3D Printing Update

Finally Finished!

Wow, it took me almost two months to build, but I finally completed building my 3D printer from PrintrBot! Two weeks ago, I put the finishing touches on it by calibrating the motors and attempting to level everything out. [The reason I'm not writing until now is because we've been focused like a laser for the last two weeks on working toward our PLTW program's 5-year re-certification, which we achieved on Friday.]

3D Printer, complete

Along the way, I had to troubleshoot various problems (most of my own making):

• not seeing an asymmetric hole pattern until it was too late
• one misaligned hole
• limit switch wire accidentally torn off
• putting the wrong gear where a pulley-belt system should go
• motors moving in the wrong direction
• a pulley-belt system that was slipping over the motor axle and not moving the extruder along the x-axis the way it should
• incorrectly feeding the plastic material into the extruder

To solve these problems, I used my own engineering knowledge accumulated over the last six years, another teacher’s expertise and tools, and PrintrBot’s online videos and help fora. As mentioned before, I feel that having made these (and many smaller) mistakes and learning how to fix them has really given me a better understanding of the gears, pulleys, bearings, ball screws, nuts/bolts, switches, motors, and wiring that go into making my 3D printer. I also think I have a more concrete understanding of how 3D printing works, and hopefully will be able to fix my printer if it were to break or need improvements.

3D Printer close-up

My First Print

I took (PrintrBot founder) Brook Drumm’s recommendation for my first print, the “Mr. Jaws” shark figure.

The program that runs the printer, Pronterface, estimated that it would take 45 minutes to complete the shark.

My computer screen, showing Pronterface with machine controls, shark figure, & program

On my first try, I had trouble getting the ABS plastic to stick to the printbed, so I increased the bed’s temperature. Here’s some filament that extruded but did not contribute to the shark design:

ABS Plastic, extruded

After a few more minutes of heating up, this time it worked!

Here is the first-layer outline of the shark:

Outline done!

Here you can see that it is starting to fill in the outlines:

And here it is after completing approximately three layers (one filling in the shape up and down, the next left and right, and so on):

I figured I would have some time to grade papers while waiting for the print to finish, but instead I was mesmerized by the printing.

Starting to get some depth to it

It was also cool to see that the program works using the same G&M codes that I teach my manufacturing engineering students to operate the CNC mill:

The G&M code program that will control the 3D printer and make a shark

It built up slowly, layer by layer.

Almost done!

In thirty minutes, the shark was finished.

The Completed Mr. Jaws

You can see some errors, like the strands between fin and tail where the filament turned a corner but the corner didn’t stick. And you can see the granularity of some of the layers is not as fine as on a more expensive 3D printer. But, all in all, for something that cost only a few hundred dollars, and that I built myself, I’m very proud of what it did!

Shark Attack!

3D Printer

As I have discussed before, 3D printing is all the rage in engineering and manufacturing circles. The price of 3D printing has come down enormously in recent years: from about eight years ago, when most 3D printers were in the $15,000-20,000 range, to now, when you can find them as cheap as $400! With this, there has also been an explosion of 3D printing services, where you can send a 3D model and have them print it out for you.

Earlier this year, I bought for my classroom a PrintrBot. It is a LaserCut, version 1, so with the teacher discount provided, my cost was less than $400.

I have been slowly building this 3D printer over the last five weeks (most days I don’t get any time to work on it; some days I can spare a half hour; every once in a while I can devote a few solid hours). I wanted to share my progress here.

As of Monday, I had completed the base structure, including the baseplate on which an object will be printed and the means by which it will slide forward or backward along the y-axis:

PrintrBot Base

Monday afternoon I completed the 3D printing apparatus (the extruder) that will melt the ABS plastic and deposit it in the right locations to create a three dimensional object:

PrintrBot Extruder

The last two afternoons, I have made quite a bit of progress on the bridge that will move horizontally and vertically (x and z axes), carrying the extruder to where the part will be printed:

PrintrBot Bridge, Monday afternoon

PrintrBot Bridge, assembled, Tuesday afternoon

PrintrBot Bridge with Extruder, Tuesday afternoon

In building it, I am coming to understand more about 3D printing, about mechanisms like gears and pulleys, about fitting things together like a puzzle, and about nuts and bolts (I even learned of a store called A&A Bolt and Screw near my school when I had to find a 3″ #6-32 bolt). I have had my share of errors along the way – for example, I didn’t notice the base rectangle was asymmetrical (by one small hole) until well into building with it, so I got to use  a scroll saw and a drill to correct my mistake rather than unscrew and untie all the pieces I had already built up. I also accidentally tore off one of the wires on a limit switch, so I asked one of the students learning how to solder in their Digital Electronics class to reconnect it for me! But I’m really enjoying all the work that goes into creating this 3D printer. And I can’t wait until it’s done, when both I and my students can see it in action!

I’d say I am 85% done with building the PrintrBot. After it is built, I will need to install software, calibrate the motors, and possibly troubleshoot any problems. Hopefully I should be done, and able to print out a part, by next week!

Ups and Downs

This comes from a conversation I had recently with a college friend. I thought I’d share my personal reflections on teaching in the below message more widely.

I’ve transitioned slowly over the last seven years, from teaching all math, to half math / half engineering, to all engineering this year for the first time. Over the last six years that I’ve been involved on the engineering side of things, I also helped build, grow, and strengthen the engineering program at my high school.

