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!

Robbie is safely enclosed!

Finished room!

Whew.  This project was a D-O-O-O-ZY!  We needed to enclose our giant industrial arm so he can’t run away and join the robot circus…

Well…maybe not for THAT reason, but when we start cutting stuff with this robot, we need to keep spectators out of his reach and make sure that if a cutting bit does break, it doesn’t go flying out into the shop and maim someone.

This entire project was the work of several people and really shows why the Milwaukee Makerspace is a great place to build stuff/hang out with friends/play with power tools, etc…

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Step 1: Design it!  I used Solidworks and modeled each and every piece of wood that went into this project.

SW screen capture

Step 2: get the wood!  We made multiple trips to Home Depot, which thankfully is only 5 minutes away and we had great weather during the whole building process.  I love having a truck!  Fortune also shined upon me, as we had a new member join up right before I started this project, Jake R., and his help in building the wall was immeasurable.

Get the wood!

Step 3: Bolt the wood to the floor so we know where to put the wall, and then build some framing!

  4 - put in windows

Step 4: Put in the windows, drywall paneling and metal wainscoting.  We were very lucky to get seven pieces of slightly-smoked Lexan from one of our members, Jason H.  We also cut small holes in the ceiling tiles and ran 4 braces up to the metal ceiling trusses above.  This enclosure is ROCK-solid stable!  Thanks to Tony W. and Jim R. for helping with that!

When I went to Home Depot, I thought my truck could handle a 48″x 120″ sheet of drywall.  Not so much… one of their employees helped me split 10 sheets of drywall in half, in the parking lot…so I would later find out that I did not have drywall tall enough for the wall corner.  Hence the need for more “framing” so I could use smaller pieces.

10 - outer framing

The large cabinet that powers the robot arm is right next to the enclosure; I placed it outside to keep it away from foam & wood shavings.  However, we will need to have the programming pendant next to the machine every now and then….hence the need for 2 small pass-thru doors next to the cabinet.

6 - hole for mini-door

11 - outer door installed

 

 

 

 

 

 

 

 

 

 

I used doweling to help hold the door frame components together…..probably not needed, but it ensures a STRONG door!

16 - drilling door frames  15 - door framing 1

Again, hooooray for the Makerspace and all its tools! We have several LONG pipe clamps that came in VERY handy for gluing the door frame pieces together.

17 - frame glued up - 1

Here’s the outside of the enclosure.  The big metal control cabinet will go right here, hence the framed “mouse hole” in the lower right corner so we can pass the cables through from the cabinet to the robot arm.

13 - outer door and mouse hole

The same area viewed from inside the enclosure.

14 - inner door and mouse hole

Here’s the ginormous sliding door.  It’s mounted on a barn-door track-rail and supported on the bottom by two custom-made wheel brackets.

23 - finished door on track

Here’s how I made the wheel brackets.  I got two lawnmower-style wheels and bearings from Tom G., then Tom K. enlarged the center holes on the wheels on his Bridgeport mill so I could use bearings for smoother action.

18 - wheels in slot - 1

I figured on four carriage bolts for a super-strong connection to the door frame.

19 - wheel assembly done

This is the track and wheel bogies that hold the sliding door to the wall.

22 - wheels and track

Bolting the brackets onto the door was “fun”…I forgot that the very bottom of the door framing is two horizontal pieces, so the very bottom bolt had to go.  ’DOH!

21 - inside door frame 1

Here’s the final, assembled view.  You can see the robot’s control cabinet in the lower right corner.

Now that the fabrication is complete, we’re working on decorative ideas for all that blank-looking drywall.

24 - finished room!

Whenever I look at this finished project it feels like to took several months to get it up, even though construction only lasted about 2-1/2 weeks.

Thanks to Jake R., Tom G., Tom K., Tony W., Jim R., and Bill W. for their assistance with this project!

MegaMax Lives!

The video shows the last few layers of the calibration cube “printing” at 414% speed (according to my LCD display).

The Bucketworks 3D printing meet-up on 8/12 paid off big-time!  Gary Kramlich helped me debug a problem that was preventing me from flashing the firmware on the controller board for the MegaMax 3D printer.  After a few tweaks I was able to get it moving.

MegaMax 3D Printer

MegaMax 3D Printer

MegaMax 3D printer based on MendelMax but bigger and minus plastic parts.

This is my on-going project at the Milwaukee Makerspace.  It is a 3D extruded plastic printer with about 1 cuft build envelope.  I want to print life-size human skulls (among other things) from CT scan data.  The printer is made mostly from salvaged parts and materials so the cost has been very low.  When it’s finished it will have a heated 12″x12″ bed (13″x13″ if I can find an aluminum plate that big) and dual extruder so it can print in two colors.

I have learned a lot on this project- some things that work and others that don’t work so well, and how to use a milling machine to drill holes precisely and square the ends of the 8020 extrusion pieces used to build up the frame of the machine.

I could not have done any of this without access to the people, materials, and tools at Milwaukee Makerspace.  Every time I go there to do some work on this project someone says something that gives me new ideas for improvements to the design.   I frequently find materials and parts left for me on the machine’s cart by other members who know what I’m trying to do.  If you have a project idea find your local Makerspace and get busy- there is nothing that will get your creative juices flowing like being around a bunch of people with similar interests and different skills and experience!

Mechanized Cylindrical Sign Build for Parade Joy (Update 1)

The Milwaukee Makerspace has agreed to participate in one of Milwaukee’s finest traditions, the “South Shore Frolics Parade”.

The “South Shore Frolics” formerly known as the “South Shore Water Frolics” is a Bay View institution. The current celebration of summer & joy starts on Saturday July 16th at 11:00 in the morning with a parade leading to South Shore Park, after which there is a festival and a variety of activities including fireworks for the remainder of the weekend. The Frolics is an event that I have participated in as long as I have been alive, and it is a very integral part of my summer. Of course I was thrilled when the Makerspace agreed that this was a worthwhile use of our time and talents.

Our goal for Milwaukee Makerspace’s representation in the parade is to produce some electric vehicles, ride some previously produced power wheels racers, as well as present a unique parade float. 

Thus far the main work was completed by Tom Gralewicz who re-powered the Makerspace’s “pots of gold” (two electric vehciles that have a parade heritage) with new motor controllers. Now that we have two functioning platforms, we of course wanted to turn one of them into an 8′ mechanized cylindrical sign. (that will resemble a beverage container) 

The build on that commenced last evening. Here are some photographs from the madness & joy:

 

 

 

 

 

Matt N. always measures twice and cuts once. 

 

I don’t know how many times these guys measured, but they always made the right cut!

 

Here the team cuts the circular bases that will anchor the piece. In the background, there is a serious discussion about logicstics…or something. 

 

Matt G. shows us the pride that comes with making.

 

Kevin B. tests out the fit and finish of the first circular support on the vehicle platform.

So far so good! I can’t wait to see how this comes together!

Come and see us at the South Shore Frolics Parade!
Saturday July 16th, 2011
Parade starts at KK & Lincoln at 11:00am
Joy will be had by all!
If you consider yourself a Milwaukee Maker, you are welcome to walk the parade rout with us & represent making in Milwaukee!