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3D Printers


Thalestris24

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Well, I bottled replacing the controller board last night, but did replace the thermistor and added another pair for the new cooling fan.  Just waiting for the extra bits I need to be able to reassemble it now.

I can't find a fault with the old thermistor.  Because the cables worked in some positions and not others I was expecting a broken wire, but there's no evidence of that.  It does look like the thermistor wires are crimped to the ends of the cable rather than soldered, so perhaps there's a problem with that.

James

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23 hours ago, JamesF said:

I've finally got at the thermistor.  Turned out to be a little more tricky than anticipated.    I have discovered that I now need some tape that works at high temperatures and probably some new insulation material for the heater block too, so I might be out of action until after Christmas unless I can find something suitable for a temporary workaround in the workshop.

The tube between the heater block and extruder was a pig to get out of the heater block, but it had to come out so I could remove the insulation in (mostly) one piece to get at the grub screw holding the thermistor in place.  The threads are quite gunged up (with PLA I assume).

Anyhow, now I just need to take some of the cable ties and spiral wrap off, remove the old thermistor and replace it with the new one and rebuild everything.  Perhaps whilst I'm at it I should add in an additional pair for the new fan.  It would save taking all the cabling apart again.

Or maybe I should just accept that since I have a fair bit of it in pieces already I might as well just go the whole hog and replace the controller board at the same time.

James

Sounds like you have the MK8/9/10 hot end - you can buy the silicone socks for those like the e3d have if you don't fancy re-insulating it and using kapton tape.

Is it the bead type thermistor? I found them to be extremely fragile. Loving the cartridge style now.

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I have seen the silicone "socks".  They look like a nice idea, particularly as they cover most of the heater block rather than just four sides.  I might try one.

It is a bead type thermistor.  I wasn't even aware they were available as cartridges.  Next time I need one I'll look out for them.

James

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E3D boots are designed for their heater blocks\nozzles and there are different boots for different configurations, whereas the cloned ones quite often have different block\nozzle sizes, so may not fit properly or keep falling off, so check before buying, preferably from the printer manufacturer.

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I have a bit of advice that might help fault-find.  If you have two thermistors by your hotend(s) and find a broken wire then find what you think is its mate - check carefully that one of the wires on the other thermistor isn't broken or you might end up as I have just done with my wires crossed!!!  Grrr...

Edited by Gina
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Had everything running nicely again last night, so printed out a couple more cooling duct designs from thingiverse, claimed to be specifically for my printer.  Neither actually fits though.  I shall have one last try with another and if that doesn't work I'll be designing my own.

One thing that does concern me is the clearance of the cooler over the little bulldog clips that hold down the glass bed.  I recognise that the bulldog clips do the necessary job very simply and cheaply, but it is hard to find a position for the one at the front ledge of the bed where it is guaranteed never to be in the way.  It's quite tempting to get a small piece of steel strip and put two right-angle bends it in together with a 3mm hole at one end so it can just fit over the edge of the glass to hold it down and then be held in place itself by the height adjustment screw at that corner of the bed.

Perhaps I really shouldn't need a clip there, but if I take it off there's a gap of 2mm to 3mm between the glass and the heatbed PCB.  Makes me wonder if the heatbed isn't very flat itself, or if I have it slightly twisted, though if I have once held fully in place the glass appears to be pretty close to level compared with the positioning of the hot end.

James

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1 hour ago, JamesF said:

Perhaps I really shouldn't need a clip there, but if I take it off there's a gap of 2mm to 3mm between the glass and the heatbed PCB.  Makes me wonder if the heatbed isn't very flat itself, or if I have it slightly twisted, though if I have once held fully in place the glass appears to be pretty close to level compared with the positioning of the hot end.

Most beds have some warp in them, hence the glass. I found a nice alternative to the bulldog clips in my local stationers, they are some sort of paper clip/staple thing. Low profile and I use them on the left and right of the bed. They are quite strong steel too so really hold it together well.

https://www.viking-direct.co.uk/en/p/ND180794

Another one I have used in the past is a small version of the thing people use to hold a table cloth onto a table outdoors but I cant for the life of me remember where I got them. Those are even lower profile so rarely had problems with the nozzle hitting them. Not as strong though.

Other than that, you can always alter your routines to miss the clips :)
 

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Once you have the printer working you can make a frame of PETG or ABS to hold the glass.  That's what I did.  Also, you can buy self-adhesive silicone heater pads that can be stuck directly to the glass giving a much more even temperature over the bed.  OTOH if you don't want the heater stuck to the glass you can get these heaters without the self-adhesive layer and hold the heater against the glass with polyurethane foam.  I currently use that system on my Mini printer (200mm square bed).

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I've moved away from glass sheets for the DBot bed, and instead use a 6mm cast aluminium sheet with a mains driven heater and a PEI sheet, attached to the surface. It's a lot quicker heating up and is very flat, i.e.

RepRapFirmware height map file v2 generated at 2018-11-12 21:18, mean error -0.022, deviation 0.049
xmin,xmax,ymin,ymax,radius,xspacing,yspacing,xnum,ynum
10.00,290.00,10.00,280.00,-1.00,45.00,45.00,7,7
  0.050,  0.025,  0.048,  0.085,  0.075,  0.080,  0.102
  0.005,  0.000,  0.017,  0.045,  0.030,  0.023,  0.038
  0.003, -0.030, -0.002,  0.003, -0.030, -0.040, -0.030
 -0.038, -0.045, -0.038, -0.030, -0.047, -0.065, -0.053
 -0.045, -0.072, -0.068, -0.070, -0.083, -0.083, -0.072
 -0.047, -0.068, -0.072, -0.072, -0.083, -0.077, -0.065
 -0.010, -0.040, -0.050, -0.055, -0.053, -0.047, -0.027
 

looks like it needs another tune-up....

