Trying to survey some info –
1.If you’re pushing PLA at 150mm/min through your hotend, what temperature would you set your hotend to? Not in printing state, simply manually pushing filament into air.
Did you mean 150mm/sec?
I think it’s 150mm/min because that’s what standalone pronterface shows in the settings.
150mm/sec sounds almost impossible @Geoffrey_Forest
Are you talking about just pushing plastic through the nozzle (extruding into air), or are you actually trying to print? If you’re just pushing plastic through, why? (it matters)
@Whosa_whatsis just pushing plastic through air, printer is idle. I’m just trying to find a benchmark to test hotends against. Or do you have a better idea?
If that’s really 150mm/min pure filament speed commanded on the extruder, with 1.75mm filament that comes out to 6 mm^3/sec. With an all-metal hot end of normal size (like an E3Dv6) that wouldn’t require an elevated temperature, that’s within the range of normal printing conditions.
As for the extruder current setting, I use the touch test: If you can touch the motor after it’s been running for a while without reflexively pulling your hand away in pain (not “ow, that hurts,” and pull it away, I mean before you even register the fact that it’s hot), the current setting is too high. Other than that, you want it to be about as high as possible unless you’re calibrating to make sure that the motor skips before the filament strips.
It also matters what it’s mounted to. An aluminum plate will link heat away and allow you to run at a higher current, but if, on the other hand, you’re using a wade’s extruder printed in PLA, you’ll need to run it at less than half of its rated current if you want that to even survive long enough to print a replacement in a more appropriate material.
@Whosa_whatsis I’m more concerned about the driver on the board than the motor. The motor is surrounded by metal and aluminum extruder. We used to always run at 0.5 amps (when the motor is rated for 1.68 amps and 3.7 VDC), but I’m thinking 1.2 amps current settings might be better? The printer quality difference is noticeably better with 1.2 Amps.
For reference I just looked at my old repetier host settings (I just push it by hand these days, but I used to do it that way), and the manual extrusion speed is set to 450mm/s. This is fast enough for you to see significant die swell as the plastic leaves the extruder.
You might tell us some more about what you’re trying to do WRT benchmarking. I’m not sure what you’re trying to measure. There are things you can usefully measure by just jamming cold filament into a nozzle, but they’re not what you might be thinking.
@Whosa_whatsis See the specs here: http://imgur.com/a/rmD5i
I’m trying to see if our hotend has more resistance than other hotends. It’s a good way to see if there’s any improvements that can be made.
.5A is definitely too low. What drivers are you using? If you’re getting them from Roy, I’d guess they are DRV8825s with nice heatsinks, so the drivers should easily be able to handle 2A, especially if there’s any airflow at all.
@Whosa_whatsis Yes those are the drivers. 2A is more than the motor is rated for though. So far we’ve been printing without heat sinks, but I think now that we’re considering upping the current we may need to add a heat sink. The 3 axis have been always printing at 0.5A though without noticeable skipping.
Well, electrical resistance is easy to measure, but I doubt that’s what you’re referring to.
The key with your low-thermal-mass design will be a fast feedback loop so that you can keep up with your temperature dropping due to heat transfer to the filament. Alternatively, this might be ideal hardware for the feed-forward system that @Rob_Giseburt was telling me about.
Without fast feedback (or feed-forward), the temperature of the inside will drop, reducing your ability to heat filament. Eventually, the sensor will measure this drop and increase heater power, but then (during actual printing) you’ll stop and retract and the filament will be getting too much heater power. Temperature will rise and power will drop, and you’ll get temperature fluctuations. That’s what you want to be looking for and trying to get rid of.
@Shai_Schechter Sorry, I thought you were talking about printing speed (movement of the print head) not extrusion speed.