Synchronizing 3D Printing Hosts with Dropbox

I use several different macs with Repetier-Host to control my PrintrBot Jr. and I’m tired of having to manually synchronize my Slic3r settings among each of the computers. Dropbox is great system for sharing files among many computer automatically and I’ll show you how to apply it to fix the configuration synchronization problem!

Continue reading

Posted in 3D Printing, Projects | Leave a comment

Johnny 4 – CMU MOBOT 2012

This year I entered the 2012 CMU MOBOT  mobile robot competition. I had a nice finished physical robot and a capable vision system but I didn’t finish in time to get it working well. Here I will document my entry for this year and discuss my plans for tuning the vision system for next year.

Me holding Johnny with his makeshift light shield before the second round of the competition. Follow below for more details.

Continue reading

Posted in MOBOT, Projects | Leave a comment

3D Design Toolflows

Having bought my Printrbot and printed some previously made models using the instructions from the Quickstart Guide, I would now like to explore the toolflow a little bit so that I can do things like resize models or even design new models myself.

The printrbot wiki breaks down the design process into several steps: CAD (Designing), CAM (Slicing), CAM (Previewing), and CAM (Printing). These seem logical to me so I will do that too.

CAD (Designing)

I have tried several CAD tools for 3D modeling: AutoCAD, Blender, OpenSCAD, Sketchup and Netfab. Netfab and Sketchup seem really great but the evaluation versions limit access to geometric transformations like combining or differencing models. The cost to purchase expanded versions starts pushing into the cost of purchasing a student license of a more powerful professional class modeling tool. That said, Netfab seems really great for fixing models which throw “model is not manifold” type errors or for performing scaling. Blender looks nice but coming from a mechanical design background I found it’s interface non-intuitive.


AutoCAD is a professional class design tool that is massive overkill for hobbyist use so I have sought out similar alternatives. The powerful features allow accurate modeling and fast rendering to allow a combination of strict mechanical accuracy while providing facilities for snapping to edges and centers to accelerate assembly of sub-parts without resorting to mathematical calculation. I have been looking at Solidworks and RHINO as alternatives with similar benefits without the enormous (complex) feature sets that are not necessarily useful to a typical 3d printing enthusiast (and of course lower cost). My University provides access to Solidworks licenses so I will update this post if I find it a good alternative.


OpenSCAD is a script-based modeler. I enjoy the “programming” nature of OpenSCAD as it allows high precision when forming geometrical models. Creating accurate mechanical descriptions is simple and parametric features facilitate flexible resizing and customization. STL files can be exported and sent off for slicing.

There are some drawbacks to OpenSCAD. First, it’s rendering engine is super slow and I’ve had trouble when importing large meshes, rendering even medium size meshes can take tens of minutes, and I’ve also observed crashing when exporting STL files. Second the precise numerical description and slow rendering feedback makes this tool a poor choice for “free-hand” assembly of imported meshes for “artistic” effect.

CAM (Slicing)

I have only tried one tool for slicing: slic3r. I have tried two different versions though because Pronterface and Repetier-host ship with versions 0.5.3 and 0.9.4, respectively. I think that slic3r 0.94 is a large improvement. I really like how it separates the configurations for the printer and filament from the slicing parameters (speeds, shells, fills). A great resource for learning about these parameters and beginning to tune a printer has been provided by “Rich” here. In particular I found the newer versions of slicer improved my models with substantial overhangs.

The other popular tool is skeinforge. I don’t know much about it because I’d heard that the number of configurations is more than a beginner to 3D printing may want to learn at first. Maybe I will revisit this if I see issues in the future.

CAM (Previewing, Printing)

I’ve tried several graphical interface tools for previewing and controlling the printer on both Mac and Windows: Repetier-Host and PrintRun’s Pronterface.


Repetier-Host is my favorite slicing and printing interface software that I have tried. The Mac version of Repetier-Host ships with a more recent version of slic3r than PrintRun and I have discussed the advantages of the newer version above. The actual user interface is less intuitive than PrintRun and I wish the authors of Repetier-Host would take some design cues from them. The USB drivers used by Repetier-Host on my Mac have been very reliable.


