Hot end / extruder troubles

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steven6282
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Hot end / extruder troubles

Postby steven6282 » Tue Jan 19, 2016 11:51 pm

So, I don't know if anyone still reads this forum or not but I'm posting hoping they do.

I finally got around to finishing all the elctronics and such on my H1, yeah I know it's been a ridiculously long time since these kits got delivered but I just kept getting annoyed with the low quality of this parts kit every time I turned around to try and do something with it. And guess, what as soon as I finish this up and try to mess with it.. more problems yay.

So anyway, I got everything wired up, got the controls working, able to move everything around smoothly and I think I've got everything set correctly so that it actually moves the correct distance. I'm using sprinter firmware on a sainguiololu board mostly because that is what originally came on it, I did upgrade the firmware to the latest version however. So after doing a little test gcode file and making sure everything moved around correctly I started playing with trying to get it to actually melt some plastic. This is where the problems start.

It does melt the plastic, if I back off the part that engages to grab the filament and push down on the filament by hand, it will melt and feed through. However, as soon as I tighten down that part to engage the filament, one of two things happens. If I tighten it down to much the gears simply slip on the bolt and it doesn't spin the internal part to actually pull the filament down. If I back it off a little everything spins but it doesn't have a tight enough grip on the filament in order to push it down hard enough to feed the plastic apparently. I can't tell if this is a problem with the poor design of using these plastic gears on a smooth bolt with only mild resistance holding them in place, or if the hot end isn't getting as hot as the thermistor reading is reporting and so isn't melting the plastic fast enough (I've tried it at both 185 and 230 cause I can't remember if I got PLA or ABS filament). I did test the thermistor resistance as best I could at room temperature and it seemed to be accurate. The thermistor I'm using is the 100k one from seemecnc.com's store. It says it is model 104-GT2 which there is a setting for in the sprinter firmware and I have set the setting to that model thermistor.

I'm not sure what else to do at this point. Any advice would be awesome.

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Re: Hot end / extruder troubles

Postby Xenocrates » Wed Jan 20, 2016 12:35 am

I don't have an H1, but I'd be happy to try to help you figure out your problems. Would you mind taking some pictures of your extruder, and specifically the parts that are slipping, for us? I hope we can get you sorted well enough to start printing. If not, I think the newer EZ struder would be able to be bodged onto your printer, and that design is much better.

Some initial ideas. Have you attempted to superglue the gears to the bolt (sand the surface of the bolt with high grit paper first). Is the plastic of the gears fairly solid? If it is, and you have access to a reasonable dremel and a tap set, you could potentially put a set screw in the gear, and a flat on the bolt. Please do note I'm just snowballing here, as I've never seen an H1, or the extruder assembly you're talking about.
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Re: Hot end / extruder troubles

Postby geneb » Wed Jan 20, 2016 8:57 am

If memory serves, the Steve's Extruder is used on the H1. When properly assembled, it'll drag a printer across the desk it's sitting on. :)

Please post pics of the extruder and I'll compare that to the Steve's Extruder I pulled from Orange Menace.

Also, considering the other injection molded parts that SeeMeCNC makes, I VERY much doubt your "low quality" parts claim.

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Re: Hot end / extruder troubles

Postby Polygonhell » Wed Jan 20, 2016 1:08 pm

Steve's extruder was always a pain to get setup correctly.
The relative tightness of the bolts that run across the extruder body are somewhat critical, as is the roller pressure adjustment.
There is/was an assembly video for it on youtube somewhere it's worth watching, since it'll give you some idea what's supposed to be tight and what isn't.
It certainly doesn't lack torque when assembled correctly, but I would never consider it reliable, it has a tendency to mash the filament into the gap behind the roller when it encounters any back pressure (though that's less of an issue on a direct extruder like the H1).

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Re: Hot end / extruder troubles

Postby Polygonhell » Wed Jan 20, 2016 1:21 pm

geneb wrote:Also, considering the other injection molded parts that SeeMeCNC makes, I VERY much doubt your "low quality" parts claim.


I guess it depends a great deal on what your expectations were, anyone expecting a snap together kit with the H1 was going to be disappointed. The H1 was basically a huxley copy with injection molded parts, and very little additional thought given to making assembly easy. The original shipped with nothing that would attach the X carriage to the belt, you literally had to drill holes in the injection molded parts and put self tapping screws through the belt. Similarly there was no real thought as to wiring, no way to mount a print surface or level the bed etc.

Now I'm not knocking SeeMeCNC, this was the norm for the 3D printer "scene" at that point in time, you got boxes of parts and were expected to put them together solving issues you encountered, and for the price point and time frame it was a good kit. I got some good prints out of mine, but if I were given one unassembled today, I wouldn't bother assembling it, I'd take the Steppers and controller (assuming it was a later one that shipped with an actual uController board rather than assume Mach 3 would be used) and use the parts to build an I3 or whatever.

