Computer-controlled Machining
So, for this project I chose to make a small stool I found on OpenDesk: Johann Stool
It is a fairly small stool, with 4 pieces. I chose it as it is a simple design and doesn't require a lot of machining.
Preparing the File
In the project's file in OpenDesk, I downloaded the files and extracted them
In the contents there is a single DXF file that has the machinable design, as it is one file so we will be needing a single sheet of wood
When opening the file with Inkscape, I was given dialog box that provides parameters for DXF import
I disabled automatic scaling and hit OK
I then resized the document's dimensions to match the MDF sheet dimensions (File > Document Properties...), just to see what I'm dealing with.
I then read the instruction that are printed in the "NO_PRINT" layer to get an idea of how to fabricate this project which lead me to actually measure the MDF sheet that I bought just to find out that it is of "17.1mm" and the DXF says that it requires "18mm" sheet.
So, I took another look at the design and figured out that the problem will be in the slots.
Then I took a closer look at one of the slots
So, here the slot width is 20.625mm this includes the 4 arcs at the corners. But I wanted to know the actual inner dimension of the slot so I draw a triangle inside the slot to check.
Here it says that it is approx. 18mm. So I wanted to change that.
I tried to subtract 1 mm from the width of this path but in Inkscape it shifted the right side of the path to the left as the X coordinate is still the same.
This means that if I am to change all the slots to the correct dimension I have to change their coordinates as well. So I decided to switch to CorelDraw to make things easier.
Started by importing the DXF file and setting the units to metric
In the vertical slots, I subtracted 0.9mm from the width. Which I did in CorelDraw by entering "-0.9" directly in the width field and it resized the width along the center point
I did the same for the horizontal slots by resizing the height.
I then created a new document, copied all the paths I wanted into it and exported it to DXF
Machining
So I used a ShopBot to fabricate this file. I created two tool paths. On from the outside for the outer borders and another on from the inside for the slots.
But as I added the file of another fellow fab academy student to the same cutting job. So the other toolpath for the slots should have began after cutting his parts.
But unfortunately the drill bit hit the sheet mounting screw and was broken so we had to call it the night and to continue the job on a later time.
