Extruder having trouble reaching 230c

[BenTheRighteous]

So I've owned my MAX v2 for about 2 weeks now and things have been going pretty swimmingly so far, printing PLA at 190 no problem.

However after some filament temperature testing I cranked up the extruder to 230c and I noticed that it presents a challenge to the machine to get that hot. I would suspect that since that's typical ABS temperature, that shouldn't be a problem.

What happens is the extruder goes from cold to about 205ish really quickly (feels like about 30 seconds, I haven't timed it), then gets to around 225-227 after about another 30 seconds, then it's a tossup whether the display is ever actually going to read 230 or not.

Once the print finally starts it's able to maintain whatever temperature it was able to reach for awhile, but then I'll check back later and the measured temp will be somewhere between 205 and 215, despite still being set for 230.

So my question is: should I start looking for a wiring problem or is this about on par with the capability of the machine? I'm wondering if it's that, or if the PEEK fan is working too well, or if I'm pushing too much "relatively cold" filament through it, or maybe the room is just too cold (thermostat is set for 70F) or what.

I did check to see if the thermistor had melted loose but it seems to still be in place.

[BenTheRighteous]

A few more details: the temperature graphs in Repetier-Host are showing a steady output of 100% so I don't think it's a PID issue - seems like the controller knows it's supposed to be hotter and is doing its best to make it happen.

Here's a screenshot of what I'm talking about in the middle of a print: temp set to 230, machine can only hold 205. But at the start of the print it did manage to hit 230.

[img]http://i1188.photobucket.com/albums/z40 ... 155510.jpg[/img]

[Eaglezsoar]

See these links:

http://forum.seemecnc.com/viewtopic.php?f=60&t=6651
http://forum.seemecnc.com/viewtopic.php?f=37&t=5273
http://forum.seemecnc.com/viewtopic.php?f=60&t=5343

Or do a search with google with your browser with this command: site:forum.seemecnc.com hotend temperature
Google will search the entire forum looking for the words hotend temperature

[BenTheRighteous]

Thanks Eagle - I'm a bit embarassed now though - I didn't mean to make you search on my behalf!

I was mostly just looking for a one-liner, something like "that's normal, don't worry about it" or "yes that is indeed a problem, go troubleshoot it..."

Anyway, thanks to you guys for making such a great printer. I'm having a blast learning all these new things, and it totally blows me away to think that someone had to think of all this the first time, before it had ever been done before.

[Eaglezsoar]

Thanks Eagle - I'm a bit embarassed now though - I didn't mean to make you search on my behalf!

I was mostly just looking for a one-liner, something like "that's normal, don't worry about it" or "yes that is indeed a problem, go troubleshoot it..."

Anyway, thanks to you guys for making such a great printer. I'm having a blast learning all these new things, and it totally blows me away to think that someone had to think of all this the first time, before it had ever been done before.

You are welcome and we are here to help. Many users do not know how to properly search a forum, that's why I always put in the google search command.
Happy printing and I hope you discover your problem soon!

[BenTheRighteous]

Ok, I did some testing with a multimeter and I think I might be fighting with an underpowered power supply... but I'm not sure. Are these readings normal? There is some drop, but it's just on the edge of what I would call significant.

Measured at RAMBO input:
Printer on but idle: 11.8v
Extruder heating: 11.7
Bed heating: 11.3v
Bed and extruder together: 11.1v

Measured at RAMBo extruder output:
Extruder heating alone: 11.5v
Extruder heating with bed: 10.9v

Measured at RAMBo bed output:
Bed heating alone: 10.9v
Bed heating with extruder: 10.8v

[Earthbound]

Check the hot end resistance. Should be around 3-4 ohms. You'll probably measure closer to 8, meaning one of the heating resistors is bad.

[BenTheRighteous]

Thanks for the idea, but it is 4.4 ohms - measured both at the extruder and at the RAMBo output (was thinking that maybe my crappy crimping was to blame, but it would seem not... this time)

[BenTheRighteous]

So in the middle of a print tonight I saw the same issue - temp set to 230, actual was hovering around 208. So I took the opportunity to measure RAMBo voltages again - extruder output was bouncing between 11.1v and 11.3v, and RAMBo input was bouncing around 11.2v and 11.5v. I was actually surprised; that doesn't seem too terrible.

[teoman]

Did you see a decrease in quality?

Check out your thermistor. If it is lose then it doesn't read the temperature properly.

[bot]

I had this same issue happen to me, as well. I had accidentally rotated the orientation of the nozzle when I tightened it. At the negative terminal of my heater wiring, the kapton-covered uninsulated crimp connector was pushed up against the nylock nut that holds the hotend frame to the effector. This nut, the screw, and the aluminum spacer were acting as a heatsink and drawing just enough heat away (from, at least, the thermistor area) to cause the printer to fail to heat up to 230 (it would get to 227-ish), and thus fail to begin printing. Simply rotating the wiring as to not contact the nut fixed the issue immediately. If this were to happen at the positive terminal, perhaps it would cause an even greater loss (of reading, at least) of heat.

I've noticed, also, that running a new PID auto-tune after ANY of the "heat-related" conditions of the nozzle have changed provides the best performance.

