Preamble

This week, we have to make something big on the CNC machine and explore the underlying difficulties such as testing joints, using fixings, adjusting feeds and speeds, depth of cut,...

As a start, Thomas from the fablab Woma in Paris gave us a presentation on CNC milling machine and woodworking. He showed us this really nice video that really inspired me:

Love Letter to Plywood. By Tom Sachs from Tom Sachs on Vimeo.

We discussed with David and Victor about what to make. I wanted to make a kind of japanese table and/or a working bench for my kids (so they would have the same as their father). David suggested to start by exploring 3D design of furnitures on Opendesk and reverse engineer those design to understand tips and tricks used to make furnitures.

Your LAB - The fablab in Andenne

This week was the opportunity to visit and use for the first time the machines of the fablab Your LAB in my hometown, Andenne, that just opened at the begining of 2017. Xavier is the fabmanager who set up the lab from the ground up and he is full of talents. I called him to come and see him.

Your LAB is well equipped with several 3D printers, a Trotec laser cutter, a huge CNC milling machine and a self-made ceramic 3D printer made in collaboration with our Fablab in ULB. The aim of this fablab is to allow to locals to use digital machine tools, allow the young generation to be immersed in these new technologies. They propose workshop, training and access to the machines.

Xavier's tips and tricks

When I arrived at the fablab, Xavier was making a table with the CNC milling machine. He is used to make furnitures. Xavier is one of those who loves what he makes and have a deep respect for techniques and materials. This was so inline with this week's assignment. He showed me tips and tricks related to furniture fabrication with digital tools and how to design in Fusion 360.

After drilling the table with the CNC, Xavier was making a chamfer around the table top using a palm router. He showed me the drill bits and we talked about the positive and negative drilling bits and also milling bits. To make a chamfer, he would take into account the drilling rotation, the motion of the tools and the wood grain to avoid wood chips as shown on the figure here below.

When drilling with the CNC, it is always a problem to make really sharp and pointy corners as we use a round drilling bits. Cutting a part from the outside, it is not a problem to make outward angles. But inward angle is a problem, so a trick is to use dogbone so we can perfectly fit to pieces together.

(1) Here is an example of two pieces can be join together. (2) Also the vendor says that he sells wood with a 18mm thickness, it is not exactly true. Here we measure 17.7mm. Also wood will continue to change its dimension during time and over the seasons. (3) this was made a few month ago and the opening of the joints was made to be equal to 17.5mm. We now measure 17.95mm. The two pieces can be joined perfectly. When designing joints, it is really important to make a few tests before cutting a furniture. The best being to make a 3D parametric design with the thickness of the material as a parameter so we can adapt really easily the drawing to the material we are using.

Xavier masters Fusion 360 like an artist. He gave me a crash course on how to make a really simple furniture in Fusion 360. That gave me the impulse to learn the basics of Fusion 360 over the weekend.

The CNC milling machine

At the fablab in Andenne, they have a large CNC milling machine, a Cyborg R-1325 with a drilling area of 1230mm x 2500mm x 200mm. This machine is really impressive and has a some really nice features detailed here below.

Calibrating the CNC

Here is the vertical touch plate that we have to place on the piece of wood that we would like to cut. The CNC will move the drill downward towards the sensor and will measure the vertical position of the piece of wood.

Fixings

To fix and hold the wood boards while drilling, we make a vacuum under the workpiece. The workpiece being in MDF which is porous, the boards are sucked onto the workpiece. Here is a video showing the technique.

Security

The machine stops when the infrared beam coming from (1) is cut or when the black and yellow security barriers (2) touch something.

The 3D design in Fusion 360.

Sketching the table top

This week, I took opportunity to learn the basics of Fusion 360. I chose to start with the low table in a shape of pear. In the sketch mode, I drew half a pear using the spline tool. I then mirrored the sketch to have a symmetric table.

A parametric design

I then created a parameter called t that is the material thickness. The material I chose is MDF with a thickness of 18mm. I will thus make this parameter a little bit smaller so the joints will be tight.

Extrusion, from sketch to body

I then extruded the table top sketch design using the thickness parameter t which creates a new body in Fusion 360.

Making the joints, combine and cut bodies

In Fusion 360, it is important to work with different components which includes different sketches and bodies which can be seen on the left menu bar. We can also easily hide them using the little light icon next to the sketches and bodies.

I decided to create half a table that I would mirror later. To create the joints in the table top that would hold the table feet, I used the combine tool and used the table top as a target and the feet as tool bodies. Make sure to tick the box, Keep tools, so you keep the feet.

Here we can see the joints in the table top, that were created.

Using fillets to smooth the edges

To smooth the edges of the feet, I used the fillet tool.

Mirror

As I designed half a table, I used the mirror tool to make the whole table.

Test your parametric design

This is a really important part ! We have to check that our design is fully parametric. By changing the thickness parameter, check that the design adapts itself in a logic maner. If not, there was a problem in the way you built the design.

I struggled a bit with the parametric design for designing this table. Next time, I will check the parametric design every time I create a new body. Repairing a file that is not well designed from the begining is really challenging.

Dogbones and preparing the sketches for export

I then, installed the dogbone addin for Fusion 360. I added dogbones to all the problematic joint edges as can be seen in the figure here below. It is important to make the dogbones with the addin at the real end with another saved design as the addin do not allow the dogbones to be parametric.

To prepare and export the sketch for the CNC, there is a really nice way of doing that. Activate the full design. Click on create a new sketch, then select the face of the body you would like to cut. It creates a new sketch in the principal design sketches (here below it is sketch 14). Then, right click on the sketch and export as DXF. Repeat the sequence for every piece face, you would like to drill.

Preparing the 2D file for the CNC

Nesting in Illustrator

I then opened illustrator, and imported all the DXF sketches that I wanted to drill. Each piece can be made with different piece of lines. It is important to join them, so the piece is made of a fully closed line. To do that, select all the lines outlining your piece and click on Divide in the Pathfinder menu. Then change the stroke weight to reveal the trace. When all the piece are placed on the illustrator file (at the dimension of the wood board), nest the pieces to save wood and export the file in a illustrator file or a dxf file.

Drilling testing joints with the CNC

Setting up the CNC with the enRoute software

First, let's set the wood board dimensions.

Then, we have to select the CNC parameters and create the toolpath.

Toolpath simulation

We can also make a simulation of the CNC toolpath.

CNC milling of the testing joints

(1) set up the toolpath on the enRoute software. (2) Checking that the fixing with vacuum is holding the board and do not move. (3) Making sure the aspiration of the wood chisp is set up. (4) zeroing the vertical position of the drill bit with the force sensor.

Here is a video of the CNC milling the test joints.

Let's now drill our table. The blue cross will be drilled inside at a depth of 10 mm. It will drill all the material inside the crosses.

We then selected the outline and changed the drilling parameter so the CNC will cut outside and up to a cute depth of 18.4mm.

CNC milling of the table

Using enRoute software we set the toolpath of the drill based on my drawings exported from illustrator.

Here is the CNC milling the table.

Team building, assembling the table

Thierry and Michele helped me assembling the table. (1) There was a problem in the exportation from Fusion to Illustrator and the curve was made of straight lines, Thierry helped me sanding the side of the table. (2) the slits for the feet were too tight, we had to enlarge the slits using a chisel. (3) Assembling the feet. (4) Sanding and finishing the table top.

we then glued the press-fit feet to the table and hold the whole tight for several hours.

Hero shot

Here is the table with the shelf of Michele on top of it. We are pretty proud of the job !