New user with questions  

Re: New user with questions

Here's an update: My other print finished, and it seemed to do fine keeping the temperature up on its own for the rest of the print. However, I started a new print of the same model, but using the "FAST" setting in Slic3r. By the time it got midway through the 2nd layer, it had dropped below 200 and it stopped with a "thermal runaway" error. 😥 I see that there's another thread about that error so I'm going to read up on it, but hopefully it's a problem I can correct.

Re: New user with questions

I've found that whenever I try to change the print speed while the printer is actually printing it always causes the extruder to skip out of place and start printing in the wrong place. Don't know why or if that's to be expected... maybe the print speed is supposed to be set BEFORE starting to print?

The nozzle scrapping the top of the print seems to be one of those things that is happening to a rare few, and as such is probably going to be difficult to diagnose.

The hotend temperature problems is something that people are discussing, as you said, and are trying to work out the cause. Many of us have never had the problem so again it is tricky to find the cause. It could be a slicer settings issue, or the result of the printed objects shape, some think it might be due to the print-fan outlet being so close and on one side only of the hotend. Try to stick to using the Slic3r profiles supplied by Prusa as much as possible as they seem to work the best in most cases. Personally I've been very lucky and not had these problems. I did have a Thermal Runaway error once when I printed with ColourFabb XT but that was caused by the print-fan coming on part way through the printout due to me messing up the clic3r settings (hence my recommendation to stick with Prusa's ones!).

I have found the printer seem to work much more efficiently in Full Power Mode.

Be aware that the speed you can print at is governed by a lot of different things, the design of the model, the material you are printing with, whether the printer is in Silent or High Power mode, the effects of ambient conditions, etc. 3D Printers at the moment are not going to be pumping out a dozen objects per hour. So don't try to rush things or at best your prints will come out looking iffy, at worse they will fail completely!

Re: New user with questions

Thanks for the reply. I can live with the scrapes for now. They are really not too bad. I'll worry about that later....for now I just want to figure out the thermal runaway problem.

From the other thread it looks like it's either a thermistor problem, a heater problem, or the way the fan reflects back onto the nozzle during flat areas like the first few layers.

The models I've been printing are very wide and flat, so it does sound very possible that it's the fan. I'll try turning down the fan and see what happens. And I'll see if it happens with other models using the default fan speeds.

Re: New user with questions

Hi miferr,

Since you are using Slic3r you can see that there are two printer profiles, one is named "Original Prusa i3 MK2 with ZHop" and implement a lift Z that can help to reduce the marks on the top you are seeing. I believe the default profile is the "Original Prusa i3 MK2 ColorPrint" profile, which does not implement Z lift.

Re: New user with questions

Thanks, I was wondering what the "ZHop" option was for. I will give that a try.

Another update: I tried my print again, and this time I tried turning down the fan during the print. It successfully completed, though I had to watch the whole print carefully because it would sometimes switch back. My question now is: what is the fan for? Is it for cooling the plastic? I imagine that's needed for bridging a gap, but not as much for the first few flat layers?

If that's the case, on this print the only place where there is any bridging is when it has to cover the infill grid with a solid layer. I'll try to figure out if there's a way to control the fan more carefully in Slic3r so I don't have to watch it the whole time. I'd like to figure it out because I want to print several more of them. 🙂 I have only used the default profiles so far.

So it seems like my printer overall is still working fine, but the fan appears to cool the nozzle a little too much when using the "0.35mm FAST" settings profile on that print. I started the castle print (which uses 0.10mm), and so far it seems the nozzle is not dropping below 206. It is currently on the 3rd layer and the fan speed is 216. On the other print I had to drop the speed down to 100 to maintain the temperature.

I'm glad there's a community of people willing to help! If anyone is willing to experiment, try printing a few layers of a 150mm x 150mm square sliced using the 0.35mm FAST setting, and let me know if you see something similar. 🙂

Re: New user with questions

My castle print finished without me touching the fan speed. For the first few layers the temp did dip to maybe as low as 200 at one point, though most of the time it was around 206. As it got higher, it eventually got back to a consistent 209/210.

I think I can turn down the fan speed or turn it off in the first few layers. But I'm back to my original question: Is there something wrong with my heating, or is this normal?

And by the way, the castle came out pretty well. It had some stringiness but it wasn't too bad. Once I removed them it looked pretty good, though it was a little rough in areas where the nozzle would start (I think) a layer of one of the towers.

Re: New user with questions

Here's the latest for me in case anyone's curious. I turned down the min and max for the fan to 35 and 80. That seems to be working much better. The nozzle is able to maintain its temperatures on layer 2, and even though the bridging fan is turned down, the first layer above the infill looked good.

I also used the Z-hop profile. I noticed it only starts the Z-hop after 1mm. On one fairly complicated part, the nozzle scratches were very evident on the first few layers. I started thinking that perhaps it is extruding slightly too much, so I turned down the extrusion multiplier a little. It seemed to do a little better on the next print, but it was still happening. I'm going to try to print the first layer of the print several times at different extrusion multipliers. If it makes a visible difference I'll try posting some pictures. Should be interesting!

Re: New user with questions

I'm learning all the time...I tried my experiment with 8 of these items on the bed, and I changed the flow on each one. The nozzle kept scratching, plus looked very uneven, even down to 87% flow. Higher layers would get better.

Then I had a breakthrough when reading through other people's posts. I was wondering why my finished parts were so hard to get off the bed. I saw suggestions to raise the Z-offset. Eureka! Maybe my Z was too low on the first layer. After raising the probe (for a different reason, see below), recalibrating, I ran the same the test again, changing the Z-offset each time. I didn't realize how much I could raise it and still have the part stick, as long as the bed was very clean. Now my first layers are coming out much better! This part seems to make a really good first layer torture test. 🙂

Now here's the other problem I had:

The dragon printed overnight, and when I checked in the morning, one of it's legs was missing! The hand was still stuck to the bed, and I found the leg almost a meter away! That's why I raised the probe, I was wondering if it hit the leg while printing. That was before my Z-offset realization. If anyone has any ideas, I'd love to hear them, but I'm not sure I want to try again. I have other stuff I want to print!

Re: New user with questions

Hi, your terminology is confusing me a little bit... you say you raised the probe, however that would lower the nozzle! Can I suggest you post a picture (side on) of your probe and nozzle so we can get an idea of how you have it set? The tip of the probe should be approximately 1mm higher than the the tip of the nozzle. Then, you use the ​Live adjust Z in the LCD menus to fine tune the height.

The best way to do this is to first print the V2_Calibration and use ​Live adjust Z to get it looking correct. Then start printing the Prusa Logo model from the SD card, while it is printing the first layer again use ​Live adjust Z to get it looking just right.

When I did it I found it easier to start with the filament over squished then work back until it looked right (So you will probably start with the ​Live adjust Z at minus values and move it up towards zero.).

Hope that helps...

Re: New user with questions

As 3Delight, I think your are confusing two things:

Z-Offset is more or less the distance between the PINDA probe position and the nozzle tip position. It's used to fine tune the right distance between the nozzle and the bed, and is used all the time during the print.

Z-lift is the value used to level up the nozzle during travel when not extruding and to level it down when it starting to extrude again.

Z-Offset is used to find the optimal first layer squish that will make a good adhesion to the heatbed.
Z-lift is used to avoid or limit scratch made by the nozzle on upper layer while traveling. It can also be used when filament do some kind of micro-warping that can explain the issue with the dragon leg, and that tend to happen a lot to the frog model as well.

Re: New user with questions

Hi, your terminology is confusing me a little bit... you say you raised the probe, however that would lower the nozzle!

Sorry for the confusion! I made two adjustments at roughly the same time, but I really did both raise the probe and the nozzle. 🙂 After I printed the dragon and got the broken legs, I started thinking about the problems I had, and came up with two things I wanted to fix:

1) I realized my first layers had been "over squished" as you say. But I am a beginner and didn't know what that meant! It's especially hard to see with black plastic. I raised the nozzle using the Z-offset, and noticed that my first layers were looking much better.

