The bed is not leveled !!!
Hello,
I have a question about a problem I noticed shortly after starting the printer. The problem is that after calibrating the bed, the shim is crooked relative to the extruder assembly. The right side Z axis is 1.8 mm lower and the back 1.5 mm lower than the left side. I understand that the printer can handle it, but I'm not happy about it. Pruši customer support told me that this is definitely not right. On the recommendation, I checked the trapezoidal nuts, all the screws are tightened. The Z motor screws that the bed aligns with during calibration are also tightened, all the screw heads protrude above the bottom plate equally. I tried to solve it with shims, but customer support told me that this is not the right solution. It seems to me that the entire X,Y assembly is crooked relative to the box, which is visible to the naked eye even in the upper part. This means that the assembly is skewed relative to the bottom plate with the Z-axis motors.
RE: The bed is not leveled !!!
I am not sure I understand what you mean by "the shim is crooked relative to the extruder assembly". I assume you mean that the bed is tilted relative to the (horizontal, square) frame which supports the whole XY transport?
If that is the case, a couple of users here have reported the same issue. To level the bed, they just turned the Z lead screws manually (while the motors were off).
You can check and adjust this quite precisely by moving the print nozzle to the three positions near the three Z screws, with the nozzle being close to the bed, and probing the distance with e.g. a credit card. Adjust to the same (light) friction when you pull and push the card -- this is essentially the same procedure as used for manual bed leveling in older 3D printers. Be careful that you don't run the nozzle into the bed while moving it around, especially early on when the bed is still tilted!
I understand that this adjustment will be lost if the printer does a Z homing (driving all Z axes to their lower end stops). But apparently that is not done often, and is not done automatically at any point in the printer initialization, so the adjustment will remain in place during normal operation.
RE: The bed is not leveled !!!
I am sorry, not the shim, but I mean bed.
RE: The bed is not leveled !!!
I solved the problem my way by putting washers of the right size on the lower screw heads, which align the bed with the x,y assembly during calibration. However, this causes crossing on the threaded and polished rods, and the Z-axis movement is then accompanied by a squeak. According to Prusa support, this is a bad solution to the problem.
RE: The bed is not leveled !!!
So, when you measure the distance between the base of the printer and the horizontal square frame which supports the XY transport -- is it different in the front and back, or on the left and right side?
I understand that homing references the Z positions to the printer's base, by driving the bed all the way down into the end stops. (You changed their effective position via the washers, right?) But then, if the XY support frame is parallel with the base, shouldn't the bed always be parallel with the XY mechanism too?
A difference of up to 1.8 mm in the Z positions seems like a lot. The tolerances of the frame can't be that large?
RE: The bed is not leveled !!!
Exactly, the X,Y frame is not parallel to the bottom stops. That means with the bottom plate in which these stops (the screw heads of the Z-axis motors) and that also means that the nozzle is not perpendicular to the bed. The Z-axis motors have to compensate for the height difference of 1.8 mm when printing. It is visible with the naked eye that the xy-axis frame is crooked from the whole box.
RE: The bed is not leveled !!!
And yes, XY transport is different in the front and back, and on the left and right side
RE: The bed is not leveled !!!
Exactly, the X,Y frame is not parallel to the bottom stops. That means with the bottom plate in which these stops (the screw heads of the Z-axis motors) and that also means that the nozzle is not perpendicular to the bed. The Z-axis motors have to compensate for the height difference of 1.8 mm when printing. It is visible with the naked eye that the xy-axis frame is crooked from the whole box.
That's really unexpected. What defines the height and leveling of the XY frame? I don't have my Core One kit yet, but going by the pictures available online, it's the two smooth Z rods in the front, and some mounting points on the rear wall of the enclosure in the back, right?
So I would assume the left and right front to be pretty exactly at the same height, since the two rods must be machined to the same length? In the back, maybe there are assembly tolerances due to hole diameters being a few tenths of a mm larger than screw diameters -- but 1.8 mm?!
Was a part cut or drilled wrong (unlikely since it's probably all CNC-controlled), or are there some adjustable mounting point which the assembly technician can get wrong? (Also not too likely, since it seems that just putting the parts together within their manufacturing tolerances should be good enough, hence manual alignment can and should be avoided.)
If you can figure out why your printer's frame is so skewed, I would be really keen to learn about the cause. It seems like something to watch out for when building the kit!
RE: The bed is not leveled !!!
I will be complaining about the printer.
RE: The bed is not leveled !!!
It's a shame there are no assembly instructions yet. I've always bought printers from Prusa in a kit to assemble, I've never had a problem. The first time I bought an assembled printer, something went wrong right away. If there were assembly instructions, I might be able to figure out where the error might have occurred during assembly. I also think it's unlikely that the error was due to the inaccuracy of the CNC machined parts.
RE: The bed is not leveled !!!
Let's hope that Prusa support can give you some specific advice what to check!
If that should not work out: Before you send the printer back for repair, maybe wait a few more days. Prusa is still confident that they can ship the first kits by the end of this month, which should mean that the assembly instructions will be published in the course of next week.
RE: The bed is not leveled !!!
BTW... make sure you have a lot of time on your hands when you get on line with them... the trouble shooting takes a lot of time.
RE: The bed is not leveled !!!
I always buy a kit. There is no assembly procedure for the Cone One yet, so I can only theorize. When building the frame, all the screws are lightly tightened, the assembly is placed on a perfectly flat surface, all the corners are pressed, and this achieves a perfect plane. Then the screws are always tightened crosswise (with sensitivity), the printer is turned on the surface several times and by lightly pressing on the corners, it is checked that there is no gap between the frame and the surface.A similar procedure will be used for this printer, but the instructions are not yet available.The squareness of the assembly in all axes is always key, I have never had the slightest problem during construction. With an assembled printer, there is always a risk that your box will lie at the bottom under the rest of the cargo for several days and maybe even repeatedly during transport, whether in a car or on a plane, rough handling is common.Wait a few days for the assembly instructions to be published, it will be more beneficial for you than sending the printer for replacement right away or solving the problem by phone or chat with support. You have time for the replacement, I advise you not to rush.
I am from the Czech Republic, I don't speak English, I translate using Google Translate
RE: The bed is not leveled !!!
Thank you all for your responses and advice. Unfortunately, we did not find a solution to the problem during the discussion with Prusa support. They gave me several suggestions, but it was always without result. I had to explain to them how and where I measured the different bed heights. They thought that only the heated part of the bed was uneven. In reality, the problem is with the perpendicularity of the polished rods, trapezoidal rods and the X,Y assembly with the extruder. I do not want to adjust the printer myself. Since I bought it assembled, I want to receive the goods in perfect condition, since I paid extra money for it.