<h1>Computer Controlled Cutting</h1> <h4>Wednesday February 07, 2018</h4> <img src="media/week4/geartrain.JPG" style="width:40%; float:right; padding:5px 5px 5px 5px;"/> ## Preamble Welcome to the first edition of Carl does Strapdown (I'm now finally writing in Markdown instead of HTML!). I'm gonna just come right out and say I don't know what I did differently from last time but this time it worked straight away and I even managed to stuff the script up enough it remembers the old theme/css. I'm using <a href="http://strapdownjs.com/">Strapdown.js</a> and one of the coolest things about it is being able to bastardise it with HTML to insert elements like images and columns, which I'm sure you've realised I'm pretty much in love with. <img src="media/week4/valentines.gif" style="width:20%; float:right; padding:5px 5px 5px 5px;"/> You might have noticed it took a good half-second longer for the page styling to update. That's the markdown conversion script going on at the end of the page's html. But I'll swallow that delay in favour of being to see what I'm writing a lot easier. I'll <em>cut</em> to the chase this week since it's the most anticipated week of the year (Laser week) and we're already a little behind. I've got a few things to show you. It also happens to be Valentine's Day today, (I'm submitting this on the final day of the week). Here's a heart I made while playing around with my construction kit that you'll see later on. <img src="media/week4/seinfeld-what-is-the-deal.jpg" style="width:35%; float:left; padding:5px 5px 5px 5px;"/> ## "What is the ___deal___ with Laser week?" Laser week is the wonderful time of year when we get introduced to the laser cutting machine (and the much less anticipated but silently very useful vinyl cutter). We get to explore different ways of making 3D structures with only 2D tools. This is also the first week where the assignment involves making something physically, as even though I've been having a bit of a play on the machines the rest of the course cohort has presumably only made things in software. 2D tools are in many ways significant in manufacturing. They are generally cheaper and more reliable, more efficient and faster types of machines. In production, having simple processes is hugely important. I'll get into what we explored but to meet the requirements of the assignment we: <li>Characterise the lasercutter</li> <li>Cut something on the vinylcutter</li> <li>Make a press-fit construction kit</li> The laser machining process produces a cut with non-zero thickness. This means any assemblies requiring tight tolerancing have to take this into consideration. This is gap called 'kerf'. It varies depending on the material, thickness of the material, focal length of the laser lens and the power setting of the laser. ## So how'd we get on? ### Characterising the laser <div style="width:50%; float:right"> <img src="media/week4/layout.jpg" style="width:50%; float:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/laser-press-fit2.jpg" style="width:50%; float:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/laser-press-fit3.jpg" style="width:40%; float:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/laser-press-fit.JPG" style="width:60%; float:right; padding:5px 5px 5px 5px;"/> </div> To do this we had to develop some tests. Salama, Bear and I worked together on the 6mm cardboard, and the other half of the class worked on the 3mm. Initially we tried a few tooth-type fitment tests with increments of 0.10mm - this was to try to figure out what dimension to program into our parametric software to ensure our press-fit kits would fit together nicely with a good amount of grip. <br> We did this but it became apparent that it might help us more to measure the kerf directly. To do this we cut a square inside another square, both of know dimensions. We also took this opportunity to make a more fine-toothed fitment comb, this time increasing in 0.05mm increments. <br> <div style="width:50%; float:left"> <img src="media/week4/printer-settings.jpg" style="width:40%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/settings1.jpg" style="width:50%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/settings2.jpg" style="width:45%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/laser-machining.JPG" style="width:45%; float:left; padding:5px 5px 5px 5px;"/> </div> <div class="row"></div> <div style="width:50%; float:right"> <img src="media/week4/fitment.jpg" style="width:50%; float:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/laser-pressfit-cut.jpg" style="width:50%; float:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/laser-kerf-penetration.jpg" style="width:50%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/kerf.jpg" style="width:25%; float:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/kerf2.jpg" style="width:25%; float:left; padding:5px 