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Re: Hot end / extruder troubles

Postby steven6282 » Wed Jan 20, 2016 6:28 pm

Yes, I definitely consider the entire parts kit from the original Indiegogo campaign low quality. Not so much in the of low grade, but poorly assembled and thought through. I'm not trying to offend anyone with that, it's just simple fact. There wasn't even instructions on how to put the kit together for like 4 or 5 months after the kits were shipped. The parts themselves are probably average grade IMO from what I've seen on injection molded parts. There were numerous areas during assembly that I had to sand or shave to fix either printing defects or make a part work where intended. But the "complete parts kit" was missing so many necessary parts and hardware that it just made the entire process of actually assembling and putting together the machine a true ordeal. It was a cheap parts kit, I'll grant you that, but I still expected a "complete" parts kit as stated.

As for the extruder itself, yeah I'm considering trying to add a pin or something to the gears if I can find some way to drill a hole through the bolt to stick a pin in. That would be the best solution from what I can think of, that way the plastic gear would have to turn unless it tears itself apart. I dunno if superglue would cut it but I can give it a try. Here are a couple of pictures of the extruder, if you want to see it from a different angle let me know.

From the top view, the white gears in the back are 2 of the 3 that simply slip on the bolt. The side view, the middle gear in the back also slips as soon as any resistance occurs. And if I back the plunger screws off enough, then the filament itself slips instead of being pulled down.

top.jpg


side.jpg

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Re: Hot end / extruder troubles

Postby steven6282 » Wed Jan 20, 2016 9:37 pm

So, I don't know if this contributes to the problem or not... but I took apart everything a few minutes ago to see what I could do to fix these problems, and I noticed the filament tube is melting at the hot end. That probably restricts flow some I'd imagine. What should I do about that?

filament_tube.jpg

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Re: Hot end / extruder troubles

Postby geneb » Thu Jan 21, 2016 9:01 am

Replace the tube. The stock hot end for the Rostock MAX has the same issue - if you over heat it, the liner will shrink a little bit and play merry hell with the filament feed.

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Re: Hot end / extruder troubles

Postby steven6282 » Thu Jan 21, 2016 12:05 pm

Is there a particular tube that I should replace it with that has a higher melting point?

I rebuilt the extruder last night, another problem I found is that the little clear piece at the top and the black piece in the middle were slightly to wide. If I tightened the middle bolt down there was still a very slight amount of wiggle in the gears. So they were not getting the full lateral engagement that they were supposed to. I shaved a little bit off the edges of those two pieces and got it to where I could fully tighten down the middle bolt and have significant lateral pressure. After doing that and reassembling it the fillament feed is much better.

I haven't had a chance to test it in actual printing again yet because while working with the hotend I pulled the thermistor out (Not sure what I should use to actually adhere to this hot end and hold the thermistor securely, I've tried using high temp copper silicon and muffler silicon, neither work well). It was late by that point and I had to let the silicon cure before reassembling and attempting another print.

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Re: Hot end / extruder troubles

Postby geneb » Thu Jan 21, 2016 3:19 pm

There isn't a higher temp material. You'll need to replace it with the same size & length of PTFE tubing.

Use Kapton tape to help prevent the thermistor from pulling out.

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Re: Hot end / extruder troubles

Postby IMBoring25 » Thu Jan 21, 2016 4:45 pm

If you want to go hotter than a lined hot end permits, you need a specifically designed high temperature hot end. Choices I've seen discussed here include E3D v6 and Prometheus. My experience is only with the former.

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Re: Hot end / extruder troubles

Postby steven6282 » Thu Jan 21, 2016 5:45 pm

What is the hottest a lined hot end permits? The highest I've gone with it is 230 as that is what everything I've seen says to use for abs plastic filament. Pretty sure that is the type of plastic filament I have. Based on how fast it was melting at 230, I don't think it'd melt sufficiently at 185.

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Re: Hot end / extruder troubles

Postby IMBoring25 » Thu Jan 21, 2016 6:28 pm

You should be OK there, provided your thermistor is reading correctly. Did you source the thermistor or was it in the kit? Do the beta and 25C resistance values for the thermistor match what's set in the firmware? Did you ever run it higher than that? Do you experience overshoot or is it stable at the setpoint?

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Re: Hot end / extruder troubles

Postby Polygonhell » Thu Jan 21, 2016 7:01 pm

You may have exceeded the recommended temperature if your thermistor was loose.

If you build the hotend as described in the H1 build instructions, and just use silicone to secure it, there is a good chance it will creep out of the hole and as it does it reads progressively lower, and as a result the temperature creeps up, so you can easily damage the hotend without it ever reading more than you expect. I destroyed my first H1 hotend that way.