While there have been some issues with students at my urban public high school (few do any homework; it is challenging to motivate all of them to do engineering and math; poor attendance; one kid swung at me last year with scissors), these are minor compared to my frustrations with administration and with the direction teaching is headed in.

To make a long story short, my dissatisfaction comes largely from dealing with a dysfunctional school administration and an outright evil district administration.

But also, more generally than my own local problems, and tying in perhaps with the national mood, I do believe standardized testing, and the more recent trend to hold teachers ‘accountable’ for student gains in standardized testing, is lessening the creativity and fun of teaching that I really enjoyed five years ago.

This is not to say I don’t still find fun in the job. Last week, I really loved teaching a group of three students some programming and number base conversions they need to compete in a virtual robot maze competition coming up soon. And a few days ago I was talking to a student about the types of bridges for more than an hour and that was great. And a month ago I got to really geek out with another math teacher as we worked together to figure out an explicit formula for the number of triangles of all sizes in a triangle subdivided into smaller triangles with n on a side. And yesterday I brought a group of students on an engineering field trip that was awesome! [Another example not in the original message: the pride I feel in what my fall semester manufacturing students accomplished.]

But still, I am feeling more and more frustrated. I’d say I do enjoy teaching still, but not all the b.s. that comes with it.

Anyway, only one more day until spring break! Yay!

It’s Pi Day!!!.

It’s that time of year again: spring is almost here, and you can almost feel a warm mathematical breeze on the air. It’s…

Pi Day!!!.

Since the number pi (π) is approximately 3.14, and today is 3/14, today is sort of a mathematical holiday. (You may have noticed that I’ve included approximately 3.14 exclamation points above and in the post title!)

I started my celebration this morning with some coffee iced with pi-shaped ice cubes:

Pi Iced Coffee

Additionally, I noticed today that I follow exactly 314 people on twitter:

Hey look – I’m following about 100pi people!

(OK, I admit, I followed one new person today to get that to work out )

Today, in addition to celebrating both the number pi and all sorts of mathematics, it’s time to start getting ready for the best pi day celebration of our lifetimes, which will be held in two years: 3/14/15 at time 9:26:53. This will be a much more accurate representation of pi than we celebrated just over an hour ago (at 3/14 1:59). Though perhaps we missed an even bigger party four centuries ago on 3/14/1592 6:53:58.

A few notes, links, and cool things for this pi day:

• Math geeks can even talk about their mania for this amazing number in the form of a palindrome: “I PREFER PI”!
• It seems that pi day is getting more popular: Companies like Oreo and GE are getting in on the action!
• Check out this video, where a few people use actual pies to calculate pi (from http://www.numberphile.com/videos/pie_with_pies.html) :

Lastly, I hope you all can read (and would agree with) the following t-shirt, tweeted by NSBE:

Picture from NSBE

Factory System

This year I wanted to challenge myself and my students by undertaking possibly the most ambitious project I have ever taught and they have ever done.

In previous years the final Computer Integrated Manufacturing (CIM) project had been handshaking between the robot arm and the CNC mill. Last year we got bogged down in building the little Lynx robots, which took three weeks out of our curriculum, and so we didn’t get to any final culminating project. The CIM final project in the curriculum has changed and is now a factory system on a small scale.

Having small classes this year, and having the equipment of a large robotic arm (which is no longer required by PLTW but was when I started teaching six years ago), I figured we might as well do our factory system on a large scale!

Factory System Setup

So I set the task for my students of recreating a factory inside the classroom–tying together all the topics they have learned about in CIM into one project that integrates computers into every aspect of the manufacturing process, from start to finish, in a multi-machine factory setting. They had to pick and design a product that we were capable of manufacturing in my lab, go through the CAD-CAM-CNC process to model and machine the product, then set up a closed-loop feedback system (i.e. handshaking) between the robotic arm and the CNC mill so the entire factory system could operate seamlessly with the robot placing the raw material into the mill and retrieving it after the mill was finished. We were on our way to mass production!

Unfortunately, we bit off a little more than we could chew / we took a step longer than our legs. In large part due to student absences, neither class was able to complete all the objectives outlined above. However, they still did some pretty cool stuff.

One class picked a key chain as their product, shown here with a machine toolpath around it. They planned later to inscribe ‘Patterson High School’ on the key chain.

Keychain with Toolpath

The other class planned to manufacture an iPhone cover:

Phone Cover 3D Model

Due to the deadline fast approaching, along with some ill-timed software glitches, the second group decided that they would not be able to create the toolpath for the phone cover, but they did want to finish setting up and programming the rest of the factory system. So they recycled one of their earlier CNC milling programs that would just carve out initials, and got the robot and mill to handshake successfully, manufacturing a block with initials instead of the phone cover. Check out their video at the link below:

http://www.schooltube.com/video/ef054cce27ab4abbbe1f/Demonstration%20of%20Factory%20Cell

Though we didn’t make it all the way there, I am very proud of what my students accomplished, and happy that we tried this ambitious project!

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Happy 12-12-12 Day!

Perhaps it could be called duodecimal day if you look at the numbers, or ternary day if you look at the digits. In either case, have a wonderful 12-12-12 day!

After being treated to a dozen similar days over the last few years (here, e.g.), we must now alas face a desert stretch of a few weeks longer than eighty-eight years until the next time the month, date, and year will all align.

Though at least we’ll have 11/12/13 next year, and 12/13/14 the year after. And of course the best pi day of our lives on 3/14/15 (at 9:26:53am). So I guess, even without repeated numbers, we still have a few good years ahead of us .