Week 7. Computer Controlled Machining

Before the Start

Introduction πŸ–Š

This week relates to the CNC machine. Probably the most dangerous tool you can find in FabLabs … in fact, it can easily get on fire, or damage the human body if the user has his / her six instincts alert!

We will learn how to make big things with it, so it will be a very creative week again! My kind of week :)

Fab Assignments πŸ“š

My Goals 🎯

Project Management

Task Time Day
Research 3h 9, March
Group Assignment 6h 10, March
Design and prepare file 8h 11, March
Milling 4h 14, March
Sanding and Assembling 2h 14, March
Documentation 8h 10 / 11 / 12 / 14 , March

Files πŸ“‚

Name Description Link
File 0 Rocking Chair Link


FabAcademy Students:

Open Soruce Chairs:

During the Process

Results πŸ––

Rocking Chair Press Fit


Group Assignment Process πŸŠβ€β™€οΈ 🏊🏾 πŸŠπŸ½β€β™€οΈ

A few days before the start, our local instructor Henk warned me to wear black clothes for the CNC experience. In fact, working with these machines results in being the most dangerous but also the dirtiest experience within Fablabs.

Safety steps 🦺

It is very important to follow Safety Instructions when using a CNC machine. These are some tips to work safely with general CNC machines at Fablabs. I found the info in the following website:

DO βœ…


Our local instructor Henk also introduced us some safety instructions to work at the Waag’s CNC:

Escape doors

In case of need, the Waag’s fablab has two emergency doors located next to the CNC machine.



Sometines, when the machine is not working properly, the dust can start making smoke within the dust bin. To prevent the fire, open the botton part of the dust bin and smell the air. If it smells like fire, use the extinguisher located next to the door to stop the fire.



The electronics panel is located on the back side of the CNC machine. In case of fire, turn it OFF.


Emergency button

There is an EMERGENCY RED BIG BUTTON located on the machine’s front. Tap on it just in case of emergency. This button will completely stop the machine. Will be needed to re-calibrate, add files and set up the machine to continue with the work.


Start the machine

Put your hands up and stay in front of the machine when starting it. There are moving parts which could be dangerous if you are too close to them.

Always clean the surrounding of the machine, make sure there are no things resting on the machine before starting it.

Clean the sacrificial surface before starting the machine.

CNC Machine Components βš™οΈ

The Waag’s CNC machine is a ShopBot CNC Mill. Attached is a photo and a scheme of the Waag’s CNC machine area:


Component Task Location*
Computer It is the connection to the machine. Use the ShopBot software to calibrate, load files, and work with the machine. Front / Left
X - axis The X - axis points perpendicular to the user position
Y - axis The Y-axis travels parallel to the user position
Z - axis There is a bridge, where the Z-axis is located
Milling head Where the bits are located Above the Z-axis bridge
Sacrificial layer MDF sacrificial layer to prevent to cut the CNC board On top of the machine’s board
Emergency button Use just in case of emergency to completly stop the machine. Front / Right. Big button. Red color
Fire extinguisher Extinguish the fire in case of emergency Back / Righ. Next to the dust bin room
CNC Button ON/OFF Turn ON / OFF the machine. Right / Down side. Red color
Air extractor Extract the dust produced during the milling Bblack / Right. White long tube connected to the ceiling
Air extractor 1st button Turn ON / OFF the air extractor Back, next to the dust bin room. Once activated, a green light turns on.
Air extractor 2nd button Turn ON / OFF the air extractor connection to the CNC machine Right. Small button. Red color
Intensity Air extractor controller Control the intensity of the air extractor Right, next to the Air extractor button. Red color
Speed control Here is were the speed of the machine is setted up to 18K r.p.m. Front / Right. The white box with the red leds to controll the speed

*Location relative to the user’s position

Machine Workflow πŸ”’

Attaching milling bits


There are many different kind of milling bits, depending on the material, speed, and final result of your work.

Important! πŸ†˜: Is important to assemble the pieces in that order, otherwise, the milling bits will have a lot grades of freedom, not work properly and the machine will scream.



Tip πŸ›ŽοΈ: leave 4 cm of the milling bit outside the nut, and check that the bit’s top is coincident with the inner part of the nut-like in the attached photo.



Tip πŸ›ŽοΈ: Don’t fasten it too much, you also need to take it out!


Important! πŸ†˜: Double-check that the dust skirt is well located, in order to ensure that it will not fall during the milling and damage the materials.

Preparing your file with V-CARVE software

V-Cave is the intermediate software needed to set up most of the parameters (ex.: speed, milling bit diameter, …) needed to work with the CNC machine. It will generate a G-code for the machine.

