Weekly Assignments Final Project About me

7.Electronics Production

This week's brief: Group assignment:

  • Characterize the design rules for your in-house PCB production process.
  • Submit a PCB design to a board house
  • Individual assignment:
  • Make and test a microcontroller development board that you designed
  • extra credit: make it with another processs

    • GROUP ASSIGNMENT
    You can view our group assignment here!

    INDIVIDUAL ASSIGNMENT

    Design

    I would be making the space invader PCB that i designed during Week06 where we did electronics designing. I cross verified the board and checked the dimensions of the design which turned out to be 48 x 66.3cm.

    Gerber To Pngs

    First thing I did was to convert the gerber files into pngs that will feed the traces and outlines to the machine.Gerber2png was the website we used to easily convert the files. It is a website that was developed in Super Fablalab, Kerala to facilitate this process.

  • Drop the gerber files on the site
  • On the quick set up drop down choose 'Generate all'. Then click Generate PNG
  • The png of the traces, outlines and drill holes(if any) will be generated
  • Download the files to upload into the mods software.

    • PCB PRODUCTION

    I fixed the PCB to the bed using double sided tape. Position the PCB so that the edges line up with the bed edge. We got a detailed explanation done by our instructor about the modela mdx 20 milling machine, which we would be using to cut out the PCB.This documented in detail in our group assignment.

    Fixing the tool to the machine

    We have to enter a series of commands related to the functioning of the machine. We need the machine to do the traces in the beginning with a 0.2mm 60 degree V bit first , then we do the drilling for the holes and the outlines with a 1/32" flat endmill at the end.

  • We need to fix the tool to the the spindle of the machine. We should be very careful while handling the bit because it breaks off very easily. So while placing and taking out the bit always be cautious of the bit not dropping suddenly.
  • Go to the mods software and then click on position to change bit. This has been set in our lab for the ease of changing the the bit . It is almost at the center of the machine so that our hands could easily maneuver the tool.
  • Now insert the tool into to the spindle and tighten just enough that the bit won't fall off.
  • Next we need to bring the tool on top of the PCB by giving values to x and y axis in the mods software.
  • Then we loosen the bit so that it drops lightly on the bed. Now tighten the bit very well. This was process was done to find the z axis level.
  • We need to set our x and y axis now. For this we keep adjusting the values of the x and y offsets until we reach the corner of the board. Keep in mind the dimensions of ur PCB so save space and position it accordingly.
  • Now that we have set the levels of the machine we can start the process to do the traces.

    • Setting up the Software(Using MODS) and operating the machine.

    To make traces.

  • Load the png file to this node . The next node ask you for the information regarding the tool diameter, depth and ... For the traces click on vBit and enter dia ad 0.2mm and the degree as 60
  • Once that is set we can confirm the values on ... Node. After cross checking click on calculate. We can click on view to see how the traces will look with the offsets and the tool path.
  • Then we can click on send file for the machine to start milling.
  • Once the traces are done ,i moved on to drill holes as it was required in my design. Clean up the dust gatherd after using the machine with a vaccum.

    • To make Holes and outlines

  • I needed to change the the toolbit to a 1/32" flat endmill to drill the through holes. As we are changing the bit we need to follow the steps that we performed initially when we fixed the V bit.
  • In MODS replace the trace png with the dillholes png.
  • Since we changed the bit we have to modify the settings of the tool node
  • After confirming the values click on calculate. Then we can clcik send file to mmake the machine start the operation.
  • After the holes are drilled, we can proceed to cut out the Outline of the PCB. We just need to replace the drillhole png with Outline Png for this step as we will be using the same toolbit for this operation.Click on send file to start the process of milling the PCB.
  • When the milling is completed we can click on view to bring out the bed. Use a scraper to carefully peel out the pCB from the bed. Make sure to clean up the dust gatherd around the machine after using it.
  • This was my PCB after cleaning the board.

    • Soldering and Assembly of the components.

    Ge

  • We were instructed to make a scaled down mockup of the design on cardboard to check the proportions and see how the fit will look like. Using the "arrange" function in Fusion360 to place all the components spread out on a plane. Then we project the components on a sketch plane which we will be required to export as a dxf file. Open this dxf file on inkscape . To scale down the model we need to find the ratio of the features . We know the the width to be 18 and height was 1521, we need it to change to 3 width and using ratio calculator the height came to me 15853 . Resize the the sketch and turn the stroke colour to red ,to denote the cutline. Save the sketch as a svg file.
  • Now open the job control app and import the svg file we just created. snap the laser pointer to snap to the sketch. Check the database and see if all the values are correct. Place the cardboard on the print bed and align the origin point. After setting up everything start the process.
  • Once the cut is done i started to sort and assemble the pieces. Some pieces of the cardboard bent a little because of the orientation they were cut in. Also i noticed that some slots were missing on the pieces so i went back to the model and checked, There seemed to be some parts that were uncut, which i resolved immediately. For the time being and since it was only a minor mistake i cut the slots using a exacto and measuring the distances properly.
    • I was quite satisfied with the fit and held up better than i thought while modelling. I also was able to figure out how to assemble the parts efficiently as well.

    Preparing the Job

    Before taking the plywood to the machine ,we need to check the thickness of the piece as it will affect the overall dimensions of the furniture. I measred the thickness of the plywood with a vernier calliper and found out that the average thickness of the piece i was given was 17.2mm. As i had made the model with a thickness of 18mm i had to change the scale of the model. I also had to take into account the offset value from the machine that turned out to be 0.2mm , which we concluded in the group assignment. The dimensions were changed accordingly. Once this was done we proceeded to start the machine operations.

    CAM

    Using VCarve We need to define the toolpaths, add dogbones and tabs to the drawing so that the machine can cut them accordingly. VCarve provides a powerful but intuitive software solution for creating and cutting parts on a CNC router. The following steps were followed to make the cutting parts.
    Reference point for drilling: We are supposed to drill the work piece on to the sacrificial layer so that it stays in place. If we blindly drill holes in random areas of the the job there is a chance that the screw may coincide with the toolpath. To avoid this from happening we run a drill path to mark refrence points for screwing the piece down. Create a few circles and place them on the edges where the paths dont meet. Dogbones : Dogbones are made to give a good fit between the inner edges of slots. I added dogbones on all of my slots and edges. Tabs: Tabs are added to give support to the cut parts which may move and cause issues when the tool . It can be quite dangerous if the tabs are not given appropriately.


    Once the drill path and the toolpaths are given we can proceed to the operations. The entire operation process has been explained in detail in th e group project.
  • First we run the drill path and mark the points to be screwed. Stop the machine and screw in the job to the sacrifcial board.
  • Then we can start the cutting process of the parts.

    • Unfortunately the bit broke twice during the cutting process and i had to halt my work for the time being until we can resolve the issue.

    Download files

  • PCB design files

    • References

  • Ratio calculator