MAE2250 offers teams the option to use the department's Laser Cutting services on an Epilog 24"x36" system.
Sheets are 11.75"x11.75" and their thickness is 0.212" +/- 0.005" . Material properties are provided by the supplier.
Laser cutting prototyping services are free. However, each acrylic plate beyond the first free plate will cost $5.
For product cost calculation, the cost is $0.10 per inch of cut, plus $1 per part, plus $5 per square foot where the price is prorated by the area of the tightest bounding box around all your parts nested together. For example, the cost of two 4"x2" L-shapes nested together into a 5"x2" rectangle is $0.10*19"+$2+$5*10/144=$4.24
To request a laser cut, follow the following steps:
Prepare your parts' outline as a SolidWorks drawing (see sample drawing)
Position the outline on the 11.75"x11.75" sheet in such a way to avoid areas where you have cut out before (you should keep track of your previous cuts). A good way to do this is to maintain a single drawing with all cuts, and then temporarily delete previous outlines just before generating the file to upload.
For precision cuts, factor in the laser beam melting width (a.k.a kerf) of approx. 300 microns.
Make sure your parts will be easy to identify when tossed in a box full of parts from other groups, or when compared to earlier versions of your own parts. It is a good idea to include in your design some kind of unique identifier.
Avoid cutting lots of small disconnected parts - this will risk some parts getting lost. If you have many small parts, consider cutting them as a single connected unit, in such a way that they can be easily broken-off later.
Be sure to round (fillet) external corners (this saves material and makes your part look nicer), and round (fillet) all internal corners (avoids stress concentrations and makes the part stronger). Use a large fillet - as large as possible without compromising functionality. Acrylic is very brittle so this step is important.
Reduce unnecessary weight by perforating large areas.
Avoid cutting very thin details. Cutting accuracy is about 100 microns. thinnest part than can be cut reliably is about 1mm.
Think organic form. For example, if you are cutting a cantilevered beam, make it thicker near the root where stresses are high, and thinner near the edges where stresses are low. Don't just cut a uniform rectangular cantilever. Manufacturing complexity is free - complex shapes are not more expensive to cut than simple shapes.
Acrylic is brittle. If you need to cut a thin part that needs to be stiff and strong, consider cutting a small groove in its center so that you can later insert a strengthening screw or dowel pin.
If you need to connect your sheet to other components, consider cutting holes so that you can later insert thermoplastic inserts.
Cast acrylic has low dimensional tolerance. Sheet thickness is 0.25" +/- 0.035". Factor that uncertainty into your design.
You can make 3D structure by joining 2D sheets. To do this you will need to cut T-joints.
If you are uncertain about some small portion of a large design, cut just that portion for testing, before cutting the entire part. This will save material and time, and will allow you to iterate more. For example, if you have a large part that includes a small interlocking snap-fit buckle connector, cut just the connector first to make sure you got the dimensions right, before cutting the whole thing. You might even cut three connectors with slightly different sizes to optimize in parallel.
Save the drawing using "Save As", selecting "Detached Drawing" (Solidworks drawings typically need a part reference, but saving as a detached file will embed the 2D projection and allow us to open the drawing without also having the parts). If you do not save as a detached drawing, the TAs will not be able to process your drawing. Name the files Section#team#_month_day_ID.slddrw, where ID is an optional ID number for you to use in case you must submit multiple files at a time. Example: "2A_10_13_1.slddrw" and "2A_10_13_2.slddrw"
Upload your file to the the shared MAE 2250 LaserCutting Dropbox Directory (If you have not received an invitation, request it). Note that files will be deleted after use. Please keep a copy.
Collect your parts from a basket in the design studio a day or two later. You may need to peel the charred protective layer off the acrylic sheet.
Track your cost. Count prototyping material cost against your prototyping allowance, even if it didn't turn out as you had hoped or you didn't end up using the laser-cut part in your final project. Laser cutting services are free, but you incur $5 per 1sqf sheet beyond the first free sheet. For product cost estimation, you only need to count the cost of the parts actually used. For product cost calculation, the last cutting cost is $0.18 per inch of cut, plus $1 per part, plus $5 per square foot where the price is prorated by the area of the tightest bounding box around all your parts nested together. For example, the cost of two 4"x2" L-shapes nested together into a 5"x2" rectangle is $0.18*19"+$2+$5*10/144=$5.77
Some common mistakes
