Hot End Thermistor install quesiton

All about the retired, first generation H-1 3D printers
steven6282
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Hot End Thermistor install quesiton

Postby steven6282 » Sun Aug 31, 2014 2:17 am

So, I'm finally assembling my H1 that has been sitting in the closet for a long time (I know it's been a while but combined with frustration of the first few months of no instructions and then just lack of time to commit to it, I'm just getting around to it).

After struggling through the first 7 steps mostly because of having to make multiple trips to local hardware store for numerous missing parts. Did others have this much trouble with their kits being incomplete? Mine is pretty horrible with how inaccurately it was assembled, some pieces missing completely, others not having the proper number. I've even got some incorrect screws that simply aren't used anywhere that I can find (example, I've got 3 x 10-32 1 1/4" Socket Head Screws that I have not see needed anywhere, they aren't even on the parts list). I'm now finally getting to the hot end and extruder assembly. Doing some research online I see that it is a little discomforting how often people have melted their hot ends. The most common reason I see for it is the thermistor not being installed properly or coming out during usage. I don't want to melt my hot end so I'm trying to figure out the proper method for installing the thermistor.

My first question is if the thermistor I have is even going to work. I have a 100k (or maybe it's 10k? Don't remember for sure which it is.. I know I ordered the wrong one originally and then ordered the correct one later) thermistor, I can't tell you where I got it because it was ordered way back before the kit even shipped to me from the Indiegogo campaign, but it does not fit in the hole provided for it on the hot end assembly. The tip of it will sit in the hole, but the hole is a little over 1/16" wide and the thermistor at it's widest point is closer to 1/8"

Do I need a different thermistor that will sit all the way down into the hole? If so does anyone have a recommendation on where I can order one? Or will this thermistor work and I just have to make sure it actually stays there?

One other thought, I'm looking at this hot end, and I'm wondering why it wasn't simply made of all metal to avoid any chance of melting it in the first place? It looks like it should be a relatively simple component to make with metal, and if the hot end nozzle and resistor area can be made of metal I imagine the rest of it could be as well. I have seen other hot ends for sale, is it fairly easy to retrofit other style hot ends into the H1?

Thanks

EDIT: Nevermind about the thermistor fitment question. After thinking about the fact that I knew I remembered ordering the wrong one first I went digging and found the 2nd one I ordered that I didn't put in the parts box, it was laying on my shelf along with a hotbed I had ordered (which doesn't fit for the record lol). The proper 100k one fits in the hole just fine. I would still like to know about my other questions though, especially the hot end being metal. I'm seriously considering replacing this 3d printed tube that screws into the metal part of the hot end with a metal tube so that I don't have to worry about it melting. Just trying to figure out if there is some reason not to do that. It doesn't make sense to me to have a 3D printed piece that close to the heat, knowing the purpose of that heat is to melt plastic to use for 3D printing lol.

Eric
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Re: Hot End Thermistor install quesiton

Postby Eric » Sun Aug 31, 2014 7:05 am

My H1.1 kit had all its parts, and I had those same 3 screws left over (along with a few extras of other parts). Never did figure out what they were for either. A thermistor did come with my kit. It was sealed in part of the sealed plastic with the hot-end parts as I recall, and was a bit hard to spot.

You're right about thermistor installation issues being a primary cause of hot-end meltdown. The current version of the hot-end is still the same in that respect, so most advice you read about thermistor or resistor installation or alternatives for the Rostock can be applied to the H1.

You can check your thermistor by measuring it's resistance at room temperature. It's supposed to measure 100K ohms at 25 C, so if it's at least close, that's what you have.

As for the plastic part of the hot-end, that's not 3-d printed, it's machined from PEEK rod. PEEK is one of the highest temperature plastics, but even it has its limits, which is why the stock hot-end may melt down at temperatures exceeding about 250 C. Its purpose is to provide a heat-break between the top of the melt zone and rest of the hot end. Often a small fan was added (optional - not included in H1 kits) to blow on this PEEK portion to help keep it cool.

If you take the hot-end apart (it unscrews), you'll notice a teflon tube inside. The H1 was delivered with two versions of that, so you could use either 1.75mm or 3mm filament. 3mm filament uses the larger tube, while 1.75mm used a smaller tube with a split larger tube around it. Use whichever one matches the filament you bought. Do not leave it out.