2) When I looked from the side as the printer was printing, the probe barely cleared the plastic. It was so close it was almost touching, and I think maybe a little piece of plastic stuck out and the probe hit it, knocking the leg off. I had been worried something like that would happen, because the probe was so close.

So first I undid the probe and turned the top nut to get it to raise up. Afterwards it was sitting at least 1mm above the nozzle. Then I redid the calibration so it would sit about normal. I did have to undo the Z-offset so the nozzle wouldn't touch the bed.

I remembered reading something about the V2 calibration being sliced at .15mm instead of .2mm, so I decided to use my part test print (the one with 8 copies of the same part) to determine the Z-offset. I lowered the nozzle until the filament would stick, but then I let it continue printing. I noticed the same issues I used to have. So I cleaned the bed really well and tried raising the nozzle. I eventually got to where the first layers were sticking, but looking nice and smooth.

It still may be "over squished" because my latest parts are still not easy to get off the bed--other posts I read described things as almost popping themselves off--but the first layers are looking MUCH better. 🙂

I do think the probe is finally set right because it is above the nozzle but it is still finding the calibration points. I'm very happy about where it is now, but if you still want me to post a pic let me know...it's printing right now 🙂 I appreciate the help!

Z-lift is the value used to level up the nozzle during travel when not extruding and to level it down when it starting to extrude again. Z-Offset is used to find the optimal first layer squish that will make a good adhesion to the heatbed.
I understand that, but the setting in "Zhop" profile appears to avoid the Z-lift for the first 1mm. "Only lift Z: Above Z: 1mm; Below Z: 199mm."
The nozzle was still scratching on the first layer, and that is eventually what got me to figure out that my first layer was too squished. With the new settings, it is still sometimes scratching a little on the first layer, but it is much, much better.

Should I change the Z-lift to start above 0mm? I thought there was a reason for that setting so I left it alone.

Re: New user with questions

No need to post a picture, it sounds like you've got it sorted! Well done! It's all very trial and error when you first start out, but you will soon pick it up and develop a natural 'feeling' for what's going on. Even with everything set perfect there is always the chance of some random thing causing a print to go wrong... a draft, a sudden change in ambient temperature, a mains fault...

Anyway have fun!

Re: New user with questions

It's all very trial and error when you first start out...

YES! That last exercise made me feel like a scientist, changing one variable at a time and checking the results. I need to start keeping a log!

Re: New user with questions

Well, I thought everything was great with my first layer, but I did notice tiny grooves in the bottoms of my printed parts. I later read somewhere that the bottom should be completely smooth. I printed a single layer and measured it with calipers, and although I had set my first slice to be 0.15mm, it was more like 0.23mm thick. So I lowered the Z offset, and found a value where the first layer readings were between 0.14-0.16mm. At that point, the bottom looked great, but the nozzle scratches in the tops of the first few layers started appearing again.

So two questions for the community:

1) I printed a single layer of an object, then measured the thickness of the layer with calipers. Is that a valid way to determine the Z offset? If so, that is MUCH easier for a novice to understand than "make sure it has a good squish." 😀

2) Is there a reason that the standard Z-hop profile does not perform the Z-hop for the first 1mm? If not, I'll just change the Z-hop minimum to 0mm.

Re: New user with questions

2) Is there a reason that the standard Z-hop profile does not perform the Z-hop for the first 1mm? If not, I'll just change the Z-hop minimum to 0mm.
We discussed it recently in another thread and didn't found any reason. I printed about 30 models after setting limit to zero and everything went ok.

Re: New user with questions

Thanks! I changed the z-lift setting to start from 0mm, and it came out great! Now I have the z-offset dialed in, and the proper z-lift settings to avoid the nozzle scratches. On my last print I noticed some rough patches in spots; some areas were smooth to the touch, and some were rough. I lowered my flow rate to 98% and that helped a lot. Now my first layers are looking great! Thanks everyone! 🙂