The Stratasys lives!

Last spring, I brought in a Stratasys FDM 2000 3D printer for the Makerspace to use for a few months before delivering it to our good friend Frankie Flood for use in UWM’s Digital Craft Research Lab.  Many people had items printed on it and wished we could keep it at the space, so I promised that the next Stratasys I acquired would indeed have a home here.  Fortunately, that didn’t take long, but unfortunately, the machine wasn’t fully working and needed a new support nozzle solenoid and had persistent jamming in the support extruder.  It functioned well enough with just the model material that we were able to run it successfully at Makerfest, but it needed much more work to run properly.

fdm2000 better wiki image

Thanks to another FDM owner, the solenoid was quickly replaced, but the jamming remained.  I assumed that it was something in the extruder tube itself, and set about a long process of clearing it of all obstruction.  Unfortunately, this provided no benefit whatsoever (but I at least got the satisfaction of a successful head teardown/rebuild and understand the internals better than before).

scumbag nozzle

Even after carefully drilling out all traces of plastic from the nozzle with tiny drills and a pin vise, it would still clog and jam.  Replacing it with another 0.012″ nozzle cured all jamming issues.

2000 first chess set print

As proof, here is a grainy, Loch Ness Monster-esque photo of a print done with support material.  Since printing Duchamp chess sets are all the rage, this seemed like a perfect inaugural print.  Much more tweaking remains – the XYZ offset of the support nozzle needs to be dialed in, there’s a bit of slack in the cable drive system that I think may be causing ripples in the part surfaces, and I’m not convinced that the ‘moonstone gray’ model material is running as well as other colors.  Regardless, full operation is within grasp – ladies and gentlemen, prepare your STL files!

SnakeBite Extruder Works!

I repaired the Budaschnozzle hot-end over the weekend and bolted the SnakeBite extruder to it and then to MegaMax and tested it last night.  There’s plenty of tuning to do, but the first print looks promising:

 

Start of SnakeBite’s first print

 

More of SnakeBite’s first print

 

Not too pretty but it shows promise.

Not too pretty but it shows promise.

3D Printable Thermal Enclosure For 3D Printer

Well, OK, not the whole enclosure, just the parts that hold it together.

MegaMax can print big stuff but he’s had problems with large prints delaminating.  The answer seems to be enclosing the printer to keep the prints warm while printing.  I designed this box and 3D printable parts to hold it together so that I can take the box apart easily to work on MegaMax or move him to other locations and put it back together when I’m done.  The box is 38″ D x 28″ H x 32″ W.

box door open

 

 

 

 

 

 

 

 

 

 

box door closed

 

 

 

 

 

 

 

 

 

 

 

 

 

The box is made of 1″ PIR foam with corners suitably notched to accommodate the printed parts.  MegaMax has a 450 Watt heater in the printbed so the box gets super-toasty inside.  I suspect it gets a little too toasty but haven’t made any measurements yet.  I’ll soon be moving the electronics out of the box.  I didn’t do anything to seal the seams in the box because it doesn’t seem to be necessary.  I did tape the edges of some of the foam boards with clear packing tape to prevent damage.

Design and stl files are available at http://www.thingiverse.com/thing:269586

Snakebite Extruder Testing

rev7 extruder with hot-end

 

 

 

 

 

 

 

 

 

 

 

 

One of the biggest problems with FDM 3D printing is hot-end jamming.  There seem to be a lot of causes, most of which are not readily identifiable when a jam occurs.  One thing I have found is that after a hot-end jam I can usually grab the filament and manually push it and get it flowing through the hot-end again, though it is too late to save the failed print.  The most common means of driving the filament into the hot-end is to pinch the filament between a gear and a bearing and have a motor drive the gear, either directly (with 1.75mm filament) or via a gear reduction/torque multiplier arrangement (3mm filament).  When the hot end jams, the large force applied by the gear over the small area of the filament that is pinched between the gear and bearing usually chews a divot in the filament thus destroying the grip.

A couple weeks ago I started designing a 3mm filament extruder for 3D printing.  My hope is that this extruder will provide sufficient force on the filament to prevent hot-end jamming from ruining prints.  My design uses two counter-rotating 6-32 nuts twisting on the filament (like the way your hands twist in opposite directions when you give a “snakebite” to your friend) to drive it into the hot-end.  One is a normal, right-hand threaded nut, the other is left-hand threaded.  When the nuts turn in opposite directions, the torque that would try to twist the filament is cancelled while moving the filament forward and reverse without twisting.

