When printing starts, the bed drops ~1,5cm on the Z-axis

[matthijsg 0]

Hi all,

I 've encountered a strange problem. Printing goes well, except with one STL. The size is 19.5cm*19.5cm and 5mm high. When Cura 13.06.4 sends the code to the printer and Ultimaker starts to print, the bed drops ~ 1,5cm. After that, the printing starts :mad:

It's confusing me, couldn't find a solution or a fix. What's wrong here?

Screenshot https://dl.dropboxusercontent.com/u/77853008/IMAG0246.jpg

STL-file https://dl.dropboxusercontent.com/u/77853008/2013-07-25-omtrekkopie.stl

 

[illuminarti 18]

I suspect that you're going off the edge of the print bed, once the skirt it taken into account, and it's triggering the end stops, and causing bad things to happen?

 

[matthijsg 0]

The object is green in Cura, so i 'consider' it's between the lines. Ultimaker can print 20.5 or 21. And, the bed drops before printing.

 

[gr5 2,265]

Good theory. You might want to disable the "skirt" and "brim" settings in Cura for such a large model. Or can you print this smaller? Scale it back by 10%? e.g. scale= 0.9?

 

[illuminarti 18]

Can you @fbrc8.com'>email the gcode to me, and I'll take a look. The bed usually drops at the start of a print for the initial priming extrusion. I suspect that what is then happening is that it is failing to rise back up, because the initial move to the start point (which is the only one on the first layer that specifies a z coordinate) wants to take it off the edge of the bed, and so is ignored.

 

[matthijsg 0]

I can't print smaller, it has to be 19.5 cm ..

@illiuminati i just mailed you

 

[gr5 2,265]

19.5cm is fine as long as the brim or skirt or support doesn't go beyond 205 or so mm. Make sure these settings don't go beyond about 2mm on each side. You didn't answer if you have skirt or brim turned on and if so what settings those are at (what's the skirt distance or number of brim passes?)

I would probably use the brim feature to help hold down this part but only 4 passes to keep from hitting the limit switches. When printing the first layer I would put my ear near the limit switches and listen for that quiet "click".

 

[illuminarti 18]

I looked at the gcode, and as I suspected, you're trying to print off the bed. While the part fits, the skirt looks to have quite a large offset that takes it off the bed.

The printer does its normal starting process, of dropping the bed 15mm, and pre-extruding a few mm. It then tries to move to the intended starting point for the skirt...

;LAYER:0

M107

G0 F5400 X-1.25 Y2.41 Z0.30

;TYPE:SKIRT

G1 F1800 X2.41 Y-1.25 E0.12174

G1 X26.24 Y-1.25 E0.68210

G1 X28.54 Y-0.30 E0.74055

G1 X205.30 Y176.46 E6.61824

G1 X206.25 Y178.76 E6.67668

This tries to move to a negative x coordinate, so the whole move is ignored. This is the only line on the layer that sets the z coordinate, however. It will ignore the next few lines too, since they're off the bed as well, but then carry on with the ones it can print. But since the only line that set the height got ignored, all the printing happens with Z still at 15.

The solution is going to be to set a smaller offset for your skirt, so it still fits on the bed, or do without a skirt.

If you wanted the skirt for priming reasons, you could instead increase the extrusion amount in your starting gcode to something like:

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 F60 E6 ;extrude 6mm of feed stock

M1 P2000 ;pause 2s

G92 E0 ;zero the extruded length again

G1 F{travel_speed}

M117 Printing...

 

 

This extrudes more plastic at the start, at a slower rate, so as not to overwhelm the head, and then pauses a couple of seconds to give you time to grab some tweezers and clean the head if you want.

 

[matthijsg 0]

Ah, thanks for the answer! I was waiting for a reply, didn't look here :wink:

Now i've to lookup what a skirt is & how to alter it in Cura .. ;-)

 

[gr5 2,265]

Up at the top of this and every forum is a link "follow this topic". If you post a question you should DEFINITELY click that.

[matthijsg 0]

Ah, it's working.

I noticed, that when you switch from 'full settings' to 'quickprint' the skirt will be added. Switching back, the Skirt is still on 0, but the Layer-mode shows a skirt. Is this is a bug?

Also, why is the model showing green when the skirt is off the bed?

 

[illuminarti 18]

There is a slight bug it looks like - which is that when you switch from Quickprint to Full Settings, it doesn't re-slice that model until you edit on of the settings. So it's still displaying the quickprint gcode (which includes a single pass skirt), while the displayed settings are whatever you had set up in the full mode.

If you click in any of the fields and change a value, you can prompt a re-slice, and then the skirt will go away (if that's how you have it set up in full settings).

I guess the point with the model coloring is that it's only taking into account the position of the model itself, not any skirt/raft etc.