Week 4

Measuring the kerf (group website)

Process

As a group assignment, we measured the kerf of one of the laser cutters we have in Fab Lab Oulu, Epilog Laser Fusion 75W CO2. The kerf is the extra width on the both side of a cutting line which laser beam cuts out from materials. When we make objects precisely, it is important to take it into account in the designing phase. Neil told us in the lecture that the kerf changes when the time goes, so it is important to measure regularly. I worked with Marta Cortes Orduna, Kati Pitkänen and Ari Vuokila to complete this task. We measured different materials: acrylic plate, MDF and cardboard with different settings of speed, power and frequency of the laser cutter.
I designed the small pieces on which have each setting engraved in Inkscape.


Ari set the focus and operated the laser cutter. With the acrylic plate, we tried five different settings and got the results from three settings. With two of the settings the laser cutter did not cut out the pieces. With MDF we tried five different settings. After finished cutting, we measured the kerf and made documentation. As measuring tool, we used digital and analog calliper. I measured the pieces with the digital calliper while Kati was measuring with analog calliper.


The result was recorded in spreadsheet by Marta and the process was documented in Word document and shared with team members.
In addition to acrilyc and MDF, the kerf of cardboard should be measured with different settings. From the experience of difficulty of measuring, I changed the design from the puzzle type of shape to a simple square which width was 20mm. I cut four pieces at the same time with the same setting, and tried six different settings. After I finished cutting, I measured the size of the square pieces with the digital calliper and documented in a table.


In Inkscape I set the width of a testing piece as 20mm, but after cutting when I checked the width again in Inkscape, it was 19.996mm. So I set original width as 19.996mm. Then I calculate the average of the size in each setting, and subtracted the average size from original size. I found the estimated kerf of the cardboard in each setting.
Since the laser cutter cuts both side of a cutting line, the kerf can be calculated as below.

width of the part where the testing piece was (on the board) - width of the testing piece which was cut out (piece)

Here is the result.
Acrylic and MDF:
Cardboard:

Comment

There are a couple of things should be improved next time. First we could design pieces which can be easily measured. Initially we designed some kind of puzzle, one convex piece and several concave pieces and tried to find out best matches. We were trying to measure the 5mm concave using digital and analog calliper, but we decided to measure just outer side of the pieces because it was quite hard to measure concave with the calliper. Second, it would have been better to measure several pieces from the same material and the same settings and calculate average to minimise the error of measurement. Although there were things which could be done better, the result would be useful for the future projects.

Making press-fit construction kit with laser cutter

Eino Antikainen, Fab Lab Oulu staff and last year’s Fab Academy student showed us basic operation of laser cutter. In Fab Lab Oulu, we have Epilog Laser Fusion 75W CO2 and Epilog Laser Mini 24.

I used cardboard as the material for individual assignment of laser cutting. First I measured the cardboard thickness. Thickness was 2.6mm.


From the findings of the group assignment, I decided to use the setting: speed 30%, power 40%, frequency 50%. The kerf for the setting was 0.12mm. I tired to design parametric model in two ways, using Slicer for Fusion 360 and setting parameters in Fusion 360. To make press-fit construction kit, I payed attention to the material thickness and kerf so that each part fit together well. I designed it in a way that I can change the values of those two items later as parameters.

Making sphere using Slicer for Fusion 360

Designing and preparing file

To design an object for laser cutting, we can use, for instance, Inkscape, Illustrator etc. I tried to use Fusion 360 slicer to create a sphere by laser cutting. I downloaded Slicer for Fusion 360. I checked several tutorial videos, such as this, to understand its basic functions.
I drew a hollow sphere with 80mm diameter in Fusion 360.


I selected MAKE> Slicer for Fusion 360 and clicked OK.


Slicer window appeared, first I went to manufacturing setting, and created a new item named test. There I can set material size, thickness and offset etc.


I set the thickness of the material and offset (kerf). In Slicer I can choose different construction techniques.


I tried several options and decided using radial slice. I can also change how I want to slice the object. I set three layers of circular plates and 10 radial plates to joint with the circular plates.


I was having a problem to change parameters from manufacturing settings, and I could not set the exact values of the material thickness and kerf. Each piece was too loose and did not fit together well. Later I realised there is the bar where I can change values of those items in the bottom of the screen, and when I changed the parameters from the bar, it worked.


I clicked GET Plans, and exported the design as PDF. In 2D vector design software, such as Inkscape, we need to set stroke thickness as 0.02mm for cutting with laser cutter. But Fusion 360 and Slicer recognise all the vector lines as cutting lines.

Operating laser cutter

I placed the cardboard in the laser cutter and prepared some settings on laser cutter for cutting.


First, I adjusted focus which calibrates and sets appropriate distance between laser and the material. I selected JOG and moved the joystick to move the laser to the middle of cutting area. Some materials might bend so it is better to measure in the middle of the cutting area and put the weight to flatten the material. I selected FOCUS and hanged the triangle shaped aluminium piece, which is the measurement tool for adjusting the focus.


