Week#7

Computer-Controlled Machining

This is the week of Computer Controlled Machining, On the 6th March Prof. Neil gave us online lecture about this week's related tasks. So the task of this week is we have to make individually something big on the CNC milling machine.
Group Task
The group assignment of this week is we have to test run out, alignment, speeds, feeds, and toolpaths for your machine.
For this we made a design in solid works and cut it in CNC.In this design we made some female-teeths of different sizes for the kerf testing, also made a cylider, a pocket, triangle and a rectangle as shown in the images.

We cut this design in CNC.

We have the MDF sheets in lab with thickness of 16.3mm. So we cutted part in that sheet, we used both outside cut and inside cut on different areas and also used pocket tool path you can also see in image and after cutting it was fixing in 16.7mm cutted area, we cutted this area with outside cut toolpath.
Individual task.
For the individual part prof. Neil told us to make something big, and When it comes to making something big, there were many different ideas in my mind. I started to search for a few design ideas, first I decided to make a press fit table I started my work on solidworks but it was not satisfing me so I decided to move for the next Idea and I decided to make a relaxing press fit chair.


I did not continue this design and moved for the final design.
  • Open the Solidworks.
  • Make a new file part for design.
  • Set the units and plane.
  • Click on the spline command.
  • Make a design for the chair.
  • Go to the features and extrude it.
  • Then make the second part of chair.
  • Extrude the second part.
  • Go to the file and click on the assembly from part.
  • Import the all parts of chair.
  • Use the mate command and mate all parts and make a proper chair.
  • Save this file.
  • Go to the file menu and click on the make drawing from part.
  • Set the ratio 1:1 and unit.
  • Set the drawing on the sheet.
  • Save the drawing as .dxf file.

  • I made the parametric design.


    the final assembled design of the relaxing press fit chair.

    I made the these file as a dxf file.

    We have need G-code for the shopbot, so for I am using the VCarve.
  • Open the Vcarve.
  • Go to the file and click on the new.
  • Set the X,Y and thicknesss of the sheet.
  • Press ok.
  • Import the .dxf file in the Vcarve.
  • Place the all parts accuratly on the bed.
  • Click on the toolpath.
  • Select 2D profile toolpath.
  • Set the Cut depth, Tool, Machine vectors.
  • Edit the tabs where you need to hold/grip the part during cuuting.


  • we have made setting according to my machine and need.



    Some information about the tool is defined in this image.

    Tool info
    In the above image you can see the values of rpm,feedrate, stepover ,tool-diameter etc. basically these are the by default values and in our lab we mostly operate the machine on these values , so for I did follow these values and operate the machine and the result was completely accurate. So for we did cut the test part on these by default vales and also cut the final part on these values.


    Tools/Commands we used:
  • Job size:_2440mm and1220mm
  • Appearance:_MDF
  • Command: Join
  • Command: Move
  • Toolpath: Profile toolpath
  • Start depth: 0.0
  • Cut depth: 17.1mm
  • Tool: 1/4" Down-cut
  • Machine Vector: Outside
  • Tabs: Edit


  • There are three types of mechine vector cut:
    OUTSIDE CUT:It cuts from the outside of the boundery/ limits that you have designed.
    INSIDE CUT:It cuts from the inside of the boundery/ limits that you have designed.
    ON CUT:It cuts from the On of the boundery/ limits that you have designed.

    Inside corners that result in a radius are a commonly overlooked issue when designing a part for machining. As of yet, there isn’t a magic way to cut a corner on a CNC router with a sharp 90º corner. This is because all CNC bits are round.Depending on your project, internal filleted corners may not be an issue for you. For some, this means your joints won't fit and you need a nice square corner.

    Inside Corner problem.
    HOW TO FIX THIS PROBLEM??
    The solution is to modify the design to compensate for this problem. W eare using Vcarve, there is a tool that will do these operations automatically.
    T-BONE:There is another way to cover that area, though. Instead of 'pushing' a circle into the corner of your design, you can push a circle directly in one direction, up or sideways. The math for this method is simpler: you only need to push a circle up by one radius from the corner.

    T-BONE
    DOG-BONE:Dog bone corners are a jargon-y way to describe the shape of a corner that is extended outside the cut area to create a perfect 90º corner that looks like the cartoon shape of a canine chew toy.We used dog-bones for this problem in the design, For this command we have to just click on the filletcommand from the edit objects menu and from there we can select dog-bone and edit the object's corner.
    For further understanding you can click HERE .

    DOG-BONE


    The tools we used for the safety precautions are the dust mask, earmuffs, safety glassess and gloves.



    CNC Milling
  • The first thing that needs to be done is to install the desired milling bit.
  • Connect the system with the shopbot software installed using the 2 USB cables provided.
  • Open the shopbot software.
  • We need to make the origin fro the drill bit so for this, open the keypad option by clicking the yellow icon in the position menu.
  • Using the arrow key move the bit to the desired origin point.Also set the z-axis. The bit should touch the bed exactly at a point that it scraps the top layer.
  • The bit can be moved slowly by clicking on the fixed button. Once the origin is set, click on zero axes and set x,y, and z as zero.
  • Now import the g-code file by clicking the cut part option.
  • Press the start option.
  • Switch the exaust on.
  • On the emergency board, hit the start button.


  • There are two main types of tools Ball-nose and Straight nose. Mostly the ball nose is used for the text or some curvy designs whrer as we are using the straight nose because I just want to cut the part there is no text or curvy shapes on it.



    Shopbot software


    Setting the origin

    Emergency board



    Finally the machine is going to cut the part.
    I place a MDF sheet(length=8feet, width=4feet)on the machine bed and made setting according to my need and Machine.

    Now the parts are ready and we making assmbly of the parts,In all these Mr Rasheed qazi(local instructor of Fab lab Khairpur) help me alot and also help me in assembly.Thanks Mr Rasheed Qazi.

    Now the chair is ready and I am relaxing on it.

    "Click here"to download all files of this week

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