Designing a comfortable armchair for JEC 2022
At CEAD, we wanted to design and print an armchair to provide visitors of CEADs booth at JEC World 2022 with the possibility to have a seat and watch live demonstration sessions with the Flexbot.
An important requirement for the chair was that it had to be comfortable to sit in. For the chair to be comfortable, we designed the seating surface to be double curved. Double curved surfaces are challenging to print because it requires a 3D printing strategy with overhangs. Each successive layer needs enough contact with the layer before to successfully adhere. If the successive layer protrudes too much, gravity will pull the plastic downwards causing drooping of the material. Printing strategies to realize complex shapes with overhangs, may include using supports or printing the part in separate pieces. These printing strategies require extra manual labour after the part has been printed, by having to remove the supports or having to put the separate pieces together.
Printing strategy on the Flexbot for complex shapes
To prevent this, we used our Flexbot and implemented a 40° printing strategy, a variant to the 45° printing strategy. The Flexbot is a 6-axis robot, whose extruder can be orientated anywhere between 90° and 0° relative to the print bed. This is one of the main advantages of robot-based 3D printing and provides more flexibility and design freedom. This printing strategy allows you to print parts containing horizontal planes or slopes without using supports. It also enables you to print the part in one go, thus not having to print the part in separate pieces. An example can be seen in the armrests and the seat.
Due to the combination of the 40° strategy and the geometry of the part, the chair could be printed as a closed object without having to use infills. By carefully tweaking the slicing settings, printing speed and layer height, while simultaneously using gravity to our advantage, we were able to print the chair in one go.
The chair was printed in 14 hours and weighs 50 kilograms. The material we used is reinforced post industrial PETG (PIPG) filled with 19% glassfiber. Glassfiber improves the impact strength of the material while offering an economical solution. The material has been provided by Mitsubishi Chemical Europe. PIPG is easy to print and thus helps realize complex prints, while simultaneously providing the chair with a neat look. Mitsubishi Chemical Europe can provide the material in every possible RAL colour. In this case, the supplier colored the material in CEAD blue.
From 3D printing to milling in one automated process
The Flexbot is a hybrid solution, which means that after the 3D printing process is finished, the print head can automatically be replaced with a milling spindle. The text was milled into the back of the chair, taking into account that the surface of the backseat was curved. Design of the chair and program computation of both 3D printing and milling were created using Siemens NX.
Pushing the boundaries of 3D printing
The challenge of this project was to realize this print in one go, despite the complex geometry of the seating surface and armrests, which contained overhangs. Using a 6-axis robot, such as the Flexbot, allows you to implement printing strategies to help realize challenging parts. This prevents having to use more laborious and time-consuming strategies.
Are you curious to find out more details about this printing strategy? Stay tuned for our upcoming blogs.
