3D Printing Report for Museum London

The following is a report of the process I undertook for creating 3D printed models of artifacts for the education programming portion of our exhibit “London Works: Labouring in the Forest City” for Museum London.

Shane Pacey, M.A. Public History program at Western UniversityFeb. 24, 2013

Creating the Models

The most time intensive part for me was the modeling of artifacts. Six artifacts were chosen, two from each of the three topics covered in the exhibit, factory labour, professionals, and domestic labour.

The first step involves photographing the artifacts. If you are modeling the artifacts in a 3D modeling program, the point is to take photos that will give you the outline and dimensions of the model. Therefore, taking 3 photos is best, one from the front, one from the side, and one from the top. These photos can then be imported into the modeling program and traced in order to make an object with a proper silhouette and dimensions. I used the free version of SketchUp as my modeling program. Blender is another free option that is more powerful but has a much steeper learning curve.

Things to keep in mind before starting:-3D printers can have trouble with overhangs unless properly supported. Sometimes the best idea is to cut the model up into pieces, print them out separately, and then glue them together. If this turns out to be the best option, plan ahead. If the model in your 3D modeling program is to be cut down the middle, separating the model earlier, and making each piece mirror components (where changes to one are automatically made to the other) can save a lot of trouble.-Whether pieces will be separated or not, spending a short time planning how you will model the artifact will also save headaches further down the road.

Steps for producing a simple model are outlined below.

First, make a flat surface.

Next, drag and drop a photo of the artifact onto the flat surface. Scale the photo accordingly and rotate it if needed in order to create midpoints that line up horizontally and vertically.

With the photo properly scaled, next change into X-ray mode from View > Face Style. This allows you to see the lines you will be drawing.

Insert reference lines that will help trace the artifact, like lines that begin and end at midpoints, and that intersect with them. This also makes the object more manageable, as one particular section can be worked on before moving on to the

next.

For oddly proportioned shapes, using the freehand option might be best. Otherwise, trace the outline with a number of straight lines, or use the curve feature. Freehand has a tendency to not look perfect the first time around, so make changes

as needed.

Rather than tracing each portion of the hat, the process can be sped up by selecting the first face made, copying and pasting it, then flipping it and stretching/shrinking it to fit the other sections of the hat.

The guidelines were deleted then the oval face pulled out to the required height of the hat. The original oval, copied before, was pasted, resized, and placed on top of the hat. This will help create the brim of the hat.

With the outer ring pulled back down, a simple top hat has been made. Having side and front profile photos will help to make the object more accurate.

All of the faces on the model must be outward facing (white rather than blue) so that the printing software can recognize what makes up the outside shell of the model. Therefore, every part of the object must be 3D, with height, width, and depth

dimensions. Notice here the body of the hat is not 3D, lacking depth, so the outside of the hat is white while the inside is blue.

The inside was filled in to make the object completely 3D, and every face of the object facing outward (white). The X-ray on the right shows the new depth dimension in the body of the hat.

This whole modeling process took approximately 10 minutes for someone practiced with SketchUp. However, making more accurate representations of artifacts will take much longer. SketchUp’s limitations with organic shapes can make modeling objects with curves difficult. For example, giving the brim of the top hat a curve took many more hours.

Another option for modeling artifacts is to use 123D Catch. This program builds 3D models by stitching pictures together, much like the panorama feature works in photo editing programs. For our process, each artifact was first place on a pedestal. Next, we circled the artifact in question, taking 30-50 pictures at a fixed standard distance. Pictures must be taken at as many angles as possible without moving the artifact. The photos were then processed through 123D Catch. However, despite 3 different group members taking their own sets of photos and running them through the program, none of us managed to produce a successful model.

Certain angles were successful, but most were not. The model was patchy and ultimately useless on its own.