5px 5px 5px;"/> </div> To get the part we'd drawn into the laser we set the machine up as if it were a printer. The drivers for the laser cutter interpret lines in different colours as different operations and we can set the configuration for all of these. <br> There are three main types of operation we used: <li><strong>Etch</strong> (raster) - Etching is a partial penetration of the material. It has different effects on materials that oxidise (i.e. wood, aluminium, copper) as opposed to ones that don't (mainly acrylic). To do this we use a process called "rastering" to slice the image into passes that the laser machine will 'colour in' using the laser. This is really similar to a regular printer travelling line-by-line down an image.</li> <li><strong>Etch</strong> (vector) - This is the same process of partial penetration, however instead of travelling line-by-line it travels along the outline or paths of an image. In order to do this we have to 'trace' or 'vectorise' the image to turn it into paths so the laser machine can follow them.</li> <li><strong>Cut</strong> - This is the same as the vector etching process but by making a full penetration. Usually you need to slow the travel speed right down in order to cut through fully (especially around corners) and also it is imperative that the laser is in focus.</li> <br> You can see in the screenshots that we are able to adjust settings for each type of operation. The major factors that affect the quality of laser cuts are power, speed, lens focus, flatness of the material and fume extraction (or airflow). <br> What we found is that the up-down kerf can be different to the left-right kerf. If you look closely at the fitment testing we did you might notice the gap on one side is larger than the other by about 0.5mm (that's huge!). <br> There are a couple things we hypothesise could be the reason for this. Potentially the machine has been set up skew, but more likely the corrugations in the cardboard are having an effect on the kerf size. One way to tell for sure would be to test on acrylic which has no grain to it. <br> Another thing to note is that these numbers were all good an well for small sized sheets of cardboard, however when using larger sheets they have a tendency to bow meaning the focal point isn't always near the surface of the material. This is quite annoying and can really affect the penetration and quality of cut. <br> Next I'll be making use of those numbers to make the press-fit construction kit. <div class="row"></div> <div style="width:40%; float:left"> <img src="media/week4/franciscos-laptop.jpg" style="width:60%; align:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/vinyl-sizing.JPG" style="width:33%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/test-cuts-and-roller-locations.jpg" style="width:66%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/dubai-original.jpg" style="width:33%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/cooked-it.jpg" style="width:33%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/dubai-unpeeled.jpg" style="width:66%; float:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/dubai-peeled.jpg" style="width:33%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/dubai-stickers.jpg" style="width:33%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/gold-force.jpg" style="width:32.5%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/gold-cuts.jpeg" style="width:35%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/hardcase.jpg" style="width:32.5%; float:right; padding:5px 5px 5px 5px;"/> </div> ### Vinyl stickers Inspired by Francisco's Beach Labs stickers I wanted to do learn how to make two-tone vinyl cuts. He showed me his technique for aligning cuts from two different colours, using locating holes in each corner of the vinyl for each cut. Very clever! Unfortunately once again I'm not gonna get the time to play around with this technique but Zahrah and I managed to get some vinyl cuts out anyway and I'll revisit the two-tone idea later. So the machine is a Roland GS-24 and it also thinks it's a printer so you just install printer drivers for it. When you first insert a piece of vinyl and clamp it down the machine will ask you whether it's a 'piece', 'roll' or 'edge'. I don't know what 'edge' does, but the piece setting will measure the size of the piece you put in by running right to left then back and forward. It'll sense this so the coordinate system on your cut is correct, and also to make sure the piece doesn't fall out the cutter when it's feeding. The 'roll' setting only senses the width and assumes your roll is at least 1.6 m length, and apparently you can set it