First Layer Problem

[budu 0]

Good evening,

I've encountered a strange problem all of a sudden. When I print from cura (version 13.06.4 under Windows 7) directly via USB, no matter what I set as ground layer height (tried from 0-0.6mm), the print starts about 1mm above the build plate. This happens only from Cura via USB. The SD works as normal and if i print from Netfabb (also via USB), the problem doesn't occur either. The plate is perfectly calibrated using Cura's bed leveling wizard. I would only use print by SD card anyway, but sadly the SD card reader on my PC got fried by a faulty card.

Anyway, I can start a print and then manually fiddle with the z-screw until the nozzle almost touches the buildplate, but that is of course no real solution to the problem. I don't understand what happened all of a sudden, but since every other way does the job fine only Cura via USB does something like +1.0mm before the build starts, so I figure it has to be a bug in Cura? Other than that everything works absolutely flawlessly!

Many thanks if someone has a fix and kinds regards,

B.

 

[illuminarti 18]

Can you post the start gcode from your copy of Cura? Most likely there's something in there that is upsetting the printer.

 

[budu 0]

Thanks for the lightning fast reply. To the best of my knowledge, I've avoided touching any code fragments for "start" or "end". Here is my "start.gcode" from the Cura version that I use:

;Sliced at: {day} {date} {time}

;Basic settings: Layer height: {layer_height} Walls: {wall_thickness} Fill: {fill_density}

;Print time: {print_time}

;Filament used: {filament_amount}m {filament_weight}g

;Filament cost: {filament_cost}

G21 ;metric values

G90 ;absolute positioning

M107 ;start with the fan off

G28 X0 Y0 ;move X/Y to min endstops

G28 Z0 ;move Z to min endstops

G1 Z15.0 F{travel_speed} ;move the platform down 15mm

G92 E0 ;zero the extruded length

G1 F200 E3 ;extrude 3mm of feed stock

G92 E0 ;zero the extruded length again

G1 F{travel_speed}

M117 Printing...

 

[gr5 2,239]

In Cura what is your "travel speed" set to? If this is a very high value it could skip steps in Z. In fact, in the ulticontroller, what is your Max Z speed and Z acceleration set to? Try lowering the max speed to whatever netfabb likes to use.

 

[budu 0]

Thanks for the answer. The travel speed is set to 150 and the acceleration settings are always the same defaults. Netfabb pushes the head around much faster even. If i run the bed leveling wizard in Cura and set the nozzle to literally touch the buildplate in all corners, i notice two things: when the print head comes to calibrating the back corner on the right, it doesn't move in parallel to the bed but rather moves noticeably "inward". When I then print the test square around the bed to finalize the process, it will go from corner to corner but only touches the buildplate slightly in each corner and the connections in between are not attached to the plate. I'm not sure, but it seems to me, like this was not the behavior at start when I bought it a few weeks back. It seems like all this "weirdness" only started after I made my first print attempt with Sli3er. During that print the printer made horrible noises, that sounded like some gearbox somewhere was tortured to death. Until I noticed that it had mad speed settings, which caused some strain on the printer. Nonetheless, the only issue is, that the first layer doesn't even touch the plate. If i turn the z-screw until the nozzle hits the plate during the skirt-print, I end up with a, as-ever flawless print.

 

[gr5 2,239]

G1 Z15.0 F{travel_speed} ;move the platform down 15mm

 

I think you missed my point. travel speed of 150mm/sec is fine for X and Y but probably too fast for Z. So I would check your Max Z speed in your ulticontroller. The values in the parenthesis above are taken from the cura settings by the same name.

 

[gr5 2,239]

it will go from corner to corner but only touches the buildplate slightly in each corner and the connections in between are not attached to the plate.

 

It sounds like either your build plate is bowl shaped, or your gantry rods are bowed.

Also keep in mind that your print bed often needs re-levelling. The wooden arms that hold it droop and also warp and change from day to day.

Also the print bed tends to get kind of stuck on the springs and can suddenly move or if two opposite screws are a little tight then it can rock on this axis connecting those 2 screws. So during the levelling process I kind of have to push and pull on the plate to make sure it is settled.

I level a lot. Every day. Still. :(

 

[budu 0]

Thanks a lot guys, for the kind, quick and helpful comments. The values on my ulticontroller are: Vmax_z = 10 and Amax_z = 100

I'm no expert on the ultimaker at all yet, but intuitively, I would reckon those values seem very reasonable (they are probably the standard values?). I posted this here, since I was convinced that the issue is buried somewhere in the Cura-USB interface, since the SD prints as well as the Netfabb prints yield normal prints from start to finish. I just really like Cura and think it does a phenomenal job. Currently I do not have the time to figure out all the features of Nettfabb, to get it running exactly as I'd like. And Cura just does the job without requiring much setting-tinkering. (Nettfabb with my current settings tends to overextrude and retraction makes mechanical sounds of death, although I've tried to use the same settings as in Cura).

 

[budu 0]

Ok, I tested it again, and it seems pretty much pinned down:

- Cura via USB: Print starts approx. 1mm above ground plate.

- Same Cura session even, just instead of ctrl-p I saved the gcode file, mailed it to another PC and from there loaded on SD card: perfect print.

So the only thing that makes sense in my head, is what I said above: Something with the Cura/PC-Ultimaker-USB interface has to be weird? Driver problem maybe?

Thanks a lot if anyone has some idea how this could be fixed.

 

[gr5 2,239]

very strange!

 

[budu 0]

i know, that's why im seeking help from the masters here

[gr5 2,239]

Could you maybe video the first couple of seconds of both methods? Include the homing step of course. I want to know if I can hear differences also.