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woodificould
(@woodificould)
Eminent Member
Newbie print failure

I just finished a MK2S kit. I printed the PRUSA name plate and the Benchy. Both prints look good. Now I am struggling to print the planetary gear. I printed it to completion and it actually works, but the front lifted off the bed by 1 mm. I tried again, but after little more than 1 mm, the front was clearly lifted off the bed already, so I stopped the print. I keep playing with the first layer calibration because I don't know what other parameters to change. I've seen where changing the bed temperature can make a different and turning off the fan for the first layer (I think that is already the case), but I don't know how to change these parameters. The first layer height seems like the only parameter I can play with.

I have been cleaning the bed with alcohol, as I've already used the two wipes supplied.

I have another print going right now. I tried using the glue stick. It sure looked like a couple of the points of the teeth lifted a bit, but it largely seems to be staying down. It's more than 2 mm high now. Still, I can see where the first layer or two is distorted in a spot. It definitely seems like an improvement, but I find it surprising that the glue stick is helping to stick it down. From what I've read, the glue stick is supposed to keep PLA from sticking to well to the PEI surface.

I expected the gcode files supplied would pretty much work and would be optimized for the printer. I was expecting to use them as proof that the printer is built correctly. Maybe that is unreasonable. Should I be experimenting with bed and hot end temperatures and fan speeds. If so, how do I change these parameters. Do I have to actually modify the gcode files?

Posted : 31/01/2018 5:10 am
digibluh
(@digibluh)
Reputable Member
Re: Newbie print failure

you would have to use slic3r to make new gcode with the temps and other settings. However you can also just go to Tune > bed temperature and set it to 60-65c in the menu when it starts heating up to print as a test.

Posted : 31/01/2018 6:27 am
olmen
(@olmen)
Active Member
Re: Newbie print failure

Noob here. I had similar problems with printing the very first layer if it's a rafting layer. They are really thin and the frills (edges) would lift and cause problems. The only semi-good workaround i've found so is to
- raise bed temp of first layer to 65 degrees C (Filament settings -> filament)
- reduce speed of first layer to 20% (Print settings -> speed)

Imho forget the glue stick. It doesn't help with this particular problem and only causes larger models to stick to good. I scratched my surface trying to remove some models =( Plus the glue must be carefully cleaned off between prints, which is a little bit messy and time consuming.

Happy printings 😀

Posted : 31/01/2018 12:04 pm
durand.r
(@durand-r)
Eminent Member
Re: Newbie print failure

99% isopropyl alcohol ?

note: To clean the glue stick, use warm water.

If your first layer isn't sticky enough, you can increase the first layer width a bit in your slic3r (0.45->0.55).

Posted : 31/01/2018 6:57 pm
woodificould
(@woodificould)
Eminent Member
Topic starter answered:
Re: Newbie print failure

"If your first layer isn't sticky enough, you can increase the first layer width a bit in your slic3r (0.45->0.55)."

I'm not actually slicing my own models yet. I'm just working with the gcode sample files. I kind of expected that I should be able to get them to print well. is that unreasonable?

Posted : 31/01/2018 8:15 pm
woodificould
(@woodificould)
Eminent Member
Topic starter answered:
Re: Newbie print failure

Here's a summary of where I got today. I ran the internal first layer calibration (the one with the printed square at the end) about a hundred times. My z axis was clearly too low and the filament was getting squished. I managed to get the bead to look really good, comparing it to the documentation. Definitely, flattened, not round, but not squished. I still was having problems with lifting whenever it hit a corner, so I raised the bed to 65 and slowed the rate to 50% and then I got perfectly calibrated layers that stuck to the bed nicely.

Then I went back to the gear. The gear is set to a 100 micron layer height, which is definitely a finer resolution than the calibration print. It seems like all that calibration doesn't even apply. The lines were round and not really flattened at all. It looks like there are three wall perimeters and they don't touch each other at all. Needless to say, adhesion was not happening. I then started the print several times and lowered the z axis until the lines started to get flattened. My feed rate is set to 50%. I tried boosting the hot end temperature by 5˚ and the bed up 10˚ and 15˚. I'm still not getting enough adhesion to do a print. All those little corners just lift up and the nozzle drags them around into a goober mess.

Has anyone else successfully printed this sample? If so, can you tell me what setting you used?

I don't know what to do next. Should I just give up on the samples and start slicing models?

Posted : 31/01/2018 8:55 pm
kevin.r5
(@kevin-r5)
Estimable Member
Re: Newbie print failure

I've successfully printed the Gear Bearing several times without any special settings (used the gcode file from the supplied SD card).

One thing that can make it difficult to get consistent first layers is that the MK2 pinda probe sensitivity is affected by heat. The solution to this is to raise your z-zxis to 100mm before you start each print (to keep the bed from heating the pinda probe). You can search the forum for more info on this topic.

You'll want to start slicing your own models - it's really a must to get the most out of your printer.

-Kevin

Posted : 01/02/2018 1:44 am
woodificould
(@woodificould)
Eminent Member
Topic starter answered:
Re: Newbie print failure

It looks like I have my first layer under control. I'm not 100% sure what made the most difference, but here is a summary of what I did that I think matters.

