MK2.5s print bed issues
Two-part question:
1) Is there a point when it's time to replace the spring steel sheet on the print bed? I have been printing for several weeks in a row and prints were sticking just fine. All of a sudden, prints aren't sticking anymore. I've check first layer height, etc. I was using a glue stick and it helped tremendously for a while, then I starting printing blobs around my nozzle again. Has anyone else had a similar issue? What's the fix? Do I just need a new spring steel sheet?
2) We started having what appears to be a "hot spot" on the print bed, where parts are getting burned (see photo). However, if I check it with a laser temp gun, that spot doesn't seem to be "hot." The print bed also feels cooler than usual and seems to have a several degree different from one side to the other (see photo). What the heck??
RE: MK2.5s print bed issues
Adhesion can be a tricky issue. I've been printing for several years with several printers and I eventually found what worked for me, but having said that, everyone goes for something slightly different. To use the PEI on steel, I would clean it with 90% alcohol and occasionally LIGHTLY sand it with 300 grit sand paper, VERY lightly. Next, I would try WITHOUT glue-stick. Or blue tape. Just work on the basics. Is your Z level low enough so the first layer is flattened? Use a magnifying glass and check your first layer. I myself have used Buildtek which I have used for years. PEI for me was a bit temperamental, others have had great luck with PEI.
PEI should last for a long time, and it is likely NOT worn out, but keeping it clean is important. Try cleaning good and LIGHT sandpaper OCCASIONALLY, but do explore other options, if inclined.
On the temp issue, it's not likely your PLA is burning. Are you using around 60C for PLA, 100C for ABS? It is pretty normal for heatbeds to vary GREATLY in temp on side to the other? Or center to outside. How much different of a temp are you seeing? Normally the center is hottest, the edges less so. Chances are it is OK. The brown looks like maybe a bit of nozzle contamination. Did you use brown before white? Or that might be from glue stick. Don't let this worry you.
You should be worrying only about one thing, getting your first layer height perfect.
RE: MK2.5s print bed issues
Update: I discovered that the filament I bought was PLA+ instead of PLA, so I found that I had to turn up my bed temperature (75 vs 60), add glue stick, slow down the speed, and turn up nozzle temperature (220 vs 215).
RE: MK2.5s print bed issues
There is lots of experimenting to find out what is best. The key to 3D printing is getting everything repeatable. As strange as it sounds, I find temps vary MORE from printer to printer than they do from one type of PLA to the next. Stick with what works best for you.