Thoughts after finishing C1+ assembly and first print
I want to share my thoughts after finishing assembly the Core One+ and testing the first print with the dual color keychain.
Let's start by saying if I were to buy another printer, I would probably not go for a Prusa - certainly not in kit. I usually enjoy assembling things, but the assembly instructions for the C1+ are at least imprecise, if not wrong.
The chapter about the first run and initial configuration are totally outdated - BTW, I cannot set Core One+ as printer model in the firmware (updated), it just offer the Core One option. The ventilation option is therefore set by default to Manual and during homing in the middle of the first run calibration it almost ripped apart the ventilation lever.
I then got stuck by the infamous (as I later discovered here in the forum) Y-axes calibration problem, for which I left a comment in the assembly instruction to make the filament sensor cable pass external to the PTF tube to not interfere with carriage movement (the image in the instructions shows the opposite and lead to having the problem).
I also had a lot of troubles calibrating the belts. I adjusted the gantry alignment, which was way off. The solution of bending the gantry as suggested in the quick gantry alignment section of the instruction seems so terribly wrong... I assume there should be some point during the assembly where one should play attention and mount things precisely to get the gantry almost aligned, instead of trying to achieve the result by brute force.
Anyway, I've aligned the gantry by tighten the belts rather than by brute force, then I used the belt tuner to adjust the belts... and that made the gantry loose its alignment and the printer fail the homing check 😩 After a lot of attempts, I've finally reached the point where the gantry is aligned and the belts are happy, but with inverted frequency resonance (92 for the upper, 97.5 for the lower). 😕 But again the manuals are extremely vague for something that should work with the right tolerances:
On CORE One, the ideal target frequency range is a maximum of 98 Hz for the upper belt and a minimum of 90 Hz for the lower belt.
On CORE One L, the ideal target frequency range is a maximum of 95 Hz for the upper belt and a minimum of 85 Hz for the lower belt.
If your gantry is out of alignment, you may not be able to reach these exact values. In some cases, the lower belt can even show a slightly higher frequency than the upper belt. This is acceptable as long as the difference between the two does not exceed 8 Hz, and both values remain within the 90–98 Hz range (CORE One) and within the 85-95 Hz range (CORE One L).
I then moved to try out the first print using the dual color keychain included in the USB key. First thing I notice, I've set the filament to be PLA and checking in the printer settings it says that the extruder temperature should be 215, but it gets to 235 while printing. Why?
Then, upon filament change the printer purges outside the bed - is this normal?
Overall, I did not have a good first impression about this printer and Prusa in general... considering I was unsure to buy the C1+ or a competitor (which I don't say) that for nearly half price offered a lot more options. I went for the Prusa for the "made in EU" stuff and because I thought I would have enjoyed the assembly and I always used Prusa Slicer even with my former printer, but honestly I would make a different decision now after the first impact.
RE: Thoughts after finishing C1+ assembly and first print
I also find it disappointing that several common traps are apparently still not addressed in the assembly instructions. And that the user comments which did address them were all removed when Prusa moved from the Core One guide to the Core One +. (Or have they been copied back in now?)
But you can't really complain if you intentionally deviate from the assembly instructions and then get unexpected results. Do not straighten the gantry by setting uneven belt tension; I think the instructions are quite clear about that. Bending the gantry is not as bad as it sounds: The material of the 90° mounting brackets is quite soft.
Yes, it would be better to bend the brackets to exactly 90° before installing them. That's how I did it, which is how I know they are soft. If you want to do the best possible job with your printer's alignment, you can disassemble the gantry and adjust the individual brackets to 90°. But at the very least, you should go back and adjust the gantry and belts following the belt adjustment guide.
RE: Thoughts after finishing C1+ assembly and first print
Oh, and regarding your other questions regarding filament handling:
Yes, purging in the front right corner is normal. The print head moves there for filament swaps, I think because that's where the curvature of the PTFE tube is the widest. And the front right position lets you see the filament color and remove the purged filament easily.
The nozzle temperature during printing is defined within the Gcode file (i.e. the file that describes the print job). When you create your own print files, PrusaSlicer will have default filament profiles which include the temperature, but you can adjust the temperature to optimize it for your specific filament brand and the object to be printed. The filament type you set in the printer firmware is used for a plausibility check whether that filament matches what the Gcode assumes. And the firmware uses the associated nozzle temperature (defined in its filament presets) for steps like filament loading and purging, which are not part of a print job.
It seems that the firmware preset temperatures were chosen a bit lower than the optimum print temperatures for typical filaments, presumably to avoid leaking filament. PrusaSlicer's default temperature for printing Prusament PLA is 230°C, and apparently the creator of the keychain Gcode file thought that going to 235°C will improve print quality for this particular print. No cause for concern there.
RE:
Filaments with the same polymer across different vendors will have different temperature ranges. Even filaments from the same vendor but across different colors or additive types will have different temps. Example Prusament PC will print optimally at a different temperature than PC-CF. However for loading and purging the filament, any temperature within range will do. That is why there are separate temperature settings in firmware and temperature settings in the filament profile which ends up in the g-code. The temperature selected on the printer UI has nothing to do with what temperature the part will be printed at. That is pretty much true on any printer.
