Week 08. Computer Controlled Machining

This week we started to learn about Computer Controlled Machining. It’s about making something big! The assignment for this week is: 1. Group assignment is to test runout, alignment, speeds, feeds, and toolpaths for your machine.
2. Individual assignment is to make somthing big. It might be a piece of furniture, and the dimension should be 4x8 foot (1.2mx2.4m).

Computer Controlled Machining

There are some project examples of computer controlled machining. Some of the well-known examples are Open Desk and Wikihouse etc. And it reminded me that the reception desk we had at Chaihuo x.factory is also a very good example of projects made from computer controlled machining.

(Reception desk at Chaihuo x.factory, right after it’s assembled It’s made of 196 pieces of compressed wood)

We can use software such as FreeCAD, Fusion 360 to make the design, and then use machines such as Roland, ShopBot to cut the parts, and then assemble them together to make a complete project. Some of the commonly-used materials in computer controlled machining are veneer plywood,OBS (Oriented Strand Board) etc.

And please keep safety in mind, do not use the machine when you are absent-minded or get bored, it might hurt you or you might hurt it, badly.

Ideas for a BIG project

I have been thinking about what BIG project I should make for this week’s assignment. And after a few days of pondering, I have two ideas:

An extendable shelf

The story

Why an extendable shelf? What should it look like? What are the functions? Who will need it? There are a lot of questions to answer. And before sharing the answers, let me tell a story first.

I have been concerning about the plastic bottles we throw away every time we have visitors to our Fab Lab. Sometimes a group of 30 people visited, and they did not finish the bottle of water nor do they bring the bottle with them. The left-over bottle together with the water adds new wastes and burden to our environment. I have been thinking about how to make use of the bottles and water.

And the extendable shelf will come into use!
Why an extendable shelf?

I can make a shelf for us to experiment vertical farming, upcycle the the bottles and left-over water, and at the same time provide a beauty (and maybe fruits/vegetables) to us.

What should it look like?
I am thinking it should look like a Swiss knife. Of course not that powerful nor with as many blades. However, with the extended parts should be symmetrical, to keep the shelf balance.

What are the functions?
It should be able to hold some bottles on each layer (I will create holes based on the bottle size). With hinges on both sides, each layer of the shelf should be able to extended to a certain angle. In this way, the shelf can be folded and remains compact, and it won’t take too much space of the office. We can extend the shelf, and put it under the sunlight for the plants to absorb sunlight to perform photosynthesis.

Who will need it?
Currently I am thinking about experimenting it at Chaihuo x.factory in Shenzhen. Will see how it works!

The Design

First of all, I tried to make a sketch of the extendible shelf on my notebook. Drawing was not really my strong point. So I googled for some ideas. And I saw this sketch is similar to what I wanted to draw. It’s a Swiss Army Knife shelf made by a Mexican designer Ivan Hernandez Quintela. Thank you Ivan!

(image from the internet)

And my shelf just needs to have more spaces between each layer, should be tall enough for placing the bootle & give some extra room for plants to grow.

And now I will need to make the design by myself. Since the CNC router in our Fab Lab needs dxf. file for cutting, I decided to use Inkscape to make the design. And when I started to make the design, I found it IS very difficult if I want each layer to “spin off” at a certain angle, like the Swiss army knife. So I decided to make it extendable like a drawer. The difference is my shelf will be extended to both sides. So when extended, the three layers of the shelf will be exposed fully to the sunlight.

And I will need the following parts:
_ Stand2 (They are the legs of the shelf)
_ Layer3 (The top layer is fixed, and the other two layers of the shelf should be extendable. And there are holes on each layer, so that I can place the bottles on each layer.)

We have 1.8cm plywood for CNC router, so I decided to use the following parameters in the Design:

1. The stands:
2. Dimension: 90cmx40cmx1.8cm (Height x Width x Thickness)

3. The slot with the dimension of (1.8cmx0.8cm) 1.8cm as the thickness of the plywood, and 0.8 as the depth of the slot.

4. The layers: Dimension: 118.4cmx40cmx1.8cm(Length x Width x Thickness)

Since the CNC router at Chaihuo x.factory needs to be fixed. I went to SZOIL to use their ShopBot make the shelf.

My initial plan was to design the slot in the shape of a lying T, and then on both ends of each layer, I will cut a slot on the top and the bottom surface as well. In this way, it will work better when we slide the shelf. However, I was told that the ShopBot couldn’t cut clots in the T shape, so I give up the plan

(A preview of my design)

• The left part: shelf leg, will need 2 identical parts
• The upper right part: the top layer of the shelf
• The lower right part: the 2nd & 3rd layer of the shelf, will be extendable

Testing on the Machine - Shopbot

When measuring the materials at SZOIL, the dimension is different from the ones we have at Chaihuo x.factory, their plywood is 1.7cm in thickness. so I modified my design a bit. We learn to use the ShopBot.

