Week 7: Computer Controlled Machining

Tasks for  the week:

  • Make something big- Furniture element/ Prototype

Task:01

Designing the BIG element

 

This week the task is to design an element that can be fabricated using the Shopbot. I decided to make the a laptop table that I can use while sitting on a bed using 8mm thick plywood board.

I started by looking at the references of the tables with a similar purpose. Above are a few images for the same.

Step:01

3D modelling the Laptop Table

 

3D modelling helps me visualise better. Hence, I started by making a 3D model of my laptop table. For this, I used Rhinoceros 5. Below is the process for the same.

I started by making a line drawing of the required form. I started drafting my components keeping in mind the press-fit joinery for all the components.

The above image shows the process of drafting using extended lines. I started drafting plan and elevations for my table.

Initially, I made rectangles that would act as cut-outs where the bottom components can fit.

Later, I converted all the junctions of the cut-outs to 'DOG-BONE' joinery. This helps in avoiding the rounded edges formed by the milling bit when it moves across the profile.

Next, I added a pocket towards the edge for the tea cup.

Further, I drafted another set of the bottom legs, with more height so that the same top plate can be assembled with these to make a larger height table.

I nested my components at one one end of the 8'x4' standard plywood board sheet. Image can be seen above.

The above image shows the rendered view I prepared to visualize the final output of my laptop table (Bed table version and the high table version.

I decided to use profile cutting and pocket cutting of the parts.

The 3D file can be acessed here.

 

Difference between profile cut and 3D milling:

3D milling involves cutting in all 3 axis- X,Y and Z whereas, profile cut includes cutting 2D planes only.

Step:02

Exporting files for Fabrication

 

Next step is exporting the files.

The files can be acessed here.

I exported the line drawing. For this, I selected the component by clicking on it, then from FILE menu I selected 'Export selected' and saved the file as 'dxf' format.

As seen in the image on the right, I selected '.dxf' format from the drop down bar to export the file in DXF format.

Step:03

Fabricating the components

I used PARTWORKS  to generate gcode for fabricating the components.

 

 

Step:01

After opening partworks, I opened NEW from the File menu. Then set the parameters as shown above.

Note:

  • Deselect the tab that says 'Use origin offset'
  • Set thickness as per the material to  be used. I used a 11 mm thick MDF board.
  • Click on the units (mm / inch)
  • Also select, Centre data in Job tab. This will keep the file in the centre of the board size.

 

 

Step:02

Next, open the DXF file that I wanted to cut.

 

 

Step:03

I wanted the inner profile to be a pocket and the outer to be a profile cut. So I made 2 different toolpaths because I was using 2 different drill bits.

For that I selected the inner profile, then clicked on the 'Toolpaths' tab on the upper right corner of the screen.

 

 

Step:04

Next, I selected the 3rd icon that says 'Pocket cut'. In that further I selected the parameters as seen above for 1/4th upcut ball nose drill bit.

Spindle Speed: 9000 r.p.m

Feed Rate: 1.5

Plunge Rate: 1.5

 

 

Step:05

Next, I selected the tool to move in ramps. The parameters I selected for pocket cut are seen in the image above. At last, I clicked on calculate to calculate the toolpath.

 

 

 

 

 

I followed all the parameters same except two for profile cut. I selected the parameters as above for the 1/4th 'straight' bit for profile cutting and also since it was profile cut, I added tabs. Rest, I followed the same process as pocket cut.

Step:06

At last, I saved both the toolpaths separately as I had to use different bits. To save, I clicked on the 'Save toolpath' icon and saved it by selected the save sbp tab as seen in the image.

Step:04

Setting up ShopBot ALPHA

 

 

 

Step:01

Pull down the two 'Single phase motor'  and 'Single phase Power' switches. (The two orange switches).

Step:02

Next, turn the key towards left. To change the bit, one needs to turn off the key.

Step:03

Now rotate the red lever to 'ON' to turn on the power.

Step:04

Press the Blue button to reset.

Step:05

The display will light up on pressing the blue button. Now, one can proceed with giving the commands to the machine.

Step:05

Shopbot Software

 

 

 

Step:01

Open the Shopbot software. Now my next step was to set Zero. For this, I clicked on the yellow tab seen on the big red tab on the right.

Step:02

Next, I moved the zero at the corner of the sheet. After  moving to the required position in X, Y and Z direction. I clicked on 'fixed' to set Zero. Now,  next step was to 'Cut Part' by clicking on the green tab that said so and loading the required file.

 

Step:03

Now, after loading the file the above screen appeared. Next step was to click on start, then press the green button on the yellow button box of the machine (the one where I pressed blue for reset) to start the spindle and get going.

 

Image showing the cutting process and assembly:

FOR FINAL PROJECT

Once all the 3D printed components were ready, I decided to finish my major component where my other 3d printed components will fix and my motor will be supported.

Preparing the file for milling:

The base of the extruder is designed in such a way that, it becomes most important member and holds all the other members of the extruder. The images below show the process of preparing files in Rhinoceros.

Below images explain the parameters that I used for milling the base.

Below image showing the x/y zero setting and material thickness of material used.

Image showing the pocket cutting path with the selected tabs.

Below image shows 2d profile tool-path and the cutting depth of the material.

Image showing the 2D profile to mill and parameters that are used for setting up the cut depth and tabs..

I used 1/8th Ball Nose bit at the following parameters for all toolpaths.

Spindle Speed: 7500

Feed Rate: 1.5

Plunge Rate: 1.5

Images of components being 3D milled:

 

Step:01

Milling the FabISP

 

To start milling the FabISP , I first understood the method of working using Ubuntu (basics).So I documented each step of opening a file and creating .rml file for milling.