During the group assignment, we learned how to use the “pocket toolpath”, “drilling toolpath” and “profile toolpath” following these steps:

Name Measure Reference
Job Size 17.5 Material’s thickness. Measure it with the caliber. Plywood is never uniform, so it’s important to measure the thickness in different parts of the sheet and make an average before adding the info to the software
Material Down Refers to the Z-axis starting level
Datum position Left / Down corner Setting up of the X and Y axes referring to the material sheet
Units mm Its possible to choose between mm and in

Important! πŸ†˜: As we learned during the laser cutting week, it’s important to cut the pocket toolpath before the drilling and the profile, since the material can move during the milling. Resulting in the pocket designs not being centered and showing cut problems.

Important! πŸ†˜: It is important to note here that the milling machine can not make 90ΒΊ corners because of the geometry of the milling bits. This is why V-CARVE offers 3 different ways to design the corners on your design. For our group assignment, we decided to try the three of them in order to check how they look in the final result.

Tip πŸ›ŽοΈ: When saving the files, order them like this: Pocket Toolpath > Inside Toolpath > Outside Toolpath. In this way the machine will follow this order to avoid milling mistakes.

Turning On the machine

Once the milling bits and the design file are ready, you can turn ON the machine and leveled it before start the milling:


Tip πŸ›ŽοΈ: Let the machine warm up a little bit before the start.


Calibrating X - Y axes

Now that the machine is ON, it is possible to calibrate the axis for the group assigment. In order to do that, we followed this steps:

Important! πŸ†˜: Always turn ON the machine before opening the software, otherwise, Shopbot will give errors because the connection between the machine and the software is not setup up.



If you want to change the origin of the X and Y axes, use the keyboard arrows to move the Shopbot to the position wanted, and then press the header option:

    [Z]ero > zero[2] axes (X & Y)

Tip πŸ›ŽοΈ: When re-calibration the X and Y axes, good advice is to take a picture of the new coordinates, in order to be able to re-start the work in case of need because of a fuse, emergency, or other problems during the milling.

Calibrating Z


Important! πŸ†˜: When calibrating the Z-axis in the CNC machine, the metal piece will be located on top of the sacrificial layer, and not on the material like we do when calibration the laser cutter machine.


Locate the material on the sacrificial layer


Load file

Double-check everything is OK


Once you double-check everything is ok, Start the Milling process following this steps:

As explained before, first we will drill the circles where the screws will be drilled. This step is needed in order to ensure that the material sheet is well connected to the sacrificial layer, and does not move during the milling.


Load the second file with the pocket, inside and outside profiles and START again the program to mill them:





Now we can check the features of our result:


Extra check with Saco Climb Vs. Conv.

With my fellow student Saco, we decided to check out the difference between the inside profiles step up with the “Climb” milling bit direction instead of the “Conventional” direction.


Individual Assignment Process πŸŠβ€β™€οΈ

As the individual assignment, I decided to design a rocking chair. I will use it to listen to podcasts, read and drink coffee every morning before the start of the day! 🌸


Design Process

Early stages

I already designed an office chair during my bachelor’s degree, thought to be made with a CNC machine. I never had the opportunity to build it up, so I was looking forward for the Fab Academy to start to be able to design a new chair, or even build up that one.

Attached is the photo of the “Men’s chair” which is designed during my bachelor’s.



First of all, I did research about the CNC chair’s possibilities already existing in the market.

Attached is the link to the Pinterest mood board which I did before start designing my rocking chair.


Since I recently started to take my time during the mornings to read and listen to podcasts while drinking my coffee, I decided that was a good idea to make a rocking chair where to enjoy my staring of the day.


Probably the most important step of designing a chair is to study ergonomics around it. I did research about the angles and measures needed to make it work before starting my 3d model.


Since I want to make a rcoking chair, the measures which I will need to take in consideration are:

Measure Number
Angle with the X 15ΒΊ
Angle with the Y 27ΒΊ
Distance from the user sit position, to the end part of the chair’s sit at least 30 cm

I checked also the measures of the Fauteuil chair to consider the general size of my rocking chair:

Measure Number
front 62 cm
side 67 cm
height 55 cm


On Friday night I felt inspired and decided to start designing my rocking chair. I did some sketches and prototypes using the cardboard from a shoebox.

As a designer, I think about my designs from a sustainable approach. Less is more, aesthetically talking, but also in terms of material consumption.

Since materials are square-shaped, I wanted to make a very minimalistic design. Using the less amount of material possible, but making the chair look simple and comfortable.


