For this week we have two small projects and one Group task. We need to learn to use the vinyl cutter. And we need to learn how to use the laser cutter, including some needed characterization. We have to do that characterization in groups. Our local instructor this time, Eino Antikainen, explained the basics&tips for the vinyl cutter and the two laser cutters in FabLab Oulu. He also gave some tips on how he calculated the kerf.

To Do

  1. cut something on the vinylcutter
  2. design, make, and document a parametric press-fit construction kit, accounting for the lasercutter kerf, which can be assembled in multiple ways
  3. characterize your lasercutter, making lasercutter test part(s), making test part(s) that vary cutting settings and dimensions(group project)

The "Doing"

Vinylcutter

It's been long since I wanted the skyline of my home city at any wall at home. So I thought this was a good opportunity to see how it would look. On the other hand, I decided to keep on using inkscape for this this task. Just because I already know it.

I started to look for some pictures. My plan was to work as in the Assignment 2, that is

  1. importing the image to inkscape
  2. use path>trace bitmap to get the paths
  3. set fill to none
  4. edit the paths as necessary

I found a picture I really liked. But the quality was so poor it was very difficult to recognize many of the buildings just with the silhouette. I tried with different settings with no better luck. Also, there were many separated parts, so cleaning the image would have been extremely difficult. Trace Bitmap of first picture

Trace Bipmap with different settings

I started my search again, and finally found a new image I liked. Luckily enough, this image was an svg which makes editing much easier. I wanted to remove the frame, the letters, and reduce the detail. Image to trace

Image to trace

Process to prepare the image

  1. Import the image
  2. Select the paths tool on the vertical menu on the left and select all the elements to check the paths. (I was not able to select because the objects were grouped. So objects > ungroup first) Paths defined in the image
    All the paths defined in the image
  3. Remove some big objects (like the letters) Remove big parts
    Result after removing some objects
  4. Focus on small objects, to remove details.
    1. Select all the nodes from a path to remove it.
      Paths
      Check paths in smaller areas
      Paths
      Select all nodes of a path
    2. Join paths: remove existing segments and create new ones
      Paths
      Select nodes from segment to delete
      Paths
      Delete segment
      Paths
      Join nodes creating segments
      Repeat this process with all necessary parts
  5. Save the final version, Selecting Fill as none Paths
    Final version of the file

Using the Vinyl cutter

The Vinyl cutter at Fab Lab Oulu is a Roland GS24. There are two options to send images to this printer: from the computer designated, use inkscape or use . I was told that using inkscape has some degree of uncertainty when trying to position the drawing. But I still tried with inkscape. vinyl cutter setting
Roland GS24 vinyl cutter(on the right)
The process I followed was:
  1. Open the inkscape svg file
  2. Open the lever on the left hand side of the machine
  3. Put the vinyl roll in the designated place behind the machine and put the edge in its place
  4. Close the lever
  5. Switch on the vinyl cutter.
  6. Choose between roll (the machine assumes you are using a big enough roll), edge (the machine will look for the edge to start) or piece. I chose Edge
  7. Check the drawing is positioned on the bottom left hand corner of the document. What I actually did, was resize the document to the size of the drawing: From the Document Settings menu, click resize the document to the image size. Then, in the printer settings dialog, (shown in the image on the right), set the correct length for your case. For the width you need to keep the one given by the machine (Get from machine)
    Resize image size
    Resize the document to the image size
    Resize image size
    Choose Printer settings

The result

The output from the vinyl cutter needed some work before it was ready.
  • Remove any small pieces with the tweezers Remove small parts
    Remove small parts
  • Remove the vinyl in the background carefully, so no small part is also removed. Resize image size
    Remove all the excess
  • Use transfer sheet to be able to place all the small pieces together without getting crazy
  • Remove the back paper, checking all the parts remain in the transfer sheet Back paper
    Remove carefully the paper on the back
  • Stick wherever you want Final
    Result of the process

The press-fit construction kit

My inspiration for this task is the Bau lamp, a beautiful design of Vibeke Fonnesberg Schmidt based in the pressfit technique. You need to mount yourself the lamp, but there is just one way of mounting it, or at least, there are very specific instructions to do so.
When looking the design closer, you can see there are at least four different sizes for the discs and a lot of different combinations for the slots.
I decided I will try
  • At least 2 different sizes
  • At least 4 slots per disc, with different slot positions per group combination
  • At least 2 different materials
BauLamp
Bau Lamp (picture from Normann Copenhagen)