to be longer if you need. There's also a bunch of white lines on the runner where the rollers slide along. These white areas indicate where the rollers should be located if you decide to adjust the spacing. You can see by this that the cutter can accommodate many types of small pieces, and then a bunch of larger sizes moving all the way to full roll width. After measuring you can set where you'd like the origin to be by holding down the 'origin' button - this is useful if you don't want your test cut to be a part of the final image! Next you can do a test cut to check your pressure settings on the blade. Some materials are thicker than others and ideally you want to cut only the vinyl and not the backing paper. The test button cuts a square within a circle and you should be able to lift the circle out without dislodging the square, without scoring the backing sheet. I'd been walking around and seeing this script on the number plates of old cars which I thought looked cool. Turns out it just says "Dubai" in arabic so I ended up taking a picture of it on a car I walked past and when I got back to the lab I un-skewed it and vectorised it 😎 To do these cuts I used Inkscape, the edge detection finds the edges in an image and converts them to vectors. From this I was able to "trace" the outline of the shape I wanted ready for processing. To prepare the vectors for cutting I had to set the thickness of each vector to 'hairline' and make sure they are all joined (not open vectors). After this I went through the Page Setup tool to adjust the vector file to fit the piece of vinyl I had loaded into the machine. Since the vinyl cutter is essentially a pointy printer, all I had to do was press print and cut data went straight from my laptop to the vinyl cutter. Zahrah and I spent a late night doing some cuts on different materials. We found that on orange and black vinyl 60 grams force (gf) worked well, and the gold is significantly thicker so it needs around 150 gf. The first couple times I managed to cut perfectly but I cooked it with setting the origin meaning I cut through a bunch of existing cuts. It's ok though, between the two screwed up cuts I did I was able to lay them on top of eachother and make a full sticker! To lay up complex stickers, Wendy showed us how to use transfer tape. It's basically a low-residue adhesive film with less stickiness than the adhesive on the vinyl. First you weed the small holes from the vinyl cut, second you apply the transfer tape to the sticker area firmly. Then carefully peeling the transfer tape AND vinyl off the main roll all of the vinyl remains relatively positioned on the transfer tape. The transfer tape is slightly see through so you can see where you're placing the sticker, and when the vinyl is stuck down to the part you peel the transfer tape off (The vinyl-part interface should be stickier than the transfer tape-vinyl interface). <img src="media/week4/burj-khalifa-2.jpg" style="width:30%; float:right; padding:5px 5px 5px 5px;"/> ### Dubai-it-yourself kit Limited edition Dubai-inspired cardboard souvenir kit, for 4 years (of patience) and above. One of the key requirements of this assignment is that the kit we build MUST BE RECONFIGURABLE. This means it must be able to assemble into multiple components. We spent a long time deliberating how we were going to achieve this, and it reminded me of how I hadn't bought any souvenirs yet! I've always walked past the stalls in the basement of Dubai Mall and thought to myself how I could just as easily fabricate a souvenir for a fraction of the price. It could also look as tacky. So I decided I was going to put my (lack of) money where my mouth is, and build the Burj Khalifa. But in resolving that, I also realised that there are a couple of similar architectural styles in and around the Dubai area! What we're aiming for is a kit that can do (or at least start) a couple of architectural styles from Dubai's most notable buildings. Let's see how we go! <img src="media/week4/burj-khalifa-1.jpg" style="width:30%; float:left; padding:5px 5px 5px 5px;"/> Darshan and I started with a <a href="https://en.wikipedia.org/wiki/Living_hinge">living hinge</a> concept, to create many of the tapering curves present in the style. We then started to think of some skeletal structures that could be reused for different buildings. Here's our first prototype tryna figure out the distance along the curve at which to place the holes for the tabs. Sure, we could have used a piece of string to guess where the holes should go instead of gluing together a prototype, but listen, today we're designers not problem solvers! After putting together this first prototype with hot glue (not canon, I know..) I discovered that the simplest form of what I needed in order