I've been working on a large format FDM printer for the last several months now and everything is going great, but I'm still running into a lot of problems that I need to get ironed out once and for all. For some reason or another I've been unable to resolve these issues on my own so I'm really hoping you guys are much smarter than me, which should not, be, difficult.
Without further adieu, the main issue that I'm having is with hot end temperature. I'll put the specs below, but basically there are two things happening. A, the temp is reading incorrectly. When measuring at the spot between the nozzle and heater block on my E3D V6, my host reads 100c (set value) and my multimeter with a type K thermocouple reads 95c. When I set my host to 210c, it reads 202c on the multimeter. I'm not particularly good with electronics so I'm not sure what that means exactly, but it's not a consistent offset, again, whatever that may mean. To get around that I've just been artificially inflating the temperature so it rests where it actually needs to be, but I'd prefer to not have to do this forever, especially since I'm sure it's causing more issues that I know.
B, recently it started doing something differently, now it will usually read a temperature higher than what I set, typically anywhere from 15-25c above what's expected. If I run a PID autotune, it will be fine for a while but then creep up to a higher temp, especially after starting a print. Ironically enough, When this happens I have to set it back down to a more normal range, but the graph still shows the measured temp reading at the higher value, just floating above my set value.
Also, for what it's worth, since my printer is large, I have to route the cable quite a distance to make it to the hot end so my wire lengths are probably around 20ft or so, but I'd have to check to make sure. Not sure if this is relevant, but I wasn't sure if after a certain length, signal strength might become and issue or not? Also, as noted just below, I'm running my printer off 220v so I can't really run my computer off the same power strip. I've seen Arthur point out in several places that ground looping can be an issue, but given my setup, I'm not sure how to resolve that.
Power: 220v w/ 24v PSU
Electronics: Smoothieboard, obviously lol
Hot End: E3D V6 w/
24v 40w heater
Semitec 100k thermistor
Note: Aside from the fan on the hot end, there are no fans or gusts of wind so I doubt there would be environmental causes for any of that stuff, for what it's worth.
I'm sure this is something stupid simple but for some reason, sometimes when I probe the bed it will ignore the sensor and keep going. Usually once I freak out and pull the plug and restart everything it will work the second time but every now and again it will do this and scare the ever living sheet out of me, not to mention whatever it's doing to my hot end, carriage, everything. I've been pretty good about going to "Safely Remove Hardware…" in Windows 7 and unmounting Smoothie before I try to do any probing.
I measured the signal voltage going to Smoothie and it reads 3.28v. I have a small trim pot for adjustments but it won't go any higher, but my understanding is that should be enough to operate properly.
Overall Print Quality
Images are huge so I didn't want to display them on here but the album can be found here: Test Print Photos (imgur com/a/uFaTf)
Beyond what I described above and how that may affect print quality, really, anything else you can see that might help with some things let me know! The image I've attached is of an attempt to print the main face piece for an Iron Man helmet. The only reason I needed to abort is because I didn't think out my support placement well enough. The thin walls near the ends started to warp upward on the right side after a certain point so the nozzle would crash into it. I was able to recover it once which lasted for 30 or 40 layers before it started doing it again, at which point I stopped it. Oddly enough the other side didn't have any issues. So I just need to plan my supports out better, but I think there can still be much to learn from what did print.
As you can see, there are a good amount of artifacts going up but they don't seem terribly consistent to me. Unfortunately I didn't log any temperatures at different points so I couldn't say what it would have measured at a given point but as I mentioned above, it does float around a little but I don't noticed an average difference between 5-6c swing in either direction from it's baseline. I've also circled different issues that I know about, green is related to the support pillars and the blue was my belt slipping, but I was able to pause it and tighten it down, although I will need proper belt clamps for sure.
One thing I've never really been sure of was if there were any best practices to getting optimal belt tension. There seems to be an acceptable amount of deflection given the length of my axis' but I'm still seeing some ringing on the "exit" side of corners, even at around 40-60mm per second. Is there a more calculated approach I can take to dialing this in?
The other photos show my backup extruder I have in case something goes wrong with my current one. The grey parts are the ones I printed and the gears in black were printed by someone else. Naturally those are pretty good looking lol It is worth noting that these parts were printed with 6mm belts on X and Y and the Iron Man mask was printed using 9mm belts. The smaller belts were a lot easier to gauge tension but the bigger ones don't give much when pulling by hand so this is partly why I'm not sure about how to "properly" tension any given belt. Part of me wants to say that this could explain a lot of what I see when I look at the mask, but I don't know for sure. Anyways, the parts printed on the smaller belts which probably had better tension also seem to have less artifacting also, still some but still less.
X and Y Drive: 9mm GT3 belts (two steppers, L and R)
Z Drive: 1/2" ACME lead screws (buildyourcnc com/item/mechanical-leadscrews-lead-screw-!5-5-starts-10-tpi) (two steppers like Y)
Stepper Size: Nema 23 (openbuildspartstore com/nema-23-stepper-motor/)
Print Speed: 35 mm per sec outer shell, 65 for the rest
Nozzel Size: .4mm
Layer Height: .2mm
I'll stop droning on now, but hopefully I've given enough info so that it might be clearer to someone who is kind enough to make it this far what is going on :) I've put a lot of work into this guy so far and I might just be exhausted but this is the wall for which my face currently resides against. Any and all help would be greatly appreciated. I know not all this is strictly speaking Smoothie related, but I'm hoping you guys can help me out all the same! Any info would be much appreciated and if you need more specs, less talky talk, I can provide whatever info might be helpful. Thanks a bunch and I look forward to hearing from you guys!