Printing weirdness continues...

I was wondering about the bed adhesion so I wanted to measure the temp of the actual aluminum heating bed (with it’s thermistor) and also measure the print surface (painters tape on my glass plate).

Interesting finding. The heating bed got to 65c fairly quickly (according to the LCD), but even 5 minutes after that the glass tape hasn’t even reach 60c. Right now it’s hovering around 59c. I’m measuring the top of the glass bed (with the painters tape on it) by taping a thermistor to it with thermal tape. I quickly programmed my Arduino Uno to read the temp from this thermistor and this is what the log monitor is showing. I was going to use my infrared thermometer but couldn’t find it when I got home so the Arduino was a good second choice. I think it’s actually better because it is a constant reading sampled every second with the script I am running.

Now 10 minutes later and its still sitting around 59 degrees. I don’t think those 6-7 degrees will make a difference, it’s just an interesting finding.

Just to compare apples to apples, I then taped the Arduino thermistor directly to my aluminum heating plate and it also strangely showed the same 58-59 reading! So, either the top of the plate isn’t as hot as the bottom (where the plates own thermistor is) or one of the thermistors is reporting bad info. The LCD is still showing 65 and my Arduino is showing 59.

I guess the only way to try to narrow down were the error is would be to measure a temperature of a known value. I’m thinking I am going to stick the thermistor hooked up to my Arduino into a pot of boiling water to see what it shows. Lol. Since I am only about 450feet above sea level at my house, then it should report back very closely to 100 degrees C.

I guess all this really doesn’t matter to my printing issues, it’s just a fun squirrel to chase. Lol.

Too many squirrels, too little time!

Sometimes my own idiocy amazing me… I went to fix my hot end this morning by removing the washers and adding a space like the pic that Bill posted shows. Anyway, I couldn’t get the nozzle off so I figured something was wrong. Glad I have jewelers glasses for this stuff! Looking at it closer, filament had oozed out in places it shouldn’t be, I didn’t have the throat in contact with the nozzle. So, I had to heat the extruded up to take it apart, that was “fun”. I got it apart and then had to run an M6x1 .0 tap through the hot end in order to clean out the shmoo. I have it cleaned out but had to take my son to school before I could put it back together. So, once I get home from breakfast I’ll be able to put it back together and start testing again.

First step, make sure that the extruder is working correctly. Then, check the bed level again. Set the Z Axis Zero and test. If that is still giving me bad first layer results, I will take off the glass plate/painters tape, and just put tape on the aluminum bed itself and see what happens. I also have a sheet of PEI waiting in the wings in case nothing else works. I would like to get the glass bed/tape at least close and then switch to the PEI but I’m not sure if that is gonna happen…

I’m guessing the two temp sensors are just a little off from each other. These kind of sensors are not great at absolute temperature correctness but pretty good at relative temps.

So if it measures 5.0C rise, it’s probably between 4.9C and 5.1C, but if it says 60C, it could be 55C.

That’s not a huge problem, because it doesn’t really hurt to set it to 65C and only get 60C.

If the glass is causing a 5 minute delay, that is a problem. If the glass is showing 5C lower, thats not a big deal.

The nozzle is a similar situation. I bet if I set 195C on both my printers, one would be 10C higher than the other. But on either printer, if I drop it by 10C, it will make a difference.

The delay in the glass heating up could be part of my problem with the first layers not sticking properly. It seems that when it starts to print, the first 30 seconds or so of print isn’t sticking, and then it starts to stick. The problem this causes is now filament that should have been stuck is being dragged around and causing issues. This is something that I am look at now. I am going to try preheating my bed, let it come to temp and then wait 5 minutes before I start the print job itself. This will hopefully give the glass enough time to heat up prior to the first layer going down. Only experimentation will tell.

I am going to throw this tip out there. It isn’t life changing but it helps a little. You can insulate the underside of your heated bed. Cork board works Excellent. Gator board (also known as foam board or foam core) works really well. Cardboard works ok. As long as your heated bed stays below something like 130 c you will not have a problem with fire. That usually helps the bed to heat faster and stay more of a consistent temp. I don’t know if it would help much in your case since the heat has to go up through the aluminum and then the glass. Like I said just throwing that out there.

Here is one of many links on the topic.

