Thursday, March 21, 2013

RFID Door - 1 of n

Often times an office finds the struggle of granting access to rooms without jeopardizing physical copies of keys. These struggles can be easily overcome with technologies such as facial recognition, finger print recognition, bar codes, radio frequency identification, and much more.
Here at I Heart Engineering, we felt the need to have awesome badges fit our daily attire, where we can have both style and access to our offices without the need of weighty keys by building a robot door.

Using the Arduino Ethernet along with Adafruit's PN-532 RFID/NFC Breakout Board, the badges were a mere grasp away from reality.

A circuit involving a relay powering 12vDC@1A to a RCI S65 electromagnetic door lock. The circuit was mounted onto an Arduino Protoboard alongside a circuit connecting the PN-532 breakout board to the Arduino.

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After the circuit above was tested on a breadboard, it was then put onto a protoboard and the Arduino set was completed. The speaker and variable resistor were used for key tones, hooked up to pin 7. This is not necessary, but it helps when debugging.

Left: Arduino Ethernet   Middle: Protoboard w/ circuit   Right: PN-532 Breakout Board
Bottom-side of the protoboard and the PN-532 breakout board
Put together into a neat package, ready for mounting

Now that the Arduino package is assembled, mounting of the rfid reader takes place. Using some masking tape and wire, a rough mounting test was enacted.

Test of mounting positions within the wall

A square was cut out into the door frame, and the RCI S65 was installed into the door frame, then hooked up to the Arduino protoboard.

Held into the aluminum with a series of screws, the lock became a neat addition to the door frame

Now we can print out our badges, put on an RFID tag, and program the UID and data into the Arduino.

Laminated identification card

Future plans include:
  • Ethernet support, adding a control panel.
  • Logging of cards (usage, amount of usage, etc)
  • Time frames
  • Proper mounting plate
  • Genuine People Personality
Arduino code is available on the Github Repository. Stay tuned for more features.

Wednesday, March 20, 2013

Open Manufacturing: Laser Cut Packaging Solutions

I don't believe anyone can argue against the merits of attractive and functional packaging on a product.  Sometimes, the way a box looks may even be enough to persuade a potential customer.  There are thousands, maybe millions of unboxing videos posted to Youtube. Great packaging delivers its contents safely and gives its consumer a reason to smile.  But, we aren't here to discuss the merits of aesthetically pleasing packaging.  This is a post about building packaging that protects the integrity of the product being shipped and how to prototype that on your laser cutter.

At I Heart Engineering, there have been a few cases in which a TurtleBot 2 was damaged during shipping.  One problem is that we currently do not manufacture our own boxes.  However, what we can do is come up with our own structural packaging solutions to protect our products working within the constraints of "stock" boxes acquired from elsewhere.  The first effort was directed at protecting the Kobuki base of the TurtleBot 2 during shipping.  Currently, the shipping department modifies the already existing Kobuki packaging to fit inside of a commonly available box and uses foam inserts to protect the plates. Our question now, is how to create support for the Kobuki base using our digital manufacturing tools, or if you prefer, the Epilog Helix Laser.

First, we need to understand the process of creating a "box."  Well, the unfolded form of packaging is referred to as a net.  This closely resembles the term flat-pattern which is used in sheet metal work.  Some techniques used by sheet metal workers can be applied when making your net out of certain materials.  In our case, we are limited to the use of 24" x 18" C-Flute Corrugated Cardboard which provided a few interesting issues.  Before you begin to CAD your net or flat-pattern, you should create a scale model of what you intend to build out of card stock. I recommend reading Paul Jackson's Structural Packaging Design Your Own Boxes and 3-D Forms for a full understanding of that process. The end results produce something similar to the picture below.

At this point, it is now okay to create your net in a CAD program of your choosing.  I should note that there is software available designed for this specific purpose, but it is not Open Source nor does it seem to be made for work with laser cutters and is geared toward industrial designers.  Parametric CAD suites like Solid Works and Creo [Pro/E] meet our needs in addition to tools such as Inkscape, GIMP, and Corel Draw.

Folding is key, how the material folds and the method of folding make all the difference in the actual design of your net. There are sheetmetal formulas for calculating the proper lengths of your folds legs.  However, in the case of cardboard and a laser cutter as a tool, things don't quite work exactly the same by our experiments.  Sheetmetal work has a principle of the neutral axis, that is, the axis between the tangent points of  a bend that is neither compressed nor stretched. In those formulas, this neutral axis is represented in what's called the K-Factor and Y-Factor [used in CAD software usually multiplying the K-Factor by number.] For this cardboard, the K-Factor is effectively 0 as all of the material compresses or stretches when bent at a 90deg angle.  This means that bend radius on the inside and outside of the bend are very close to 0 for all intents and purposes, but you still have to account for the material thickness when designing the actual folds in the net.  In other words, it is a good idea to offset some of your fold lines by some of the material's thickness to get a better fit.  I also recommend that you shorten the lengths of your tabs to avoid fold interference and using corner reliefs everywhere applicable.