Some considerations for 123D Catch that could have helped us:

-We did not have a properly suited background during our photo session. Our objects were mostly dark earthy colours, and the background, in the Museum London vault, was also filled with dark-coloured artifacts. I believe 123D Catch uses colour contrast to identify the shape of the objects, so having a colour-contrasted background would probably have helped.-Extremely shiny artifacts that produce glare, like porcelain and glass, also caused trouble. For a program that requires colour contrast, glare acts like a coat of white paint that covers fine detail and constantly follows the camera. Coating the artifacts in an inert substance like chalk powder should help to reduce the glare, but conservation needs may override this. -Even lighting is required. In the processed models from all 3 separate group members, the same side was clearly not registering properly. This problem was perhaps due to shadows we were casting as we circled the artifacts, caused by uneven lighting.

Converting the Models

3D models that have been completed must be converted into .stl files for the next stage of preparation for printing. I downloaded a converting plugin for SketchUp here:http://www.guitar-list.com/download-software/convert-sketchup-skp-files-dxf-or-stl

Once it is installed, you simply need to select the object, and convert it.

The next step will ask you to save the file. You must save it as a name, followed by .stl

If the model is overly complex, it might be a good idea to process the .stl file through software that can fill in holes and reorient faces. SketchUp seems to have trouble as models get more complex. Faces that were fine before can become splintered, and lines that were straight can become warped. This problem usually occurs when you use the function Intersect Faces, an almost essential part of making multi-part objects.

The nice shapes on the outside turned into a mess on the inside after intersecting the faces

Some stand-alone programs provide the function of ‘fixing’ objects, like MeshLab and netfabb, but netfabb’s cloud service is the most user-friendly option found so far. It will process the model online and send a notification email when the model is fixed and ready for download. However, these programs can also mess with your model, so more changes may have to be made to the original in the 3D modeling program.

After processing through netfabb cloud service, preexisting oddities in this model became clear, and some new oddities were introduced as well!

The netfabb cloud service can be found here:http://cloud.netfabb.com/

Preparing the Models for Printing

The next step involves processing the 3D models for their final printing stage. Programs for processing the models slice the model up into the layers that will be put down by the 3D printer. Since the lab at Western University recently purchased a MakerBot Replicator 2, I used

the MakerWare program designed for it. This program replicates the build environment of the printer, and allows you to position the model on the build plate, rotate it, and scale it up or down.

The box represents the build area for the MakerBot 2, a very impressive size

Once the model is properly prepared, it can be processed with the Make It function. A number of different options are presented that allow for complex tinkering of the printer’s capabilities. My recommendation for beginners, change nothing other than the quality level, and whether or not the model needs rafts or supports (to be discussed in the next section).

Many options abound, but other than choosing quality and raft or supports, most should be left alone by a novice.

MakerWare produces a .x3g file that can either be sent directly to the printer via USB connection, or be saved onto your computer and transferred to the printer via an SD card. Be

cautioned, my personal computer is a mid-class 2012 laptop, but spent up to 2 hours processing the models for high-quality output. Mid-quality took less than 1 hour.

For personal 3D printing options or for institutions with cost considerations, the MakerBot Replicator 2 is likely not an option. Costing around $2,000 at the beginning of 2013, it is a top-end personal printer. Smaller and lower quality printers can be found for much more affordable prices, some of which have a large do-it-yourself building component. Some can be found in the $100s dollar range, but that have the same basic functionality as higher-end printers. One example is the ROBO 3D printer. Information on its amazingly successful kickstarter can be found here: http://www.kickstarter.com/projects/1682938109/robo-3d-printer

Since MakerWare is proprietary software, ReplicatorG or Slic3r may be the program options for smaller open-source printers. I used ReplicatorG with the MakerBot 2 and while the processing times were much faster, problems seemed to occur with the scaling function, perhaps due to differences in the software.

If you do not have your own printer, search for 3D printer services online or in your area. Sculpteo is one such service that allows you to upload models in a variety of formats directly to their site and receive a quote. The objects can be printed in a variety of materials, and will be shipped to you once completed. http://www.sculpteo.com/en/

The Printing Process

Before doing any printing with your machine, make sure you’ve read the manual. You’ll need to be checking it, most importantly at the beginning of a print job. You’ll need to know how to make minor physical adjustments to the machine, and how to clean it up and change out the plastic if needed. You’ll also need to be aware of what kind of extra tools or equipment might be needed. In the case of our machine, we covered the build plate in blue painter’s tape. This primarily helps the PLA plastic we used stick. The plastic was biodegradable, non-toxic, and smelled like a hot glue gun when the machine was at work.

