Interlocking Parts & Tolerances in 3D Printing

Here at the Makerlab we get lots of requests to print objects that have interlocking parts. Some examples of these type of objects are meshed gears, built in axles or hinged boxes. These objects are really neat examples of what 3D printing is capable of, but there are many considerations to be made when designing and printing such parts. Here are some tips for designing objects that are meant to fit inside another piece or are themselves a number of interlocking pieces.

1. When In doubt, give as much room as possible.

When a machine such as a 3D printer is building an object, there are always going to be variations in what the design specifies, and what is actually printed, this is called the tolerance. Tolerance means the machines ability to get as close as possible to the designs specifications. Here is an example where a cube has been designed to be nested inside another cube.


The cubes on the left have a difference of .5 mm between the outer wall of the small cube and the inner wall of the cube it is nested in. As you can probably tell, these cubes are fused together. The cube on the right has a gap of 1 mm and the cubes are not at all fused together.

We have found that a 1 mm gap has been a safe number when building these sorts of objects, but it is not always easy to ensure this throughout the entire part. When you are making your first print of an object with these sort of interlocking parts, it’s always best to give it as much room as possible while still keeping the design function.

2. Give special consideration for holes in round fitted parts.

STL files, the type of file that any 3D printer uses to build objects, consist entirely of triangles that make up the geometry of your object. When design software is trying make a circle, in our case the kind that would be in a round fitted part, then it has to do so with triangles. As you can imagine, it has to make some compromises. When the design software makes these compromises, especially in the case of round holes, it will always choose the circle to be smaller rather than larger, as holes are easier to drill out, rather than made smaller.

Here is an example of a hole that has been designed without this factor in mind. The smaller hole has been designed for a 3/16 inch dowel to be inserted. As you might guess, the hole that has been printed is much too small for this to happen.


The hole on the left is scaled by a factor of 1.2 and fits the dowel perfectly. Unfortunately this number can’t be used as a rule of thumb for any hole, or even any printer from that matter. To make a long story short, between printer software, printer calibrations, and the various tools that are involved, your best bet is to make a few test prints that have the fitting that you want to make, and adjust your design as you find necessary.

3. Reduce Flow rate to improve spacing between parts.

In general, the software that will run your print has a good idea of how much plastic needs to be extruded from its nozzle to produce an object close to your specifications. As shown in the previous tips, this amount may be more than your design had specified, making the fitted pieces in your objects fuze together or not fit at all. In addition to the methods above, you can change the flow of plastic for the entirety of the print. In many cases this fixes some or all of the problems detailed above, without having to change your design. This is especially useful when you have downloaded a design that someone else has made and you are not familiar with design software.

This method of course has its limitations. Often, although the interlocking parts of your object now fit together, other parts of your object now no longer have the right amount of plastic fill. This can appear as features being under-defined, or top layers  showing holes.

by Corbett Larsen, Student Assistant for the Web and Emerging Technologies Unit at Albertsons Library


“History of Idaho Comics” presentation at Albertsons Library

Join local comic book artist Al Asker for his “History of Idaho Comics” presentation on Wednesday October 7th at 6pm in Special Collections and Archives on the 2nd floor of Albertsons Library. 

Asker is the leading authority on the history of comic books in Idaho and has given presentations all over the Gem State. He wrote an article for Boise State University's The Blue Review titled “The Wild West of Sequential Art: A History of Comic books in Idaho” (https://thebluereview.org/idaho-comic-book-history/) and an article for Idaho Magazine called “Tarzan Loves Idaho” (https://www.idahomagazine.com/article/tarzan-loves-idaho/). He is the editor and publisher (and sometimes writer/artist) of Idaho Comics Group, the purveyor of the officially licensed Tarzan and the Comics of Idaho anthology and Idaho Comics.

Asker’s presentation coincides with the Idaho Comics exhibit currently on display in the Library. The exhibit feature selections from Boise State’s collections including works by Dennis Eichhorn, Jay O’Leary, Shanae Lavelle, Al Asker, Randall Kirby, Scott Pentzer, Allen Gladfelter, Jon Kiethley, and Todd Clark.

Special Collections and Archives maintains a growing collection of comic books, graphic novels, zines and small press publications by Idaho artists, authors, and poets.

Everyone is welcome to explore the collections in Special Collections and Archives, and Asker’s presentation is free and open to the public.

For more information contact archives@boisestate.edu.


Campus Read @ The Library 2015-2016

This year’s Campus Read selection is A Deadly Wandering: A Tale of Tragedy and Redemption in the Age of Attention by Matt Richtel. It’s available in print http://boisestate.worldcat.org/oclc/889949815 or electronic formats http://boisestate.worldcat.org/oclc/890913503 at Albertsons Library.

