3. Computer-Controlled Cutting
Assignments
Here you can find a recording of the lecture from the 29th of january.
This week's assignments and learning outcomes, see here:
Group assignment:
- do your lab's safety training
- characterize your lasercutter's focus, power, speed, rate, kerf, joint clearance and types
- Document your work to the group work page and reflect on your individual page what you learned.
Individual assignment:
- cut something on the vinylcutter
- design, lasercut, and document a parametric construction kit, accounting for the lasercutter kerf, which can be assembled in multiple ways, and for extra credit include elements that aren't flat
Hero shots
Summary
This week we went through safety training in our Fab Lab, got to know our laser and vinylcutter better and designed projects for these machines. I began by characterizing our laser and did both a raster and vector test. Then I told the story of making a stamp in Pre-Fab last november and december.
Then I characterized our vinyl cutter, adjusted the knife and did a cutting test. I used the logo I designed in Pre-Fab to make a sticker.
My instructor told me to do the group project on my own because here, in Fab Lab Austurland (Neskaupstaður), the laser cutter and the vinyl cutter can differ from the machines in Ísafjörður, where the others in my group are. But here is the group page if you want to see what the others in the group did; see here.
Work process detail
The laser
Epilog mini 24
We have the Epilog mini 24 laser cutter in our Fab Lab with table size of 305x610mm. Here is the manual. I used the manual as a guidance when characterizing our laser.
Safety procedures
According to the manual the laser uses embedded high-power CO2 and the technology is the same as laser pen pointers and it can be harmful if the beam shines directly into the eye. The laser beam is dangerous and it is invisible! For that reason the machine should never be operated with any cover open.
The laser can vector cut many types of materials, f.ex. wood, acrylic, rubber stamp and leather. It can also raster glass and metal, but it can not engrave on bare metal, it has to be coated with f.ex. laser ink before starting the engraving.
The high intensity beam of light can cause fire. For this reason you should stay close to the laser when operating it and always be ready to react quickly if the material starts burning. Neil mentioned in the lecture that first reaction could be to try and suffocate the fire by throwing a fire blanket over the flames. If that isn't enough or the fire is growing you could use a fire extinguisher. In the manual it is recommended to have a fire extinguiser at hand at all times, a Halotron extinguisher or a multi-purpose dry chemical fire extinguisher. The area around the laser should also be free of flammable materials.
It is recommended to use Air assist when vector cutting. It reduces the risk of fire.
By cleaning the laser regularly the risk of catching fire is reduced. Small pieces of material fall from the cutting table and into a drawer. This drawer has to be emptied on að regular basis because these small parts can catch fire.
But the fire hazard isn't the only hazard. As Neil mentioned in the lecture, you should always make sure that the material intended for cutting and rasterizing in the laser is free of dangerous chemicals.
Cutting or rasterizing material with PVC or vinyl can be harmful to people or the machine, because of corrosive fumes.
Focus
Our laser has an autofocus function (see pages 75-76 on focus). When activated the table with the material moves up until it pushes the plunger and it senses the pressure. Then the table moves back to correct focal distance. On page 76 in the brochure it is recommended to use this with precaution. The reason is that if the material is irregular in shape the plunger can get caught and that can cause damage.
The safest way to measure the focus is to use the v-shaped tool that comes with the machine. You place this tool, called manual focus gauge, on top of the carriage. Then you manually move the table upwards until the material you are going to cut or engrave touches the manual focus gauge. If there are irregularities in the height of the material you should choose the middle point. The focus needs to be within 3mm changes in height because if the focus changes for more than 3mm the work will most likely become fuzzy.
Cleaning and maintaining the laser
See pages 69-74.
The Autofocus plunger has to be cleaned regularly with a cotton rag and Isopropyl alcohol or Windex or 409. The optics (mirror and lenses) should be cleaned on a weekly basis with Reagent or laboratory grade alcohol.
Once in a while you should clean the optical encoder strip and the reader assembly. First, you remove the x-beam cover and clean the encode reader and the optical strip with a cotton rag/swab and distilled water or with mild dishwashing soap. Then you can use alcohol and cotton swab to clean the the bearing tracks of the X-axis rail. After cleaning the X-axis Bearing rail should be lubricated with special grease.
Finally, the length of the right and left side Y-axis rail should be cleaned with a soft cotton cloth, but this axis should not be lubricated. The vents, down draft ports and rear exhaust port should also be cleaned with a soft, dust collecting brush.
Characteristics
Raster test
I decided to do the setup for the raster and vector test in a similar way that can be seen here and was done by Andri Sæmundsson and Hafey Hallgrímsdóttir
Colour mapping
Hafey Hallgrímsdóttir made these directions about Inkscape and in it she explains how to use Colour mapping to define the power and speed for each colour.