Thanks Aaryn, any tips and hints are well worth throwing out there. I have been thinking of insulating it, just haven’t had the chance. I really need to sit down this weekend and just run tests on this to get it working.

Calibration consistency on those sensors really sucks … it’s one of the reasons why they are so cheap. I’m running a PEI sheet on top of the aluminum and also see about 5° lower on the top surface than reported by my thermistor. I just tell the heatbed to be 5° higher than I really want and it comes out OK. :slight_smile: If you really want to get a correct calibration test your sensor in boiling water and in ice water. My guess is both will be off by the same amount.

My next step if I can’t get the prints to stick consistently to my glass/tape will be to put my PEI directly on my aluminum and just go from there.

I have to do more testing after I check all my slic3r numbers and then post video of the beginning of the print. I think the first layer is really what’s causing my problems in my prints.

I like the idea of testing heating the bed for a few minutes before starting a print. You can add a 5 min pause to the starting gcode:

G4 S300

If the 5 min wait helps, then I would just change the bed temp to 70C and take out the pause.

I have PEI on the aluminum, but the bed isn’t very flat. I hope your glass is flatter.

The PEI will stick better than the tape. Another thing you can do to make the tape stickier is to clean off the grease with iso. alcohol.

Can you try printing just the first layer, and canceling it after 1 layer and posting a picture? That should help (us) see if it’s doing well enough.

Are your later layers looking any better? The cube you posted before looked pretty rough.

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Things are improving. I think I’ve finally got my hot end/extruder figured out and setup properly. I’m gonna spend time this weekend testing everything. I think putting the PEI on the glass will be my next step. The glass should be flatter then the aluminum.

I also didnt realize I need to clean off the tape in between prints, lol. I’ve just been knocking the print off an reprinting. Lol.

so much to learn…

Also, any way in Slic3r to adjust where the print goes on the bed? It always autocenters and I can’t figure out how to stop that…

Left mouse drag, I think.

I do that, but as soon as I let go of the mouse button it just snaps back to the center of the print bed. I’m at gotta be a setting I’m missing. I am launching slic3r through repetier so maybe that’s causing it? I position the part in repetier where I want it, but then slic3r does it’s own thing. If I use Cura through repetier, it works fine… strange. I need to dig in deeper to slic3r to see what is going on.

Ah, there is a checkmark in the Configuration -> Preferences -> Auto center.

Thanks Jeffe! I’ll check for that this afternoon.

This is strange. I had that option unchecked so it shouldn’t be autocentering, so I just checked it, closed out of slic3r and then unchecked it again, and not it is working as it should… lol.

Ok. Here are my latest prints. Just the first layer, using the default settings that Ryan listed on the extruder assembly page for my Slic3r settings. It looks to me like my print head is too close to the bed? It also appears that it is “pushing” a glob of filament in front of the head.

These are 2 different pics from 2 different tests.

So, here are some videos of my latest testing. Leveled the bed as good as I could but I seem to have a slight variance in the Y Axis on the Left side of the printer (the one with only 1 leveling screw) that I can’t get out. It’s only about 0.08mm but it is there.

Anyway, the PEI sheet seems to be helping but things still aren’t sticking correctly. I heated the bed up to 65c and let it sit for 10 mins before I started printing just to give it enough time. As per my post above, my slic3r settings are the ones from Ryan. It looks to me like I’m either too close to the bed (which doesn’t make sense) or not extruding enough filament. The filament is “curling” up behind the print head and forming an arc before it touches down on the PEI sheet. It’s like it is hitting the sheet right out of the head with enough “force” to then make it come back up off the sheet before it flops back down again. Hopefully the linked videos can help you guys help me because I am loosing my mind! lol.

 

the videos are great help.

The nozzle is too far away form the bed. The first layer the nozzle should be close enough to the bed to cause that round bead of extruded filament to have a flat top surface. Not so close to the bed that it causes the sides of the bead to deform into a rough jagged pattern. Difficult to explain. but I hope that makes sense.

Thanks Aaryn, that does make sense. I was thinking I was too close but your explanation makes sense. I’ll modify my gc0de to drop it closer to the bed and see what happens.

I agree with Aaryn. I think you need to get between 0.1-0.2mm closer.

I personally would use the Z endstop screw to bring it down. If you turn it in a bit more, the Z will go lower before it hits it.