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Well, I printed something out last night and it went fine, but this morning when I tried it again the print was all over the place -- really poor adhesion over the first few layers and looking as though there wasn't enough material being deposited.  Having spent the day on and off trying to find out what the problem was I think I'm coming to the conclusion that there's a partial blockage somewhere.  I've just removed the PLA from the extruder and it looks very chewed up, as if the extruder gear has scraped along it whilst trying to push it through into the hot end.

Once it has cooled down I'll take the nozzle off and check the extruder behaves properly without a nozzle, then perhaps replace the nozzle.

*sigh* All this worked fine until the thermistor packed in :(

James

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17 minutes ago, JamesF said:

Well, I printed something out last night and it went fine, but this morning when I tried it again the print was all over the place -- really poor adhesion over the first few layers and looking as though there wasn't enough material being deposited.  Having spent the day on and off trying to find out what the problem was I think I'm coming to the conclusion that there's a partial blockage somewhere.  I've just removed the PLA from the extruder and it looks very chewed up, as if the extruder gear has scraped along it whilst trying to push it through into the hot end.

Once it has cooled down I'll take the nozzle off and check the extruder behaves properly without a nozzle, then perhaps replace the nozzle.

*sigh* All this worked fine until the thermistor packed in :(

James

What type of printer/ hot end do you have? If its a MK8/9 there is a usually a piece of teflon tube inside that I found blocks up very easily and is really a consumable. PITA to replace it but usually got great prints everytime I did. The teflon gets soft if your temps go too high (like during a thermistor failure) and can get damaged.

 

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It is a MK8 hot end.  The tube looks fine as far as I can see -- I did check it when I had the hot end apart to replace the thermistor and having taken the nozzle off the filament seems to run through very easily.  I have some replacements though, so I'll look at that if replacing the nozzle doesn't help.

James

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4 minutes ago, Gina said:

Hmm...  I don't like Teflon (PTFE) in hotends and much prefer an all metal version.  In fact I only use all metal hotends nowadays.

It was a weekly occurrence for me, but I spent ages believing that all-metal / e3d hot ends were just overpriced and couldn't really be that much better.

Then I bit the bullet and got the E3D 1.75 kit - the difference is night and day and would never go back to teflon inserts now. Next job is to switch from the direct drive to bowden and remove the excess weight of a PG27 nema on the gantry.

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Well, I tried Bowden feed a while back and gave up on it.  OK I know many manage to use it successfully but unless you want a double extruder I thing direct feed is better.  Using the E3D Titan extruder with lighter weight stepper motor and geared feed the extrusion is excellent and the weight is minimal.  I print at up to 120mm/s.

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Looks like we're good again.  Replaced the nozzle, reset the bed height (don't have automatic adjustment on mine) and set a print off.  Wasn't happy with the adhesion again, so lifted the bed a teeny bit more and it all looks good, though the trial print I'm doing isn't as big as the one that was failing earlier today.  It's a test piece to check sizing for a new holder for all the hex bits I have for my cordless drill/driver.  The current case is falling apart, which I'm inclined to forgive after getting on for fifteen years, so I'm going to make a new one.

James

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3 minutes ago, Gina said:

Well, I tried Bowden feed a while back and gave up on it.  OK I know many manage to use it successfully but unless you want a double extruder I thing direct feed is better.  Using the E3D Titan extruder with lighter weight stepper motor and geared feed the extrusion is excellent and the weight is minimal.  I print at up to 120mm/s.

The Titan may be a good alternative, im using the original extruder/motor on the Tevo Black Widow with a genuine E3D hotend, which according to specs the motor alone adds around 600g to the gantry. My ender3 uses bowden and it works a dream though so torn both ways.

Maybe I should have bought a titan and reused this motor for my focuser project instead of purchasing a new PG27 motor for it yesterday. Doh! ?

3 minutes ago, JamesF said:

Looks like we're good again.  Replaced the nozzle, reset the bed height (don't have automatic adjustment on mine) and set a print off.  Wasn't happy with the adhesion again, so lifted the bed a teeny bit more and it all looks good, though the trial print I'm doing isn't as big as the one that was failing earlier today.  It's a test piece to check sizing for a new holder for all the hex bits I have for my cordless drill/driver.  The current case is falling apart, which I'm inclined to forgive after getting on for fifteen years, so I'm going to make a new one.

James

Great news, manual bed leveling is an art isn't it! I have found a set of feeler gauges removes some of the guesswork and lets me set it to 0.10 accurately enough every time most of the time.

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I use auto-bed-levelling but that needs a probe to measure the bed at a number of points (usually 4 or 9).  This feature is available in Marlin and a number of other firmwares.

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5 minutes ago, upahill said:

Great news, manual bed leveling is an art isn't it! I have found a set of feeler gauges removes some of the guesswork and lets me set it to 0.10 accurately enough every time most of the time.

Oddly enough I was just thinking about buying a set of feeler gauges for my "3d printing toolkit" :D

James

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