I’ve also used PrintRun’s Pronterface and I’m very happy with it. The simple manual control and home finding interfaces make calibrating the end stops really easy. I initially chose it because that was recommended by the PrintrBot Getting Started guide. I had issues with the Mac version not using a good USB serial driver and had to switch to running the Windows version in a VMWare VM: that worked great. I would definitely recommend it at first but still prefer Repetier-Host.

The other commonly used tool is ReplicatorG. I don’t know much about it other than most people who use it slice with Skeinforge.


This printer is the funnest but figuring out which tools to use is not very fun so I hope that my experiences will help save you time in choosing. Modeling has not been a priority for me but I’m very hopeful that Solidworks will meet my expectations. Slic3r seems to be getting better with time and I hope to stick with it because of it’s relatively simple configuration interface. Repetier-Host is probably the way to go for printer control but it has limitations. You may notice that I’ve left firmware choices completely out of this discussion, that’s because I’ve been so overwhelmed by the other choices that I haven’t even gotten there yet. The choice of firmware can greatly affect output quality and speed but the default shipped with my PrintrBot — Marlin — seems pretty good. This whole space seems to be rapidly evolving so I’m sure I need to keep looking out for what’s on the horizon.


Posted in 3D Printing, Projects | Leave a comment

Portland Marathon 2012

Last weekend I flew to Oregon run the Portland Marathon. My friend Laura was also running the race and we both had a great time. The course started downtown and looped up over the St. Johns bridge and then back down the east side and over the Broadway bridge. My goal time was 4:30 but I finished the race in 4:55:39 tag time (5:09:16 gun) at a pace of 11:17. Continue reading

Posted in Running | Tagged , , , | Leave a comment

Printrbot Jr. First Print

I got through most of my unboxing and made my first print! It’s a Mr. Jaws by Mahoney.


It didn’t turn out great. The bottom broke off when I pulled it off the bed. I don’t care though. The second one turned out great!

Posted in 3D Printing, Projects | Leave a comment

Printrbot Jr. Unboxing

Last weekend my friend Matt picked me up a Printrbot Jr. while he was working at the Maker Faire in New York City. I’m super excited to get involved in the 3d printer. There were no instructions included in the box or on the printrbot website. I’ll use this post as a scratch for answering my initial questions and then probably follow up with posts about getting the Printrbot Jr working.

Continue reading

Posted in 3D Printing, Projects | 1 Comment

vmitools Setup Instructions

For my thesis work I study virtualization and I was interested in trying out the vmitools project with a Windows 7 guest. Unfortunately I found the installation instructions a little difficult but I eventually muddled my way through. Below are my instructions but comment up if you need any clarifications! Continue reading

Posted in Projects | Tagged , , , | 1 Comment

Steelers 5K 2012

Yesterday Matt Beckler and I ran the Steelers 5K on Pittsburgh’s North Shore. I particularly like the Steelers 5K course because you run out along the river and back to the stadium past the Warhol museum and the Pirates Baseball stadium. I mostly took it easy because I ran a 20 miler the day before: 27:43 chip time (8:56 pace).

Also you can buy ribs after the race at the bbq cookoff.



Posted in Running | Leave a comment

Brookline Breeze 5K

Yesterday I ran the Brookline Breeze 5K. The race was an out and back course with some pretty substantial hills. There was no starting line chip sensor so no chip time, only starting gun time, my guess is that I had about 10-15 seconds getting to the line. I ran a bit slower than the Father’s day 5K, which I attribute to the rolling hills and heat not having Patrick breathing down my neck, at 25:23 (8:11 pace).


The shaved ice guy was running the race instead of making frozen treats, so I had to settle for Rita’s and pizza.

Posted in Running | Leave a comment

DIY Oculus VR Mockup

Today at work we got real excited about the Oculus VR Kickstarter. We argued about whether the resolution was sufficient or if it would look like taping a pair of gameboys to your face. Ending the argument required a “Virtual” Oculus VR paper mock up.

The specs given for the E3 demo screen was 1280×800 display split over both eyes (640×800 per eye) and 110 degree diagonal field of view per eye. Assuming that the x and y dot pitch for the display are equal I surmise that a 7″ diagonal 640×800 pixel image 4 inches from my eye ought to recreate the oculus visual experience.

Print out your own simulator and check it for yourself!


Posted in Toys, Uncategorized | Leave a comment