(I do enjoy getting my hands on tools! :D)

Software Needed:
1. V-Carve4: It will help convert the dxf. file into sbp. file which will be understood and deciphered by ShopBot.
2. ShopBot: It is the main software that manage ShopBot.

Hardware Needed:
1. ShopBot - of course! :D
2. Vacuum cleaner - for cleaning the wood ashes
3. Wrench - for changing the drills (if necessary)
4. Electric screw driver - fix the wood onto the machine or remove the used wood/materials
5. Computer - connected to the ShopBot, to control the ShopBot
6. Flash drive - to transfer the design file onto the computer for cutting
7. Goggles - to protect our eyes
8. Mask - to prevent inhaling the ashes into our lung

SOP of using the ShopBot:
1. Open V-Carve4 client to convert dxf. file into sbp.file
(1) create new file
(2) set job size
(3) change unit to “mm”
(4) select resolution as “standard”
(5) click “OK”
(6) File => Input (choose “vector file”)
(7) save as sbp. file
2. Open ShopBot client on the PC：calculate => show the path => close => click ”save“ icon => select the profile => save toolpath
3. Operate the machine
(1) turn on the “switch” button on the wall power
(2) turn on the switch of the ShopBot (a yellow/red switch) and open the “lock” (when the key can’t be pulled out, it means it’s in ‘open’ condition)
(3) turn on the “safety switch” (pull the knob to the highest point, and then press “ReSet”)
(4) turn on the drill switch (First, press the “LO” button, and then Press the “RUN” button)
Press “STOP” to turn off the drill switch before changing the drill
(5) To set the drill level: press “to move tool” button on the ShopBot client to move the drill. When it’s close to the cutting surface, press “save the origin”.
Turn off the switch, use wrench to change loosen the drill and adjust its height/level.
(6) when the drill is set. Press “ReSet” => “Cut Part” => Import File => Start => Yes => Yes => OK. And then the ShopBot will begin cutting.

With the theory knowledge learnt and recorded. We changed the material with a 1.7cm thickness plywood, using screwdriver to fix the materials onto the cutting bed. And then we began cutting some small parts of our design to test whether the material, its thickness and the design matched.

I chose a corner part of the shelf leg and a corner of the top shelf. It turned out the joints are a bit rough. So I used a piece of sandpaper to grind the edges, and then used a hammer to help put these two pieces together. It worked.

(My test parts worked)

It seems it will be even more difficult if the whole project needs grinding to make the joints work. So I upgraded my design a bit.

However, after cutting my test parts, we noticed the ShopBot did not work as we expected. Because when it cut Aisling’s test parts, it ran out of the present job size area. So we need to figure out why the origin was not in the right place. So sad that we did not get a chance to verify how the SOP we learnt previously.

And it was already 11pm when we figured it out. We need to come back before starting to actually cut our designs. Meanwhile, my colleague asked the technician to come fix our our CNC Router at Chaihuo x.factory. I thought it will be ready by noon today, but it turned out the motor needs to be replaced and the technician did not have the motor with him. So he will come back tomorrow to fix the machine. I will be able to use the CNC router at Chaihuo x.factory to finish this week’s assignment. Will update the pictures of the finished project later.

Cutting the Design with Machine (Brand: TIANCHENG XINLI, Model: TC1325B)

To use the CNC Router at Chaihuo x.factory, I need my colleague CY to instruct me how to use it. And here is the update of the hardware & software I’ll need:

Software Needed:
1. Inkscape to build the 2D dxf. file.
2. MasterCAM - for converting my dxf. file into the file recognizable by the CNC router.

Hardware Needed:
1. CNC Router (Brand: TIANCHENG XINLI, Model: TC1325B) - for cutting the pieces 2. Vacuum cleaner - for cleaning the wood ashes. (We have the tube installed in the workshop, so it’s all set)
3. Wrench - for changing the drills (if necessary)
4. Screws & wood blocks - for fixing the board onto the machine.
5. Computer - connected to the CNC Router, to control the CNC
6. Flash drive - to transfer the design file onto the computer for cutting
7. Goggles - to protect our eyes
8. Mask - to prevent inhaling the ashes into our lung

And after looking at my design, CY suggested I updating the design, with the following reasons:
1. The length of 1.2m might be a challenging if I only have two legs on the both sides to support. And we’ll need more than 1 piece of 1222*2444mm wood to make this project.
2. The holes are too big and we’ll need strings/threads to hold the bottles of the water. I should make the hole only a tiny little bit bigger than the bottle.
3. If cutting a slot of 0.8cm for holding the two layers, the left-over parts might to two thin to hold & support the weight (especially after we add soil & water for planting the flowers).
4. With only two legs to support, the legs might be deformed as time passes by.
5. The top layer design will need extra materials (glue or nails) to make it stick together. Why not try a new design that can press fit instead.