In terms of cutting the net and fold lines, Vector cutting the entire net is your best option for rapid and mass production.  Using the raster feature to whittle away at the fold line would consume far too much time to make it useful in production.  Also, because the cardboard is corrugated, it doesn't provide any actual advantage at all in this situation.  There was no point in trying to vector the fold lines on low power to mimic a raster for that reason.  Instead, I opted to test various methods of vectoring the fold lines from replicating the SNIJ Hinge to dashed lines of various lengths.  I found that for our purposes a series of dashed lines similar to perforation were most effective in getting the cardboard to fold in a suitable manner for our purposes.

After many iterations, a version was made that is sufficient for packaging our TurtleBot more safely than it was before.  I will continue to iterate on it's design to make it even more effective, but this version was found to be sufficient.  Also, it would be greatly appreciated if anyone knows where we can purchase E-Flute corrugated cardboard in 24" x 18" sheets.  I have reasons to believe that it may be the most suitable size for this operation.

Here is a link to the net posted on Thingiverse:

Wednesday, March 6, 2013

Open Manufacturing: A Home for the Beagle Bone Part 2

The 80/20 rule supposes that 80% of your results comes from 20% of the work you did. It has further been argued that the last 20% of a project is the most difficult and important. One can understand how these two ideas tie together and they indeed have some sort of merit. Those last few stages in preparing to bring a product to market/project to close are critical because the details are important. The last post ended with the Beagle Bone Case being at the 80% stage. The design language and major features have been settled. Now is the time to take the case and sort out imperfections, adjustments for changes in new/changed constraints, cost effective production and so forth. Basically, the iteration and revision of a design in the stages prior to being salable.

In this case, additional feature requests were made that changed core parts of the design. Room needed to be added to accommodate an additional shield or board, as well as any wiring. This resulted in the case being expanded 10mm on the sides and increasing the height by 18mm. Time was also taken at this stage to refine existing features. The SD Card port was enlarged for easier access and the press-fit to close system improved alongside adding Greebling to the case top. This version of the Beagle Bone Case was then 3D Printed.

Unfortunately, there is a problem with the case as designed; it takes over 5hrs 30min to complete in addition to suffering from curling due to its new size. Internally, a design that takes longer than 180-225min to 3D print is no longer affordable to offer as a product. The time removes full 3D printing as an option for manufacturing after including the cost of running the 3D Printer and man power.

Highlighting the curling on the edges. 
MDF as Case Top in Composite Test
Perhaps the design could be reworked, turning the case into a composite of materials? Doing that would reduce the print time, lowering the plastic used. So, I removed the roof of the case and instead opted to laser cut a top that would glue into place. The idea here being that the roof layers generated by Skeinforge take much longer to complete than the layers for the walls themselves. But while the print time was reduced, it was not reduced enough to justify offering the case as a salable product. That is not to say the Beagle Bone Case would be a poor product, it is just outside our current manufacturing capabilities to offer it as a product made and sold by I Heart Engineering.

Engineering asks that problems not only be solved by building something, but building it in a manner that is practically useful to all involved parties. This lead to the decision that the final version of the 3D Printed Case can still be offered to the community via Thingiverse to do with as they please and a new method of housing the Beagle Bone on the TurtleBot must be created. Another alternative would be to outsource the handling of the 3D Printing to a partner like Shapeways or travelling down the road of injection molding with services like Protomold. The injection molding route may yield the best results, but it comes with it's own requirements so the case will enter another lengthy design phase. In both situations, crowd sourcing initial interest would be the smartest way to judge whether its a worthwhile endeavor.

To reach this point, over 6 versions of the Beagle Bone Case were created, not including any of the test parts used. The project spanned 10 regular working days. More than 24 hours of actual 3D Printing Time were logged.
Overview of various case part iterations
Where the Project is Now

Testing Inserts Effect on Acrylic
Although the Full 3D Printed Case as a salable product was not achieved, the product idea itself does not die. The plan now is to scale back the design and focus of the simplicity of the intended function. We need a way to mount the Beagle Bone to the TurtleBot. The simplest and most effective way to achieve this is to create an adapter for the Beagle Bone to the TurtleBot. This can be achieved with a formed plate containing mounting points for the Board and TurtleBot. While not as consumer market friendly as the full case, it serves the core functionality, is within our current manufacturing ability, and is useful to our current and future customers.

Fortunately, we already have all the necessary dimensions and constraints on hand due to earlier work. Because this makes creating the adapter a much faster process, there was a realization that we can make this adapter plate universal between several development boards at once. What started as an idea to build cases for boards that had universal mounting points, is now a simple adapter plate that works with the Beagle Bone, Raspberry Pi, and Arduino suite of Boards.

The adapter is made of 1/4" thick Acrylic featuring 16 Brass Heated Inserts for 4 different hole patterns that comfortably accommodates the Beagle Bone, Raspberry Pi, and Arduino suite of Boards. It comes ready with Board Adapter Plate, (4) M3 1/4" spacers, (2) M2.5 1/4" spacers, (6) 10mm M3 socket head screws, (2) 10mm M2.5 socket head screws, and (4) 10mm M4 thumbscrews.

Pre-Oder your TurtleBot Universal Board Adapter here [Lead Time: 1 week]: