AP projects 2015
Posts by Kotryna Valečkaitė
As the final working week begins, we must decide what precisely our explorations in production methods will lead to. In the beginning of the project our supervisor Maaike said that the priority and goal of the project was to “revive” chosen historical objects. She did not specify how leaving us to decide what it is supposed to be. As seen in the first post, we took the task very directly, thinking that filling the holes in different methods will bring the most successful results. After four weeks it is clear that archaeological ceramics can not only regain their original use, but also become a game or a party attribute. Therefore, it is essential that we decide how these ideas can be smartly introduced to our peers and supervisors: interaction and functionality being the first priorities.
To begin with, we would like to introduce the cup as a relatively cheap party attribute. Last week we strove for two solutions: paper printing and vacuum forming. Only the latter could come into life, but as it is, the cup could be called a high fidelity prototype for cold beverages containment.
Secondly, the cup as an interactive object. The idea behind this is rather simple: providing the user with a kit consisting of cup shards and color-able glue, both child-safe and heat resistant. Interpretation of the objects would vary with the user: it could be interpreted as a DIY project, treasure hunt for children or possibly an exercise object for amateur archaeologists. For the presentation we will have the shards and the glued cup ready for the exposition, making it again a high fidelity prototype.
Another idea, consisting of two solutions, is to restore the original function of the cup. The first silver bullet was to underline the cracks by making them in different material. In the end we decided on rubber, which gives a rather pleasant feeling for the cup bu making it partially flexible. The second solution is at least 70% rubber, which makes the flexibility a problem. Due to that, an inner structure is introduced, making it possible to implement very interesting spacial compositions. The latter cannot be fully explored before the end of the project, but a simplified version will be given to explain the main idea. In other words, during the science fair we will present the structure prints instead of two material prints: the cost of rapid prototyping in 2 materials is too high for research models. As for the first idea, the design is almost complete and therefore these costs can be justified.
Hope to see you in the science fair on the 27th of October, 12:00 in the faculty of Industrial Design Engineering, TU Delft, Stevinweg 1, 2628 CN Delft.
As promised, we would give the summarized results for the two scanning sessions that we had: with CT scanners and with Artec Spider scanner.
Part of the results of the latter unexpectedly disappeared during the post-processing. The scan which promised the most for us, Hermione handle detail, was among the missing files. We hoped to get better results of the floral ornament and combine it with the CT-scan body, only the chosen comparison model and Harry survived.
As seen, for the comparison we chose the finest model we had. The lice-comb teeth were approximately 0.5 mm diameter with even smaller gaps between them. Due to this, the scanning technique used by Artec Spider could never achieve a proper result: too much was not visible, even with the precision of 0,05 mm. In other words, the grid which the range finding device projected could not be interpreted in the gaps and the result was a block with a texture instead of a comb. Moreover, looking at he scan of Harry we can see a big inconvenience for us: only the outer surface and the sections at the breaks were captured. Moreover, the cracked surface texture was not captured, because we got the file only in a mesh file.
Therefore, it would be expected that this problem would not be so apparent in CT-scans. This technique captures the sections of the object, instead of making an interpretation of surface. Just then these sections are interpreted into 3D files. However, the precision of 0,3 mm proved to be insufficient for the artifact we chose:
As seen, the result was a more consistent file, which could actually be printed. Nevertheless, it was far from what we would call sufficient. Expecting this, we also made micro-CT scans of the object. The sneak-peaks of the object in the lab itself looked very promising. Yet our and publicly available computers could not handle the size of the data set (over 2000 sections!) and could only give results in the lowest resolution, leaving us with the following model:
As seen in the picture, the separate teeth are clearly visible, although the main body is missing. This can be easily solved if the used computer has 16GB RAM, since we could get a proper model in Avizo a few moments before it crashed due to memory insufficiency.
To conclude, only the micro-CT scanner offered the sufficient results for the compared artifact. The Artec Spider is very interesting if surface detailing in necessary or if textures/colors have to be captured. However, if not enough scans are made and combined, you will get an object lacking details, thus resulting in incredible amount of work hours in post-processing. Another solution for this would be to make CT-scans and combine them with the Artec Spider scans only for the details.
