So i replaced my hot-end and this is happening!

[helifrek]

Hey guys,
A few days ago I had an M2 that was producing near perfect prints, and it has been that way for a year! Well, I finally got a clogged nozzle. I wasn't sure what it was at first because filament was still coming out "sort of". I thought maybe the extruder motor was going bad. I took everything apart and spun the extruder gear by hand and it made an awful clicking noise, much like that of a damaged brushed motor. I removed the gearbox and spun the motor again without the gears on it and it was very smooth with no issues. I opened up the gearbox and cleaned it and re-lubed it and it was also spinning smooth. The smaller gear that fits into the little gearbox and contacts the three little gears seems to be worn down some but there is very little slop in the setup. After I put it all back together the noise was gone, and I have no idea what was causing the noise. I put everything together and tried to print again and the print was still failing! So I figured it was the nozzle and went ahead and ordered a new nozzle! in the meantime I borrowed a torch and went about taking apart the hotend, I got to just the nozzle itself and heated it up and slide some .25mm wire in and out of the nozzle (before this I tried a "cold pull" and got a lot of gunk out of there! with the nozzle super hot, I turned it over and tapped it on my vise and a tiny round object fell out, it looked to be made out of carbon, it was very fragile and pretty much turned to dust! Was that supposed to be there or was it some formation of carbon buildup from a years use?


Anyways, Today my new hot end came in! it is very slighty different than my old nozzle. The heater block is black instead of silver and the thermistor (is that what it is called?) has a white wire instead of black.

I attached the new hot end, re-leveled the bed, redid my Z height and tried to do a thin wall calibration box, the first was too tall and too wide so I adjusted the numbers. The next box is closer to the right numbers but both boxes look terrible!!!! I am uploading a picture, maybe you guys can tell me what you think is wrong!

The layers are barely bonded together and the corners are not square, I am thinking it is just the heat needs bumped up because the design is slightly different. I am going to try it and see what happends.

I am using rsilvers .35mm PLA profile with temp at 220 and 60, printing black hatchbox PLA. ideas?

Thanks guys!

[Jules]

I print black Hatchbox PLA at 200°C - you might be seeing what happens when the PLA doesn't cool off fast enough and it tends to slump from heat soak (or whatever the heck they call that). Try cutting the temperature and if it's not bonding well - adjust your Z-Offset to bring the bed a little closer for the first layer. (That looks to me like the bed is still too far away. The thread is just floating down.)

(And yes, that was probably a little plug of carbonized plastic that fell out. If you hit it with a torch, that's what it does to any plastic that was left in the nozzle.)

[jimc]

the hot end is the same. the heat block on your old one was black when it was new. the anodizing dye fades away from the heat after awhile. in addition to what jules said, with the hot end cool grab the nozzle with your fingers and try to move it around. see if it feels solid in the groove of the filament drive. if its sloppy and has play then it will cause issues with alignment.

[helifrek]

So last night I tried printing the thin wall cube again at 230 and then at 240 and the they were both just as bad! So I tried again at 200 and the part came out much better but not perfect! I was thinking completely reverse on the issue.

I could swear my old hot end has always been silver! I guess I never paid much attention to it. It Is very sturdy in its mount so I don't think that is an issue. My 20x20x10 hollow cube came out at almost exactly 10 tall with first layer height set to 100% so I don't think that is the problem either. One I get home today I am going to print a bunch of hollow cubes starting at 180 and working my way up by increments of 5 degrees until they start looking perfect again.

You guys know any good temp calibration guides?

[jimc]

Dont print one cube at a time. Print 4 or 5 to allow proper cooling. As jules said you get heat soak and each layer doesn't have enough time to cool. This makes the part rubbery and print sloppy.

[Jules]

Just what you are planning on doing. I print at 200°C for that particular brand of Hatchbox PLA, but i have no fan guard on my machine, and it tends to cool things off by about ten degrees. You can probably improve things further by taking the temp down more.

It doesn't take much to melt PLA, and it's actually worse to overheat it (starts to cook it into the nozzle if you take it up to 240), so you'll want to avoid that - it will eventually build up and clog again.

[helifrek]

I am printing the thin walled cubes now, I am printing one at a time just because that is how I used to do it and I know what a good cube looks like. I want to be able to reference the new cubes to my old ones by printing them exactly as I used to.
I do not have a fan guard and I am using a duct to direct airflow towards the nozzle, I believe it was posted here by a member somewhere. It is printing fairly slowly.

Anyways, I have printed the 180, the 185 just finished and the 190 is in progress! The 180 looks a million times better! The 185 looks about the same as the 180. After they all finish printing I am going to inspect each one and then try pulling them apart to see which one bonded the strongest.

Any ideas why the results from my old hot-end and my new one would be so different? I have always printed at 220 on my old hot end....

I appreciate all the help, this is one of the many reasons I love my M2 so much! help is only a few keystrokes away!


One more question: I remember reading somewhere about the thermistor not being 100% accurate on the temps because of the position or something like that when I first bought my M2 and it cause the temps to be off by about 20 degrees. Has this issue been fixed, it this why the old and new hot-ends vary so much?

[jimc]

The temp difference is from when you went from a v3a to a v3b with a heating block. No issue to fix really as therr was nothing wrong. Just temp reading im a different place. I think you had a v3b before so this wouldnt apply anyway. There is a variance from thermistor to thermistor but generally not that much. 5% maybe.

[helifrek]

Ok, I have always had a V3b so that isn't where the difference is. After printing all the cubes, the 195 and 200 seemed to be the best and strongest so I will stick with 200. I used to print ABS on my flashforge at 220 so I always though it was weird that 220 worked on PLA so well on the M2 but anything less didn't seem to come out very well. I did notice that on my old hot end that the thermistor slides out with zero effort, maybe it wasn't getting an accurate reading?

Either way, the panic is over! She is up and running like a champ again, will be doing a good 30 hours of printing this weekend, can't wait!