3d parametric design

I did use parameters for the 3d development of my design. I considered it cool to make as a parameter the joins dog bones, in this way I could play with them and choose the size which functionally-esthetically I liked the most.

I started designing the profile part, this is which take me the longest time to make it work with the rest of the poieces.


Prototyping with cardboard

Once I had my 3d model, a good practice is to always make prototypes to make sure things work actually fine - and not just in your mind.

I came to the Waag and make a few prototypes of the rocking chair using the laser cutter machine.


During this process, I thought it will be nice to have a hang holding to be able to easily move the chair. So I did some tests and finally choose a design with the dog bones joins.




In order to mill my rocking chair, I followed the steps previously learned for the Group Assignment.

I first measured the material thickness and did an average with 5 numbers measured in different parts of the board. My material thickness resulted in being around 17.6 mm, even if it should be 18 mm.

I then located the material on the CNC sacrificial layer with some extra help from our local instructor Henk.


I did have some mistakes when preparing the file with V-Carve.

Since our X axis is in the position of the Y axis if we look at the machine from the front. When preparing the file, I reversed the measurements to work with our CNC machine. So, starting to drill the holes, the machine crossed its limits.

Tip πŸ›ŽοΈ: Always double-check your CNC axis before setting up the material features with V-CARVE.

I did try 3 different offset numbers in order to find the perfect parameters to work with my design.

Firstly, I tried offset -0.4. Since I design my own dog-bones shape, the machine travel was eating too much material and the pieces were loose when fitting together.


Secondly, I tried offset -0.2, adding also a “separate last pass” to the design to make the inside profile smoother. The result was fitting perfectly using the hammer, but I had some trouble taking out the tabs from the inner profile.


Finally, I tried the offset -0.3, using fewer tabs in the inner profiles. The result worked okay, but I could see in the -0.2 sample that the joins were fitting much better rather than in the -0.3 sample.


Finally, this are the parameters I used to set up the inside and outside profiles of my design:

Measure Number
Start Depth 0 mm
End Depth 17.6 mm
Tool 5 mm milling bit - same parameters as the one used for the group assigment
Allowance offset -0.2
Do separate last pass yes
Tabs Lenght 8 mm
Tabs Thickness 3 mm

Tip πŸ›ŽοΈ: Always recommend doing some first tries to check the tolerance needed for your material thickness if you want to make a design like mine without using glue to stick the parts to each other.

Another mistake that I did was starting the milling without turning on the machine spindle. Yeah, I know … but it can happen when making tests and turning ON/OFF the machine multiple times in a row … When making this mistake, luckily the milling bit did not broke because I saw the mistake in time, but the Z-axis did move so I had to re-calibrate the axis. Luckily since I had an empty part from the sample tests, I was able to recalibrate the axis using the sacrificial layer.


When milling the pieces, one of the inner profiles did not have enough tabs, so it moved and I had to stop the machine, take apart the leftover material and start it again.

Important! πŸ†˜: When stopping the milling, always make sure that the milling bit is traveling from one point to another of your design, otherwise the friction between the material-bit when it is ON again could start a FIRE!

After a raw day of learning how to use the CNC machine, my design finally worked out and I could not be happier.

Attached are photos of the milling result and my fellow student Jonathan helping me to unscrewing the material sheet :)



Last but not least - in terms of time - I did the sanding of my new rocking chair. It took me a long time leave it smooth and well looking, but I did it!

I used a few tools which the Waag’s workshop has, like the sanding paper and the sanding machine to do the profiles.



The assembling part was probably the most satisfying. Putting all the pieces together, seeing that everything was perfectly fitting, and swinging on it was a really self-enhancing moment!

My roommates were also excited about the result and had some fun rocking for a while!


Retrospective πŸ€”

Probably the most empowering week since the Fab Academy started.

As an industrial designer is always a big pleasure being able to make real our ideas, passing from the prototype to reality is a big empowering step to do! I can say, thanks to this assignment I did a βœ… on my design to-do’s list.

Most of the problems that I had were with using V-CARVE and when using the milling machine for the first time. I did have luck because the mistakes which I did were not irreversible, so I could properly end the individual assignment and be proud of the result!

Working with the big CNC machine has been a challenge in terms of learning how to use it with respect and not being too much afraid of starting a fire / getting big troubles with it / or not making it properly work. I have to admit that its dimensions and the tragic stories behind it made being a bit afraid of it. Especially when I started the individual work.

At the end of the day, I felt that I at least learned the basic important principles to have good use of them, which has been a very empowering feeling. I already have new ideas which I would love to make with it. 🌸