Lab LogoFletch's Fab Academy 2014 Blog

05. 3D Scanning and Printing

This weeks assignment had a few parts:

05.01 Design and Print an Object

For this I though it would be cool to make a 3D print of one of the minions from Despicable Me, I used the image below as inspiration.
Minion Dave

I designed the model in Kokopelli, I've added a loop to his head so that he can be used as a key fob.  The script is available here, it needs a little tidy up to make it fully parameterised.
Kokopelli Minion DEsign
There are a few parts of this model that need work such as the mouth and the angle of the shoulder straps.  After completion of the Fab Academy course I plan to investigate some of the other shapes and transforms in Kokopelli and put together a little tutorial showing them all.  I'll also include how I built this minion model in the tutorial. 

Note that when I export the STL from Kokopelli, it generates this infinitely thin strip of triangles on the back of the model (see image below of the model in Meshlab).  I'll drop objects from the model at some point to investigate why it does this.  As the triangle strip is so thin the printer ignores it, so I eventually stopped trying to clean the mesh and just printed the STL's as is.
Kokopelli export error

Here is the part printing on the Ultimaker.

Minion Printing

The initial part only took about 5 minutes to print but was too small and the printer couldn't resolve some of the detail in the model, so I scaled it up in the Ultimaker printing software 'Cura' by a factor of 2 and re-printed it.  I had a few failed attempts here as my laptop went to sleep during the print process, leaving me with a partially printed model!   But finally I got a complete one as shown below.  Note these early test versions didn't have the arms that the model now has and the large model still has the support material that Cura automatically added around its feet.

Minion Printing

I then added the arms to the model and printed a copy on both the Ultimaker and the Dimension 1200 to compare the quality.  Picture below shows the model from the Dimension printer with it's support material still in situe, and some of the tools use to 'gently' remove it from the baseplate.  Note that one of the arms was snapped off removing the model from the base.

Minoin printed on Dimension Printer

Theoretically the Ultimaker has a better resolution than the Dimension printer, however as you can see in the image below, the print from the Dimension (white plastic) is actually more consistent and cleaner.

Comparison of Ultimaker and Dimension Prints

The fact that the Dimension printer prints a removable support material opens up all sorts of possibilities and I plan to extend this task to print a one piece minion with a rotating head.

05.02 Scan an Object

There are a large number of 3D scanning methods available and we wanted to try as many of them as possible, so the other Manchester students and I decided to split this task and do some individual scanning as well as testing some methods as a group.  The group worked on these methods together and then picked one each to write up.

05.02.1 Group Work on Scanning

This is a list of the scanning methods we tried, with links to the individual write ups.

05.02.2 Individual Work on Scanning

In addition to the group work above, I used Autodesk 123D Catch to scan a variety of objects.  I chose thing of different sizes and types to see how well the system performed with each.  All my 123D scans were captured using the iPhone app and the built in camera on my iPhone 5.  I also printed out some of my 123D scans.  The online version of 123D Catch proved to be too slow (even on my modern Mac Book Pro) to reliably edit or clean up the captured meshes.  I eventually ended up downloading the meshes and either printing as is or cleaning up in netfab and meshlab.

Scan of the same pencil sharpener used in the Modela scan above, each scan is from a set of between 30 and 40 photos.  Object size approx. 20mm.
123D Pencil Sharpener 1123D Pencil Sharpener2

I scanned this twice, once with the object flat on a table top and once with the object suspended in mid air on the end of a screw.  In some of the other scans I had done, object on a table type surface did not have clean boundaries between the object and the surface, 123D understandably had trouble distinguishing the two.  Hence I tried with the object in mid air, this also allowed me to get the camera in at a better angle all of the way around such a small object.  I was expecting better results from the mid-air scan and was surprised that it was worse.  More investigation required to understand why.

123D scan of a turned wooden bowl that we had at home.  Scan from a set of about 50 photos.  Object size approx. 200mm.
123D Scan of wodden bowl

123D scan of an interesting building (Dovecote) in our local park.  Scan from a set of about 50 photos.  Object size approx. 4000mm.
This nicely highlights how 3D scanning can be used fro archival purposes to keep a record of historic artifacts.
123D Scan of dovecote

STL Files for all of the 123D Catch models can be downloaded from my 123D Catch page http://www.123dapp.com/MyCorner/JamesFletcher139-21142139/models.

05.03 Print the Scanned Objects

I also printed both the wooden bowl and the dovecote, the image below shows the prints of all of our 3D scanned objects.
All our printed scanned objects

05.04 Build the Scanner

I'm fascinated by the concept of structured light scanning and I'd like to build a structured light scanner, however I ran out of time this week.  Maybe building it, working on improving the resolution and making it a Rasp Pi powered self contained device would make a good final project.
I also think the the now considered 'ancient' concept of a '3D arm' type scanner is much under rated.  It seems to have been usurped by the 'cool crowd' of laser scanners and photogrammetry.  However I think it still has a place as very accurate way of scanning certain types of objects.

05.05 3D Printing Update

In later weeks I've found time to modify my Minion model to have a captive rotating head and re-print it on the Dimension printer.  Newer design files here.
Minion with rotating head