March 17, 2013

This past Saturday I had the great opportunity of attending an event called Maker Day.  It was sponsored by CoLab, Inc. in my home town of Chattanooga, Tennessee.    CoLab is company dedicated to fostering innovation in the Chattanooga/Hamilton Country area and this was the first event organized specifically to demonstrate 3-D printing.    CoLab is a tremendous complement to our city, which is becoming well known in the southeast for technological advancements.  We also are very fortunate to have the “SIM Center” located on the campus of the University of Tennessee at Chattanooga.  That organization provides project work involving “computational engineering”; an incredible technology in itself. 

 If you remember an earlier posting from last year, you remember 3-D printing is an “additative manufacturing” technology depending upon metered deposition of material in a proscribed manner determined by solid modeling.  There are several “additative manufacturing” processes as follows:

In each case, the following processes are followed thus producing the model:


  • Create a 3-D model of the component using a computer aided design (CAD) program.  There are various CAD modeling programs available today, but the “additative manufacturing” process MUST begin by developing a three-dimensional representation of the part to be produced.  It is important to note that an experienced CAD engineer/designer is an indispensable component for success.  As you can see, RP&M processes were required to wait on three-dimensional modeling before the technology came to fruition. 
  • Generally, the CAD file must go through a CAD to RP&M translator.  This step assures the CAD data is input to the modeling machine in the “tessellated” STL format.  This format has become the standard for RP&M processes.  With this operation, the boundary surfaces of the object are represented as numerous tiny triangles.  (VERY INDENSABLE TO THE PROCESS!)
  • The next step involves generating supports in a separate CAD file.  CAD designers/engineers may accomplish this task directly, or with special software.  One such software is “Bridgeworks”.  Supports are needed and used for the following three reasons:
  1. To ensure that the recoater blade will not strike the platform upon which the part is being built.
  2. To ensure that any small distortions of the platform will not lead to problems during part building.
  3. To provide a simple means of removing the part from the platform upon completion.
    1. Leveling—Typical resins undergo about five percent (5%) to seven percent (7%) total volumetric shrinkage.  Of this amount, roughly fifty percent (50%) to seventy percent (70%) occurs in the vat as a result of laser-induced polymerization.  With this being the case, a level compensation module is built into the RP&M software program.  Upon completion of laser drawing, on each layer, a sensor checks the resin level.  In the event the sensor detects a resin level that is not within the tolerance band, a plunger is activated by means of a computer-controlled precision stepper motor and the resin level is corrected to within the needed tolerance.
    2. Deep Dip—Under computer control, the “Z”-stage motor moves the platform down a prescribed amount to insure those parts with large flat areas can be properly recoated.  When the platform is lowered, a substantial depression is generated on the resin surface.  The time required to close the surface depression has been determined from both viscous fluid dynamic analysis and experimental test results.
    3. Elevate—Under the influence of gravity, the resin fills the depression created during the previous step.  The “Z” stage, again under computer control, now elevates the uppermost part layer above the free resin surface.  This is done so that during the next step, only the excess resin beyond the desired layer thickness need be moved.  If this were not the case, additional resin would be disturbed.
    4. Sweep—The recoater blade traverses the vat from front to back and sweeps the excess resin from the part.  As soon as the recoater blade has completed its motion, the system is ready for the next step.
    5. Platform Drops–The platform then drops down a fraction of a MM.    The process is then repeated.  This is done layer by layer until the entire model is produced.  As you can see, the thinner the layer, the finer and more detailed the resulting part.
    6. Draining–Part completion and draining.
    7. Removal–The part is then removed from the supporting platform and readied for any post-processing operations. .
  • Next step— the appropriate software will “chop” the CAD model into thin layers—typically 5 to 10 layers per millimeter (MM).  Software has improved greatly over the past years, and these improvements allow for much better surface finishes and much better detail in part description.  The part and supports must be sliced or mathematically sectioned by the computer into a series of parallel and horizontal planes like the floors of a very tall building.  Also during this process, the layer thickness, as discussed above, the intended building style, the cure depth, the desired hatch spacing, the line width compensation values and the shrinkage compensation factor(s) are selected and assigned.
  • Merging is the next step where the supports, the part and any additional supports and parts have their computer representations combined.  This is crucial and allows for the production of multiple parts connected by a “web” which can be broken after the parts are molded.
  • Next, certain operational parameters are selected, such as the number or recoater blade sweeps per layer, the sweep period, and the desired “Z”-wait.  All of these parameters must be selected by the programmer. “Z”-wait is the time, in seconds, the system is instructed to pause after recoating.  The purpose of this intentional pause is to allow any resin surface nonuniformities to undergo fluid dynamic relaxation.  The output of this step is the selection of the relevant parameters.
  • Now, we “build the model”.  The 3-D printer “paints” one layer exposing the material in the tank and hardening it.    The resin polymerization process begins at this time, and the physical three-dimensional object is created.  The process consists of the following steps:
  • Next, heat treating and firing may occur for further hardening.  This phase is termed the post-cure operation.
  • After heat treating and firing, the part may be machined, sanded, painted, etc until the final product meets initial specifications.  As mentioned earlier, there have been considerable developments in the materials used for the process, and it is entirely possible that the part may be applied to an assembly or subassembly so that the designed function may be observed.  No longer is the component necessarily for “show and tell” only.

 The entire procedure may take as long as 72 hours, depending upon size and complexity of the part, but the results are remarkably usable and applications are abundant. 


 If I may, I would now like to show several JPEGs from the event.  A very short description will follow each photograph.  I would like to state that I’m not Ansel Adams so some of the photographs are a bit borderline in quality.  Please forgive me for that.  Hopefully the content is worthwhile and will demonstrate the equipment used in the 3-D processes. 

 Assembly Hall (1)

 The demonstration was held in the Hamilton County/ Chattanooga Public Library.  The photo above does not really indicate the number of people attending but the day was a great success.  I’m told approximately three thousand (3,000) individuals did attend during the five-hour presentation.  Great turnout for the very first exhibition.

3-D Printing with Computer Image(2)

This photograph will demonstrate that the first step is developing a three-dimensional model of the part to be printed.  The computer screen to the right of the printer will show the model being produced.  The “black box” is the printer itself.  The purple coil located in the back of the printer, is the material being deposited onto the platform.   The platform indexes as the material is being deposited. A better look at a typical print head may be seen as follows:



Print Head (2)

One of the greatest advances in 3-D printing is the significant number of materials that now can be used for the printing process.  The picture below will show just some the options available.


The assembly below demonstrates a manufacturing plant layout assembled using 3-D printing techniques.  Individual modules were printed and assembled to provide the overall layout.  Please note the detail and complexity of the overall production.

Astec Plant Layout-3 D Printing(2)

One of the most unique methods used in 3-D printing is the four-bar robotic system.  That system is demonstrated with the JPEG below.   Again, please note the spool of “green” material to the lower left of the JPEG.  This material feeds up and over the equipment to the dispense head shown in the very center of the photograph.

4-Bar 3-D Printer(3)

 This is a marvelous technology and one gaining acceptance as a viable manufacturing technique for component parts as well as prototypes.  I certainly hope this posting will give you cause for further investigation.  Many thanks.

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