Illegitimi Non Carborundum

One thing I’ve noticed in some of my prints is the tendency to “drool” a bit on the edges, sort of like a hernia.  This is caused by the extruded plastic layer still being soft when the next layer is put on top of it, causing the bottom layer to bulge out a bit (or even a lot).  This will typically be seen when the perimeter of the piece is small (makes sense, right?).  The obvious solution is to give the layer time to solidify, and easiest way is to simply slow down the speed of the head.  I recently ran a small experiment to test the effect of slower speeds.

For my test piece I chose something from Thingiverse called “cthulhu2”.  It’s not too big, so it’s not overly expensive in terms of time to print … that is, I can do it in the evening after work.

The normal speed that I use is 60 mm/second (recommended by the manufacturer).  For testing, I tried 30 mm/second.  Overall, this seemed to help, but wasn’t a complete cure.  I also tried printing at both 0.1 and 0.2 mm/layer.  The following pictures show the results.  If the pieces are numbered 1 through 4, left through right :

piece  layer  speed            infill      time-t0-print

(mm)  (mm/sec)                  (minutes)

1          0.1         30                1.5        162

2          0.1         60               3            192

3          0.2         60              3            75

4          0.2         30              1.5        85

Reducing the amount of infill certainly improves the speed, but there’s always a danger of droops at the top or at overhangs.  There’s no evidence of droop at the tops here, but #4 does show a bit of a problem on the tummy, just below the hands.

You can certainly see the effect of printing at 0.1 and 0.2 mm/layer, both on the quality of the print and the length of time it takes to complete the print.

I list the SLIC3R parameters after the pictures.

Here are some pictures of the pieces.  Keep in mind that these correspond with the piece#, from left to right.   You’ll want to zoom in to see all the types of issues, and how it changes from piece to piece.

front view

right hand side

rear view

left hand side

top view

The STL files were sliced with the SLIC3R program.  Here’s a sample printer ini file :

# generated by Slic3r 0.9.1 on Sun Sep 30 13:36:08 2012
bridge_flow_ratio = 1
bridge_speed = 60
brim_width = 0
complete_objects = 0
external_perimeter_speed = 100%
extra_perimeters = 1
extruder_clearance_height = 20
extruder_clearance_radius = 20
extrusion_width = 0
fill_angle = 45
fill_density = .15
fill_pattern = honeycomb
first_layer_extrusion_width = 200%
first_layer_height = 100%
first_layer_speed = 70%
gcode_comments = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0
infill_speed = 60
layer_height = 0.2
notes =
output_filename_format = [input_filename_base].gcode
perimeter_extruder = 1
perimeter_extrusion_width = 0
perimeter_speed = 30
perimeters = 3
post_process =
randomize_start = 1
skirt_distance = 8
skirt_height = 1
skirts = 2
small_perimeter_speed = 30
solid_fill_pattern = rectilinear
solid_infill_speed = 60
solid_layers = 3
support_material = 0
support_material_angle = 0
support_material_extruder = 1
support_material_extrusion_width = 0
support_material_pattern = rectilinear
support_material_spacing = 1
support_material_threshold = 45
threads = 2
top_solid_infill_speed = 60
travel_speed = 160

Here’s a fascinating dinosaur fossil model.  It’s the top half of a jaw+skull, scanned by a company named Artec, which manufactures 3D scanners.  This model was then sliced into 4 pieces for easier printing (http://www.thingiverse.com/thing:14173).  I’ve printed the two pieces of the front half :

tarbosaurus (work in progress)

Printed with 0.2mm layers.  The bottom part took about 4 hours, and the top part about 2 hours.  There are 2 more pieces to print, and they’ll take similar times I think.

So far my two favourite things to print are fossils and mathematically-based models.  The former because it’s almost impossible for most people to have hands-on access to fossils, and they really are fascinating.  The latter because it’s the ethereal made real.  There are some excellent artists out there who are not only creating mathematical models, but also sharing them.

This one is a twisted cylinder with a Veronoi surface applied to it :

Veronoi Tower

It’s printed with 0.2mm layers, and stands 3.5-inches tall. It took about 3-1/2 hours to print, if I recall correctly.  From http://www.thingiverse.com/thing:23496

It’s hard to get a good picture of these 3-dimensional constructs.  This is really shown by the next object :

Cellular thing

Source : http://www.thingiverse.com/thing:19104

Printed with 0.2mm layers, but could really use 0.1mm judging by how some of the thing strands turned out.  It’s shape, if you can’t quite see it, is like a hollow donut with the skin formed by an open-celled membrane.  It stands just shy of 4-inches tall (the limit of my printer).  As you can see, it needs a bit of cleaning up … but that’s pretty normal.  It took about 6 hours to print.

Here’s a little something that I printed out in time for Halloween!

This lovely critter stands almost 90 mm tall.  He was printed with 0.2mm layers, 30% infill, and took about 5-1/2 hours to print.

The file was obtained from http://www.thingiverse.com/thing:31264

Despite some initial problems, I’ve managed to make a few good prints.

owl print

I get a lot of the 3D files from http://thingiverse.com, by the way.  Lots of stuff there,from trivial to utilitarian to just-for-fun.  One really neat thing is 3D scans of fossils!  It’s the closest someone like myself will ever get to handling fossils (and that’s a good thing, actually).  One nice one is printed in several pieces that need to be assembled.  So far I’ve printed two of the jaw pieces :

part of a dinosaur skull being printed

Another fun thing to print out are mathematically-based creations :

veronoi_D_tower being printed

It’s something of a process to get from an “image file” to the printed product.  I’ll discuss that next time, but thought I’d show you some of my successes before showing problems and failures.  But it’s all great fun!

My latest toy is a 3D printer.  Basically it prints 3D objects using plastic extruded through a hot nozzle.  They’ve been around for years, but have cost tens of thousands of dollars.  In recent years, however, a variant has emerged that is orders of magnitude cheaper, making it affordable by mere mortals.  Very much like the early days of desktop computers!

So anyways, after doing a lot of reading and even more lusting-after, I finally bought one!  It’s made by a local company called Eckertech (http://www. eckertech.com).  Although tempted to buy the kit version and save some money, good sense triumphed and I bought the assembled version.  It really is a well put-together unit, and came with a figurine printed as a final test, 1-lb of plastic filament, and a few other useful bits and pieces.  Here’s what the Eckerbot looked like out of the box :

Eckerbot taken out of the shipping box. It’s well packed!

After carefully unpacking :

Unpacked and ready to go.

I installed the required software (Repetier) and … and … nothing worked.  ACK!  ACK!  Long story short, it didn’t work under Linux (my o/s of choice) but worked fine under Windows XP (my secondary o/s).  Ok, so with the printer talking to the software I printed a simply test object (a cube) and got :

first attempt at printing

Not too impressive, is it?  In fact, it is crap.  The printer came with no instructions of any sort , so I glared at it, read some more stuff on the Internet and realized that the extruder head was too high off the bed.  Well, that didn’t make any sense.  After a couple days of emails with the manufacturer, we determined that the home-switch for the Z-axis (vertical up/down) was too high.  It probably got bumped while I was unwrapping everything.  Pretty obvious after the fact, but tough to diagnose for someone unfamiliar with such things.  So then I had to move the switch … which was set too low, and the head drove itself off the shaft.  ACK!  Long story short, I have become pretty good and re-aligning everything!  And have managed to get some stuff printed off :

Early printing attempts.

AAs you can see, some attempts were more successful than others!  But each failure is a step along the path of learning.

The journey begins.