You want to wrap the heater block of the hotend in Kapton or Silicone tape to hold the thermistor in place, the silicone sealant is not an adhesive.

Also be careful, I have the vague memory of the original thermistor with the H1 being a 10KOhm thermistor, almost all the firmwares expect a 100KOhm one, so verify the temperature with a thermocouple at a lower temperature before raising the temperature to printing levels.

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Re: Hot end / extruder troubles

Postby steven6282 » Fri Jan 22, 2016 12:47 am

My kit didn't come with a thermistor, I had to buy one separately but it is a 100k thermistor from the seemecnc store. I have it set correctly in the firmware. The thermistor was not lose really, until I yanked it out the hot end on accident last night. I've ordered some kapton tape to put on it as well.

Now I won't be able to mess with it anymore until Saturday evening though because I've discovered that one of the pololu stepper drivers isn't working correctly. It must have a bad trace or something cause it will only move the attached motor in one direction regardless to the dir pin being high or low (I've verified that the pin is changing states on the the driver board, and swapping a different driver in to the same axis works fine). And then while trying to figure it out I didn't pay attention and plugged one of the boards in backwards and now that one doesn't work at all so I probably fried it sending voltage down a wrong pin... oops. So I had to order some new driver boards as well. :P

However, before all of that happened while testing the filament feed was WAY better. When I tried a print with it is when I discovered the driver problem only going in one direction because even though it was feeding the filament I wasn't getting any plastic on the bed. It was all gathering on the tip and not sticking to the bed. Not sure why it was doing that, but anyway I noticed the gears would spin faster occasionally on the extruder and realized it was trying to retract the filament during periods when it would just be moving and not actually putting down plastic. Maybe that is what was causing it to stick to the head by it pushing a bunch of plastic down to fast, I dunno... will have to play with it some more when the new driver boards get here.

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Re: Hot end / extruder troubles

Postby Polygonhell » Fri Jan 22, 2016 11:44 am

The driver boards are pretty easy to destroy, any voltage over the rated maximum will kill one, and you can generate that by pugging or unplugging the motor connection with power applied.

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Re: Hot end / extruder troubles

Postby steven6282 » Sun Jan 24, 2016 1:01 pm

Ok, so I got my new driver boards in and they are working well. The filament is feeding really well now.

But now my problem is that the plastic isn't sticking to the print bed, it's sticking to the extruder tip instead, see attached picture. What can I do about this?

Oh and just to note, no it's not printing from that high, I backed the z off to take the pic after stopping the print. It's printing the first layer maybe about .2mm - .4mm from the bed.

tip.jpg

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Re: Hot end / extruder troubles

Postby Polygonhell » Sun Jan 24, 2016 1:33 pm

I wouldn't print directly on that surface, it's likely not very flat or level, you want to mount something you can level and then a sheet of glass on top of that.
IIRC I used 3 machine screws, with springs to adjust a sheet of aluminum, and a piece of window glass on top of that held with binder clips.
It doesn't need to be aluminum, anything flat will work.
You could probably get away with just a piece of window glass right on the bed if you have some way to shim it level.
The height of the first layer is absolutely critical especially without a heated bed, one of the hardest parts of getting your first printer running is knowing what a good first layer looks like.
Without a heated bed you'll be limited to PLA, and you'll want to cover the bed surface with 3M Blue Painters tape, and your looking for a slightly squished first layer.
The Z belt on the H1 also makes leveling the head left to right much more painful that it needs to be, designs with 2 steppers for Z, it's relatively easy, just hold one still and adjust the other one.

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Re: Hot end / extruder troubles

Postby steven6282 » Sun Jan 24, 2016 2:11 pm

yeah, I have a heated bed that I bought, but it's to big for this unit :(

I was reading some other stuff and thought the bed level might be part of the problem but was hoping I was wrong. Didn't count on a "complete kit' having a bed that wasn't acceptable to be used as a bed lol. Chalk it up to another piece of poor design on this 3d printer I guess.

I don't know if I have the means to make a properly leveled print bed myself. I don't even have the tools to accurately determine that precise of levelness. A simple bubble level says the current bed is level.

What is the difference between pla and abs in regards to a heated bed?

I'm not sure I follow how the machine screws, springs, and aluminum would help you level a piece of glass. Did you tap the plastic print bed and screw the screws in from the bottom? If so then yeah, that means I also have to buy a tap set to make something like that work. And I don't see why you would need the aluminum, could you not just level the glass directly in the same fashion? As for shimming, about the only thing I have thin enough to do shims on something like this would be paper.

The glass itself is a problem as well if you mean actual glass. I remember when I was first building this printer I looked for a piece of glass to use as I read that it would work to protect the print bed. However none of the local hardware stores could cut any glass to size, and specialty window shops wanted a ridiculous amount of money to do it. I do have a piece of plexi glass that I tried once and it didn't seem to do any better.