I dedided to use this method to adjust the power and speed in a raster test and a vector test on birch plywood. I made the base files last year and was planning on doing this just to get to know our laser better, but I never got to it. So now I began by opening the basic Raster Test file. I chose each diagonal line and changed the colour. On the right you can see the settings in RGB. When using the colour mapping when adjusting the settings for the laser, the RGB colour settings need to be the same for each colour.
Making a file for each horizontal line
Then I saved five new files, one for each horizontal line. In the first file I deleted the coloured rectangles in lines 2-5, but in the files for the other lines, I deleted everything but the line. In the lower photo to the left you can see the file for the bottom line.
Bottom line
This is the file for the bottom line. I was thinking about having a cutting line in this file but got worried that the color mapping settings would affect the cutting line, so I made a special file for cutting in the end.
Easy to change settings in colour mapping
I had to change the settings for the speed in every file, but that was easy since it was the same number for all colours. Notice that I checked in the Raster box but left Vector box unchecked.
Raster test finished
Here you can see how the raster test turned out.
Files for raster test
Vector test
Same process with the vector test
I did the same as in the raster test, but instead of using settings for rasterizing I used settings for vector cutting in Inkscape. Note that when you adjust settings in colour mapping for the laser, you can check in either vector or raster. I made the lines thicker just so that they could be seen in the photo. As you can see I used the same colours as in the raster test.
Settings in colour mapping for vector test
In the colour mapping settings I checked in the box for Vector and unchecked the Raster box.
Not all was cut through
Notice on the backside how some lines almost cut through and others did not cut through. This test gives good information on which settings are adequate.
Files for vector test
Kerf measurement
Jóhannes Andrésson, a student in my group, sent me a file that I used to do the Kerf test. The file is here:
File for kerf test
Measuring the kerf
Árni Björnsson explaining how to use the Vernier scale here.
In this part I had to use a Vernier scale. I am still trying to get used to it and if I'm not quite sure, I can check out the explanations that Árni Björnsson made. I think they are very clear. I decided to measure the kerf the same way that Svavar Konráðsson, my instructor, did here.
I cut the test out of plexiglass. Then I used a caliper to measure the gap, which was 2,1mm. Since this gap equals the ten cutting lines made in the laser I could divide 2,1mm with 10 so the kerf in our laser is 0.21mm.
Parametric construction kit
Circular pattern used for slots
I wanted to use leftovers of plexiglass in our Fab Lab to make parametric construction kit. I decided to design it in Fusion. First I made a sketch of a centered rectangle. Then I added a slot to one side. I mirrored it so that I would have two slots on one side. Then Svavar Konráðsson showed me that I could use the Circular Pattern option to create similar slots on the other sides. He also showed me how to use Parameters. Instead of writing the thickness of the material in the drawing, I wrote the letter t. Then I added another parameter; kerf. Then I could define the width of the slot with t-kerf instead of adding the number in the drawing. This means that I could open the parameters and edit the thickness of the material I planned on using and then the program would calculate all changes and make all slots the right size.
Circles
I created another sketch and drew a circle. Then I drew one slot and used the Circular pattern again to distribute more slots around the circle. In this command you can choose how many slots (rectangles or other forms) you want to create in the pattern. I made six slots.
New sketch - Project - Export DXF - Inkscape
To export the drawing I clicked on the green plus for Create sketch. Then I clicked on Create and Project/Include and then Project. Then I chose both the forms I wanted to use and clicked on Finish sketch. After this I right-clicked on the sketch (Project) and chose Save as DXF. Finally I opened Inkscape, chose Import and imported the DXF file. Then I changed the lines to cutting lines and cut the forms out in the laser.
Parametric design made from leftovers
Here you can see parts of the design I cut out.
Note! Plexiglass varied in thickness
I was very surprised to find out that the plexiglass plates were of different thickness. One plate can even vary in thickness between corners/sides! This can affect how well pieces fit together so it is important to measure the area of the plexiglass plate that you are going to use.
Tight fit or too loose because of plexiglass being of different thickness
As you can see in these videos the fit was different depending on the thickness of the material, even though all the material was bought as a 3mm plexiglass.
Tight-Fit
Loose-Fit
Problems with uploading mp4 videos
Videos not playing
I ran into problems when I wanted to add videos to this page. To begin with I dragged the video from the files in VSCode and held the Shift button when I released my hold of the mouse. Then I could choose from the three possibilites that you can see on the right. I tried this three times and each time I chose different option to try them all. None of the videos played on my website.