If you come across this stuffed car in the library stacks, bring it to the Circulation Desk for an entry into a drawing for a $10 Starbucks gift card. Find the car as many times as you can -- entries will remain in the box till the end of the scheduled drawings. The drawings will take place on 10/16, 10/30, 11/13, and 12/4. Winners will be notified via email, and need not be present to win.

Good luck!
Access Services Crew


Cinema Night @ Albertsons Library

"Rashomon (1950)" by japanesefilmarchive is licensed under CC BY 2.0
The Cinema Society at Boise State (CSBS) is a student group interested in bringing the world of cinema to Boise State. Each month, in coordination with Albertsons Library, this student club will show a different film from around the world accompanied by optional readings and discussions hosted by Boise State students and staff.

The goal of these readings/discussion is to provide a platform for students interested in the culture, theories, and analysis of filmmaking. Attendees are not required to have any knowledge of films or filmmaking in order to join in our film community. Love talking about movies with your friends? Come hang out with us. A get-to-know-you session will be held before the movie so come on in and enjoy good company, fascinating conversation and snacks.

Cinema Night will start at 6pm in library room 201C. Here’s the schedule for fall semester:

Thursday, October 1st: Following, directed by Christopher Nolan
Thursday, October 29th: Rashomon, directed by Akira Kurosawa
Thursday, November 19th: The Spirit of the Beehive, directed by Victor Arice
Thursday, December 10th: The Tin Drum, directed by Volker Schlondorff

Learn more about the club and the movies that will be shown with this guide http://guides.boisestate.edu/cinema.

Shelly Doty & Elizabeth Ramsey,
Albertsons Library 


Meet Amy, one of our new librarians!

Hello! I’m Amy James and I am the newest Assistant Professor/Librarian here at the Albertsons Library. Not only am I brand new at Boise State, but I am also new to this area. I was born and raised in Michigan (just outside of Ann Arbor—Go Blue!). I have lived in Michigan my entire life, so coming out to Boise was a huge adventure for me. My husband, Grant, and our cat, Sutton, were excited to come along for the ride (well…not so much the cat—but that’s another story!).

I received my undergraduate degree in English Literature and my Masters in Library and Information Science from Wayne State University in Detroit, Michigan. As a graduate student, I concentrated my coursework on academic librarianship and emerging technologies. When I graduated in 2012, I worked as a librarian and branch manager for one of the Genesee District Library’s 18 branch locations in Flint, Michigan. But, I always wanted to work in academia…so I decided to continue to pursue academic librarianship. About a year later I ended up with a tenure track Emerging Technologies Librarian position at a small private Christian Liberal Arts College in south central Michigan called Spring Arbor University. SAU was a great place to launch my career as an academic librarian. I was there for two years before ending up here at Boise State.

My position here focuses mostly on instructional design for information literacy sessions. I also help to incorporate technology into library curriculum, create library instruction video tutorials, and help students and faculty with their information needs! I am currently serving as the liaison to the Organizational Performance and Workplace Learning (OPWL) department.

Okay, okay…so besides working, I love to run. I have enjoyed running through the foothills and on the greenbelt since arriving. I am excited to run in the City of Trees Half Marathon here in Boise this October. I also love hiking, biking, kayaking, reading, drinking coffee…lots of coffee, learning about different cultures and trying new foods! Please stop by the library and say ‘hi’ if you get a chance—I’d love to meet you!


Register for the Openness Symposium

Amber Sherman, ScholarWorks Librarian at Albertsons Library has organized an Openness Symposium devoted to principles of Open Access, and the tools and resources available to help you incorporate Openness into your teaching and learning. The Symposium will be held September 30, 2015 in the SUB, Jordan Ballroom A.

Speakers will include:
  • 9am: Dr. Chris Haskell, Boise State EdTech professor, will demonstrate Open Badges
  • 10am: Leif Nelson, Interim Director of Learning Technology Solutions at Boise State will discuss teaching students about free and open content online
  • 11am: Annie Gaines, University of Idaho Scholarly Communications Librarian, will present on Open Textbooks
  • 1-4pm: Betsy Russell, Boise bureau chief for The Spokesman-Review, will lead a workshop on Open Government: Public Records and Open Meetings.
The symposium is a pre-conference offering at the Idaho Library Association's annual conference, which is being held at Boise State this year. Registration is open to the community; register for the symposium at http://idaholibraries.org/conferences/ila-annual-conference/.


Library Closed on Labor Day

The university and the Albertsons library will be closed on Monday, September 7th for the Labor Day holiday. Regular library hours resume on Tuesday, September 8th.

Have a safe and happy Labor Day!