AP projects 2015
Posts tagged production techniques
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.
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.
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|
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).
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!