This week we focused on production techniques, yet not all of them proved to be possible to produce. In the background we also finished up processing all of the CT scans, of which an overview article will follow next week.
To begin with, we made multiple 3D prints: plaster prints of all of the loose pieces and a tryout of structural solutions in Ultimaker2. The first one we decided to translate into a game during the science fair, while the second one was primarily made for the mid-project presentation. Moreover, we made a form with a CNC milling machine which was later used for vacuum forming. This proved to be the cheapest, easiest and the most user friendly object so far.
Secondly, we discarded paper printing as a possibility due to two main reasons:
- Our files were too large to be opened in multiple programs with which we could have given the surfaces color;
- The delivery times were too long
This led us to choosing another form which would work the best in the Connex printer. Yet that would lead to rather large expenses, exceeding 100 euros per object. What is more, using soft materials would mean that we strive more for a visual than a functional prototype, since the objects could not withstand warm drinks or even a dishwasher. However, some of this could also be achieved by simply printing the different materials apart in the Ultimaker2. Simply put, we are still struggling to determine what fidelity level we are looking for and what each prototype can achieve. Moreover, instead of having a single idea to work out we actually multiple interpretations of the same object:
- Cheap, everyday object (vacuum form)
- Object focusing on the aesthetics of historical footprint/3D printing (Connex prints/plastic injection molding)
- A game, interactive cup (plaster print of shards)
In other words, it means that the objects form their own trajectories and cannot be easily compared with each other.
To conclude, we now have to focus on what precisely we want to achieve in these trajectories and how to do it using rapid prototyping techniques. That is not what we planned during the first week, but that will lead to more evenly divided workflow and, hopefully, more interesting results.
After multiple emails and a Skype talk we finally acquired a trial version of Mimics. According to their representative, the program is mainly focused at medical uses. Most importantly how do bones, implants react to friction and temperature changes.
This got us interested, since this was also rather important in our project: we were using CT scans to determine the break-line positions and in the end also fill up the missing shards with (possibly) other materials. In other words, it would be very interesting to see how different connections between materials would influence the durability of the object. I must add, that this is only a presumption after a talk with their representative and we might not be able to go so deep in the subject due to the time limitations. Yet this could be very interesting as a research subject for future students.
Having only a week of work left till the presentation, we decided to only check what were the possibilities of the translation (CT-scans to .stl) procedure and if the results could be better than from Avizo.
The interface seemed clear, but more limited to what was offered at the latter program. It seemed actually very similar to already mentioned Seg3D, which is also focused on medical use.
After comparing multiple objects we came to conclusion that this program does not offer better translation. The meshing is coarser and even though the stepping is less visible, so are the break lines.
In conclusion, this program might offer higher possibilities going deep into material interaction(3-matic research), but for simple .stl translations Avizo is still the best option.
P.s. For post processing use MeshLab (open source!): there you can both reduce the fineness of the mesh and smooth it.
Today as a part of our minor our student group was introduced to CNC milling and 3D printing with Ultimaker2. Since we were free to choose the tryout objects, we decided on one of the .stl files we extracted from the CT scans.
“Harry”, as our focus object, seemed like a great begin. Yet just after loading the files to Cura (the Ultimaker software), we noticed that the model was not completely straight. That was due to its original position during the scan. In other words, the object nested in-between two other objects was not completely parallel to the ground plane. This we tried to fix by manually rotation in Cura. In the end, it was not perfect and due to that the bottom edge of the cup was sketchy. Moreover, Ultimaker 2 seemed not like the right machinery for such task. That was mostly because we had many open, hanging edges and pieces which had to be supported. The latter is possible with the same material, but that leaves clear marks on the surface.
Parallel to 3D printing we also did some CNC milling. Just like in Ultimaker, we used “Harry”. For this production technique we used DeskProto. This program both translates the files for the machine and helps to create a frame for the object (mostly necessary to get a clear reference point). However, the latter can also be manually done in other CAD software.