1) If you are not experienced (this is my first printer) then the First Layer Calibration is not for you. I cannot look at those pictures and compare them to the lines I see and have much of a clue how well I am doing. Instead, search for calibration_surface_75x75@200um_v3.gcode (there's actually a v4 version), download it and print it. It makes it super clear exactly what you're trying to achieve, which is to adjust the Live Z Axis until all the lines are just touching, creating a completely uniform layer of plastic..

2) The newer firmware versions have a Bed Level Correct option. Using the calibration print above, I was able to see that my left bed side was slightly lower than the right. I was able to compensate by adding 15 microns to the left side to dial it in. Note that you can create your own model for your own calibration file. This one is just a single square that is .2 mm thick, but you can make whatever you want. For example, you can make a smaller square and place them in different spots on your bed to give you a better idea of how level your bed is. Or you could make a centered cross to hit wider X and Y ranges while reducing the print time. The key is that you are setting the Z axis height with a particular set of first layer parameters and then using those same first layer parameters in your models, even if the rest of the model uses different parameters.

3) I cleaned the bed many times with the supplied wipes, alcohol and acetone. When it dried I noticed some swirl patterns. I can't say that they actually go away completely, but they definitely become minimal. If you have obvious swirl patterns then you are probably pushing residue around. Keep cleaning. Slight streaking seems OK, keeping in mind the next item.

4) One way to get a perfect bed is to print a single layer and then pull it off. I have found that my first attempt at a first layer doesn't always stick. I stop the print and restart it. The next time goes further. If it still isn't perfect, I stop it and try it again and it goes further. I repeat (maybe two or three times) until the first layer is laid down perfectly. The thing I have noticed is that, in these cases, I can see on the bed where the plastic was laid down and it seems like that's where I will then get perfect adhesion. I first noticed this effect after printing the calibration square. It left a perfect square on the bed when I pulled it off and then my model, which fit inside that square, adhered perfectly. Of course, the perfect footprint for you model is your model, so you don't have to print an unnecessarily large square. Just print your first layer until it is perfect.

5) It's one thing to lay down a perfect uniform square, but it is quite another to print something very complex. I've been struggling to get a perfect planetary gear. That model is very intricate and produce quite a lot of small, violent motion. For this model, I just crank down the speed to 50-75% for the first layer. You can actually build that into the gcode when you slice the model yourself. Or you can just do it live and then crank the speed back up to 100% after the first layer.

6) I don't know if it matters, but it is winter here and sometimes my programmable thermostat drops the temperature to 62˚F. I am now making sure my room temperature stays reasonably warm.

7) Going from a cold bed to just printing from the SD card does not guarantee a uniformly warm bed. It makes sense to do a preheat first before starting a print from a cold machine.

8) The gcode sample files definitely were created against older firmware. Now, that I have started looking at gcode and generating my own files, I can see that clearly. The sample models that were used to generate them are not included in the firmware download for the latest version. They are in the software zip file for your OS. There is a folder named "Objects". You can create your own gcode files using the models. Once you are satisfied with the first layer calibration, slice these models yourself using your parameters for the first layer. The point of the whole exercise is to come up with a good set of first layer parameters to use with your models.

9) Basically, all of the important parameters can be set by the gcode at any time during the print. In fact, many of the parameters are set at multiple points during the print. Critically, the temperature parameters are set before and after the first layer. I was finding that I would go into the Tune menu and bump up the temperatures, only to find that they were reset to some lower value once the print started. One benefit of doing your own slicing is that you can set these parameters yourself in the file, rather than fighting with the printer during the print.

10) Another benefit of slicing your own files is that you can insert your own gcode. At the end of each print, the X axis is homed and the Y axis is pushed forward to, essentially, present the bed with your part on it to you when complete. But the Z axis is set very low. There has been some suggestion that the probe can be effected by the bed while preheating, so I added a Z100 to automatically push the head up at the start and end of every print. I was doing that manually, but doing all of these experiments made that tedious.

I actually never got a good first layer until I went through all of this. There was always some lifting on some part of the model. With something like the tree frog example, it was catastrophic because the front legs would pop off the bed at some point. The planetary gear example is another really good stress test. It took all of this effort to get a perfect first layer. When I was done and I sliced the model myself with the first layer height matching the calibration file, I did not use glue or anything on the bed. It stuck perfectly. In fact, for the first time, I actually struggled a bit with getting the finished part off the bed. The bottom was perfectly flat. I could see the lines formed by the path of the first layers, but they were all fused together very nicely. It's quite amazing to see.

That model also stresses the machine because of all the small, jerky movements. As a newbie, I didn't realize that even the extruder moves rapidly in both directions. After my first layer problems were solved, I was having weird random under extrusion problem that cause gaps between layers. I finally figured out that the extruder hobbed gear was slipping and I needed to increase the tension with those two spring loaded screws. Now, my test print are coming out near perfect! I no longer want to beat the machine with a hammer! 🙂

I'm going to switch to PETG filament. I may need to redo the first layer calibration. I really don't know, but at least I no how to do it now.

Posted : 03/02/2018 6:02 pm
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