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phil_O_matic

Smooth bottom layer by targeted over extrusion

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I want to create an as-smooth-as-possible bottom layer. The thing that bothers me most is that the individual extrusion paths are still visible in the final part.
I had the idea to let the printer lay down the outer perimeter as usual, but as soon as that's done increase the extrusion for the rest of the bottom layer. In theory, this should force the molten filament to squeeze in the small gaps bothering me. From my current (very little) understanding that's only possible by directly manipulating the G-Code but that shouldn't be too big of a problem.

Did somebody try something like this? I found a couple threads concerning a smoother bottom layer, but I never saw a solution similar to my Idea.

 

greez Phil

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Hi @phil_O_matic, well I am sure we have all tried different things over the years. What has been working really well for me for some time now is...

 

1. Squish the 1st layer down well, i.e. reduce the distance between the nozzle tip and the print bed

2. keep the 1st layer extruder temp the same as the normal print temp.

3. You are going to get over extrusion now - set the 1st layer flow to 70%; I then move the flow back to 100% over the next two layers.

 

Now none of this is done via gcode. I use Repetier Host to print my models and the GUI allows you to modify flow and temps , speed etc almost instantaneously. It takes some seconds but my guess is that maybe it has to flush the buffer before the changes take effect; only a guess I have no idea. I set the flow to 70% before starting the print. Oh and I print 1st layer at 20mm/s

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2 hours ago, smartavionics said:

There is a setting in the Material section called "Initial Layer Flow".

Also worth trying is using a heated bed and printing on blue tape rather than a shiny surface.

The initial layer flow sounds promising but I fear that I will get an elephats foot if I crank it up until I get an smooth surface. Thats why I intendet to do the most outer layer at the normal 100%.

I use a heated bed but blue tape is a good idea because I'm a bit afraight of prints bonding permanently to my ultrabase if I squish the first layer down too hard.

 

2 hours ago, yellowshark said:

Now none of this is done via gcode. I use Repetier Host to print my models and the GUI allows you to modify flow and temps , speed etc almost instantaneously.

Up to now I was a bit afraight of squishing down the first layer too hard but with bluetape this shouldn't be a problem. Using a remote print service doesn't make sense for me with my printer being in my basement without a network connection so everything should be done through the slicer

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6 minutes ago, phil_O_matic said:

The initial layer flow sounds promising but I fear that I will get an elephats foot if I crank it up until I get an smooth surface. Thats why I intendet to do the most outer layer at the normal 100%.

 

Understood. In that case you will probably want to check out the "Initial Layer Horizontal Expansion" setting which is designed to compensate for the Elephant's foot. Right now I am printing a part using 110% initial layer flow and -0.2mm of initial layer horizontal expansion (on blue tape!) and the result is pretty much perfect.

 

Here's an example (not yet cleaned tape fluff off).

IMG_20181025_130450944.thumb.jpg.571087054cdc9fbd6b97d08a533ff578.jpg

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10 minutes ago, phil_O_matic said:

The initial layer flow sounds promising but I fear that I will get an elephats foot if I crank it up until I get an smooth surface.

It's possible to get best of both.

 

There's a feature called "initial horizontal expansion".  I set that to roughly negative half the nozzle width (-0.25 to be more precise for my 0.4mm nozzle).  This compensates for the elephants foot.

 

Regarding your original question, every printer brand is different but they all need some kind of leveling.  This leveling procedure is where you set how hard it extrudes.  You want it to extrude pretty hard on that bottom layer because if you don't the part won't stick well to the bed (regardless if it's blue tape, glass, etc).

 

For Ultimaker's the typical way is to use the calibration card which has a known thickness and then they have you level it such that... Let me back up.  When the nozzle is barely touching the glass that is supposed to nominally be Z=0.  Ultimaker's procedure levels such that the nozzle hits the glass when Z=0.5 or so.  It depends on the firmware and such and there are different versions and different printers (UM2, UM3, S5) but in general it's levelled a bit tight-to-the-glass on purpose to get that first layer well squished which avoids having your part come off the bed half way through a print.

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Not sure why you think there is a remote service is involved. You have Cura on your laptop and you connect it to your printer - no idea how but USB I presume, unless of course you have to faff around with an SD card

I have Cura on My Laptop, Repetier on my laptop and connect my laptop to the printer with a usb. End of

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