Testing Size: Making a Half-Scale MDF Mock Up

At this point, I decided to push forward with my latest 3D print advancement in order to scale it up. The 3D print is only about 5 inches long, which is helpful in identifying the form but not so much the function. I wanted to see how stable the piece would be in a larger scale, as well as to see exactly how big the final product should be. This latest print has a simple curved form that varies in thickness from one end to the other. It is able to be placed in four different positions while staying upright and each position is useful for different activities. The main position it stays in allows it to subtly rock and spin since the widened base has a slight curve, which is enough to initiate movement while keeping safety in mind:

Form6bForm6a

I proceeded to take the CAD file for the model into a program called 123D Make, which allows you to turn your 3D model into a two dimensional build plan. The program takes the three dimensional form you have created and slices it into layers upon your direction. I was able to choose the direction and width of the slices it would be made up of based on the material it was cut from. In addition, I hollowed out the inside so that I could fill the end piece with sand in order to test the shift in weight when placed in different positions.

In order to choose the size of the larger scale model, I researched the average measurements of a child in the age range of my user group. It turned out that the average height is about 31″, so I decided that the overall length of my first test piece would be 36″. I figured it should be a little bit larger than the child so that they can sit on it and interact with it without it being too overwhelming to them. Since the CNC has limitations due to the material choice, I had to create an 18″ half scale model. It would still allow me to test the function on a larger scale than the 3D print and pave the way for future iterations.

I chose MDF as the material to use for the model because it comes in large sheets that are easy to sand once the pieces have been assembled. After setting up the material onto the CNC, it was time to start cutting out the pieces. 123D Make works with the CNC router so the new file had to be transferred to the machine, allowing it to then follow the line paths that were programmed.

After all the pieces were cut out of the MDF sheets, the assembly process began.

I had to remove all of the unnecessary material from the interior and exterior of each part. I numbered them in size order to keep track of the way in which they would be glued together.

I was left with only the pieces required for my model and I continued to work on each one by hand. I used a hand file to clean up all of the edges to give the overall piece a smoother finish at this stage. Although somewhat time-consuming, it saved me time later on in the construction process.

During the sanding process, my thesis advisor, Professor Stan Rickel, and I discussed the best way of going about assembling the pieces. It required multiple wooden dowels to be placed through pre-drilled holes in order to keep the pieces from shifting during the gluing process.

I proceeded to widen the pre-drilled holes after all of the sanding was complete so that there would be room to apply wood glue around the dowels to keep them securely in place without falling out. I then split the parts into two piles and glued the pieces into two separate halves. This would enable me to fill the piece with sand before gluing the two halves together. I hoped that the sand would create the weight-shifting ability I wanted in the final design, however, the MDF was too heavy a material for it to really make much of a difference. I would like to test it out with a foam model, which would allow the sand to make more of a difference due to its lighter quality.

Both halves were carefully glued and clamped to ensure a close fit. I left them to dry overnight, added the sand to one half in the morning and then glued the whole piece together. I gave the piece more time to dry this time since the next step would entitle sanding down the entire surface to shape and smooth the exterior.

I clamped the entire piece securely onto a table in the industrial design studio’s sanding room. Using a hand grinder, I went over each section of the piece so that there would be a continuous surface over all of the glued pieces. I had to continuously rotate the model and re-clamp it to ensure an even surface all around. In the end, the room was completely covered in MDF dust from the excess material removed and my piece had been sanded down to the necessary form.

When the time came to finish the surface of the piece by removing all of the sanding marks, Stan happened to be in the industrial design studio with furniture designer Wendell Castle. Wendell uses a wood stacking technique similar to this in many of his pieces, so he took the time to give me advice on how to complete mine more efficiently. I carefully removed the markings from the hand grinder so that the curves would have a better flow and a smoother surface.

After the piece was completed, I began to take notes of its qualities. A thinner wall would be better, allowing there to be more hollow space inside for the sand to partially fill and allow a more noticeable shift in weight. When it came to size, this definitely help me see a more realistic scale of the final design. Even though it was just a half scale representation of what the final form would be, it allowed me to see that at full scale the piece would be too large. Instead of 36″ long, it would be sufficient for the piece to be minimized to approximately 25″ long. A smaller size will allow it to be used properly without being excessively large. In addition, no extra material will be wasted and the proportion to the child will be more in scale.

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One thought on “Testing Size: Making a Half-Scale MDF Mock Up

  1. Pingback: Observation/Shadowing & Product Scale Testing | Liana Beer: MFA Thesis

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