Mechanical Design


The Project

 

Mechanical design was covered as part of a group project to build a functional computer controlled machine.

Brainstorming

The first step of the project was to decide what kind of machine to make. Tim, Matt, Karen and I all came up with a number of good ideas. We considered each of the possibilities and decided to make a fab wind chimes machine. We then got together and determined what needed to be done to complete the project and delegated the different task among the members of the team.  I volunteered to build the FabNet board and program the machine.

Building the machine

Building the machine was definitely a team effort. Everyone on the team was responsible for some part of the project but we also helped each other. For example, after Matt laser cut the parts, I helped assemble the linear axis and test them manually to make sure that there was no binding. Tim and I then worked together to assemble the main frame structure.  I also helped with the documentation.  One of my contributions towards the team documentation was to take the stl file that Karen made for cutting of the parts and uploaded it to my SketchFab  account so that there is a 3d model that can be rotated and view and is placed on our main group page. 

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Once the axis were assembled I tested them manually to make sure they did not bind. 


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Assembling the frame




Making the Fabnet board

 

            To make the fabnet board I used the eagle files and exported the layout as a gerber file for my LPFK s63 rapid prototype machine.  After cutting the board out I soldered the supplied RS485 cable and resistors to the board.  I also soldered 4 and 8 pin headers for cable hook ups.  The hardest part of making the fabnet board was creating the cable to interface with the gestalt boards.  To make sure I had the right pin-outs I used the documentation from Nadya and a multimeter on the old cable to make a pin out.  After that I stated to make the cable and when I was done I tested and it worked.  To make sure the  fabnet board will hold up a little bit better I used some hot glue on the rs485 wires and the 8 pin header to increase the strength.  

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Picture of the wiring diagram for the cable.


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Starting programing

 

 

The first item I had to do was install the pygestalt framework.  I cloned the library and then ran sudo python steup.py install. 

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The next item was to find and run an example to make sure the fabnet and the gestalt board are working.  I found the simple single x axis example and ran it from the command line.


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While testing the single x axis i tried to see the max range the axis could travel by increasing the position until the platform stalled at the end of the housing.

 

After a simple a simple test I decided to hook up two axis and try the x-y plotter code.

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Once I knew that it worked I read through the code and started to change the speed with stage.xNode.setVelocityRequest(12) line to see how fast I could get the stepper motors to run.  This was about 16 in that function before it was too fast and started to skip.   If you have the axis move too fast the connection to the lead screw will pop and the platform will not move or move very erratic.   After playing with the speed I changed the code to find the max limits of travel and how to add more paths to the code.  For the final code we used the single node code that imported a csv file that has some random moves to make the chimes seem more natural.  We also found out the initial speed of 16 was too fast and we slowed it down to 12 and the chimes sounded and ran better. 

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LCCC Group Project