I used the joystick to change the height of the stage to where the piece just touched the surface of the cardboard. I pressed the joystick to set. Next, I selected JOG and operated the joystick to move the laser to the place I wanted to start cutting. I pressed the joystick to set origin.

I opened PDF format design file of the object and selected Print. There I can set the values, such as speed, power, frequency and other values depending on the operation. There are some already defined settings for different materials, so I can refer to them.


I selected the settings as speed 30%, power 40%, frequency 50% and sent the data to the laser cutter.



I chose JOB and selected the file I sent. I checked to make sure the ventilation is working. As Neil also emphasised in the lecture, we should pay attention to its safety when we use the laser cutter. We must make sure the ventilation is working before start cutting, and keep eyes on laser cutter when it is operating. There is an emergency stop button on the machine, but it also stop cooling system of the laser cutter, which means it might break the machine because of over heat. I pressed GO and cutting was started.
I got pieces of cardboard to construct a hollow sphere.

Making press-fit construction kit

I made circle shaped press-fit construction kit. I designed in Fusion 360. I set the parameters of diameter (d), thickness of the material (t) and kerf (k).


I drew a circle and put the parameter of the diameter (d). Next I drew a rectangle for a slot. I set the slot width as the sum of the material thickness and kerf (t+k). (* later I realised the width of each slot should be “t-k”.) I changed the height of the rectangle from Sketch> Sketch Dimension, and set it as quarter of diameter (d/4). Next I created midpoint of width of rectangle’s shorter side.


I selected the rectangle and clicked Modify>Move/ Copy to move it. I chose move type as Point to Point and selected midpoint which I created as original point and the cross point of the circle and Y axis as target point. I wanted to have four slots in each piece so I copied and pasted the rectangle.


I removed the unnecessary lines by using Trim.


I got the design in Sketch.


This is the 3D image of a piece.


I went to drawing mode in Fusion (DRAWING> Drawing from design).


I duplicated the object by selecting DRAWING VIEWS> Base Drawing. I exported as PDF.


I selected the setting as speed 30%, power 40%, frequency 50% and sent the data to the laser cutter.


I used Epilog Laser Fusion 75W CO2 and followed the same process described above for the setting of the laser cutter.



After cutting, I realised that the slot width is too wide and they don’t fit each other. I miscalculated the width of the slots. I set the width as the sum of the thickness of the material and the kerf (t+k), but I should have subtracted the kerf from the thickness of the material (t-k). So I fixed the problem by changing the parameter and gave another try. This time, each piece fit together nicely. The left one was made with wrong parameter and the right one was made with the correct parameter. The right one doesn't have space between pieces.

Comment

I experienced parametric modelling in two ways, using Slicer for Fusion 360 and setting in Fusion 360 by myself. In Slicer, it is easy to set the values for material thickness and kerf. After I changed these values, I did not need to fix anything in design. However, in Fusion 360, when I changed the values, some parts moved regarding to the changes. So I had to move back them to the correct places. But in Fusion 360, I can design freely, compare to Slicer which is limited by a few options of types of slicing.

Vinyl cutting

Eino also gave instructions how to cut with the vinyl cutter. To use the vinyl cutter, we need to send data with correct settings, and set the machine. We have vinyl cutter, Roland CAMM-1 GS-24, in Fab Lab Oulu.


I tried two different vinyl cutting using different software and processes to create stickers from the vinyl sheet. We can design in different software, such as Inkscape, Illustrator, and CutStudio is software for Roland vinyl cutter. The vinyl cutter starts cutting from lower left corner, which is different from laser cutter, so we should place design in the lower left corner in the worksheet when we design. There are two ways to create stickers, positive and negative. Positive means we stick the design we draw and remove other parts, and negative means we remove the design we draw and stick the frame the other parts as a sticker.

Cutting a world map with Roland CutStudio

I need to make a globe for my project. I have several ideas to make it. One of them is to put the world map on a sphere. Making 3D globe from 2D world map is not easy but I wanted to try how it looks like. I searched world map on the internet. I chose a sinusoidal map from this website and saved the image. I measured the circumference of the ball I had, and calculated the diameter. The circumference was 185mm and the dimeter was 58.9mm. I imported the image in CutStudio. I traced the image outline and deleted the original image.


I changed the size as width 185mm and height 58.9mm and placed at the origin point, lower left corner. (* later I realised that I miscalculated.. its height should be 1/2 of the circumference, which means 185mm/2=92.5mm) Now the design is ready.

Operating vinyl cutter

I set the machine, Roland CAMM-1 GS-24. First I set the sheet. I pushed down the lever in the left of the vinyl cutter and placed on the left edge of the cutter. I placed the sheet between two rollers.

I chose sheet type. There are three options for sheet type, ROLL and EDGE for the sheet is rolled, and PIECE for the sheet is not a roll but a piece. With PIECE and EDGE, the machine automatically finds the edge and starts cutting from the edge. I selected sheet type EDGE and pressed ENTER.


