3D Objects, Engineering, Optimizing 3D Prints, Sustainability

Optimizing 3D Prints- Experiments: Statistical Conformity

Experiments: Statistical Conformity

While determining the quality of the 3D printed objects, it was important to make sure that all the prints conformed to the specification. The two measurements of interests were the height of the object and the diameter, as they are required to determine surface area of the objects. When the right-circular cone and right-circular cylinder were modeled, they were designed to have a height and base diameter of 30 mm each. The statistical software, Minitab was used to analyze the data. Three factors were considered.

The first was pigmentation. It is important because it has an influence on the final print-shape. The user always has an option to use colored PLA filament. Adding colored pigments to natural PLA will give it different properties [25]. For an extruder temperature above 493 K (219.85 °C), the pigmentation becomes relevant as it affects the roughness of the final print [23], hence a lower optimal temperature was chosen. The temperature can also alter the printing material’s crystallinity, depending on its color [25], which will, in turn, affect the appearance of the printed object. In this experiment, the colors used were natural (translucent), pink, and blue.

The second factor was the amount of infill. The amount of infill has a range of 0 to 100%. An infill level of 20% and 80% are commonly used [23], and on top of that, the two extreme levels of 0 (hollow) and 100% (solid) were chosen along with them. For a shorter print duration, a lower infill is chosen, for better stability, a higher infill is chosen [23].

Finally, the third was the type of shape/deformation of the object, i.e., whether it gradually tapered (cone), or didn’t (cylinder). There are several other factors which can contribute to the quality of print such as the temperature of the nozzle, size of the nozzle, rate of filament retraction and many more [9,20,21,26]. They are not considered in this experiment.

Once the prints were complete, they were measured using a digital Vernier caliper for accurate measurements, and the grand averages of the values of the height and base diameter were obtained. The area of the base was also calculated. Each experiment was replicated to check for bias. The test used to perform the analysis was Anderson-Darling test using Minitab. The collected data was confirmed to be normal with a 95% confidence interval, as shown in Fig. 2 for cones of 80% infill. Similar data for other infill levels of all objects also exists and is made available in the supplementary material.

Fig. 2 Graphs showing normality of the measurement data in the case of 80% infill level.


In Fig. 2, the factor that determines the significance of the result of the normality test is p-value. Since the p-values were higher than 0.05, the data collected is normal and does not have false-positives. The closer the p-value to 1, the more normally distributed is the data [18,19]. It also shows the standard deviation of the data.

Experiment-1 was a 2k factorial design, where k is the number of factors; each factor has two levels. The pigmentation factors were selected to be natural (translucent) and pink, and the shape was tapered or none. Each time the experiment was performed, only a pair of the infill factors was chosen to keep the levels consistent. i.e., a combination of two among hollow, 20%, 80%, and solid were chosen. Depending upon the combination, an appropriate level was chosen to be the lower infill and higher infill level. This was done to determine the optimum levels of infill if the choice were among the combinations. The shape/deformation factor were tapered and none.

Experiment-2 was the same as the first, except the pigmentation was changed from pink to blue. Finally, Experiment-3 factored the colored PLAs (pink and blue) for analysis. Table 1 shows the factors and their associated levels. For simplicity, they are labelled as factors A, B, and C in the table and henceforth.


Factor Level 1 Level 2
Factor A (Pigmentation) Color 1 Color 2
Factor B (Infill) Lower Infill Higher Infill
Factor C (Shape) None Tapered

Table 1. Factors and their levels



References can be found in the Introduction section.

3D Objects, Engineering, Optimizing 3D Prints, Sustainability

Optimizing 3D Prints- Experiments


To determine the optimal configuration, two kinds of analyses were performed on 3D printed objects of select shapes or deformation. The deformation here indicates whether the overall shape of the object is tapering or not. The shapes chosen were right circular cylinder and right circular cones. These objects were printed at different levels of infill and with different colors. The colors are referred to as pigmentation, especially in the figures.

The first was a statistical experiment, performed to determine whether the shapes conformed to the specifications. The second was a tomographic scan to determine the variation of structure and the layers of the printed objects.