The MakerBot Replicator 2 with its blue tape.

The printed objects really stick to the tape like cement, so one immediate thing to consider is the construction of ‘rafts.’ Rafts refer to a grid that is laid down on the build plate before the actual model is printed. The most obvious benefit of a raft is that it helps keep the model elevated, and therefore prevents the full surface area of the object from completely sticking to the tape. Leaving the tape off and printing right onto the acrylic build plate might also be an option, but since the machine belongs to the university, and removing the objects sometimes needed some careful work with a dull pair of wire clippers, I had to limit my desire to experiment here. Scratching the plate is not something I want to do!

The grid shown is the raft, and the first outline of a gavel is being laid down on top of it

One full layer is put down before building up the next one.

The internal layer is not laid down as thin as the external one. Also, large open spaces in the model are supported by a lattice faintly seen in the Xs above, rather than being completely filled in. This saves a great deal of time.

The building-up process can be quite interesting to watch!

Support structures are also important to consider. They act somewhat like rafts but build up with the whole model in order to support overhangs, rather than just forming a base. The hot plastic laid down by the ejector will run and sag if it only has a minimal structure to support it from underneath.

In this case, I doubt even supports would have helped!

The overhang on the handle of this cup is probably reaching the limits of the kind of unsupported overhang that can be done.

The short distance between the connecting pieces helps.

The overhang on these hats did not work well with the first prototype, leaving an uneven surface with bumps and sags. Adding the support structure ensured the final product came out as intended.

Checking your printer every now and then is a good idea. Sometimes problems happen in the ejector and layers of plastic simply are not put down properly. On narrower sections of a

model, this is especially common. Plastic that has not had a chance to cool down can get gummed up as the ejector runs over it again. These kinds of problems may indicate issues with your 3D model rather than the printer, though. And remember, high-quality prints can take quite a long time to complete. Although one half of a gavel I produced took 30 minutes, a small cup took 3 hours.

The ejector had some trouble about 30 minutes into this print, going dry and gumming up some of the layers, noticeable here. Thankfully, the damage was minor and reloading the plastic seemed to solve the problem.

Finally, when removing printed objects that feel like they are cemented to the build plate, try to pry them free from the corners, and make sure you only pull on solid parts of the body. Fragile pieces will probably break off long before the body of the object comes free. If a raft was made, pry the raft up near a corner then pull up. With any luck, the object will soon come free. If all else fails, grip the base of a corner with some dull wire clippers and push down on them gently until the object comes loose.

Finishing the Printed Objects

Once the objects have been removed from the printer, some final steps may be required. If rafts or supports were used, they will have to be removed. Supports may be broken off by hand without damaging the model, but a raft will need to be separated with a knife. Both leave behind sharp and uneven ridges that will have to be trimmed with the knife or filed down.

The visible sections of these rafts can be broken off by hand, but the sections stuck to the underside of the body will need to be removed by knife or sanding.

This wrench has a raft and supports, needed to stabilize the uneven form of the object.

These supports were broken off by hand.

Along with the supports comes a lot of excess that needs to be trimmed off by knife or sanded down.

If the object was printed in parts, they will need to be fastened together. With the PLA plastic a 2-part epoxy was used on some items and superglue on others, both with success. And after the objects have been finished, you can even get a little creative. Spray the pieces with a primer and paint them, and then spray them again with a gloss varnish to seal them and make them smooth. You might even be able to sell them for money!

This gavel was originally two parts. Their bases were trimmed and leveled with a knife, then glued together with a liquid superglue.

Our intentions for this project were to fabricate these models for an educational activity for Museum London. The activity, geared towards early elementary students touring the museum as school groups, is meant to be a tactile guessing game. After listening to the tour guide explain the exhibit, students will reach into a bag one at a time and identify them with the artifacts in the case. Afterwards, the tour guide has the opportunity to discuss the 3D printing process and the printed models themselves.