9. Textile as scaffold¶

crystal

shopbot - CNC machine¶

We learned how to use the big and famous CNC milling machine, before saying anything it's a very powerful and helpful tool. We need to follow carefully the instructions and make sure to check all the boxes in the checklist. One of the reasons to be very careful with this machine, is that it uses a lot of power and also is an open machine.

SAFETY RULES:

The entire bridge in the X axis goes from side to side all the way. Whatever you are doing make sure to have everything clear on the surroundings, no wooden piece, plastic or whatever;
The dust tube collector goes in the big vacuum into the little room in the back, be sure to be on;
Be careful - if you are using a wooden sheet with screws or any sort of metal, the metal can provoke sparkles and this sparkles are going into the vacuum bag and it can all catch fire, we don't like fire;
Tide up your hair, previous acident happend with long hair getting pulled by the bid spinning 1800 rpm!
Never stand by the bridge sides, as the tool needs to move up and down;
If you are pausing the machine do it when is traveling around and not milling, otherwise heat can be generated and FIRE problem again! If you want to pause when it’s milling you have to tell the computer and manually to lift the z axis;

Shopbot dimensions are 1.22 x 2.44 m, the standard size of wood sheets as well.

PARTS WORK 3D software - preparing the stl file¶

We used the PARTS WORK 3D software. Place the usb stick and copy your files into a folder on local drive.

The main settings are:

Orientate and Size model : here you need to open the stl file and check the orientation you want to place it on the table, your file might be mirror so you need to flip it as well. Check if the size is correct and press Apply;
Material Size and Margins : this is where you input the material size and also place your file into the material. You can trick the software giving a smaller material size then reality, so you know where is it going to be placed. Also make sure to have the Machining Margins around Model less then the width of your bid, so it doenst need to do multiple layers on the borders;
Roughing Toolpath : the rough toolpath removes the “excess” of material. Here is the End mill setup, pass depth and stepover as well (the higher this number, less precise but faster the cut is). Strategy: should be Raster Y, because is easier for the machine to move along Y then along X. Press Calculate. The stepover is the distance between the lines of the mill bid;
Finishing Toolpath : the settings here should create thinner lines, you can also choose a different mill bid. Again the direction should be "Along Y"
Cut Out Toolpath - didn't use
Preview Machining : nice video ;)
Save Toolpaths : after doing all the settings you need to save the toolpath .SBP. When you use the same tool/tip you can save both paths together, if you are doing two different ones then you can save them apart. Is also good to save the Parts Work file as well, in case you need to check some of the settings;

After having the TOOLPATH FILES ready you go for the machine setup

MILLING MACHINE - preparing your working space¶

Clean the table, put the double-sided tape in the bottom to attach on the table and attach it with wood and screws both sides
Place your screws to make sure the foam is super fixated to the table
Collet and Bid should be fitting tight. The nut is the piece that goes into the machine

SHOPBOT software¶

Turn on the machine
Open the program. Only open the software when the machine is on, otherwise it gives you error message.
Press K to work with the machine manually, the yellow box comes up. Bring the tip close to you and move it up on the Z axis (Pg up command)
Unscrew the butterfly in the back to lift up the skirt so you can work in the tip
Then you connect the bid, nut and collet. Measure how much you want to have out. See videos

tool

Move the skirt up amd tide up the butterfly in the back
Zero the X-Y axis (Machine home point). Click on the buttom “Tool is now zeroed...” press ok
Need to define the job home (diff then the machine home) - press K and move manually the tip to your job home point. The yellow box values are the job home. Always have a picutre of this, in case you need to go back to it
Press zero so the software will know that this is the job home. And now is the new red pannel with 0 and 0
Level the Z axis. Using the metal plate that is stored in the machine, put it under the milling bid. The metal plate itself is the sensor, but creating an eletronic circuit it knows that the tip of the bid touched it (the machine knows that the metal plate tickness is ~3.007 mm)
Test if the sensor is working by touching the metal plate in the bid a light comes up in the first hole
Press "Zero Z" to level the z in the middle of the place where you are cutting; weird message shows, Press Ok
Now the only thing you can do is to move up, so PRESS K AND PAGE UP > to remove the metal plate
Open your file
Turn on the dust collector
Turn the vaccum buttom on the table
Take the key an turn the milling on
You need to change the speed turning manually. Most of the times the rotation speed is 1800 rpm (like the settings, but if you need to adjust is by hand here)
Then press start on your file!! The tip goes to home and then starts milling
If you need to pause the machine you need to be traveling, you can see that on the lines that the machine is following. Just press space bar to pause and if you need, press QUIT.

foam crystal - mold¶

I decided to make a simple, straight line, geometric shape. So I did in Rhino with Grasshopper a diamond/crystal shape and transformed it into a mold. I sourced the intructions on how to do it from this video:

designing the shape | Rhino & Grasshopper¶

The crystal shape was made only with the Voronoi command inside Grasshopper. Here is the step by step how I did it:

Make one single point
Multiple points to play arround
Box creating the edges
Having done the inputs you can play around with the dots to create the shape intended, when it's done you need to bake it, so the shape goes to Rhino.
I designed a positive and negative mold. Because we have limitation in therms of height, I made it in 4 different layers to later assemble together. In Rhino I created boxes with the height of the foam I was cutting in the CNC milling machine (30mm) and later used the command BOOLEANSPLIT, so the crystal shape was splitted in four different parts. OBS: If I would make it again, it is important to leave some margin on the height, so 29mm instead of 30mm, because the milling bid got into the table a little bit.
Positive parts ready to cut
I used an offset of 5mm between the positive and negative shapes (I now just figured out that this difference is too big and it could have been 1 or 2mm only)
To create the negative shapes, I also used the boxes. This time I adjusted them to 28.5 mm height.
On the top part of the negative mold, I wanted to have some "escape" pipes, so if Im casting something it would just have a place to get out and also for breathing purposes.
These are all the cutting for the negative shapes