The printed layer thickness was set to be approximately 200 µm. The printer used was Ultimaker 2+ Extended. It was set to the following settings: nozzle size of 0.4 mm, nozzle temperature set at 210 °C, default build plate temperature of 60 °C, and PLA filament thickness of 2.85 mm. Fig. 1 shows a selection of print samples of different colors, shapes, and infill.

Fig. 1 Print samples from one set of experiment

2D designs, Engineering, Interactive Design, Optimizing 3D Prints

Heat Maps

It’s 3.14! Happy Pi Day!

A heat map is a graphical representation of collected data, where large data points are plotted in such a way that it represents the concentration of those points through colors. The color scheme depends upon the choice of the user. Normally, a darker color represents higher density and a lighter color, lower density of the data points.

Using heat maps often help identify the flaws within physical objects (if one knows what to do and how to use it), and movements of mouse cursor, or density of visual concentration while eye tracking in interactive displays.

This makes them very useful in user experience and usability studies to understand why people choose certain parts of a website or a software, and where they have their eyes fixed while using it.

Below is an blurred image of a website (left) and its heat map generated (right) while I was testing it to improve its usability.

Below is a time lapse video of heat maps generated by scanning hundreds of layers of a 3D printed object using an X-ray CT scanner for one of my projects, which has something to do with optimizing 3D prints. More on this another time.


3D Objects, CNC and Machining, Creative, Engineering


Ideas are more or less a mental representation of an object. What thought provoking idea do you have today, I thought some time ago. Then it hit me like a light bulb popping out of thin air in cartoons when the character gets an idea.

Why not make that?

So meta!

Anyway, I had a long desire to make something out of wood, but it had to be 3D. Without any tools in my hand to make a 3D object out of wood, I had to make it 2D. Neither I, nor my tools would budge, so we compromised and decided to make it 2.5D.

Why is it 2.5D? Because I only had access to X,Y and half of Z axis.

In the end, it came out as I had planned. Just like a light bulb popping out of thin air in a cartoon. but this time, out of a block of wood.

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Well, it is called emergence because it emerged like an idea. But it also true that it looks like the idea is still forming while it reveals itself. Enjoy this video, it is a bit longer than usual since this will be my last post on using CNC… For now.

Thank you for reading!

2D designs, Creative, Engineering, Interactive Design

Circular shapes

Circle― the most beautiful 2-dimensional shape, the infinite sided polygon…

No! No it’s not; it’s a limit curve of a regular polygon say the math nerds.

Alright, I agree. But as long as we agree that circular shapes are very pleasing to the eyes. Any object with curved corners looks great― phones, mugs, rings. Even throughout history, circular shapes have influenced the progress made by humanity. I will stop now and get to the point.

So, while designing the Elmentory Atom, I had the option for making these plug and play devices in any shape. Atom itself has 4 types of units. Originally, the plan was to make each unit a different shape. But after doing some research, it was evident that different shapes would be a bad idea. Circular was the best choice.

But, because we were using tiny electro-mechanical components to build them, each unit could not be perfectly circular, but had to have flat edges to accommodate for the rectangular connectors. I don’t know if you can see them― each of them is 35mm or less in diameter― in the images below, but the black connectors align perfectly with the colorful boards.

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Apart from the shape, the other important feature was the symmetry of each device. Each component was placed in a particular spot on the board to make the board look symmetric at least along one axis.

Finally, the most important part (I’m writing this last instead of first because of the title) was to make sure the devices were easy to use. Each of these devices can be connected to one another. But if they are connected wrong, it would not work, yet neither will it harm the user, i.e. the child playing with them.

Each device had a name on the top, and a specific color based on how it operated. Some inspirations were taken from common objects such as traffic lights to specify the color. The bottoms of the devices were mostly white, and helped the child identify if they were connecting the devices correctly.

This project was fun, because I had to literally think like a child to see what could go wrong. Fortunately, there were also several usability tests made with real kids during development to improve the product before releasing it.


