Trouble with raft first layer, possibly due to incomplete perimeter print?

[bobrich 0]

Hey folks,

I'm new to everything, cura, gcode, 3d printing, etc.  I'm currently using Cura 15.04.3 and a Wanhao Duplicator i3 printing with PLA and ABS.  I'll try to describe the problem I'm having, unfortunately I don't have an easy way to get pictures at the moment.

Basically when I print a raft, the very first layer consists of a single perimeter 'bead' that traces the outline of the raft, followed by fill lines that run every 1/8" or so across the width of the raft.

This seems to work pretty well, except for the fact that every single time there is a bit of this perimeter missing from the print.  It's just that there's no PLA laid down for maybe 3/4" or so.  Then, when the fill lines are laid down, they ALWAYS curl up right at this part, presumably because there's no perimeter to stick to?

Is there something I can do to help with this?  I'm running the DiiCooler which tends to snag on these curls and basically the print gets hosed before it gets off the ground.

Any suggestions are greatly appreciated.

Thanks!

Bob

[Nicolinux 288]

I have trouble visualizing your issue. Maybe you could somehow manage to post a picture.

[DinoBot 0]

This is actually happening to me as well. To describe a bit more in-depth (at least for my issue). It seems like the extruder starts to push filament through and print before the nozzle is making contact with the print bed. This causes a portion of the raft perimeter to not print and subsequently provides nothing for the supports to stick to so they curl or drag with the nozzle marring the raft. It looks like it tries to start printing while moving to the starting position but while the z axis isn't far enough down.

[BNN 0]

I have same problem. It causing warping of the raft. I thing that solution is adding an option of 2 perimeters first raft layer, or printing skirt and raft both. Unfortunetly i didn't found way to set it in Cura yet.  Maybe new feature for 2.1.X? Little suggestion for Team Ultimaker.

[Nicolinux 288]

This still does not sound right. Either the bed is not leveled properly or the extruder temp or filament diameter is off so the system has trouble extruding consistently.

[DaHai8 74]

I have this issue too, but it doesn't seem to effect my prints because my cooler is 3mm up from the nozzle tip:

The print head moves from home to the start position of the raft. Its at the proper Z height and travels around the perimeter of the raft but doesn't extrude any filament for at least 30mm or more. Its trying to extrude, but the nozzle is not pre-primed.

Now I have an incomplete perimeter of the raft as it starts printing the surface lines. Because there is missing perimeter on part of the raft, those edges tend to curl up.

A possible fix:

In the Start gCode there is this:

 

G1 F200 E3              ;extrude 3mm of feed stock  

 

Try increasing the E value. Maybe 5 or more until you get your nozzle properly primed for when it starts printing the raft perimeter.

The Start gCode is on the Start/End-Gcode tab in Cura 15.x

Edited July 28, 2016 by Guest

[Nicolinux 288]

If you are using an Ultimaker 2 then it uses UltiGCode flavor and there is no start/end tab in Cura. The firmware does the priming automatically.

But just to test @DaHai8's assumption, you could go into the advanced menu (on the printer) and select "move material". There rotate the wheel at the front until filament comes out. Keep rotating slowly until you have a filament strand that touches the bed and curls up a few times there. Then remove the excess filament, go back and start a print. The nozzle should be fully primed now.

[Kevparang 10]

I have this problem as well on the Monoprice Select Mini, It might be a leveling or clogging issue, I got it fixed partially. You need to make sure you are leveled with a good adhesion surface.

Edited July 28, 2016 by Guest

[twoprops 0]

Sad to see this problem hasn't been addressed in over a year. I have both a Monoprice Maker Select (Wanaho Duplicator) and two Monoprice Select Minis (Mylan M200). They all exhibit this exact same behavior. It's not a bed leveling problem (I used to have a job maintaining optical tables to Angstrom tolerances: I know level beds). It isn't a surface problem -- I've used many. On prints that can use a skirt instead of a raft, I can make it work by increasing the Skirt Line Count -- but there's no equivalent for rafts. Using different bed and filament temps doesn't change it. It's definitely, 100% certainly a problem in the Cura-generated gcode and how it interfaces with these Monoprice printers.

 

I'm going to try disassembling the gcode this weekend and see if I can figure out a way to fix it, but an option in Cura to increase the line count of the frame on the first layer of a raft would be quite welcome.