Next I used arrow buttons to move origin point where cutting is started. With EDGE setting, I don’t need to set origin of up down direction, so I only set horizontal position. When the blade is on the correct position, I kept pressing to set origin. I set the blade force as 0. Now the vinyl cutter is ready.

I selected Cut in Roland CutStudio and change Cut Setting. I set the cutting area by information from the machine and pressed OK.


After finished cutting, I cleaned the sheet. The vinyl cutter cuts layers of sticker sheet and paper sheet and the glue between them. But after a while, the glue might stick together again, so we need to clean the sheet after cutting. I removed the extra parts from the paper sheet and put whole paper sheet on the transfer sheet and removed the paper sheet.




With transfer sheet, we can keep the places of individual parts. I put the parts with transfer sheet on the ball, and removed the transfer sheet. I lost some of the small parts while I was removing the paper sheet and transfer sheet.

Cutting a sticker with Inkscape

I also tried to design a sticker in Inkscape. I made a sticker to put on the card to my friend. In Finland, Valentine’s day is called “Ystävänpäivä” which means friend’s day. People send cards to friends. I made the sticker from the photo of a reindeer I took on the other day in Lapland. First I imported the photo in Inkscape. I started outlining the reindeer using Bezier Pen. I created nodes on the outline of the image. Then I modified the places of nodes using Edit Paths by Nodes for better natural curve lines.


After I drew outline of the reindeer, I used Clip to remove the background. I filled inside of the outline path I created with blue and reduced the opacity. I selected the original image and outline and applied Clip.

(*Later I realised that this reindeer doesn’t have good contrast of brightness and shadow. If the photo had good contrast, I could also use the shadow for my sticker but at the end I used only this outline as a sticker.)
I changed the document size as a card size, width 148mm, height 105mm. Next I wrote the message. I wanted to make it curve. I drew a curve line using Bezier Pen.


I selected both the curve line and the text and applied Put on Path (Text> Put on Path). I selected the text and make it as path (Path>Object to Path).


I deleted the curve line.



This time I cut the sticker directly from Inkscape. I set a piece of the sheet in vinyl cutter. I selected “PIECE” as sheet type. I followed the same sequence described above. In Inkscape I clicked Print and selected Roland CAMM-1 GS-24. I went to Preference> Cutting area> Get from machine to get information from vinyl cutter. The width of the sheet was set from the machine. I set the length as the same size as the worksheet in Inkscape and clicked OK. The vinyl cutter started cutting.


After it cut out, I removed unnecessary parts from the sheet with the tweezer.


Then I put transfer sheet on the sticker, and removed the paper sheet.


I placed the sticker with transfer sheet on the card and carefully removed the transfer sheet.

Comment

It was quite hard to put a sticker on the sphere surface. I carefully placed it but it was impossible to smooth all the wrinkles. I should have used a world map which is cut into vertical smaller parts, like this. So that I can place them on the surface of the sphere better. I cut sticker for the first time from Inkscape directly, it was easy and it went well. When I copied and pasted the design from Inkscape to CutStudio the lines were not clear. So when I use Inkscape to design stickers, it would be better to cut directly from Inkscape. I only need to make sure the sheet size and document size is correct. The object was cut 90 degrees rotated from the view in Inkscape. I suppose it was because of the document size. I set the document size for a card, width 148mm, height 105mm, but perhaps the vinyl cutter recognises height should be always longer than the width and it automatically rotated the deign.

Reflection

Although I have used laser cutter and vinyl cutter before, I got many useful findings during working on the assignment. Firstly, about laser cutting, I hadn’t taken the kerf into account when I created press-fit projects before. I thought it was okay without thinking these details, but after I calculated and cut my press-fit construction kit with the kerf calculation, I could feel big difference between the ones I didn’t think about the kerf and the ones I took it into account when I attached each piece. I learned those details are important to improve my designing skills for laser cutting. Secondly, I learned the importance of parametric modelling. During the process, I miscalculated the kerf and had to fix them. I had set parametric for the kerf before so it was easy to fix it. This kind of mistakes and modification can often happen during fabrication process. It is important to reduce errors, but also important to be prepared for modification for the errors. Setting parameters also helps us work on projects in the way of spiral development. During the process of spiral development where we start something small and keep enlarging the spiral, we will have something that we need to change in the next spiral. In those cases, parametric modelling is useful to reduce the amount of work for modification. Thirdly, about vinyl cutting, I learned usefulness of the transfer sheet. One thing I haven’t been able to find out is setting for cutting in Inkscape. The vinyl cutter cut the sticker in the different direction than I expected. I assume it was because of the document size. I should have tried several times with different settings, but I couldn’t have time in this week. I will figure it out some other time.

Files

Here are the files of this week's assignment.

Laser cutting

• Press-fit sphere made by Slicer pdf format
• Press-fit construction kit f3d format
• Press-fit construction kit pdf format

Vinyl cutting

• Sticker of world map for sphere svg format
• Sticker for card svg format