I find the reasons are very valid. So I updated my design again, with the following features:
1. Dimension: 900x900x400mm (Length x Height x Width)
2. Dimension of the wholes: 65mm in diameter (the bottle is about 62mm in diameter)
3. Add two lines of slots on both sides of the previous slots, and use an extra piece of wood (50mm in width) as the holder of each layer.
4. Add another two parts at the bottom as extra support.
5. Add one line of slots (similar to item 2) for putting the first layer.

And here is the updated design.

(a preview of the upgraded design)

Notes: - Part 1 & 2: the legs of the shelf
- Part 3: top layer of the shelf
- Part 4 & Part 5: 2nd & 3rd layer of the shelf
- Part 6 & 7: the bottom support parts of the shelf
- Part 8: the holders of the 2nd & 3rd layer. (I only need 8 pieces, but cut 10 pieces in case there are extra needs)

The first time we tried to use the machine, it did not work well. The machine couldn’t go back to the origin as expected. What’s more, there is a big tolerance, the machine won’t be able to cut the line straight, there are a few degrees of angle tolerance. So we asked the technician to come and fix the machine again.
And now it worked. I began using the cutting my design into pieces. And this time I used HDF instead of plywood, because we do not have enough plywood in the space at this moment.

Here is the procedure of operating the machines:
1. Turn on the power of the machine (press to start) [Note the mushroom shape knobe is the urgent switch]
2. Turn on the power of the host computer
3. Open the CNC’s client (in Chinese 耐刻)
4. Click “go to the machine origin”
5. Click the arrows to move it to the origin.
6. Place the material onto the cutting bed.
7. Open the CAM client “MasterCAM” and open the file for cutting.
8. Click the mouser to show the coordinate axis (in yellow cross shape)
9. Click “transfer” => “move” => “select” => “select” => “execute” => “between two points”
10. Create new tool => toolpath => operating management => chart => right click the mouser => toolpath => contour milling => cascade => click the file => execute
11. “key” => create new tool => plane blade => set the diameter as “8mm”
12. Set the tool parameters:
- feed rate: 5000
- feeding speed: 500
- raising speed: 5000
- spindle speed: 5000
13. Set the milling parameters:
- unselect ”reference height”
- select “safety height(50)”
- feed position (1)
- depth: -20 (please note my material has 18mm thickness)
- reserved value for XY direction: -0.05
- unselect ‘engage/retract vector’
- contour milling => helical gradual slanting
- select “gradual chamfering” => vertical postion = chamfering depth: 3
- confirm
- confirm
14. click “graphic (1) cascade”
15. right click “cascade” => change compensation direction
16. execute post-processing => change post-processing mode
17. select the MPFAN.pst file in Disk C => open
18. confirm => confirm => save
19. screen => configuration => file => file name => slect MPFAN file => confirm.
20. adjust the origin’s height
- click “main axis” => spinning (click F11 to stop)
- select “0.5mm”, click the downward arrow, when the dril dip touches the wood, stop.
- click “working axis”: X 0, Y 0, Z 0;
21. Code: open & load => choose the file => open
22. Press key F8 to simulate the milling process, re-press F8 to stop simulation.
23. Press F9 to start cutting. (If there is anything wrong, press F11 to pause.)

(It statrs cutting on the CNC Router at Chaihuo x.factory)

It took about 2 hours to cut all the pieces.

And some of the pieces were not cut well, so I used a rasp to sander out the extra parts.

(Corners to be grinded)

（the rasp I used)

And for the parts that are large and along the edge, I used the table saw to cut out the extra parts.

(extra parts to be cut out)

(cut out extra parts with table saw)

After all the parts are finished cutting & grinding, I assemble them together.

(All parts are ready to be united into one)

(Assemble the Parts into a Shelf)

And you can see how it works in the following short video.

(A video showing how it works right after finished assembly)

And here is a look of the finished extendable shelf, put into our office!

(Voila! The extendable shelf)

The flower seeds I bought online also arrived. I will begin planting flowers. Can’t wait!

Special thanks to my colleague CY for giving suggestions about upgrading the design and in teaching me how to use the CNC Router!

A toy house for pets (cats specifically)

I recently had a little kitten as our new family member. And her name is Summer. I have been thinking about making a toy house for Summer for a few weeks. So I think it’s a good opportunity to make one this week. It took me more than 1 week to make the first project - the extendable shelf! I won’t be able to make another project for now. If I do make, will surely share!

Downloadable Files:

1. dxf file
2. Inkscape svg file