Production of the object took merely 15 minutes, but we did not strive for the highest resolution. That meant that we took the biggest cutter available (d8mm) and got a sketchy cup with clear stepping. Moreover, due to the cavity in the cup and flexibility of the material, mistakes were made (seen in the picture below) and the model was very flaky.
Since we had more than 1,5h left, we proposed to make another model in CNC machine. This time to see how much detail we could achieve. For this task we chose “Hermione” as the model, yet due to the time limitations we could only take a piece of it. We worked on the object from 3 sides, starting with 8mm cutter and finishing with 4mm. This procedure took at least twice as long as the previous one. What is more, during the first try the foam melted, completely destroying the model. In the end, results of the second one were not as clear as in the digital model, but still quite amazing: knowing that we used very soft foam, could not precisely put the model on the reference point and that we did not use the smallest cutter.
In conclusion, the CNC milling could be an option for the final product, if we went for a single material transparent/translucent look. This would be possible by milling stacked and glued plexiglass. 3D printing in single material is also very interesting, but with this we would have to sacrifice some of the qualities of the end product (historical footprint, practicality, aesthetics).
As promised a day ago we would keep you posted about our adventures with image processing software. Even though we did not receive the trial version of Mimics, Avizo provided a very pleasing outcome and it also read .dcm files.
The program itself is very user friendly and incorporates visual programming with automatized properties, thus giving the user just enough freedom to not crash his computer or make the process incomprehensible. In this sense it is very similar to 3Dslicer, yet Avizo has more options and more finesse in the details.
The final result is not yet perfect due to rather clear “stepping” in the final 3D model. This, according to our “informer” from the Industrial design engineering faculty, could be solved with Geomagic. However, now we can clearly state that the plan A mentioned in this post is actually possible.
To keep you up to date we would like to introduce of pending and active processes of the project.
Currently we are focusing on two main subjects: production techniques (Jorinde and Irene) and image processing (Sander and Kotryna). For the first one we plan to publish a page later today which will be updated as we gather information. For the second, we have already posted an overview, but since we are still waiting for the trial versions of some of the programs a second article will follow.
As expected, we are lagging with the step “CT-scans to .stl”. The reason for that is the low quality of already produced .stl files and inability to open the .dcm files.
Our plan A is to finish with it today or tomorrow depending on the outcomes from the trial versions of the program. Then on Thursday make the individual models of object “Harry” with production technique ideas. We will pitch them to each other on Friday morning, hopefully resulting in 2-3 final ideas which will be sent for production in the same afternoon. Most important notes for the preparation of these pitch files are:
- Thinking about the ability to produce
- Retaining the historical footprint
- Trying to make smart joints between different materials, since the current holes have very rounded corners (also a part of 1.)
Plan B would come into action if we cannot get the .dcm files to work or the quality of the scans is very low. This would lead to post-processing of already prepared 3D files of object “Dobby” to make the surfaces smoother and the break lines sharper. That would mean that we would loose a lot of data: including the micro-scans, which would be used for the comparison of all the scanners that we used. Yet we would still follow up the plan A from Thursday by shifting it 4-5 hours.
In conclusion, even though we are slightly behind primary schedule, we have received valuable insights in what programs to use and what to expect of them. Moreover, even if we loose the .dcm files, we would still be able to produce what we strove for in the beginning: just the final model would be less spectacular.
Keep your fingers crossed for us and till Thursday!
Directly after receiving the scans on Tuesday we jumped into processing them into 3D models. To keep it clear we used “Hagrid”(obj. 5) as an example for all of the programs.
As noted in the previous post, this process has multiple steps and in order to gain the highest level of detail, a lot of tweaking is necessary.
The usual procedure goes as follows:
(0. Changing the .ima or .dcm files into program compatible format. Most of our scans were made in .dcm format which was not compatible with multiple programs: so far we tried RenameMaster, which did not work)
- Loading the .dcm or .ima files into a 3D processing program. These file formats actually contain only 2D information: the sections of the object. In other words, the 3D model is an interpretation of multiple sections and therefore steps between them might be visible, if the resolution is not high enough.
