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Folger Tech 2020 Prusa i3 Build Log

#62
It sucks that you are dealing with these troubleshooting loops, but blown analog ports on the arduino can cause this problem. And it is the last bit in the system that hasn't been changed.
 

markyoe

Senior Member
#63
It sucks that you are dealing with these troubleshooting loops, but blown analog ports on the arduino can cause this problem. And it is the last bit in the system that hasn't been changed.
I am waiting to see what Folger Tech says. So far, the costumer service has been great.
 

markyoe

Senior Member
#64
I measured the resistance of the hot end thermistor again, and now it reads different values usually between 90 and 100. I found that by reading the resistance with the multimeter and pushing the leads of the thermistor down(at the part where it just comes out of the hot end), the reading would jump down to 0.00. Once I stopped holding it down, the reading went back up. Are these the characteristics of a thermistor short?
 

jhitesma

Some guy in the desert
Mentor
#65
That definitely sounds like a bad thermistor or at least a damaged wire right at the thermistor. Though it could also be the wires shorting out when you push down.

I don't have any 3D printer experience yet (REALLY interested in the FT and been reading a lot about it though....and saving...wife says if I put an equal amount into our savings account first I can get myself one...but that's going to take a little while!) but I've been doing electronics projects for about 30 years and thermistors aren't anything new to me ;)

With that said, I'm not familiar with the mechanical details of the thermistor installation in the FT and haven't been able to find any detailed close up photos. Would you be able to take a few showing how the thermistor is mounted?

Also, I saw in the FT build manual that you have to install the pins yourself. If you don't have a proper crimp tool this could be where the problem is. Are you reading the termister from the pins in the connector or right off the wires? When I use crimp sockets/pins without a crimper I usually tin the wire then heat the pin to reflow it just a bit. Too much solder and you can affect the fit of the socket in the shell and how it fits on the pins...but just reflowing the solder from tinning the wire can help make sure you've got a good connection with the socket.

But it sure sounds like either an internal break in the thermistor or an issue along the wires - depending on where you're taking your readings.

Glad to hear FT has been so helpful with the issues at least, but I'm dying to see you do some successful prints :D
 

markyoe

Senior Member
#66
Would you be able to take a few showing how the thermistor is mounted?
Here are a couple pictures of the hot end.
hot end.JPG
hello.JPG

But it sure sounds like either an internal break in the thermistor or an issue along the wires - depending on where you're taking your readings.
I press the prongs of the multimeter on the exposed parts of the connector. The hot end thermistor did not come without a connector at the end, so I soldered a length of wire, that had a connector, onto the end. The length of wire with the connector came with the kit but was not specified to be used for the thermistor or anything else.

I'm dying to see you do some successful prints :D
Me too!
 

Attachments

#67
We're still only guessing. To find out for sure, you'd have to measure the resistance while the controller is turned on. If the controller throws a temp error while you measure ~100Kohm, then at least you know there is a problem with the controller, which is still my guess. Alternatively, pick up another 100Kohm thermistor from your local electronics shop and see how that goes. IF they dont have thermistors, surely they will have a resistor that you can also use for testing (thermistor is basically a resistor that changes with temperature).

As for the thermistor shorting; I dont know how hard you are pressing, but at some point its perhaps no big surprise it will short out. May or may not be a problem, difficult to tell.

Also, probably not your current problem, butI have to ask, whats underneath those black heat shrinks? Did you solder those wires or did they come like that? If that is the side you soldered, keep in mind the thermistor will reach >250C when printing ABS and the heat will flow easily through thin wires for a short distance. At those temps, the solder could melt. They should be crimped. If they came like that from the manufacturer, then I'll assume they are crimped. The other side of the wiring near the board is no problem (and neither is cable length).
 

markyoe

Senior Member
#68
We're still only guessing. To find out for sure, you'd have to measure the resistance while the controller is turned on. If the controller throws a temp error while you measure ~100Kohm, then at least you know there is a problem with the controller, which is still my guess. Alternatively, pick up another 100Kohm thermistor from your local electronics shop and see how that goes. IF they dont have thermistors, surely they will have a resistor that you can also use for testing (thermistor is basically a resistor that changes with temperature).

As for the thermistor shorting; I dont know how hard you are pressing, but at some point its perhaps no big surprise it will short out. May or may not be a problem, difficult to tell.

Also, probably not your current problem, butI have to ask, whats underneath those black heat shrinks? Did you solder those wires or did they come like that? If that is the side you soldered, keep in mind the thermistor will reach >250C when printing ABS and the heat will flow easily through thin wires for a short distance. At those temps, the solder could melt. They should be crimped. If they came like that from the manufacturer, then I'll assume they are crimped. The other side of the wiring near the board is no problem (and neither is cable length).
No, my soldering job on the thermistor wire is just a few inches from the Ramps, so hopefully those parts are crimped, like you said. I measured the thermistor while the printer was plugged in and I think the numbers were jumping all over. Should I be able to pull out the thermistor from the hot end without harming anything? Are there any chain stores that would have a thermistor? Radio Shack? My city doesn't have very many techy stores. :)
 
#69
Your thermistor is embedded in that copper piece whatever you call it. Ive never seen one like that, i dont know if you can just remove it, sorry. You should be able to remove the copper piece though, its probably just screwed in the heat block, but doing so wont tell you anything.

As for shop recommendations, again sorry, no idea, I live on a different continent. If Radio shack is still anything like it was 25 years ago here, they might have it and they certainly will have resistors. While you're shopping, see if they sell Kapton (or similar polyimide tape), so you could mount it on the hotend and start printing if it turns out to be the thermistor.
 

markyoe

Senior Member
#70
Your thermistor is embedded in that copper piece whatever you call it. Ive never seen one like that, i dont know if you can just remove it, sorry. You should be able to remove the copper piece though, its probably just screwed in the heat block, but doing so wont tell you anything.

