Week #7 COMPUTER CONTROLLED MACHINING




Assignment





Week workflow

This is how I see my week


Softwares used


Decide what do I want to make



A vermi-composter



I decided to use an already designed model for a vermicomposter designed to be made from a single sheet of wood with CNC-routable. AKER.me, proposes the sources files on Github . This wormhouse will be very helpful for cultivating worms or black flies to feed the fish in the aquaponics system.

Parametrisized the 3D model



Having the 3D and Nesting model from Github was not suffisant since the files were for a certain thickness of a certain kind a material (i.e. plywood). At the Green Fab Lab we had to use OSB, so I had two choices

:
  • Restart the design from scratch, taking into account the thickness of the material
  • Having a good fabacademy friend knowing how to parametrisized a 3D model
  • STEP 1: Mesure the thickness of the material



    Fig.1: Mesuring in different parts to ensure we have an homogeneous thickness

    Fig.2:Our OSB is 15 mm

    For the parametric design I will need:

  • Thickness
  • Mill bit diameter
  • Clearance gap
  • STEP 2: Find out the right clearance gap for our joints using GrassHoper



    We want to make sure that our hole is a little bit larger that the thickness of the other part of the joint.

    Definition: Clearance : space between male a female part of of joint

    To find the right clearance, Gregoire (another Green Fab Lab academy student) generate with Grasshoper a file with several tests that increase the clearance value of 0,25 mm delta from -0,25 mm to 2 mm

    Fig.3:Generating a clearance gap increase of 0,25 mm delta from -0,25 to 2mm

    Fig.4:Identifying the 0,25 mm clearance

    Result: 
    With a clearance gap of 0 mm or 0,25 mm, our jointr fit nicely. 
    As the joint system of the wormhaus model is made with dowels, the 0,25 mm seems to be the most adapted.

    Fig.5:Worhaus joints with the right clearance gap

    STEP 3: Using Solid Works to parametrisized the 3D model



    As I still don't have Solidwors, Gregoire (another Fab Academy student) helps me to parametrisized the wormhaus using the following parameters.

    Fig.6:Variables used for the parametric design

    We then exported a .dxf that I will be able to work on with Rhino.

    Fig.7:Solidworks.dxf file imported on Rhino

    STEP 4: Import Nesting in Rhino



    Create differents layers that will serve as the strategy to follow in the CAM process.

    Layers terminology
            - Pocket Xmm: is a zone where you need to mill an extra layer and this As there is many different depths, a good tips is to associate one color / one layer = one depth >>> create a layer called "10 mm pocket"
            - Inside Profile:The edge of the millig bit is from inside
            - Outside Profile:The edge of the millig bit is from outside
            - Engraving:The edge of the milling bit goes along the line indicated. Good to know for engraging. 
            - Screw: They help to ensure that you plywood is flatten. Put them on a separate layer >>> The more pin down the better to ensure you have a flat surface. Always good to triangulate the screw. Othgerwise you buy a vacum machine
            - Tabs: Help to avoid flying parts
            - Peck drilling: Drilling zone


    Starting by defining the stock perimeter



    We will work with an 15 mm OSB sheet of wood of (width: 1250mm x lenght: 2500mm. This is the first part we need to draw for our nesting.

    Fig.8:xxx

    Profile - inside // Dog Bones



    How to make rectangular hole ? The milling bit can't do a 90° corner, so we need to design what we call "Dog Bones" by creating put a curvature in the corner.

    Fig.9:xx

    To do them properly, you need to consider the mill bit diameter (in our case it's 6 mm), the right strategy is NOT to put the circle center on the corner but the extremity on the corner to enable the milling bit to pass

    Fig.10:xx

    Fig.11:Profile inside

    Peck Drilling



    Fig.12:xx

    xx

    Pocket 7.75 mm and 9 mm



    Fig.13:xx

    Fig.14:xx

    Our local guru, recommends to do pockets a little bit larger than the edge "offsetting the pocket" so that after during the "outside profile" you will get a nice / plan oustide cut.

    Fig.15:xx

    Profile oustide



    Fig.16:xx

    Screw



    Triangulation

    Fig.17:xx

    Make sure every curves are closed



    Use "Selopencrv" command

    Fig.18:xx

    Make sure every curves are on z = 0



    Fig.19:xx

    I think we are ready to go !


    STEP 4: Using Rhino CAM to generate tool path and export as Gcode



    Before doing the entire job, I will do a first test milling only one stackable level to test if all the joints are OK

    Fig.20: Joint 1, Joint 2, Joint 3

    Workflow
            1. Open Rhino CAM
            2. Defining the Bounding box strategy
            3. Defining Pins downs strategy
            4. Defining Inside profiling
            5. Defining Pocketing strategy 
            6. Defining Drilling strategy
            7. Defining Outside profiling strategy
            


    Defining the Bounding box strategy



    Stock 
            - Indicate the size of your stock /  copy model Bounding box 
            - Indicate the thickness of your sheet wood stock
            - Press generate 

    Fig.21: Bounding Box

    Defining Pins downs strategy



    Pins down layer
            - Go to Machine operation
            - Select 2 axis
            - Select your type of strategies for your layer 
            - Select reference "select drill points // Select drill points & circle

    Fig.22

    Go on Pins down layer // select  objects  // press OK

    Fig.23: Selecting Pins Down layer

    Select tool / drill bit / 6 mm

    Fig.24/legend>

    Check Speed // Check sense of mill bit Clock-wise // Change speed to 20 000

    Fig.25

    Clearance : how heigh you want to go passing from one point from another one + press generate