- Selecting threshold and filtering the right information. Depending on the program this step might be automatized. If not, it might be very heavy on your computer. Therefore, a device with a good graphics card and 16GB RAM is advised (it would work on 6 or 8GB RAM, but it goes slow and tends to crash often).
- Loading the 3D file into a volume renderer to get an editable mesh (.stl).
To begin with, we started with Seg3D. This program did not want to read .dcm files, thus we only worked with test files, which were in .ima format. The interface was clear, but to extract minuscule details it needed a lot of filtering and playing with histograms. That was extremely hard on our computers (6-8GB RAM, 2.0-2.03GHz) and took over an hour to get a decent file. Moreover, the final result is given in .nrrd format which later has to be translated to .stl with the help of ImageVis3D. The file looked rather detailed in Seg3D, but the final .stl was worthless.
Later on, we received a tutorial from an past student of our supervisor Maaike. It suggested using DeVide. Unlike the previous program this one works on the basis of visual programming. Thus all of the steps can be easily retraced. This program can directly export to .stl reducing the possibility of getting a very rigid mesh, like with Seg3D. Unfortunately, the program did not want to work on our computers.
After this failure we contacted one of the researchers in the faculty of Industrial Design Engineering. He adviced to try out the following programs:
- 3D slicer (open source)
- Avizo (paid, evaluation copy available after contacting the firm)
- Mimics (paid, evaluation copy available after contacting the firm)
The first of the list (3Dslicer) proved to be very user friendly (although it did not read the .dcm files). The information is collected automatically after choosing a preset and is quite precise. One can also select if to smooth the surface: both outputs are interesting in form, with the edgy one as an expressive interpretation of a kitschy object of the past. If used for the final product, more mesh post-processing is necessary
To be continued…
As the project slowly went into motion we had the first digitizing session in the laboratory of Geosciences&Engineering. Our group was provided with the luxury to first hand observe both micro- and macro-CT scanners in working. Both with their advantages and limitations, they gave us a new perspective of how to order and process given archaeological objects.
When Maaike came in with boxes full of ceramics from the Archaeological archive of Amsterdam, we understood that it was neither efficient, nor possible to scan them all. At this point selection was crucial. At first sight we had three main groups of objects: lice combs (highest level of detail), broken colored ceramics bound with metal strings (necessity to make more detailed scans to understand the technique) and sets of white ceramic tableware lacking multiple shards.
The latter seemed to be the closest to the issues visible in the goal of the project. Yet the other two gave us interesting side paths which would improve overall understanding of the methods and possibilities of 3D scanning. Based on this, we made a queue sorted by importance, which would lead to at least one object of a group scanned.
After the first inspection of the digitized forms we were rather amazed that the precision of 0,3mm was not sufficient for some of the fine-detailed specimens. E.g. the combs lost their teeth, metal bindings were muffled, crack lines barely visible. Consequently we were offered to work with much finer machinery (micro-CT scanner) mostly used for small scale material research. Yet the time and money needed for this method led to only two specimens scanned: the finest ivory comb and a detail of a metal connection. In total we got 13 scans, excluding identical scans in higher precision. The notes and conclusions after this are as follow:
1. There are 2 CT-scanners in the Geoscience&Engineering laboratory:
- Macro-scanner can be used to scan rather big objects, but the fine details are almost completely neglected; object is stationary, thus there is a small chance of damage. Precision 0,3mm.
- Micro-scanner is very slow (1h per object) and has very limited object size: till 100-120mm in diameter; object is rotating, thus it needs to either be glued or fixed, which requires extra attention not to damage the object. Precision 0,03mm.
- Both scan only the form and not color; they can detect cavities, but not slight changes in the material density
2. The digitized forms are saved as 2D images of section cuts in .dcm or .ima file format, which need multiple steps to be converted into editable 3D objects. Even though we were informed that it is a very quick procedure, to gain fine details it is necessary to have a powerful computer(16GB RAM) and correct software (which is usually paid).