Initial design
Discs parametric design
The initial plan was as follows:
  • Create one disc with the slots, with all the dimensions defined parametrically
  • Copy the disc varying the parameters of the slots
  • Cut, varying the size dimensions, and with the corresponding thickness and kerf
The plan was modified on the go, while I learnt how to use Fusion 360 to achieve what I wanted:
  • Create one disc with one slots, with all the dimensions defined parametrically
  • Copy the disc
  • Create patterns to repeat the slot in different ways
  • Cut, varying the size dimensions, and with the corresponding thickness and kerf

Design Process

  1. Create the disc and define parameters

    2. This is quite simple.
    • First, sketch a circle, Create > New Component, then, select one of the planes (Front in my case) and then Sketch > Circle and center a circle in the origo, with a diameter of 40mm
    • Second, define the first parameters for the design. For this, get the parameters box from modify > change parameters and fill the values
      Parameters box
      1 Parameters box
      Add new user parameter
      2 Add new user parameter
      User parameters to model parameters
      3 Assign user parameters to Model parameters
      Combine values
      4 Combine values from different parameters
      I defined the following parameters:
      • Diameter = VALUE (Diameter of the discs)
      • Material Thickness = VALUE (Thickness of the material to be cut)
      • Kerf = VALUE (Estimated kerf or amount of material overcutted)
      • Slot Deepness = f(Diameter) (how deep the slot go to the center of the disc)
      • Slot Width = Material Thickness - Kerf (How wide is the slot)
      • Slot Translation = f(Diameter) (Define a translation of the slot positioning)
      • Separation = Diameter + Slot Deepness (Separation between discs)
      Finally, select the circle and Create > Extrude a total of MaterialThickness mm Use parameters
      Use the parameters we have just defined

  2. Create the slot

    • Sketch > Rectangle > 2-Point rectangle to draw a rectangle over the disc. Use the 2 points to define the rectangle as symmetrical as possible respect one axis
    • Sketch Palette > Tangent To set the lower side of the rectangle tangent to the pont in the circumference that intersects with the axis
    • Define the dimensions of the rectangle to the parameters Slot Deepness and Slot Width
    • To completely align the slot with the circle axis: create a construction line (Sketch > line and Sketch Palette > Construction) between the middle point of one of the segments of the rectangle and the central point of the circle. Set it to be vertical (Sketch Palette > Horizontal/Vertical)
    • Create > Extrude, select rectangle and set distance to Material Thickness
    Slot sketch
    Sketch the rectangle that defines the slot

  3. Replicate the slot

    4. Sketch> Circular Pattern open a menu to define:
    • what to repeat? The slot. This means PatternType to Faces and in Objects select the three inner sides of the slot
    • how to repeat? Around the main axis of the To define an axis that goes through the cylinder Construct > Axis through cylinder). Now you can select that axis
    • where to repeat? Every 90 degrees. THis means that, selecting how many slots in which arc (I select full and 4)
    Circular pattern
    Circular pattern to repeat the slot

  4. Copy the disc

    5. This part was a real headache. It took a while to understand the difference between copying components and bodies and how to use fusion time line
    I started copying the component. I tried to do that in several different ways, but the result is always the same: as of today, if you copy a component you always copy-link. That means that whatever change you do to any of the copies or original, it will also affect all the other copies or original. And that is not what I wanted, as I wanted the slots to be differently arranged in each disc.
    After many backs and forwards and a bunch of read posts in the forum, I managed understand...
    How to create components with a similar base, but unlinked.
    1. Create a component (main component), for the basic shape, common to all the shapes you want to replicate. In my case, the disc with just one slot and all the parameters needed
    2. Create as many components as you may need.
    3. Copy the body of the main component to the other components. Define where to put them. From now on, you have a a set of components that:
      • you can modify independently, working in each component AFTER the point in the time line they were created.
      • you can modify together, working in the main component BEFORE the point where they were created.
      • They all share the same parameters.
    Now, what would happen if you wanted to do the same, but after creating and modifying 6 disks. Here is when you need to check on the Time line.
    1. The time line after creating 6 disks in on the bottom 6 parametrical discs
      6 disks already created as defined before
    2. You need to move cursor of the time line to the place of your interest, in this case, just before I created the other components Move Cursor timeline
      Move the cursor in the time line
    3. Then, Create a new component and copy the body of the main component and paste it in the new one. Now you are prompted to define where to put this copy. NOTE: I did this parametrically, but it turns out Fusion 360 is not ready yet for that, and it just saves the actual value. So when I increased the size, I had to reposition all of the components Define Position
      Define position of the new body
    4. From now on, there is a new disk in your set of independent components. Note the new component in the time line. Circular pattern
      New component added
    Now, it is possible to tailor the last disk independently, without affecting the other 6. For example, by translating the slot it and the defining the desired circular pattern (as explained before). The translation of the slot is just moving it with the desired parameters: Slot translation
    Slot translation to create a different slot pattern