to keep the structure together was a bar with spaced square holes in it for the tabs of the living hinge sections to go. <img src="media/week4/fusion-edit-parameters.png" style="width:50%; padding:5px 5px 5px 5px;"/> Like all obedient parametric software, Fusion 360 has a parameter utility which allows you to add parameters and then refer to them while sketching/dimensioning. To do this you add a new parameter i.e. slot_width, and set a value for it. Any time you type 'slot_width' it will refer to the value you originally specified, meaning you can change the value of all variables named 'slot_width' just by changing the value of the initial parameter. If I had more time I'd be looking to chamfer the edges of the tabs on the living hinge side since they do have a tendency to collapse if not inserted quite square. Also a word of warning if you are intending to do a living hinge design - the laser machine slows down for curves so I would recommend not filleting the cuts (even though you should, especially for acrylic) because it will save considerable time. ### Here's the results! <img src="media/week4/burj-khalifa-2.jpg" style="width:30%; padding:5px 5px 5px 5px;"/> <legend>"So here's the Burj Khalifa for reference."</legend> <img src="media/week4/burj-diy.jpg" style="width:33%; float:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/burj-diy2.jpg" style="width:33%; float:right; padding:5px 5px 5px 5px;"/> <img src="media/week4/burj-diy4.jpg" style="width:33%; float:right; padding:5px 5px 5px 5px;"/> <div class="row"></div> <legend>"And a semblant 'Khalifa-inspired' model made with the Dubai-it-yourself kit!"</legend> <img src="media/week4/al-arab.jpg" style="width:30%; padding:5px 5px 5px 5px;"/> <legend>"The Al Arab Tower (which I haven't yet visited)."</legend> <img src="media/week4/al-arab-diy.jpg" style="width:50%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/al-arab-diy2.jpg" style="width:50%; float:left; padding:5px 5px 5px 5px;"/> <div class="row"></div> <legend>"And if you blur your eyes a bit (maybe, a lot..)"</legend> <legend>"I tried 😂"</legend> <img src="media/week4/address.jpg" style="width:30%; padding:5px 5px 5px 5px;"/> <legend>"They haven't even finished this one yet.."</legend> <img src="media/week4/address-diy.jpg" style="width:50%; float:left; padding:5px 5px 5px 5px;"/> <img src="media/week4/address-diy2.jpg" style="width:50%; float:left; padding:5px 5px 5px 5px;"/> <legend>"Beat them to it!"</legend> <img src="media/week4/dubai-skyline.jpg" style="width:30%; padding:5px 5px 5px 5px;"/> <legend>"And for the finale, the Address towers with the Burj Khalifa."</legend> <img src="media/week4/dubai-skyline-diy.jpg" style="width:100%; padding:5px 5px 5px 5px;"/> <legend>"A construction-kit take on the Dubai skyline."</legend> ##More on this next week: ### Setting up Little Red I'm planning to set up the mobile laser machine just so I can have some quiet time with a laser when Big Red is busy. They used this in the mobile Fab Lab (Mercedes Truck edition) but since moving from the old FabLabUAE to the new one this machine has lived on this trolley. <img src="media/week4/little-red.jpg" style="width:100%; padding:5px 5px 5px 5px;"/> ### Machining a gearbox For my final project I'm going to need a gear box. I'll be modifying one I used to use on the racecars back in the day and cutting it out of 3mm acrylic. Here's an old version of it (not done during the course) that employed roller bearings and dowel press-pins which I will likely not have access to at this lab. The new version will incorporate a clutch disk for efficiency of operation (I'll explain this bit later just trust me for now). <img src="media/week4/geartrain2.jpg" style="width:100%; padding:5px 5px 5px 5px;"/> Edit: You can find the results of this project in my <a href="assignment05.html">Week 5 Preamble</a>, as I have some additional laser cutting work there. ### Etching a logo I also was hoping to etch some logos into a panel for a box I was working on but realistically I could do that any day now that the settings for the laser machine are figured out :) [edit: April] I finally etched that logo for the hard case! I used a silver reflective styrene and it looks pretty space-age. You can check out the final piece in <a href="assignment11.html">Week 11</a>. ## That's a wrap! <legend>"Here's a colourful snippet to end and summarise this week's work, despite being a couple days behind I got a lot out of it (feat. gold vinyl stickers and an acrylic clutch disk for the gearbox)."</legend> <video width="100%" height="50%" controls><source src="media/week4/end-of-week.mp4" type="video/mp4"/>Your browser does not support the video tag.</video> Design files for this week can be found at <a href="design-files.html">Design Files</a>.