What's going on here....

What’s going on here… when printing an overhang my printrbot (extruder 220, bed 70) seems to cause overhangs to curl up.

; layer_height = 0.3
; perimeters = 2
; top_solid_layers = 3
; bottom_solid_layers = 3
; fill_density = 0.4
; perimeter_speed = 10
; infill_speed = 20
; travel_speed = 130
; scale = 1
; nozzle_diameter = 0.5
; filament_diameter = 3
; extrusion_multiplier = 1
; perimeters extrusion width = 0.70mm
; infill extrusion width = 0.70mm
; first layer extrusion width = 0.60mm

I get a similar problem on my Makerbot Cupcake a lot as well, Generally it is fixed by holding a small fan near the print while it’s running, to cool the print (but not too much)

Is that ABS or PLA ?

maybe the section curling up is not cooling enough b/t each layer. PLA or ABS? Do you have a fan? Do you have cooling enabled?

Sorry, ABS, extruder set to 220 for the first layer 200 thereafter. I have a fan but generally don’t use it for most prints. I’ll try it.

Would support material help pin it down too?

200 seems awfully low for ABS - although i have found not all thermistors are made equal :slight_smile:

What issues will 200 for abs cause? I thought the idea was to go as low as you can

You are absolutely right, as low as you can. I’ve had trouble printing PLA at 200 but now you come to mention it I may be using the wrong lookup table for my thermistor.

I tend to go a bit hotter so that I can print faster and get a smoother surface. Sounds like you are doing all the right things though.

What I don’t understand very well about this phenomenon is that putting a fan on the print would hopefully cause it to cool and prevent that squishy rebound like you’re seeing, but on the other hand I thought uneven cooling of the layers would also cause warping because of thermal expansion.

I guess you need to print with support. The overhang is slightly bend down by the plastic stream. And that layer on layer.

If you would use support, then it wouldn’t be able to bend down so much.

its because the bottom of the print isnt sitting flat. the print is moving and your end is staying the same. so if you start your print a little closer to the bed you should be fine im sure.

I had a similar overhang curling issue trying to print the small heart gears on my printrbot. I ended up using a fan and that made a big difference. FYI, my extruder is set to 210 for ABS, but I agree with @MikeDX that temperatures between machines vary based on where and how the thermistor is mounted.