There are other hot-ends available, including all-metal hot-ends, if you later want to go that way. Pretty much all of them could be used on the H1 but you'll have to make your own mount for them using the two mounting posts available on the extruder plate. On metal hot-ends, the heat-break function is usually obtained by using a thin metal tube between the melt zone and the heat-sink areas. A fan is nearly always used on the heat-sink. Metal hot-ends can be run hotter, allowing you to extrude plastics other than PLA and ABS.

So, did I touch all your questions? There are people still here who have built the H1 or H1.1 in the past and can help you if you get stuck. There are even some assembly videos linked in a few threads.

steven6282
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Re: Hot End Thermistor install quesiton

Postby steven6282 » Sun Aug 31, 2014 1:32 pm

Thanks for the reply. Yeah my kit was one of the very early original Indiegogo backer kits. It did not come with the thermistor or resistors nor the upgraded H1.1 parts (which I can't seem to find a list of anywhere to see if they are upgrades I should make, if I could even source the upgraded parts, which at this point seems unlikely). I think an upgraded hot end was part of the H1.1 parts to though from what I have glimpsed of it so I wonder if this PEEK rod you speak of was only in the upgraded H1.1 kit. The tube on my hot end has little lines in it just like an injection molded print, and it shaves just as easily using a hobby knife on it as well. But perhaps it is still made of a material with a higher melting point than the abs plastic spools. My kit also only came with a 1.75mm tube, don't think they added the 3mm tubes until the H1.1 upgrade kit.

The Thermistor I have now that fits inside the hole nicely is directly from seemecnc's shop though, so hopefully it will work ok. I've read all the tips of not using soldering to connect wires and such so hopefully I can avoid any issues there and not melt this thing on my first print lol.

I will hopefully be finishing the build up today, I only have a few pieces left to assemble, and then I have to wire all the electronics. But I've got to make yet another trip to the hardware store because I've discovered the packed 2 few 1/4 - 20 lock nuts :( Going to put the extruder together before I go though so that hopefully there are few enough things left that I can determine if this is the only hardware piece left missing before I go. Wish they would've packed this kit more intelligently. I cannot figure out what logic they used to pack it, there are parts all over the place. The same exact part may be sealed in 4 or 5 different areas (some washers for example). Nothing is labeled leaving me to guess at some things (I'm still not sure which washer is supposedly a #6 washer vs a #4 vs a #8, I've just been using whichever one seems to fit the best for the usage lol). I don't understand why they didn't simply package all the same parts in individual bags or sealed areas and labeled what they where and how many there should be. Would have made it far easier to find parts and determine if I had the correct count. As it stands I basically just had to dive into building it step by step and find the missing parts as I went lol.

EDIT: Well that was quick... start looking at the extruder assembly and see I'm missing a 1/4" ID x 0.28"L Drive Spacer... no idea where I'm going to source a substitute for this thing. Guessing that length is somewhat precise with this being a gear spacing.... The inaccuracy of this kit is seriously appalling lol.

Eric
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Re: Hot End Thermistor install quesiton

Postby Eric » Sun Aug 31, 2014 2:57 pm

Well, obviously I can't speak about how early versions of the kit were packed. Your experience is your experience.

As for the spacer, 1/4" aluminum or nylon spacers probably are findable at Home Depot or the like. You won't find that exact length, but you can grind/sand a longer one down.

By the way, the surviving documentation ended up here: http://reprap.org/wiki/Seemecnc_h1. All the old links in forums to the seemecnc site are dead.

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BrainSlugs83
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Re: Hot End Thermistor install quesiton

Postby BrainSlugs83 » Mon Jul 06, 2015 5:18 am

Nice. Looks like I'm not the only one who waited until 2014 to put their printer together. :-) -- guess it's 2015 now -- and well... the printer part was together... still toying with the damn thing anyways...

I actually assembled most of it when I got it -- found it was missing several parts as well -- but the SeeMeCNC folks were really good about getting me the missing pieces when I told them about it -- now though -- you're probably in trouble, 'cause I doubt they even have any of those parts anymore (well, the screws and off the shelf hardware maybe) -- they used to sell all kinds of upgrades too, print beds, and such... now though -- they're like ... pretending it never happened? I don't know. -- I was really excited when they announced the first delta bot, but it seems like now that's all they do, is delta bots...

I found the reprap wiki page for the H1 to be helpful (that seems to be the only resource I can find on it, they have the STL files and some of the old PDFs and stuff):
http://reprap.org/wiki/Seemecnc_h1
http://reprap.org/wiki/SeeMeCNC-H1_Build_Notes


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