3D Objects, Creative, Engineering, Redesigning Something That Exists

Infinitely Remoldable Substance

When I was working on Mobility devices for the Elderly project, my team and I had to do design research on why/how the seniors in the greater New York area used assistive devices for ambulation. While we uncovered many different insights, one of the thing that struck out was the ergonomic nature of the device itself.

Seniors used walkers, canes, rollators, shopping carts and also other make-shift devices to support themselves when they moved from place to place. No matter what device they used, it had to be comfortable to use. Comfort here doesn’t equate to the psychological feeling of stigmatization, rather, it is the congenial ease in using the device itself– hence the ergonomic nature.

When working on the ‘Adaptacane‘, we came across many materials to use it for the grip of the cane, such as memory foam. However, the best material that one could possibly use while making the grip of the cane is polycaprolactone (try saying that a few times). This material, sometimes shortened as PCL, can be molded by applying heat from, say hot water, and shaped into anything, including the shape of the inside of a gripping hand. It is also biodegradable!

Let’s look at an example:

The best part of using this material was that it could be remolded any number of times. The handle (white) of the adaptacane prototype below was made using PCL.

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Pretty cool stuff!

3D Objects, CNC and Machining, Creative, Engineering, Redesigning Something That Exists


The 2010s can be divided into two eras — the time before and after fidget spinners came to existence. The weird part is that they came out of nowhere, and now they don’t seem to exist at all!

In fancy MakerSpaces, it is quite common to make these using 4 cylindrical ball bearings, and printing the shell. However, where’s the fun in boring old 3D printing? Besides, it takes quite a while to print. And not to mention, there is always going to be tolerance issues, because low fidelity printers are not supposed to be accurate.

Truth be told, using a thick piece of acrylic and laser cutting is perhaps the fastest way to do this. But a laser cutter is limited to cutting at most an eighth to a  quarter of an inch, beyond which one will have to repeat the trace on the piece of acrylic. And this would cost, surprise, surprise… the tolerance.

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Regardless of the backstory, I was thinking of using multiple machines to make something. The plan was to use my trusty desktop CNC milling machine along with the water jet. I used delrin to make the case or the shell, and the caps. Then, I cut a thick piece of steel slab into circles, to give the spinner some weight.  All in all, it worked exceptionally well!

P.S. I’m not making another one, not in this way… ever. Also, I don’t think fidget spinners make good Christmas presents.

2D designs, Creative, Engineering, Interactive Design

Holy Diver

With Halloween coming soon, I though about posting a wearable game that my classmate Sam and I made some time ago. It is called Holy Diver.

The principle is that a demon is throwing fireballs at you, while you can catch them and throw it back at it, or defend yourself by joining your palms. However, if you get hit thrice, it is game over!

The game is very small, and it’s prototype can be downloaded here.

The game ran on unity. Well, the song Holy Diver by Dio was meant to be played in the back while playing the game, hence the logo on the costume. It was one of the first time I used a laser cutter on fabric. Laser cutters can be handy in making burned effects on clothes. A costume was made for the game, using Adafruit flora.

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CNC and Machining, Engineering

Water-jet cutting

Water-jet machines are a special class of CNCs which use highly pressurized jets of a mixture of water and powdered abrasive, such as garnet. This can be assumed to be similar to Laser Cutters. They can only cut objects in 2 dimensions. However, unlike a laser cutter, the water-jet can cut through thick metals like steel, aluminum, and even carbon nano-fiber sheets!

Here is an example of a circular disc I cut from a steel slab for a funny little project, which uses the delrin from a previous post.

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Here is another example of water-jet cutting to make a keychain.


Engraving Tools

Engraving on metallic surface doesn’t necessarily need an engraving tool. Depending upon the kind of application, the type of tool can be different. For example, when milling PCBs, a engraving tool can be substituted for a flat end mill tool for better accuracy when it comes to having very minute spaces between tracks, pads or holes.

It is not just the size of the tool that matters, but also the type of the tool used. In a previous post, I had used an engraving tool. Here is just an example of how different it looks when a different tool is used to engrave on a aluminum surface. I used a ball end mill, which is used to give effects of curving or filleting on the edges of the object. Spoiler alert: it did not turn out as I wanted it to.

Check out the video; the process is short and quick.