Printer nozzle hitting lower layer.

[3D_guy]

I've printed a few things with my new printer, but this last thing I was trying to print my nozzle started hitting the layer below.BOWL FOR FRUITS-120120308-32621-1akvp5d.jpgMy printer nozzle would do a few layer counter clockwise and they would go good, then a few layer clockwise and because of the design the nozzle would hit and not around the tips, then counter clockwise and it would go good and so on and so fourth. I'm wondering if there is a way to fix this, be it a setting so that my printer only goes one direction for a specific print or something like that. I have a AW3Dhd printer.

[Roxy]

If it is hitting the layer below it, you may be running into a common problem of the edges curling upward. Think about it... If the layer really is 'below', how is the nozzle hitting it? Perhaps it is curling upwards?

If so... This is a common problem with many many different approaches. You can try switching plastics. You can print at a lower temperature. You can try adding a fan that blows cool air on the plastic close to the nozzle.

But first, let's verify that what I'm inferring is true....

[3D_guy]

If it is hitting the layer below it, you may be running into a common problem of the edges curling upward. Think about it... If the layer really is 'below', how is the nozzle hitting it? Perhaps it is curling upwards?

If so... This is a common problem with many many different approaches. You can try switching plastics. You can print at a lower temperature. You can try adding a fan that blows cool air on the plastic close to the nozzle.

But first, let's verify that what I'm inferring is true....

How do I verify that it is true? I look at it and honestly can't tell if its really gone down or not because the layers are so small. I know this is a noob question, but would a fan right at the nozzle not adversly effect the nozzle temp and/or the filament as it comes out of the nozzle? I'm open to trying anything though, I'm testing out a few basic prints so I know it's limits and the more tricks I know the better I can print. other prints I have printed however have come out fine, and don't look curled, but I'm still new to this and maybe its smaller curls than I can see. Thanks for answering so quickly too!

[Roxy]

How do I verify that it is true? I look at it and honestly can't tell if its really gone down or not because the layers are so small. I know this is a noob question, but would a fan right at the nozzle not adversly effect the nozzle temp and/or the filament as it comes out of the nozzle? I'm open to trying anything though, I'm testing out a few basic prints so I know it's limits and the more tricks I know the better I can print. other prints I have printed however have come out fine, and don't look curled, but I'm still new to this and maybe its smaller curls than I can see. Thanks for answering so quickly too!

Answering your questions in order:

1) How do I verify that it is true?

I think I would watch the nozzle very critically as it is printing. I don't know what your printer looks like, but I have a Prusa i3 variant. I have two Z-Axis screw rods that adjust the height. Every time the printer finishes a layer, both of the screw rods do a quick kick of about 1/4 turn to move the nozzle up to the next layer. For starters, you should be watching that it really is kicking up a layer every time it finishes a layer. Especially if you see the plastic being pushed down by the nozzle. And I would bet if you see the plastic being pushed down by the nozzle, it is very close to the edge of something where that happens.


2. but would a fan right at the nozzle not adversly effect the nozzle temp and/or the filament as it comes out of the nozzle?

I don't have a fan, but I'm tempted to reprint my extruder with one. The answer to your question is "No!" The reason is your electronics is monitoring the temperature of the nozzle at all times. What will happen is the duty cycle of the nozzle current will increase. It will have power applied to the heating element (probably a big power resistor) more often than it did without the fan, but as long as it can get to temperature, it will be fine. Your power bill might go up a $.01 or two for a long print!

3. I'm open to trying anything though, I'm testing out a few basic prints so I know it's limits and the more tricks I know the better I can print. other prints I have printed however have come out fine, and don't look curled, but I'm still new to this and maybe its smaller curls than I can see. Thanks for answering so quickly too!

Different shapes are more prone to curling than others. 90 (or 120) degree corners are going to be worse. If you are sloping out from where you already have a layer, that is where I usually run into problems. Try this: Make a file called test.scad and put this stuff into it. You won't be able to finish the print because you will probably lose adhesion half way through the print. But these lines of Open_SCAD code will let you see the issue of edges that are sloping outward:


test();

module test() {
difference() {
sphere(r=15);
translate([-25,-25,-64]) cube([50,50,50]);
}
}

Put this in a file and install Open_SCAD. Compile and render the design. Export it as an .STL file and then slice it. I suspect you will say "I see what you mean about the edges curling upwards."

[3D_guy]

Thanks for the quick replies! Most of my prints turn out fine, it's just the ones with coral design that my wife wants for home decor that this usually happens too. I printed that file you put here and I had to cancel at 1/8" because it was really curling up. I think I'm going to get a fan within the next few days and try that for one print, anything else I should try or know when I get the fan? I also watched my z-axis rod withch lowers the print bed and it turns an eighth of a revolution every layer, I'm assuming that the bed is working fine though because most my other prints turn out just fine.

[Roxy]

I haven't done it... But some people suggest putting a fan somewhere close to the printer blowing air down at the bed to see if it will help before getting one that attaches to the nozzle. And then you have people going the exact opposite route where they print a skirt (using Slicer) that goes up very high around the part just to keep any drafts away from the part.

My guess is you are printing with ABS plastic. If you switch to PLA you might have better luck. I like ABS, but for big parts I have problems with it warping and PLA works better for me when doing big parts. The bottom line is you are going to have to try different things and figure out what works for you! But at least you understand how printing thin edges that slope upwards causes problems now!