4. Computer controlled cutting¶
In one assignment of the week it is necessary to design and cut something on a vinyl cutter. There are many things that can be done in such field, for example stickers for a laptop or silk for t-shirts. Another task to do this week is to design and create a press-fit construction kit. Using base forms cutted in a laser cut it is possible to create complex shapes and even assign a meaning for them.
It was selected some pictures to draw the image to use in the vinyl cutter. The first image was a monkey holding a banana. This image was added in an Inkscape document, drag and drop the image in the document and confirm the window that will open. Select the image, and use the menu Trace Bitmap… (under Path) to create the bitmap of the image as vector image that can be send to the vinyl cutter. Inside this image there was some water mark that create some inconsistency in the bitmap image generated. They should be removed for a better quality image for the vinyl cutter. In the left side of the inkscape, there is the button Edit paths by nodes that allow you to edit the points genererated in the bitmap trace. Select the points that create the water mark in the bitmap image and delete them. The result is a clean image that will be used in the vinyl cutter.
Original image -> Bitmap of the image -> Image without the water marks
Other two images were converted to their respective bitmap using the same technique explained above.
Original (left) - SVG Image (right)
These images were used to cut stickers and it will be used later to stamp t-shirt.
The machine used was Brother ScanNCut CM300 because it is very easy to operate. The machine also allow to scan a drawing and instantly cut it out using different materials. It also possible to draw in Inkscape and import the design via USB-stick to the machine.
Some configurations for different types of grid mat.
I have used a standart mat.
Then place the grid mat in the machine. It is used to calibrate it and to have the starting point of the vinyl cut.
The material were placed correctly in the grid mat, positioned in the beginning of the machine.
The images (in vector design - SVG) were uploaded using a USB stick (the machine provides an USB connection).
Once the USB is loaded, the list of files in the USB stick will be shown in the little screen. Selecting your design, the software of the machine will place the images designed in the best way to avoid waste of material.
Now, I just needed to press start to make the vinyl cut.
Try and error¶
I have learned in this part of the assignment that the machine that performs the vinyl cut will cut all lines in the image, even if the lines are overruled by another lines. For a better result, the image drawn should have only the external lines and they should be connected.
Sticks resulted from the vinyl cut machine
Press-fit construction kit¶
The idea is to draw a base that will press-fit together to be stand in a surface and attach leaves in the top of this base, using one of the type of join snap. The leaves would be squares adapted to attach each other and the sides of the square will be in the shape of a tree leaf. This task started designing the base. It will be necessary two peaces for keeping the structure standing. The base should be long for stability purpose.
Design - Base structure¶
- Open fusion 360
Define parameters for designing the base of the structure. The draw will use two rectangles, one in the base and another in the top. create parameters for the dimensions of both rectangles (menu: MODIFY > Change parameters). Create a parameter for the thickness of the material as well. You can create a parameter for the lenght of the hole that will do the press-fit of the base (optional).
Start a new sketch (CREATE > Create Sketch).
- Draw a rectangle (menu: CREATE > Retangle > 2-Point Rectangle) in one of the planes and use the parameters to set its dimensions (base_width and base_height). Centralize this rectangle in the origin point, this will make easy to rotate the second piece of the base.
- Draw another rectangle using the parameters top_width and top_height as its dimensions. Centrilize it with the first rectangle using the menu MidPoint (in CONSTRAINTS)
- Draw a line between the edges of the rectangles that allow to change its shape (menu: CREATE > Spline > Fit Point Spline). Change the line for a desired curve with your mouse using the blue dot in the extremes of the line.
- Draw a construction line in the middle of both rectangles. First draw a line in the middle, right click on it and select the menu Normal/Construction.
Create a mirror of the line added in step 6 using the construction line as Mirror Line.
Create a rectangle with the width of thickness (where it will be the press-fit of the base) and the lenght of base_height + top_height. This rectangle will join the extreme top and the base to allow creating the press-fit later. Draw a line in the middle of this rectangle. Bellow the resulted sketch.
Start a new sketch to draw the snaps that will connect the pieces of the base. Select the same plane used before. Draw a rectangle in the top of the base with thickness of width and 2 * thickness height (to create a snap more resitent varying according to the thickness of the material used). Draw a square in the top of the previous one with 2mm that will press-fit the second structure. Create a new parameter snap_dist equal to 6mm and place the internal line of the snap to the center of the base sketch.
Create two extrudes for the first piece of the base, but create two separate bodies, one for the base and one for the snap. The extrudes should have direction Symmetric and measurement Whole Lenght, this will enable rotate the next piece easily. The snap will be replicated afterwards for the other side of the press-fit piece.
Use the menu MODIFY > Chamfer to shape the snap in a way that the next structure can be placed correctly. Select the line where you want to apply the chamfer and the size of it (I choose 2mm to make a perfect triangle in the snap).
Create the second extrude for the base (using the same direction and measurement attributes), and rotate it 90 degrees (right click in the body > Move/Copy, move type circular and axis Y). The axis to choose depends which plane you start to draw. I started in the plane XY, that is why I selected axis Y to rotate the extrude.