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Re: Hot end / extruder troubles

Postby steven6282 » Sun Jan 24, 2016 10:44 pm

So, it's pretty horrible quality but I completed my first print.

Part of the quality is print settings I'm sure, but I've also got some pretty horrible backlash in the x-axis. But I can't say I'm surprised by that. I expected the quality of the print to be pretty horrid with the impreciseness of the design of this kit. I'll probably have to do some pretty major changes to make this thing work respectably.

At least I can say that I finally "finished" it though.

queen.jpg

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Re: Hot end / extruder troubles

Postby Xenocrates » Sun Jan 24, 2016 10:56 pm

Yeah, a lot of it looks to be the settings. Adding a layer cooling fan and tweaking temps and speeds will probably help a lot. I'm afraid there's not a whole lot that's unexpected about a now long retired printer design that was the first commercial product from a company to enter a market in it's infancy being less than stellar. I mean, compared to the prints I saw on the first repraps I got to see, it's great. But when you've got things like the Max to compare it to, it's far less than ideal.
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Re: Hot end / extruder troubles

Postby steven6282 » Sun Jan 24, 2016 11:16 pm

Xenocrates wrote:Yeah, a lot of it looks to be the settings. Adding a layer cooling fan and tweaking temps and speeds will probably help a lot. I'm afraid there's not a whole lot that's unexpected about a now long retired printer design that was the first commercial product from a company to enter a market in it's infancy being less than stellar. I mean, compared to the prints I saw on the first repraps I got to see, it's great. But when you've got things like the Max to compare it to, it's far less than ideal.


Eh, I could blame part of it on it being the companies first commercial product, but a large part of it also is just that it's cheap. With plastic bearings that you can't tighten down to remove the play without locking them up, poor design in some areas like a belt driven x axis with no built in tensioner, etc.

I'm not sure yet what I can do about the backlash on the x axis, it happens because when the belt pulls in different directions, the entire extruder assembly rotates slightly in the direction being pulled before starting to move. If the "bearings" could be tightened that could take a lot of the play out that allows it to rotate, but they can't be without squishing the plastic and locking them up. It really needs real bearings on everything but that would cost to much for this machine IMO.

I don't know how much more time I'll invest in this 3d printer. I mostly just wanted to actually complete it since I've been working on it off and on for so long. But I'm not going to invest huge amounts of money into making it a respectable printer. I'm currently in the process of building my own CNC (using far superior quality parts on it so it will actually work lol). Once I finish it, I may use it to revisit rebuilding a new 3d printer and scavenge what useful parts there are on this one. I've learned a bit from this machine, so that's something at least :)

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Re: Hot end / extruder troubles

Postby Polygonhell » Sun Jan 24, 2016 11:51 pm

steven6282 wrote:I'm not sure I follow how the machine screws, springs, and aluminum would help you level a piece of glass. Did you tap the plastic print bed and screw the screws in from the bottom? If so then yeah, that means I also have to buy a tap set to make something like that work. And I don't see why you would need the aluminum, could you not just level the glass directly in the same fashion? As for shimming, about the only thing I have thin enough to do shims on something like this would be paper.

The glass itself is a problem as well if you mean actual glass. I remember when I was first building this printer I looked for a piece of glass to use as I read that it would work to protect the print bed. However none of the local hardware stores could cut any glass to size, and specialty window shops wanted a ridiculous amount of money to do it. I do have a piece of plexi glass that I tried once and it didn't seem to do any better.


The idea is that you want a surface that can be "easily" adjusted at 3 points, so you make the bed out of two layers, the top layer sits on screws and is pushed away from the bottom layer by the springs, level can then be adjusted by tightening the screws to adjust the level.
levelness in this case is relative to the motion of the printhead, you're looking to have exactly the same clearance from the print head at each corner being "level" in the spirit level sense isn't important.

My local ACE hardware will cut a piece of window glass for well under $10.

The problem with plexiglass or acrylic is it melts at temperatures close to the meting point of the plastics your printing, it can be a very good surface for printing ABS, but if you're bottom layer is too low, you destroy the print surface.

FWIW other "complete" kits at the time were no better, it actually ends up being a better printer than most Mendel kits at the time at a significantly lower price point, the smaller diameter lead screws for Z eliminate a lot of the issues with Z wobble. The printer Kit business though has come a long way in the last few years, part counts have been reduced drastically, the use of Chinese sourced LM8UU bearings has eliminated the whole using skate bearings in 2 and 3 way configurations, the combination of these has caused costs to plummet.

As I said above it was basically an reprap huxley with injection molded parts in place of the printed parts. Compared to most modern kits, the H1 was pretty basic, compared to what was available at the time, it was actually pretty good.

And as I said above if I had one right now, I'd canabalize the parts and build an I3 or a mendel 90 or if money were a driving factor, buy a printrbot.


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