Videos worked with HTML code
I googled and tried different things, but nothing worked. Then I decided to ask Svavar Konráðsson and Þórarinn Bjartur Breiðfjörð. Þórarinn pointed these two sites out: Tips on adding videos and MkDocs videos. I tried following the latter site and added a plugin in my gitlab-ci.yml and then settings in mkdocs.yml. Then I tried to add the videos, but nothing worked. Then Svavar told me to check out his site to see how he used HTML to set up his videos. I copied his code from his repository here and adjusted it to my site. I thought I was supposed to copy the path to my video in my repository, but that was not correct. Svavar told me to use the https:// path to the video and it worked!!!
Files for Parametric Design
Stamp and logo
In Pre-Fab i made a stamp and a logo. You can see the Pre-Fab site here. It was interesting to cut the stamp out in the laser.
Designing a stamp handle in FreeCad
Tutorial
I followed Svavar's directions on how to draw the handle. The directions can be found here.
I made the drawing on the XZ-plane. I began by drawing all straight lines and using constraints to set the length, hight, width, radius and the incline degrees. Then I made the arching lines and made sure that the nodes were connected. To soften the parts where a straight line meets an arch I made the arch tangent to the line. I created a guiding line at the top and made the arch tangent with it. To create a guiding line (construction geometry) you can click on this icon. Read about it here.
The final sketch for the handle
This is the final sketch:
The stamp handle drawn in 3D:
At last I chose the Revolve in Part workbench to revolve the drawing around the Y-axis to make a 3D model. Read more about revolving here. After revolving and saving the file I exported it as an 3D Manufacturing format (*.3mf). Finally I prepaired the model for 3D printing in Bambu slicer and 3D printed it in Bambu X1 Carbon.
Designing a logo
Designing a logo in Inkscape
This tutorial shows how you can make logos with custom text treatment in Inkscape.
I decided to use my first name when designing my logo. At first I used my name without the Icelandic letters, Olof instead of Ólöf. I clicked on the text icon in Inkscape and chose a font. By holding CTRL and SHIFT I could scale the size and still keep the same proportions. Then I converted the text to path by choosing Path and then Object to path. After that I clicked on Object and Ungroup.
I clicked on Object and Fill and stroke. There I changed the Opacity from 100 to 50. That way the letters were a little bit transparent and I could see them all when they overlapped each other. By holding CTRL while moving a letter, the letter was locked on the horizontal axis when moving them around. Then I could select more than one letter by holding SHIFT while clicking on all letters I wanted to select when moving multiple letters at the same time.
By selecting one letter and clicking on CTRL and D I duplicated the letter. Then I changed the color of the letter by clicking on a color in the color palette at the bottom of the screen. I went to Path and Path effects. Then I clicked on the arrow to the right on the screen, below the Path effects text and chose Offset. Then I could use the plus symbol to increase the offset until I was happy with the size. After that I held the Shift button and clicked on the letter beside it. Then I chose Path and Difference. This is the outcome:
I wasn't really happy with the outcome, so I kept on trying different ways. I used the Impact font and arranged my name in a rectangle.
Then I added a pink rectangle to the logo.
I used the Typographica font that I found on the website DaFont.com, resized some letters and arranged them in a fun way to make this logo:
Inline blocks
This looks like an emoji! I think it would be fun to learn how to use Blender to change this logo to an emoji. I could call it Baffled face, expressing the feeling that can come over people when learning something new in Fab Academy.
Then I tested how it would look with the ComicSans font:
The final design
I found the Pricedown font on DaFont.com, stretched some lines and created an outline.
I made two versions of the final logo, with and without the Icelandic letters.
Problems with settings for logo and favicon
I ran into some problems when I tried to use the logo on the website. The logo didn't appear when I followed what Svavar had done. Then I tried to follow the instructions on this site, but it didn't work either. I checked if there was any difference in using .jpg, .png or .svg and I also checked if they would work in the image folder or just under docs in the repository. When none of this worked, I asked Þórarinn Bjartur Breiðfjörð. After looking into what I had done he suggested that I would not write the folder name before the name of the file and it worked. I do not know why this worked better, but I was glad that it did.
Logo and favicon made clearer
The logo and favicon were not as clear as I wanted. When I had many tabs open on my browser the favicon was just a black blob. When I changed it to pink it was easier to find it. I also decided to change the logo and make all white spaces between letters and lines bigger.
