for screws to connect to the motor. Is this a defect I should correct or a revision?
I also wondered about that, Szerby, and contacted the Makerbot folks. They replied and said that those holes had been removed from plates 1 & 2 and are no longer used - it's just the 3 holes that go through all the plates now. The wiki instructions didn't get updated for the new plate cuts.
Not sure why they made this change. It seems like it would have been a little easier to assemble with those holes in plates 1 & 2. Maybe they had problems with bolts being a little long and either digging too far into the motor or pushing up on plate 3. Dunno.
For those that haven't seen this, it's steps 3 & 4 at http://wiki.makerbot.com/plastruder-mk4-assembly#toc53. I guess these two steps should be removed..
edit: and I just stacked the thing up on my bench then moved the whole assembly to the motor. I think you can drill plates 1 & 2 if you really want to or just do like I did..
In the Trim and Tin section it say "Once they are separated, you'll want to trim the leads to a length of 25mm." This appear to be talking about the thermistor's leads which is not what is shown and sounds wrong because it would put the plastic insulation on the wire very close the hot extruder. Am I just confused or is this wrong?
Edit: Never mind. I was being stupid and read 25mm as 2.5 mm. Still 25mm seams a little short I've cut mine to 35mm.
The instructions have me a little confused. Both ends of the nichrome wire are soldered to the ends of two separate copper wires, and this makes it difficult to wrap the nichrome around the heater barrel without overlapping because it's basically a loop. Am I doing this right?
Both ends of the nichrome wire are soldered to the ends of two separate copper wires
On my batch #12 Cupcake, they sent me two wires - a green wire and a red wire. I cut the red in half then soldered one half to one end of the nichrome and the other half to the other end of the nichrome. The green wire doesn't come into the picture yet - that's for the thermistor.
If that's what you mean, you're doing it right. And yes, it's a bit tricky to get it wrapped up - I remember wishing I had another hand or two while I did that part of it.
I guess what I did wrong was twist the two green wires together before I wound the nichrome around the barrel. I probably should re-do that bit.
I am currently assembling my CupCake (#1328, Batch XIV) and noticed that your Parts-List is wrong. You have listed only 14 M3x16 Socket Cap Bolts in the Hardware Kit. You basically forgot the two bolts you need to mount the Insulator Retainer. (7 bolts go into each Dino)
No big dieal for me, as i have enough spare screws from the Kit, but for someone who only buys the Plastruder-Kit for a RepRap or RepStrap machine, that could get a bit tricky. So, please update the Parts list and add these two bolts to the Plastruder-Kit.
On a sidenote, i've noticed that a lot of pictures in the wiki do not show the flat M6 nut. Especially in the "Attach Heater Barrel" section of the wiki, there are a lot of close-up shots of the heater-assembly where you can clearly see there is no nut between the barrel and the big steel retainer washer. For someone like me, who likes to use pictures as reference, this can get a bit confusing, as the correct stackup (nozzle, heater, big washer, M6 nut, PTFE thermal barrier) is only mentioned in the text somewhere along step 3 of the heater assembly.
And i did not really see a problem winding the nichrome and adding the thermistor with the steel washer and M6 nut already in place on the heater barrel. A second flat M6 nut to hold the big washer from both sides in place would have helped a little tho. Maybe something to consider adding to the hardware kit. ;)
i did not really see a problem winding the nichrome and adding the thermistor with the steel washer and M6 nut already in place on the heater barrel.
Amen. I rebuilt my heater barrel assembly 5-6 times following the given instructions and had nothing but trouble. The insulator/heater barrel assembly was just too touchy to be doing twice. It was too difficult for me to get the insulator barrel back on the second time without leaving it too loose or tightening it so much that the plastic deformed and choked off the channel. Finally, I just started the assembly process with the retainer washer & nut already on the barrel (with nozzle firmly attached).
Loosely screwed on the insulator barrel, stuck a bit of plastic filament through the lot so I could feel whether the passage was choked off or whether the barrel was so loose there was a gap. When I found the "Goldilocks" tension I threaded my thin-m6 nut up so it just touched the insulating barrel. I wrapped the insulating layer of Kapton tape on the end of the heater barrel and I just kept wrapping so that the base of the insulating barrel and the thin-m6 nut were firmly taped to the heater barrel. Slid the retaining washer over the insulating layer of Kapton tape, used some more tape to make sure it wouldn't move on me, and wrapped the rough outer edge of the retaining washer with tape as well so I wouldn't accidentally scrape insulation off the wires. Only then did I wrap my nichrome wire.
I stripped my nichrome before wrapping the barrel, but I did NOT attach the crimps or insulated wire until I was happy with the way my barrel was wrapped. I felt I was putting too much wear on the nichrome when I wrapped it with the lead wires already attached, so I just left that for last. It was a little tough to add the crimps with the wire already wrapped, but at that point I wasn't going to be handling it anymore, so I didn't need to beef up the crimp joint with solder and big wads of tape. I just wrapped the crimp and exposed wire in Kapton tape to prevent shorts and then secured the lot firmly in place with several more layers of Kapton.
Unfold
Re: Missing parts and some "wrong" pictures in the wiki by 
MoleOfProduction, 23 May 2010 22:09
This is very helpful advice. The design of the nozzle leaves much to be desired. Wrapping the nichrome is darned near impossible, because of the loop formed by the wire and the fact that the threads run the wrong way for the wire to sit in them. The nichrome insulation is fragile and a single mistake means you need to order a new length of wire and start from scratch. At the rate I'm going, it seems quite likely that the whole project will fail for my inability to get this to work.
It's probably best to go ahead and assemble the heater with the retainer washer the first time rather than after it's wrapped — this way you'll be sure to get the spacing correct.
I taped everything up a bit too high on the barrel without realizing I wasn't leaving enough space for the retainer washer. The washer takes up a bit of space and if you don't get it right this space will end up causing the dreaded gap between the top of the heater barrel and the PTFE thermal barrier.
Based on the wiki, I assume only insulated nichrome wire can be used and not bare wire. Is this correct?
That is correct. The brass barrel is electrically conductive so you must use insulated nichrome.
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