Poor quality ABS print - blobs, delamination

First, I apologize if this has been discussed 100 times and I just can’t find it. I swear I’ve tried, and I’ve been putting putting this post off for days in hope that I would find a solution, but no luck so far. I’m trying to print a few replacement gears for my TAZ 4, as practice and to have them on hand before it’s too late. I’ve had the printer for 3 or 4 weeks, have used it quite a bit, and am mostly happy with the results. Anyway, I’m using gcode straight from Lulzbot to make these gears because I assume that their gcode should be optimized for the printer. Unfortunately, I’m getting bad results. I get little blobs all around the perimeter of the part, and some delamination. I’m printing with a bed temp of 90C and an extruder temp of 230 with black gizmo dorks ABS. The results are not impressive - poor surface finish and very weak. Maybe I’m just using bad filament? If anybody has any suggestions, I’d really appreciate it.

Update: ran the same original Lulzbot gcode with Lulzbot ABS and got similar results. I was hoping that was my issue, but I’m not that lucky.

Do you have an enclosure around your printer ?

What infill are you using?

Which profile are you using, fine,medium fast ?

I would suggest downloading the stl file for the gear and slicing it yourself with the settings you are using to slice other parts.

I was printing the same part yesterday, with somewhat similar results. I have attached a photo that shows the effects of just changing how the fan is run.

The AutoFan feature of Slic3r doesn’t work well with small parts without changing some of the values.

Notice that without a FAN, I was getting melted gears. Not usable.
With the default values for the time, and just setting the fan speed to 0 to 100%, the fan ran at 100% the whole print, and I got significant cracks.
I changed the fan range down, and this print still had a crack in the base (looks like a shadow in the photo). But it was better. Fan pretty much ran at 60% the whole print.
I then narrowed the time values (its a small object), the fan finally changed speeds during the print and I got a part that was very workable (the last frame in the photo).

NOTE: If you look close in the photo, you will spot some “dents” in the collar area. These are being added by Slic3r or my printer has a very reproducible print flaw as they are consistent across the models. I suspect its where the slice starts and ends.

No enclosure, although that’s an investment I’m considering making. It’s Lulzbot’s gcode - settings they used are below. I just finished printing a couple gears with 60% infill that I sliced with S3D and they look great and are very strong. I’m sure I could get similar results with Slic3r, but I’m not going to spend the time. I crushed on with some pliers and it failed the way that I want it to - as one piece, rather than a bunch of layers.

; generated by Slic3r 0.9.9 on 2013-06-04 at 18:30:48

; layer_height = 0.30
; perimeters = 2
; top_solid_layers = 2
; bottom_solid_layers = 2
; fill_density = 0.75
; perimeter_speed = 100
; infill_speed = 110
; travel_speed = 155
; nozzle_diameter = 0.35
; filament_diameter = 2.89
; extrusion_multiplier = 1
; perimeters extrusion width = 0.37mm
; infill extrusion width = 0.50mm
; solid infill extrusion width = 0.37mm
; top infill extrusion width = 0.35mm
; first layer extrusion width = 0.37mm


Your speed is way too high in my experience.
Also fan should not be working at all with ABS. You can use it only for some bridging and overhang stuff

Enclosure for the printer is a big change in the quality. You don’t have to invest anything at first, just use the box that came with the TAZ and cut it some way to fit over your printer.

Also, you need to print several small pieces at once, that will improve the quality.

no fan
enclose with box
print 2 parts at the same time
speed down to 30 or something similar

So I think my issue was 40% code, 60% filament. As I said earlier, re-slicing last night and printing with the same ABS resulted in a significantly better part. Running that same code today with a new brand of filament I ordered resulted in what I consider to be a pretty perfect part. Thank you all for your suggestions. When I have some time I plan to run some with/without enclosure experiments.

Actually, the fan working for the small gear is written into the gcode straight from Lulzbot and produced the best looking gear I was able to print.

The small zig-zag details of the herringbone teeth were FAR cleaner with the fan running per Lulzbot code than with the fan off.

Since it’s a very small part, and it prints quickly, it’s worth trying both ways.

But with a full enclosure around my printer keeping the ambient temp around 90-95 F - having the fan running gave me best results.