Posts in category Week 3

Reproduction Methods

As told in the planning, each of us would come up with a multiple reproduction methods for Harry. We pitched these ideas to each other and discussed which would suit the purpose of this project best. Afterwards everybody choose their favorite and best method, making sure we had a diversity of production techniques.

cupe◄Click on me!

Sander Plaster Print
The goal of this technique is to recreate Harry as well as possible. Therefore, the existing cup will be plaster printed in several pieces. Af varnishing the inner and outer surface, these pieces will be glued together in order recreate the cracks. The holes shall be filled with separately (Ultimaker) 3D-printed parts.

Irene Paper printing
Using the technique of 3D printing paper it is possible to make a relatively inexpensive product using a 3D printer. We don’t expect this technique to be waterproof. By experimenting with lacquer or varnish we can find out the possibilities to make the cups usable for daily usage. To print the rough version of Harry it will cost €34,- euros.

Kotryna 3d printing/plastic injection molding

With this technique we could achieve a very sophisticated look for a high end product. With this design we would bring out the beauty of 3D printing by making an expressive carcass which will either support the cavities in the structure or the whole structure. This also accentuates the historical marks on the object, which is necessary because the original form is then recreated in transparent material. The latter can either be achieved by plastic injection molding (which is beneficial if this is produced in larger numbers) or by using a Objet500 Connex printer (very convenient, because the whole object can be printed out in one go). Moreover, this design would be very interesting if steel 3D printing could be achieved in very small diameters, since then the translucent material could be glass.

Jorinde Vacuum Forming
The main reason for choosing this technique is because 3d printing is too expensive for a consumer product, so the product is still not used for its purpose. The most used cup has got to be the plastic disposable cup. This cup is made with the technique thermoforming, but this is not achievable in the short amount of the we have. Therefore the simplified technique vacuum forming will be used. With vacuum forming s sheet of plastic is heated and forced against the mold by the suction of air. It is important that form is mold-releasing.
With this technique it isn’t possible to use different materials or make holes. To preserve the historic character of the cup the difference between the shards will be made visible with a difference in height. CNC milling at PMB cost 10 euros.

 

Basic (existing) shape Cracks Holes Speciality
Sander Plaster, several separately printed parts Through glueing the parts together Seperately 3D-Printed Trying to recreate Harry as well as possible
Irene Paper Different colour Low budget
Jorinde Plastic, vacuum formed as one part height difference

between the shards

Holes have to be filled, visable with height difference Making an old thrown away cup into a useable and disposable product
Kotryna  Plastic, (partially) 3D printed (and plastic molding)  Surface texture, carcass deformations  Carcass or carcass deformations (depends on the final design)  Showcase of 3D printing possibilities and accentuating historical footprint in newly added  details

CNC milling and 3D printing

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.

Removing support structure

Removing support structure

Final product

Final product (1:2)

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.

foam harry

“Harry” from foam (1:1)

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.hermione  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.

Foam "Hermione"

Foam “Hermione” (1:1)

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).

Comparison of image processing software 2

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.

Interface Avizo Hagrid

Avizo interface

Hagrid in rhino via Avizo

Detail in Rhino

Meeting recap (6th of October)

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:

  1. Thinking about the ability to produce
  2. Retaining the historical footprint
  3. 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!

Comparison of image processing software 1

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)

  1. 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.
  2. 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).
  3. 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.Capture

Hagrid_Seg3D to ImageVis3D_128x128x54mesh_detail

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:

  1. 3D slicer (open source)
  2. Avizo (paid, evaluation copy available after contacting the firm)
  3. 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

3DSlicer_screenshot

Hagrid_3DSlicer_nonsmoothedges_detail (1)

Hagrid_3DSlicer_smoothedges_detail

To be continued…

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