Cutting Process

  1. Prepare the file

    2. PDF file from FUSION

    1. Model > Drawing > From designOpen a projection of your design. Select the components or the model
    2. You can select the projection and place it in the drawing with the desired scale (1:1 in my case) Projection view
      Projection View for the 3D model
    3. Remove all the borders and forms in the document
    4. Export as PDF

    Prepare the PDF file in inkscape

    1. Open pdf with inkscape
    2. Select all and and set the Fill and stroke values for cutting: No fill, stroke 0,02
    3. I wanted to double the figures, so I copy&paste the block. Then saved.
    4. Open with Reader and send to laser cutter. Then, in the properties > advanced, choose the settings. The settings are mainly
      • Speed: How fast the laser moves through the material. (Slower means deeper cuts, but too slow might burn the material)
      • Power: The power of the laser beam. (More power means deeper cuts, but too much power might burn the material)
      • Frequency: The frequency of the laser pulses.
      You can select the default settings for the chosen material (in my case firstly MDF 3mm, which are 10% 80% 20%, and secondly Acrylic 3mm , which are 8% 100% 100%) by selecting the material in the list.
    5. Finally, send to the laser cutter

  2. Prepare the machine

    3. I am using the Epilog Laser Fusion 75 W. This is the list of tasks to start using the laser cutter
    • Check that the ventilation and the air pressure are on.
    • Calibrate the Focus. This process positions the material at a given distance from the laser head. The distance is determined by a metallic triangle you hang from the laser head. Select focus in the menu and move the tray up and down until the material touches the triangle, without pushing it up. Then press the joystick.
      triangle focus
      Triangle to determine focus
      focus
      Set focus with the joystick
    • Set the Origo. This determines where the machine will start to cut. Always remember it will be the top left corner of your drawing. Select Jog in the menu and ove the head with the joystick; press the joystick when ready
    • Select Job in the menu, select the file from the list and press Go
      Projection view
      Choose file from the Job list and press go
      Projection view
      Cutting

  3. The result

    4. I finally cut
    • 2 different sizes: Diameter 40mm and Diameter 60mm
    • 2 different materials: MDF and Acrylic.
    • 3 different kerfs for one model: This was because the first Kerf I chose (0.17) was not smooth enough, although it fitted. I did not thought it OK, so I cut changing the kerf to 0.18. These obviously fitted even worse. So finally I cut with kerf 0.16
    kerfs
    3 different kerfs
    all
    3 materials 2 sizes
    all
    3 materials 2 sizes

Conclusions

  • Follow the steps to prepare the machine! I missed some joystick pressing, so the origo was not set, so the head started in an unexpected place.(STOP-> RESET-> and start again)
  • Need to do some small tests with the material before you start, in order to get the correct kerf
  • I found not that big differences between the options with 0.16, 0.17 and 0.18. Does the kerf also depends on the focus setting?

Group work: Characterize the laser cutter

Link to group assignment page

Note: There was some confusion on how to document the group assigment. The group documentation can be found in the group page, in the link above. The text below is my version of it I did just in case, before we got the decision.

As we are 8 people doing the Fab Academy in Oulu, we were instructed to split in 2 groups so we could work more comfortably around the machines.
In my group we were Ari Vuokila, Kati Pitkänen, Megumi Iwata and me.

