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!

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

Can you guys build me a…

Work It!

Every so often we get a question from someone along the lines of “Hey, can you guys build me a…” where the thing in question might be easy to build, or hard to build, or cheap, or expensive, or… a dozen other things.

It might be worth explaining how Milwaukee Makerspace works, for those who are not quite sure. Milwaukee Makerspace is a number of things: it’s a physical place (a hackerspace or makerspace) but at its heart, it’s also a social club for people who like to make things.

Most people who join Milwaukee Makerspace already have personal projects in mind that they want to work on. Others just want to learn new skills; like forging metal, or wood working, or digital fabrication. At the weekly meeting people talk about what sort of making they are into, and it ranges from electronics to photography to welding to sewing. There’s a lot of skills in the group, and that’s good!

When people contact us asking if they can hire us to build something, the answer is usually not as simple as yes or no. It’s complicated…

No one ‘works’ at Milwaukee Makerspace we’re all just members, and we are not a business. We’ve done group projects for other organizations in Milwaukee, but it’s usually to help people in need, support a community effort, or for fun.

So here’s the deal: if you want someone at Milwaukee Makerspace to make something for you, or help you make something yourself, your best bet is to come down to a Weekly Meeting at 7pm on a Tuesday and introduce yourself, talk about what you want, and see if anyone is interested in helping you out. You never know, you might find someone up for a new challenge, or just as excited about your potential project as you are.

(If you just can’t make it to a meeting, consider posting on our mailing list. But if you can attend a meeting, it’s definitely better to meet up in person than just shoot emails back and forth.)

Ho Ho Lights

My Husband and I wanted to put up some kind of Christmas decorations in our apartment windows over looking the city. After talking about it for a while, I decided to make lighted letters saying, “HO HO HO” …but since we only have two pairs of windows, it would have to just be, “HO HO”.

In the wee hours on Black Friday, we got the materials: 4 sheets of wood, 4 boxes of 100 count LED lights, and extension cords. After sketching out the design…

…and cutting out the letters…

…it was time to drill the 400 holes and hot glue all the lights in place.

It only took a weekend to make and hang these and I think the end result is well worth it.

MAHRER CHRERSTMAHS

Holiday Make-A-Thon 2012

Make-A-Thon

It’s no secret that we love making, but did you also know we love helping others make things as well? It’s true… and one of the ways we like to help others is by taking part in the Holiday Make-A-Thon that happens at Bucketworks the day after Thanksgiving.

Why bother putting up with the malls and the traffic and the crowds so you can try to get some great deal on the latest gadget that will be out of date in six months. You’d be much better off joining us at the Make-A-Thon where we’ll help you make something that will serve as a great gift this holiday season.

We’ve got a few things planned, including ornaments you can decorate yourself (new designs for 2012!) You can also learn how to solder, and walk away with an awesome electronic blinky Milwaukee Makerspace logo. We’re also hoping to let people design their own cookie cutters that we will then 3D print for them. Exciting! Who doesn’t love whimsically shaped cookies!?

There will be other activities and things to make, but you’ll have to join us to find out what they are. So head down to Bucketworks on Friday, November 23rd, 2012 from 12pm to 5pm and make with us. (More details? See the Facebooks.)

(This is a family-friendly event, and it’s free to the public, though we might ask for a donation to help support the event so we can keep doing it every year.)

Make Magazine

Make Magazine

Do you subscribe to Make Magazine? You probably do… but if you’re ever at the space and want to look something up that is in the current issue… now you can!

After we appeared on Make: Live the fine folks at Make were kind enough to provide our space with a subscription.

So keep an eye out at the space for the latest issue, and give it a read if you’re so inclined. (And if you’re not a subscriber, what are you waiting for!?)

Holiday Make-A-Thon 2011

Holiday Make-A-Thon 2011

We’d love it if you joined us at the 2011 Holiday Make-A-Thon happening Friday, November 25th, 2011 at Bucketworks.

This is a family-friendly event where the focus is on making things for the holidays. It can be gifts for others, of gifts for yourself! Members of Milwaukee Makerspace will be on-hand teaching people how to solder, so if you’re expecting an electronics kit this year, you’ll be ready!

We’re also working on a variety of ornaments that you’ll be able to paint or otherwise decorate. Keep them yourself or give them as a gift.

If you’re into knitting, care to try your hand a painting at gourd, or just want to wrap the gifts you already bought… join us and celebrate the spirit of making!

Detail? See Facebook, and then join us on Friday (the day after Thanksgiving) from 1pm to 5pm. Black Friday? We like to call it Make Friday. :)