As for shop recommendations, again sorry, no idea, I live on a different continent. If Radio shack is still anything like it was 25 years ago here, they might have it and they certainly will have resistors. While you're shopping, see if they sell Kapton (or similar polyimide tape), so you could mount it on the hotend and start printing if it turns out to be the thermistor.
I will give them a call when they are open. Folger tech actually sent some kapton tape. Thanks for your help.
 
#71
Was Folger Tech willing to send a new thermistor assembly?

It looks like it is a brass collar that is crimped over the PTFE tubing on the thermistor leads and then the collar is held in the heater block with a set screw. If either of those (the crimp or the set screw) are too tight, you could damage the thermistor.
 

jhitesma

Some guy in the desert
Mentor
#73
Radio shack is nothing like it was 5 years ago let alone 25 years ago :( They're basically a battery and cell phone shop now.

My local one managed to survive the massive closings last year...but they removed about 90% of the remaining electronics stuff. They have some arduinos at crazy high prices and one set of drawers of parts that they never seem to restock. I wouldn't even expect to find a 100k resistor anymore it's gotten so bad :( I can't remember the last time I saw a thermistor at a radio shack.

Looking at that thermistor I wonder if the crimp on that copper piece may have damaged the insulation on the wires and be causing an intermittent short...but I'm just guessing.

You may want to cut off the heat shrink and check the connections closer to the thermistor - then check the readings from there to rule out the rest of the wiring....you can always put fresh heat shrink on...

But Z&B has more experience with 3D printers so I'll gladly defer to him. It just sounds more like a bad thermistor than a problem with the RAMPS/Mega board but can't really rule that out yet either.
 

jhitesma

Some guy in the desert
Mentor
#74
Would something like this work or is this the total wrong piece? http://www.radioshack.com/100k-ohm-1-4-watt-carbon-film-resistor-5-pack/2711347.html

I am waiting for another response from Folger Tech.
If your local store actually has them in stock then yes, that would work as a "fake termistor" to rule out a problem with the ramps/mega.

I'd probably just find some old toy or device and unsolder a suitable resistor from a board I don't care about than pay radio shack prices for one just to test with...but I'm silly that way :D

Then again even though I have literally boxes of spare resistors I've been known to give in and pay RS prices for a few just because I'm too lazy to dig through the boxes to find the right resistor :D

Never claimed I was consistent!
 

markyoe

Senior Member
#75
If your local store actually has them in stock then yes, that would work as a "fake termistor" to rule out a problem with the ramps/mega.

I'd probably just find some old toy or device and unsolder a suitable resistor from a board I don't care about than pay radio shack prices for one just to test with...but I'm silly that way :D

Then again even though I have literally boxes of spare resistors I've been known to give in and pay RS prices for a few just because I'm too lazy to dig through the boxes to find the right resistor :D

Never claimed I was consistent!
My local Radio Shack does have those in stock. You said "fake thermistor" because it wouldn't actually read the temperature, and it would just take the place temporarily?
 
#76
"Thermistor" is a contraction of resistor and thermo, ahm.. something :)
Its a little device that changes its resistance with temperature. A normal resistor, like the one you linked, doesnt do that.. So yes, the idea is just to see if the controller works and measures a reasonable value as temperature if you replace the thermistor with a fixed resistor. You will not be able to print. And I second jhitesma, just about any old piece of electronics is likely to have several such resistors. They dont even have to be 100K Ohm. Im not sure about the exact range, but at least half or double should work too, just give a different temperature readout.

If you dont want to wait for the vendor, here is a "naked" thermistor you will have to mount with some kapton, like I linked earlier:
http://www.amazon.com/RioRand-10-100Kohm-NTC-Thermistors/dp/B00GD471PO

Or one packaged like yours:
http://www.amazon.com/Modular-Therm...p5sw66L&dpSrc=sims&preST=_AC_UL160_SR160,160_

10x as expensive, but still hardly a fortune and easier to install.
 

markyoe

Senior Member
#77
Woo hoo! I found the problem...I think. I removed the thermistor from the hot end just to investigate it. The end of the thermistor had a brass piece crimped on it. Using pliers and being careful not to break the glass thermistor end, I kept squishing the brass piece and eventually broke it off. I separated the wires coming from the end of thermistor so that there was no possibility of a short and Kapton taped it to my hot end. Fired up the printer, and bingo! No MAXTEMPS error....yet. The next step is to make sure the temp of the hot end is consistent with what it reads in Repetier Host. More updates to follow...
 

markyoe

Senior Member
#78
Here are some pictures of one of my recent prints. The troubleshooting continues. :)

IMG_20151022_090502.jpg IMG_20151022_090520.jpg IMG_20151022_090529.jpg IMG_20151022_090609.jpg

Definitely better than the last pictures I posted.

I printed it again with a higher flowrate, lower federate, slightly lower bed temp, and 10 degree higher extruder temperature, and it turned out almost exactly the same. Here is a picture of the second one.

IMG_20151022_091519.jpg

I noticed that the bases of both of them are really thin.

IMG_20151022_091537.jpg

Any suggestions?
 
#79
Have you calibrated the extrusion?

If you have, then it could be a clogged nozzle. Remove the nozzle (you may have to heat it to get it lose easily), then use a blowtorch to burn it clean.
 

markyoe

Senior Member
#80
Have you calibrated the extrusion?

If you have, then it could be a clogged nozzle. Remove the nozzle (you may have to heat it to get it lose easily), then use a blowtorch to burn it clean.
No, I have not calibrated the extrusion. I should have it extrude 50 and measure if it actually used that much? Does it measure according to how much it uses of the filament or of how long the strand is, that is coming out?