    Fig.26:xx

    Sorting // Select minimum distance

    Fig.27 Selecting minimum distance option

     Press "Generate" 


    Defining Inside profiling



    Go to Machine operation // Select 2 axis // Select Profiling 

    Fig.28

            Select "control geometry" /  remove all
                Select "Select Drive / Containment Regions"
                Go on your "Inside Profile" layer 
                Select objects
                Press OK
            Select your tool 
                Edit / Create / Select tool / Flat Mill
                Check Speed 
            Cut parameters / "cut start side"
                Check use "outside/inside...." / check "inside"
            Cut levels
                Total cut depth= 16
                Rough depth = 5
                Rough depth cut= 3 (to indicate that we will do 3 rounds)
                Finish depth=1 (to finish) 
                Finish depth cut= 1 (to indicate that we will do 1 round)
            

    Fig.29

            Entry / exit point : 
                - Select None on the two sections ( VERY IMPORTANT to avoid error entry and exit offset and destroy the material + !!!)
            Avanced cut parameters " Bridges/Tabs"
                - Check "Create Bridges"
            Sorting
                - Minimum distance
            

    Fig.30

    Press "Generate" 
    Add a picture of dark blue line and another one to show how to

    Fig.31: Dark Blue line

    Fig.32: Option to resolve this problem

    Add a picture with resolution

    Fig.33: Option to resolve this problem

    Pocketing



            For Pocketing layer
            Go to Machine operation
                Select 2 axis
                Select your type of strategies for your layer > "pocketing"
                Select "control geometry" /  remove all
                Go on your "pocketing layers" and "select  objects"  layer / press OK
            Select your tool >  Edit / Create / Sellect tool:
                Check Speed 
                Check sense of mill bit Clock-wise. 
            Cut parameters
                Total cut depth=7.75
                Rough depth = 6
                Rough depth cut= 2 (to indicate that we will do 3 rounds)
                Finish depth=1.75 (to finish 
                Finish depth cut= 1.75 (to indicate that we will do 2 rounds)
            Entry / exit point : 
                - Select None on the two sections ( VERY IMPORTANT to avoid error entry and exit offset and destroy the material + !!!)
            Sorting
                - Minimum distance
            Press "Generate" 

    Fig.34:xx

    Outside Profile



    For "Outside Profil"
            Go to Machine operation
                Select 2 axis
                Select your type of strategies for your layer > "Profiling"
                Select "control geometry" /  remove all
                Select "Select Drive / Containment Regions"
            Go on your "Profiling" and "select all objects" on your holes layer / press OK
                Select your tool >  Edit / Create / Select tool:
                Check Speed 
            Cut parameters / "cut start side"
                Check use "outside...." / check oustide
            Cut levels:
                total cut depth=16 (if stock thickness = 15mm)
                Rough depth =12
                Rough depth cut= 6 (to indicate that we will do 2 rounds) !!! If you have a 6mm drill you can go  to 6 mm rough depth) !!!
                Finish depth= 4 (to finish) 
                Finish depth cut= 2 (to indicate that we will do 2 rounds)
            Entry / exit point : 
                - Select None on the two sections ( VERY IMPORTANT to avoid error entry and exit offset and destroy the material + !!!)
            Avanced cut parameters " Bridges/Tabs"
                - Check "Create Bridges"
            Sorting
                - Minimum distance
            Press "Generate"
            

    Fig.35:xx

    STEP 4: Shopbot



    Workflow:
                - Open software
                - Turn on the key + button
                - Check Emergency button
                - Retry control
            

    Fig.36:xx

    Fig.37:xx

    Fig.38:xx

    Fig.39:Setting z=0

    Load Gcode file // last check in the Gcode // Change MS speed

    Fig.40:Changing the Milling speed directly from Gcode

    Putting pins down // Make sure there is no gap between your sheet of wood and the sacrificial board

    Fig.41

    Results from test 1



    The joint #1 and joint #2 (i.e. Fig.20) are fitting well.

    Fig.42

    However, the joint between X1 part and X2 part was to stretch

    Fig.43

    I will have to do another test increasing the pocketing value



    I decided to give another function to thus stackable with my laptop

    Fig.44: Creation of a new pocketing strategie with 8.6mm

    Results from test 2



    From test 1 results, I've done two changes in the pocketing and inside profiling value

    Change Pocketing value (to adress problem illustrated in Fig.43): From 7.75 mm width to 8.6mm width
    Change the inside profiling from 15mm to 17 mm to ensure  

    Fig.45:

    Final cut



    To clean up every edge, a very usefull tool is sand paper

    Fig.46: Your best friend to clean up your CNC object - sand paper

    Fig.47: Every piece are ready to be assembled

    Last surprise, an error of 4mm on the horizontal square avoiding me to assemble correctly the stackle. To adress this issue I decide to use an XXX

    Fig.48: Adjusting the 4mm error with a XXX

    And after this long week, and multiple surprise, here we go !! a vermi composter

    Fig.49:

    Fig.50: The aquaponic system welcome it's new friend.

    Final Project evolution



    Fig.51: After installing the LED lighting system + build a shelve structure from CNC left-overs


    Interesting readings


  • 50 DIGITAL WOOD JOINTS
  • Download


    You access and download all the files generated during this week from my google drive:




    Conclusion


    Measure the material thickness at the beginning
            Do several tests on your joints playing with different clearance before doing your final cut
            Parametric Design is key with CNC