Select the menu CREATE > Pattern > Circular pattern to replicate the snape in all sides of the base. Select the type of patter (Bodies), choose the body of the snap, the axis as reference (again axis Y), and the amount of patterns (4 because the snap need to be in all sides of the base to attach the next structure). Notice that appear one body to each patter separeted.
Design - Leaf structure¶
- Continue using the same file started to design the base structure. Start a new sketch (menu: CREATE > Create Sketch) using the plane in the top of the base.
Draw a square and set the sides equal to 2 * snap_dist. Adjust this square in the center by setting up the distance of the sides to the center equal to snap_dist (that will enable the press-fit by the snap).
Create a new parameter leaf_width equal to 7 * snap_dist.
Draw a second square with dimension leaf_width. Place the square in the center as well, by setting the distance between the sides and the center to leave_width/2. outside square
Draw a rectangle with dimensions thickness and leaf_hole (create a new parameter). Place this rectangle in the center of one of the sides of the big square.
Create the extrude for the leaf (CREATE > Extrude). When created the extruder of the leave,
To make the leaves rounded, create a fillet for the edges of the extrude added in step 6. Select the four edges lines of the square, select menu MODIFY > Fillet, and enter the dimension of 15mm.
Now, create a fillet for the internal edges of the hole of the press-fit, creating the shape of the leaf. Select the internal edges wished to create the round corn, use the menu Fillet with dimension of 5mm. A bigger dimension will cause error when creating the fillet.
I noticed the tooth of the snap were big than the leave. I forgot to adjust the height of the tooth of the snap. I just come back to the sketch of the snap and change the distance of the tooth to the base to thickness. To easily find the sketch of the snap (created in the step 10 in the base section) you can use the time line created by fusion in the bottom of the window. right click in the skect of the snap (it will be the second item) and edit.
The base structure and the snap are two different objects (bodies). Select the menu MODIFY > Combine to join the two snaps in each base of the press-fit. This is an important step to generate the correct image to be used in the laser cut machine.
Bellow what is expected to achieve after using the laser cut machine.
Drawing for lase cut¶
The object designed with fusion should now be converted to an image that can be used in a laser cut machine. In the tab were it was designed the object, select the menu DESIGN > Drawing > From Design. A new tab will open and you can add the designed object from different point of view.
In the window, select the scale 1:1 to create the image in a good dimension and the orientation Front. After confirming disable the bodies that represent the base structure. It will be draw only the leaf structure in the document.
Click in the menu DRAWING VIEWS > Base View to include another design, using the same scale 1:1 but orientation Top. Disable the bodies from one side of the base and the leaf. The image should contain one piece that will be used in the laser cut.
Using the same menu, Base view, include another design (same scale) with orientation Left. Disable the bodies leaf and the side of the base enabled in step 2.
Save the image resulting from these steps as PDF file, you can edit an Inkscape document and create as many pieces as you want.
Our lab has different machines to lasercut different types of materials. I have decided to use the machine Metaquip because I have used before and I had some knowledge about it. This lasercutter has a large work surface 600mm x 1000 mm. It can cut through thicker materials, for example I have cutted once 8 mm plywood poplar. It also cut’s very fast.
This machine works with lightburn software that is very easy to operate. We need to adjust the drawing into two colors: red and blue. The former one (red) will cut the material and the second one (blue) will engrave the material.
Each color has its own configuration depending of the material used. We just need to use the correct speed and power to cut/engrave (red star) the material and after placing the material in the machine, we press start button (green box). You can also use the button Frame (orange box) to check if the material in the machine is enough to cut your design. Bellow the parameters to cut (snijden) and to engrave (graveren) for different materials that can be used with this machine.
The laser head of the machine need to be positioned in the correct size of the material to cut/engrave correctly. The machine has a height regulator, similar to the image bellow that need to be used after putting the material to set the correct height of the laser head.
The head can be moved using the arrows of the machine interface or the z-axis movement.
I decided to use wood in this assignment because the machine were loaded with it and the laser head height was calibrated. The wood has 3mm of thickness, and as I wanted to cut it I used speed 45 and power 80. After importing the image in the lightburn software (just drag and drop in the software), the software automatically converted the lines to red (because cut was the default option in the software).
We cannot forget to turn on the ventilator of the machine, to avoid inside dust and smell of the material being cutted. Depending of the material, the smoke is toxic and it can harm human life. Be careful, and always check the datasheet of the material, specialy the safety section, to avoid harming your life and your collegues.
Try and error¶
The first attempting to use the laser cut to make the press-cut fail. The tooth of the snap were big and did not let the square of the leaf fit it. From this experience it was changed the shape and size of the snap.
The second try, the square fit better, but I still had to adjust the thickness of the material to the correct size. The material I was using were 0.3mm smaller than the design.
The third attempt were a good result, but the snap were not flexible enough to connect the other piece. As the square were bit, I could adjust the leave to it. Then, it was noticed that trying to connect two leaves were not possible using both holes from the press-fit. It was still possible to create a decorable structure. It still needs some adjustment, but due to the lack of time I could not make it for this assignment.The size of the leaf could be adjusted using the parameter leave_width.