The stamp
I created another file in Inkscape for rasterizing and cutting the stamp rubber. I coloured the logo pink. Then I used Path and Union to union all the elements in the logo. I found that it did't always work when I chose more than two elements at a time so I only worked with two elements each time. Then I drew a cirkle with 30mm diameter. I copied it and pasted to make another cirkle. I clicked on the other cirkle, chose Object and Fill and stroke. There I turned off the fill, turned on the line and made it red. Then I set the line to 0.02mm. In the other cirkle I turned on the fill and made it black.
When making a stamp you have to mirror texts and images, unless images are reflected on the Y-axis. I mirrored the letters and aligned them with the black, filled cirkle by clicking on Object and Align and distribute. Then I aligned them on both x- and y-axis. After that I clicked on Path and Difference to make the logo change to a negative space. Then I selected both the cutting line and the logo/filled cirkle, clicked on Object and Align and distribute and aligned them.
If I would have selected the filled cirkle with the logo as a negative space, clicked on Object and Fill and stroke, turned on the line, made it red and set the line to 0.02mm, the cutting lines would also be added to the lines/letters in the logo. That is the reason why I added the circle with the cutting line.
Rasterizing and cutting the rubber stamp
How to rasterize and cut rubber stamp
Svavar used this site as reference when making his stamp. I used it for reference when adjusting settings for the raster and vector. On the website it is recommended to go three seperate passes when rasterizing to get a good depth but after two passes I stopped and thought it would be enough. I should have done the third pass, as had been recommended, because the stamp smeared ink easily around the logo. Since it only took two passes to cut through the material but the rasterizing should have been done three times, it might be a good idea to make two seperate files, one for rasterizing and one for cutting.
Settings for rasterizing (using 600 dpi)
Speed: 45
Power: 100
Three passes should be adecuate.
Settings for cutting (using 600 dpi)
Speed: 18
Power: 100
Frequency: 600
Two passes should be adecuate.
Important
I could see many flares both when rasterizing and cutting, so it is important to be ready to act if fire breaks loose. This is always important when working with a laser and especially with materials that can easily catch fire.
I fastened the rubber to the handle by using double tape. It worked well and here you can see the stamp!
Stamp and logo files
The vinyl cutter
Roland GX-24
We have the Roland GX-24 in our lab. Here is the manual. I used the manual as a guidance when characterizing our vinyl cutter. The width of the material used can be from 50 to 700mm and if the material is on a roll, there is no length limit, but the maximum cutting area is 584mm in width and 24998mm in length. Cutting material thickness can be up to 0.1mm. With the backing paper the maximum thickness is 0.3mm. The blade force can be set from 30 to 250gf.
Safety
It is important to keep your hands, hair or loose clothing away from the cutting carriage/moving parts of the machine while it's operating.
The electric cord should never be bundled or rolled up, because heat can build up and cause fire. The same thing goes for other electric cords, like the cord with the laser.
Cleaning and maintenance
See pages 58-59. Make sure that the machine is switched off before cleaning or maintenance. The machine, pinch rollers and grit rollers, should be cleaned with a cloth that has been moistened with water and then wrung dry. If there are materials residues around the grit rollers, it's best to use a soft brush to remove it.
The machine should not be lubricated.
The blade can become dull and then it is replaced by loosening the screw and lifting the blade holder. A pin is pressed to release the blade. When the new blade is in place and the blade holder is put into place, it is important to hold a finger under the screw to support it. Otherwise the quality of the cutting can be poor. Then the screw is fastened.
Testing knife and cutting settings
Knife and cutting settings
I followed the directions here when adjusting the knife and cutting settings.
Too much extrusion of blade
I removed the blade to check if the extrusion of the blade was ok. I cut U-shaped lines in a piece of vinylsticker. I was surprised to see that I cut all the way through the backing, so the blade extruded too much. This was my mistake since I changed the blade a few months ago, but then I didn't realise that I had to check this out. I thought it was all about how much force you would use.
Vinyl sticker cut out
I did a cutting test on the vinyl cutter by clicking on the Test button on the vinyl cutter. The test looked good; it was easy to peel of the piece and it did not cut through the backing. Then I decided to use the logo I designed to cut out a sticker. I created a new Inkscape file and changed the raster settings to vector settings. I put the sticker on my computer.
Sticker file
Learning outcome
I learned so much this week. I think it's important to know all the safety precautions and how to maintain the machines. The raster, vector and kerf tests will be useful and it was fun to use the colour mapping. Designing the parametric kit in Fusion was a great lesson. I want to get better in using Fusion and now I know how to create pattern and use parameters. It was also a surprise to see that 3mm plexiglass isn't always 3mm thick and the thickness can vary between corners or sides of the same plate. When the thickness of material matters, it is necessary to measure it.