[BenTheRighteous]

I have checked the thermistor and while I haven't tried to pull it out, I have nudged it a few times and it seeeeems to still be seated firmly.

I'll have to check out my wiring like bot suggests for any unintended heat sinks. Thanks for that idea! I still have 10 hours left on my current print so I'll have to wait until tomorrow, but I hope that's the cause since that would be a trivial fix!

[Earthbound]

A few more details: the temperature graphs in Repetier-Host are showing a steady output of 100% so I don't think it's a PID issue - seems like the controller knows it's supposed to be hotter and is doing its best to make it happen.

Here's a screenshot of what I'm talking about in the middle of a print: temp set to 230, machine can only hold 205. But at the start of the print it did manage to hit 230.

[img]http://i1188.photobucket.com/albums/z40 ... 155510.jpg[/img]

I'm thinking now that the thermistor is getting cooled by airflow.

1. In picture, you're printing ABS. I would not expect it to extrude well if the nozzle was actually only at 205. So thermistor is showing a lower value than nozzle is reaching.

2. In picture, the layer fan looks to be on. Leave it off for ABS! Thermistor may be cooled by the layer fan.

3. In picture, if Z tower is 12 o'clock, PEEK fan appears to be at 8 o'clock position, correct? Where is thermistor on the clock face? Ideally it is on same side as PEEK fan, so that PEEK "exhaust" air doesn't reach it.

[bot]

Based on his bed temp I'd assume that was a PLA print.

[Earthbound]

Based on his bed temp I'd assume that was a PLA print.

Maybe. I print PLA on a 40C bed. Over 50C the bottom layers don't stay flat. I've not had any PLA that got friendlier above 215C so a hot end target of 230C seems odd for it.

[BenTheRighteous]

Actually yes, it's PLA! I know 230 is pretty dang hot for PLA, but I did some temperature testing and with the filament I have, 230 produces the best prints. Printing at the 190 range produced parts that easily broke apart by hand, 210 range produced parts that were difficult to break by hand, and at 230 I had to use tools to break them apart. It's from MatterHackers if anyone is curious.

Earthbound, my thermistor would be at 5 o'clock in that picture. It's possible that it is being hit by the air from the layer fan after it bounces off the print surface - that makes a lot of sense actually - it explains a lot of what I've been seeing.

- Before the print starts and the extruder is heating, the layer fan is not on, so the extruder can reach temperature (albeit slowly)
- Once the print starts and passes the first few layers, the layer fan turns on. Explains why after awhile I see the temp drop to around 205.
- I noticed this morning that doing a print with tall columns, the issue is much less pronounced. Extruder is at 225/230. My theory is that with the extruder being so high in the air, there's nothing for the layer fan air stream to bounce off of and it misses the thermistor.

I still have an hour to go on my current print, so once that's finished I'll try these great ideas you guys have given me. Thanks for the insight!

[Eaglezsoar]

I believe your first idea is correct.
We have a lot of posts about the power supplies not delivering enough current which would explain why your voltages are so low.
Put in a high grade power supply.

[teoman]

Could you try wrapping the hotend with kapton tape?
That remedied my problem.

And if you notice an immediate positive outcome we can say that your problem was heat loss. If not, you may have some more serious issues.

[BenTheRighteous]

I repositioned my layer fan so that the airflow wouldn't bounce back toward the thermistor, rerouted some wires, and recalibrated the PID settings. I'm hoping that was sufficient; I'll report back here when I have some results!

[teoman]

check out the spiderbot thermal shield design.

[BenTheRighteous]

I rerouted some hotend wiring, checked for accidental heat sinks, made sure the thermistor was seated well, and adjusted my fans' airflow. The problem is improved somewhat: the printer seems to be able to maintain a temperature of 220 now. I haven't wrapped the hotend in kapton tape as teoman suggested, which I still may yet try, but my suspicion is that the power supply is the culprit. I do have a spare laying around but I'm not sure how the wattage compares.

Thanks again for all the ideas! I'll keep updating this thread with developments, but it might be awhile until I can really dig in and investigate.

[Captain Starfish]

Have you confirmed the hotend is actually at 205 - 230º?

I had a similar issue and, putting a thermocouple off a multimeter onto the hot end, determined that the hotend was sitting at 260º (how the PEEK didn't slag I have no idea) and the thermistor was badly out of calibration.

[BenTheRighteous]

Nope, at this point I'm just trusting the thermistor. I decided to order a thermocouple meter off amazon today (thanks for the idea), as well as some power supply extension cables so that I can install some regular molex plugs into the machine, making easier to swap out power supplies in the future.

[geneb]

Ben, there's enough variation in the thermistor that you're really going to want to validate it against a thermocouple. Use the "corner" made by the nut shape on the nozzle and the bottom face of the heater block as your measurement point.

Since a thermistor is essentially just a resistor that changes value with temperature, it's likely got the same accuracy range as a typical resistor - 5% or so. A 5% overshoot at 190C is 9.5 degrees, and it could just as well be biased in the other direction.

Either way, a thermistor falls squarely into the "Trust But Verify" category.

g.

[bot]

Teoman's suggestion of wrapping the hot end in kapton is good. It helped my hot end.