Finally, it seems a lot of mistakes are made by second guessing the instructions. Common ones like misrouting the belts because it seems odd the teeth face the pulley surface or not manually bending the gantry because it seems "off". The instructions are quite explicit about gantry alignment and the process for ensuring it is square.
RE: Thoughts after finishing C1+ assembly and first print
And this is why you are not passing calibration checks. You need to follow the instructions on proper gantry alignment. Doing so by differentially tightening the belts is incorrect.
RE: Thoughts after finishing C1+ assembly and first print
But you can't really complain if you intentionally deviate from the assembly instructions and then get unexpected results. Do not straighten the gantry by setting uneven belt tension; I think the instructions are quite clear about that.
Not so much clear:
4. Slightly loosen both the belt tensioner bolts. Loosen the bolt on the corner with play less than the other.
This reads to me like uneven belt tension.
I tried to follow the quick gantry alignment procedure by fully loosening the tensioner bolts and forcing the gantry to align. However, when I tight both tensioner both by the same amount, a gap reappears on one side. I need not to use even both tension to reach a point where the gantry is aligned and belts are properly adjusted.
But things gets more confusing considering that results from using the belt tuner app doesn't match results by using the belt tuning wizard (frequencies doesn't match). Also, the procedure needs to be repeated multiple times, since changing one belt tension affects the other belt, so if you set the upper belt, then change the lower belt, if you check back the upper belt you'll find it's no more as it were before - and this is not explained in the manual nor checked by the belt tuning wizard.
RE: Thoughts after finishing C1+ assembly and first print
If you read the instructions carefully, you will learn that after aligning the correct angle with the belts loose, both end blocks on the portal must touch the tensioner blocks simultaneously without any gaps. This achieves the basic assumption and therefore the perpendicularity of the portal. And the belts are tightened simultaneously on both sides of the portal and by the same angle of rotation of the screws alternately left and right, while constantly checking with a stroboscope. And count on the fact that the angles of rotation of the screws will be very small towards the end. Setting it as you practice it, i.e. first one and then the other belt to some "made up" fictitious value leads to the fact that you send the laboriously adjusted perpendicularity of the portal to hell and never adjust the belts. And the frequency value of the individual belts should be "approximately" around 95 Hz. And the portal should hit both front stops at the same moment. So once again: Don't do your "experiments" and really "slavishly" follow the instructions. Otherwise, you won't adjust the printer exactly and you will wonder why your calibrations don't work. Oh, and comparing values obtained using different measurement methods is nonsense non plus ultra in this case. So far, the most accurate is the stroboscope method.
RE: Thoughts after finishing C1+ assembly and first print
I start with the belts completely loose and just at the point before the tension screw comes out of the nut. Then I tighten both screws 2 rotations at a time alternating left/right until the belts start to get tight. I then start plucking them with my finger (by now I can do it mostly by ear). I turn each 1 turn until I get into range then each by 1/4 turn. I always turn both screws by the same amount. If for example I loosen the left screw by 1/4 turn then I must do the same to the right etc. If you do it this way, the gantry will stay square.
RE: Thoughts after finishing C1+ assembly and first print
The robots at Facebook recently permanently deleted my 11 year old account for linking to my own site, but I tend to write more than can be stuffed into a simple post. You might find some of this useful as I tried for a more detailed explanation of how and why things work: https://conradhoffman.com/3d01.htm
RE: Thoughts after finishing C1+ assembly and first print
I'm not old enough yet to hang out on Facebook.
RE: Thoughts after finishing C1+ assembly and first print
Also, the procedure needs to be repeated multiple times, since changing one belt tension affects the other belt, so if you set the upper belt, then change the lower belt, if you check back the upper belt you'll find it's no more as it were before - and this is not explained in the manual nor checked by the belt tuning wizard.
I don't see how this is an issue when using the stroboscopic belt tuning wizard in the firmware. It is designed to be aware of the interaction between the belts. It always lets you measure both belts, then gives you instructions to align both belts in sync. Did you follow these?
Don't use the sound-based belt tuner app anymore. It is less precise and reliable, and it does not handle the interacting belt tensions the way the stroboscope wizard does.
RE: Thoughts after finishing C1+ assembly and first print
I've found that when starting with the belts completely loose, prior to tightening both screws evenly and alternately, I'd do a sanity check.
Lightly press your finger across both belts by the linear rail or just tug on each belt a bit. Check for gross unevenness between the belts. The belts are still very loose at this point, but you can get a rough idea of a good starting point. What was happening to me was, I'd fully loosen both, check the gantry, and then do the even and alternating tightening only to find out I'd pull it out of square along the way. Once doing this early sanity check, I had much better results with the final tension using the method described by others here.
It's like getting a course adjustment incorrect and then it can't be pulled in with a fine adjustment later on.