Process> Planning, cutting and measuring

We first decided a time that was suitable for all. And after the introduction from the local instructor, we started to plan how would we proceed. We asked Eino how did he do it last year, and we used that as an starting point. We thought together how to proceed: we would draw some pieces that we will afterwards cut with different parameters and in at least two different materials. The plan was to engrave in each piece the settings we would use to cut each piece.

Projection view
Planning and starting to work

Megumi started to draw the designs while we together discussed the different sizes we would need in order to better determine the Kerf of the lasser cutter, Ari started to write a document to describe what we did and I started an excel document to write and later share with all. We all the pieces to be 10mm wide, habing the male pieces a tooth of 5mm or 5.1 mm, and the female pieces slots of width 4.7mm, 4.8mm, 4.9mm, 5mm and 5.1mm. Soon, Kati started to prepare the laser cutter to start cutting. We would start with Acrylic 3mm, and the default values for speed, power and frequency. We would then vary the speed. And later, do the same with MDF 3mm.
Projection view

Planning and starting to work
We had two Vernier calipers, one digital and one analogical.
Projection view
Caliper analogic
Projection view
Caliper digital

Out initial plan was to measure the slot of each female piece (5) plus the tooth of the male pieces (2) for each of the 10 different settings we planned. But when we started to use the calipers we realized it was going to take long time. What we ended up doing is measuring the outer part of two different pieces.
Projection view

Working and discussing results

We measured both with the analog and digital caliper. Megumi and Kati meassured while I was writing the data and Ari was describing the process. When I later organized the data, we decided to just keep the data from the digital caliper, as the other data differed a lot from average values we could find in the internet or from last years projects.

The pieces we cut:

Acrylic
Acrylic 3mm
mdf
MDF 3mm
cardboard
Cardboard

Data summary: Calculations

I created some summary tables with the data. The outer pieces should be 10mm. So calculating 
Kerf = 10mm-ValueMeasured
we got the following values for kerf:

S6 S8 S10 S12 S13 S15
Acrylic 3mm (P100,F100)
piece 1 0.2 0.17 0.09 NO CUT - NO CUT
piece 2 0.22 0.13 0.12 NO CUT - NO CUT
MDF 3mm (P80,F20)
piece 1 - - 0.18 - 0.16 -
piece 2 - - 0.16 - 0.14 -
MDF 3mm (P100,F100)
piece 1 0.2 0.2 0.14 - - -
piece 2 0.15 0.15 0.15 - - -

What we did with the female/male pieces was to test how well one fitted to another. We matched the best case for each combination of material+settings and we got the following values, represented as male[mm]/female[mm]:

S6 S8 S10 S12 S13 S15
Acrylic 3mm (P100,F100)
piece 1 5/4.7 5/4.7 5/4.8 5/4.7 NO CUT - NO CUT
MDF 3mm (P80,F20)
piece 1 - - 5.1/4.8 - 5/4.8 -
MDF 3mm (P100,F100)
piece 1 5/4.7 5/4.7 5/4.7 5.1/4.8 - - -
If we consider that in this case 
Kerf = (Male[mm]-Female[mm])/2
then, in most of the cases kerf value is 0.15

As she was planning to use cardboard in her pressfit project, Megumi decided next day to cut some cardboard squares with different values and meassure them. Those values can be found on the group assignment page.

Conclusions

  • Clearly, the kerf depends on the material
  • The kerf depends on the speed (decreases with the speed)
  • The values are clearly orientative. Test always first!!
  • If I desig for Kerf X but
    • the actual kerf is HIGHER: the female slot is wider/ the male tooth is narrower
    • the actual kerf is LOWER: the female slot is narrower/ the nmale tooth is wider

Resources

Once done

Summary

  • I have learnt how to use the vinyl cutter, by doing my own project
  • I have learnt what is the kerf and how to calculate it, with my classmates
  • I have learnt to do a parametric design of a 3D model using fusion 360
  • I have designed and cut a pressfit kit
  • I have documented it all

Difficulties

  • Understanding the timeline of fusion 360 took a while, and how to copy with no link
  • Still pending: check how to move components parametrically.

Learnings

  • There are always going to be last minute testings and adjustments with the laser cutter
  • I need to learn to position better the origo to make a better use of the material

Tips

  • Always follow the task list when preparing the laser cutter
  • Do not forget to set the origo in the laser cutter!

Files