Now that I’m free of final exams – and not a small amount of unpacking – I can write a bit again!  To start, about three weeks ago this got published.  It’s the first of two pieces I was asked to do for Make’s 3D Thursday series, and I was excited to share what we’ve learned from running that many machines with such a high throughput at the Invention Studio.  The second piece should be up in a few more hours, and covers a bit of a different subject.  Additionally, I hope to have another big post on what I’ve been doing with the printer-formerly-known-as-HPRINT online soon.

In the first piece I wrote, I got some comments regarding what I believed to be oversights and deficiencies in the design of MendelMax-style printers.  Without further ado, here’s a list of the aforementioned issues:

  • Insufficient Constraints: In some design variants mechanisms are left underconstrained and are able to move excessively, causing artifacts to occur in prints.  Some machines have under constrained Z-Axis screws, while others may have under constrained X-Axis carriages and beds.  Taking care to ensure sufficient constraints exist on a machine is critical to keeping undesired movement from occurring, impacting print quality.  In MendelMax designs, it’s usually the Z-Axis screws that have this issue.
  • Excessive Constraints: In other cases, MendelMax variants were made with care to avoid issues that arise from insufficient constraints and instead went too far.  More than three constraining features is usually excessive for a plane, particularly if two are hard constraints with no allowance for movement and the third is able to make up the difference with a small degree of movement.  This can get tricky because you can have more than three constraints, and they can all be capable of small amounts of movement or deformation individually;  care must be taken to only allow this movement in certain directions which are irrelevant to the positional accuracy of an assembly.  Most often, this pops up in having too many bushings, bearings, shafts, and very occasionally nuts or bolts.
    In MendelMax designs, this can occur in all of the above areas depending on the machine; in AO-101s, I believe some of the issue crops up most frequently in the nuts for the z-axis screws and the leveling screws for the bed.
  • Ill-Planned Drive Systems: Many printers use very small neoprene belts for their drive systems strung over long distances with tensioners included as an afterthought, if they are included at all.  This leads to a great deal more backlash than would otherwise be present in machines which could be avoided by using wider belts across shorter distances with spring tensioners, or at least printed clip-on tensioners (and if you wanted to splurge, fiber reinforced belts that don’t tend to stretch as much).
  • Poor Material Choices: Some hot ends are made entirely of aluminum; while this is great for thermal conductivity, this is bad for both assembly and disassembly.  Aluminum parts have a tendency to bind as they rub against other parts made of aluminum, sometimes badly enough that they’re impossible to separate without destroying both.  Switching to materials that either bind less or more easily slip against each other can reduce this annoying occurrence.  In a similar vein unrelated to MendelMax machines, anything using wood as a main structural element will change shape ever so slightly under varying humidity; this means calibration may need to occur much more frequently than machines that use metals and plastics for their structure.
  • The Combined Effects of the Above: Let’s say you have an under constrained Z-Axis screw and shaft setup and over constrained nuts for the Z-Axis screws.  This means the screws both wobble slightly as they rotate, and as a result the nuts drag the XZ-Assembly along on the XY-Plane as a result.  This is going to result in worse prints than either problem individually.  Add to that some stretchy belts, and the problem is magnified even more.

That isn’t to say these can’t be mitigated in machines that have these problems.  With a little bit of adjustment beyond the setup work already done by LulzBot on the AO-101s before shipment, we were able to almost entirely eliminate these problems with no additional parts except for a few printed tensioners.

-Jeff Out

As I mentioned in the Hello World post, I volunteer as an Undergraduate Lab Instructor at the Georgia Tech Invention Studio.  Recently, we had a video made to give a better picture of what the Studio is, what its mission is, and how it operates:

In essence, it’s very similar in its general purpose as a hackerspace but geared toward the kind of curricular and extracurricular projects you’d expect to find at a top-ranked engineering school.  This year we’ve fleshed out our space to a total of five rooms, which each has its own specialized purpose:

  1. The Waterjet Room – As its name suggests it’s the room that houses our OMAX waterjet cutter, probably the crown-jewel piece of equipment the Studio operates.  It also houses our three Trotek laser cutters and much of our equipment for doing light metal work.  Previously it contained tools for wood working, but to extend the longevity of our other tools by reducing dust those have now been isolated to….
  2. The Woodworking Room – Previously this was our command center called ‘The LaserLounge’, containing a single 40 watt Trotek laser cutter and our electrical equipment, with a single large table for general assembly work, a small couch and two armchairs from Ikea.  Now it contains all of our hand tools, and just about every piece of equipment we possess capable of being used on wood.  With the recent addition of a 4’x8′ CNC router it’s starting to get a bit cramped, but our tetris skills have thus far kept the room sufficiently open to ensure safety requirements are met.
  3. The ElectroLounge – The new command center and home to all of our electrical equipment – and the aforementioned Ikea furniture – plus a motley assortment of 3D Printers.  Before we moved in we had the space renovated to improve visibility and to allow us to more easily monitor the surrounding space, including the Woodworking room.  It is currently the easiest room to find thanks to a gigantic, student-made LED backlit aluminum sign installed over the main entrance doors.
  4. The Digital Design Room – This used to be one of two well-worn computer labs on this side of the building, containing somewhere in the neighborhood of 10-20 workstations.  After expanding into the space, we’ve reduced that number to four dual-screen workstations with some expanded capabilities: three of them are equipped with MakerBot Replicator 2’s, and the fourth is equipped with our vinyl cutter and 3D Scanning equipment.  The rest of the space is currently set up for group work with three long butcher block tables, which have been popular with Senior Design teams.  A final addition of equipment to the room will be a suite of Lulzbot AO-101 printers, set up as the first Central 3D Printing Service at any university in the US.  Setting up this room’s equipment has been one of my personal goals, and should serve the Georgia Tech community for many years to come.
  5. The Machining Room – Some of us call this room ‘the Danger Zone’ in jest, as it contains what are considered our most dangerous and complex tools: mills and lathes, of the manual and CNC variety.  As such the room is not regularly opened except to individuals who have been properly trained to use the equipment, and when in use the person using a machine is always accompanied by at least one Undergraduate Lab Instructor.  The room also contains some other equipment including a vacuum former, a small injection molding machine, a set of abrasive tumblers, a motley assortment of light prototyping tools and resin casting equipment.
What most people don’t realize about the Invention Studio is that it is entirely staffed and operated by student volunteers.  That’s right, there is no head machinist in charge of these spaces; the only faculty and staff involved act in a support capacity, primarily as interfaces with the rest of the school.  This is the first such space of its kind at any university in the US, and possibly anywhere in the world.  As such, great care is taken by the Undergraduate Lab Instructors to ensure the space remains safe and functional, and that new Undergraduate Lab Instructors who are selected are able to maintain the same high standards.  This has truly been the key to the Studio’s success, allowing it to grow rapidly and yet remain flexible to the changing needs of the entire student body.
However, up until the publication of that video it’s been a bit of an up-hill battle for the Invention Studio to be noticed by the public at large.  That changed in a big way when Dale Dougherty, founding editor & publisher of Make magazine, wrote this post.  Here’s to hoping for more of the same in the near future!