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Just cannot get that first layer right

Posted by gemors 
Just cannot get that first layer right
March 10, 2016 05:24AM
Hi All,

Any idea why this is happening, I just can't get that first layer correct.

It almost looks like it's not feeding all the time and leaves empty streeks.

thanks

G
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open | download - IMG_0559.JPG (54 KB)
Re: Just cannot get that first layer right
March 10, 2016 07:38AM
I think you are right that it stops extruding as its regular and even your 2 wall perimeter only has one in some places.
Could check the max extruder temp limit in the firmware is above your hot end temperatures. I don't know how that's implemented in the firmware but assume it just turns back on when the temperature drops. If your PID tuning is poor then you could overshoot the target temperature and trip this limit.
It does seem to be based on either time or distance and this implies it is a control system issue not a mechanical/filament issue.
Sorry I can't tell you what the fault is.
Re: Just cannot get that first layer right
March 10, 2016 07:40AM
What is the surface material you're printing on? What type of filament? What temperatures? What layer thickness?


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Just cannot get that first layer right
March 10, 2016 08:43AM
Looking at the image I think that the layers/traces are not fully sticking to the surface and curls up at the edges. Might be a combination of bed surface, bed distance and temperature and possible under extrusion
Re: Just cannot get that first layer right
March 10, 2016 04:03PM
Quote
the_digital_dentist
What is the surface material you're printing on? What type of filament? What temperatures? What layer thickness?

And what Extrusion Multiplier?
Re: Just cannot get that first layer right
March 10, 2016 09:13PM
Heatbed with glass top
Extruder temp set to 210
Heatbed temp set to 85
Layer thickness 0.4
Filament PLA 1.75mm White
Multiplier is currently set to 1.1

The filament seems to stick pretty well as It's not easy to remove while the bed is hot.

I can do a print, say 20mm high to check for if the extrude feed continuously. Will report back on this.

thanks for all the help and comments
Re: Just cannot get that first layer right
March 10, 2016 10:55PM
Why is the extrusion multiplier set to 1.1? What is nozzle diameter? Does PLA stick to plain glass?

It looks like over extrusion- when the nozzle passes by the previous line it tears it loose from the bed because of the overlap/overextrusion.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Just cannot get that first layer right
March 11, 2016 01:28AM
Also depending on the nozzle size, .4mm is a fairly high layer height.

With a .4mm nozzle I print mainly at .2mm layers.
Re: Just cannot get that first layer right
March 11, 2016 07:23AM
Quote
Floyd
Also depending on the nozzle size, .4mm is a fairly high layer height.

With a .4mm nozzle I print mainly at .2mm layers.

Good point. And even if the nozzle is capable of extruding .4mm layer heights, that also means that the volumetric extrusion rate is going to be pretty high, so unless the print speed is low the extruder may be limiting. Is there any sign of the extruder not keeping up, such as clicks from the motor, or bits of filament/powder from the gear chewing through? A slipping drive gear could also cause problems.

What print speed is being used? 15mm/s is a good place to start for the first layer.
Re: Just cannot get that first layer right
March 13, 2016 04:58AM
Finally got to do some testing.

- Lowered the print speed
- Decreased the extruding multiplier
- Lowered the retraction for non print moves
- Printing at 0.2mm layer height and not 0.4
- increased extruder temp to 225

Over all things are much better based on applying a bit of advise from all the posts.

Thanks heaps for all the help
Re: Just cannot get that first layer right
March 13, 2016 05:10AM
Greeting all,

Test when well until about 15 minutes into the print, I was printing a Pawn for a chess set.

I could here the extruder feeder slipping and took a closer look. No filament was coming out... I paused the printing, released the pressure on the feeding gear and pushed the fillement down by hand. Gently as first normally i's enough to let it flow through, yet now I had to apply a lot of pressure before I could get it to flow through again.

Something seems to block the filament after 10-15 minutes of printing.

Any sugestions on where to start?

thanks all
Re: Just cannot get that first layer right
March 13, 2016 06:30AM
check the filament for issues with it's thickness\width
Re: Just cannot get that first layer right
March 13, 2016 07:31AM
What sort of hot end are you using, and is the heat break cooling fan running continuously? PLA is prone to jamming when heat moves back up the throat and softens the filament, because pla softens at a lower temperature than most plastics. If there are any gaps or joins in the feedpath the soft pla then expands into them and makes it very difficult to extrude or retract. If you get a jam like this you can sometimes pull the filament out and see the shape it expanded into. PLA also sticks quite well to stainless steel, so the ideal setup for pla is to run a ptfe liner from above the point where the pla will ever soften, right down into the heater block where the throat meets the nozzle.

Since the extruder motor started clicking, it's also possible that you have the Vref for the extruder set too low so that it isn't generating the necessary force. If the motor and driver are both running cool, and/or you've measured the Vref and know that the calculated driver current is well below the motor's max, you could consider increasing the driver Vref to get more torque.
Re: Just cannot get that first layer right
March 13, 2016 08:27AM
Pull the filament out and see if there's a divot chewed into it by the extruder drive gear. If there's a divot, it means that the pinch roller isn't pressing the filament into the drive gear hard enough. Tighten up the screws/springs to increase the pressure. The extruder motor should click/slip if the hot-end jams instead of chewing a divot into the filament.

Why the hot-end is jamming is another matter. Does the hot-end have a cooling fan? Is it running?

Pictures would help a lot here.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Just cannot get that first layer right
March 15, 2016 04:47AM
mm,

I've just removed the fan on the E3d and noticed that the hot end is moving free from the heatsink, tightened it up and will see how we go, reporting back soon
Re: Just cannot get that first layer right
March 15, 2016 05:44AM
I pulled out the fillement and again there was a little blob at the end, so I pulled the extruder appart...

Looks like there was a small gap between the Nozzle and the heat sink, this is likely the cuase I guess.
Re: Just cannot get that first layer right
March 15, 2016 07:03AM
Depends on the shape of the blob. There is always (and has to be) a slightly enlarged area at the end of the filament, which is the region where the melt flows back up the hotend, cools and solidifies to form the seal that then drives the melt out of the nozzle. The key to this area is that it has to be smooth to slide down the throat. Frequently this part gets left in the hotend when you remove the filament, but depending on hotend design sometimes you see it. On the other hand, if the blob is larger than the filament on either side you've found a problem where the melt/softened filament has expanded into a gap in the feedpath.
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