The motor has to turn about 1.26 times to move 1mm of filament so there is a huge torque to axial force conversion.   The gear diameter is about 30mm.  That 1.26 rev moves the gear about 119mm at its perimeter.  That means there is about a 119:1 increase (ignoring losses in the gears, bearings, and nuts) in the force at the filament compared to the force at the gear.  That force is applied over a larger area of the filament than the usual pinch arrangement, so it is less likely (I hope!) to carve the filament and lose grip.  I tried stopping the filament by grabbing it with my fingers and holding as tightly as I could but it didn’t even slow down.

The firmware in the printer has to be tweaked so that it knows exactly how many steps of the motor are required to drive 1mm of filament.  The formula is:

32 rev/ 1 inch  X     1 inch /25.4 mm   X    200 steps/1 rev    X  16 microsteps/1 step   =  4031.496 microsteps/mm

For initial tests I just input 4031.5 using the rotary encoder on the LCD interface to the RAMPS board in MegaMax.

Here are the parts that I used:

Left hand threaded tap:  http://www.amazon.com/gp/product/B006YITGY8

5mm brass tubing:  http://www.ebay.com/itm/360828686174

5x16x5mm (625Z) bearings:  http://www.ebay.com/itm/321062568303

Plastic gears:  http://www.sciplus.com/p/PLASTIC-GEAR-SET-WITH-BUSHINGS_40234

I also used a NEMA-17 motor from a QU-BD extruder.

You can DL the STL files for the printed parts here:  http://www.thingiverse.com/thing:261037

Test printing will start in the next day or so and I will post another video showing success or failure.

Fingers crossed!

Further Adventures in CT Scan 3D Ego Printing

 

 

After a long series of manipulations, the CT scan derived  face was successfully used to make a pencil holder (of all things!).  It is about 100mm high and took about 9 hours to print.  You can find files that you can use to make your own mash-ups of my face on thingiverse: http://www.thingiverse.com/thing:203856

3 face cup 2

Successful CT scan processing into 3D printable file

Today was spent researching all the manipulations involved in getting a CT scan into printable form and I managed to get a print out of it.  The process starts with DeVide where the dicom data from the CT scan is processed using a dual threshold, decimation filter, and stl writer.  The stl file contains a lot of unwanted stuff, in this case, soft tissues inside my head that add triangles but won’t be seen in the print, so those are removed by applying ambient occlusion followed by selecting and deleting vertices by “quality” (which will be very low values for vertices on the interior of the object).  This process invariably blows small holes in the desired surface, so you apply a “close holes” filter to fix that (which closed up the nostrils very nicely).  Next you open the stl file in netfabb and rotate and clip unwanted external stuff and apply repairs as necessary.  Finally, drag it into slicer and scale it. slice and print.

First successful ego print!

First successful ego print!

CT Scan Processing into 3D printable STL files

CT Scan with lower threshold swept

CT Scan with lower threshold swept

While investigating software to extract bone data from CT scans and turn it into 3D printable STL files, I played with a CT scan of my own head that was used to treatment plan orthodontics.  I have been using DeVide to process the data and finding it is not only easy to use, but a lot of fun!

The animated gif was made by sweeping the lower threshold of a dual threshold module from -800 to 900 in steps of 100 with the upper threshold fixed at 1400.  The effect is to strip away the lower density tissues leaving only dense bone at the end of the sweep.  I saved the result of each run as a png file then converted to an animated gif using an on-line service.

3D printed webcam-to-microscope adapter

I recently acquired a B&L Balplan biological microscope (about $200 on ebay) to look at really small critters and decided it would be nice to be able to record some of their antics.  After a few measurements with a caliper and about 30 minutes with Sketchup, the design was ready to print on MegaMax.  Initial test results, seen below, look pretty good!   The camera is a Logitech Quickcam Pro for Notebooks (seriously, when are they just going to start using model numbers?) that can capture video at 960×720 and 15 fps.   The camera is not a current product at Logitech but can be picked up for $10-20 on ebay.  The still and video were captured using quvcview running on my laptop (ubuntu 13.04).  Logitech’s software works great on Windows.  The image below shows “horns” on the head of a pinhead sized bug that was crawling around in my work room.  Magnification is 640X!

The adapter design and .stl files will appear on Thingiverse soon.

Since dead bugs don’t move the video is just the focus being swept:  

Camera in microscope adapter.

Camera in microscope adapter.

uscope mount 2

Another view of the camera in the microscope adapter

uscope mount 4

Camera and adapter attached to microscope

Horns on a tiny insect's head magnified 640x

Horns on a tiny insect’s head magnified 640x