Laser-Cutting Isn’t 3D-Printing
Designing a keyguard for laser-cutting is very similar to designing one for 3D-printing, but there are a few limitations. The most important limitations are:
- A laser cutter only cuts the acrylic sheet at a 90-degree angle, so there’s no way to angle the opening down into a cell. As a result, you may find the edges of the openings and the edges around the outside of the keyguard are too sharp.
- If, like most people, you put your keyguard in a protective case, you only have two options for mounting the keyguard: slide-in tabs or no mounting features at all. In the latter case, you’ll have to use micro-suction tape or wedge the keyguard into the case (if it’s soft-sided).
- Because a laser-cut keyguard is constructed from a flat sheet of acrylic, it can’t have any raised elements like cell ridges, bumps, or horizontal/vertical ridges.
Getting Started With The Design
Keep this tab open in your browser as you step through the instructions for designing a keyguard. When you are told to choose a “type of keyguard”, choose “Laser-Cut”. That way the image displayed for you will always look like a laser-cut keyguard. You may also want to skim the instructions below as you step through the process. Definitely come back here and read through the page thoroughly when you’re done with your design.
Keeping Things Reasonable
We turned to the folks at Keyguard AT for their recommendations regarding the design of a laser-cut keyguard. They had some specific recommendations for the thickness of the rails and the shape of the openings. Keyguard AT will even cut your design for you (more on that below). keyguard.scad supports the Keyguard AT recommendations in two ways.
First, you may find that the Customizer pane ignores or limits the choices you make for the following options:
- preferred rail height, keyguard thickness – your final design will be 3 mm (i.e., 1/8″) thick… what the laser-cutter uses is a 2D representation of your keyguard (think of it as the bottom layer of the print),
- bar-edge slope, rail slope – all slopes will be 90 degrees,
- keyguard edge chamfer, cell edge chamfer – no chamfers on the edges of the keyguard unless it’s further processed with a milling machine.
- mounting method – only “No Mount” and “Slide-in Tabs” are supported,
- case opening corner radius – the case opening corner radius has to be at least 2 mm (an exception is made when you add custom case additions),
- shape of opening, rounded rectangle corner radius – all rectangular openings will be rounded rectangles and the minimum corner radius of each rounded rectangle is determined by the size of the rectangle,
- slide-in tab length, preferred slide-in tab thickness – you can specify the width of slide-in tabs and the distance between them but the length of the tabs will be 3.175 mm (for easy routing) and 1 mm thick,
- add a ridge around these cells, height of ridge, thickness of ridge – you can’t add any features that would stick-up above the surface of the keyguard.
If you choose values for options in the Customizer pane that oppose these limitations, keyguard.scad will ignore your choice. Don’t get mad, keyguard.scad is just trying to ensure that your final keyguard design will be as durable as possible.
Note, you can override these recommendations by setting the value of “use Laser Cutting best practices” to “no” in the Special Actions and Settings section.
Second, some aspects of your keyguard are affected by multiple choices you make in concert. In that case, keyguard.scad won’t stop you from choosing those values but will warn you that there are problems.
Basically, there are several things that can affect the amount of plastic around the outside of your keyguard and Keyguard AT recommends that he outside edge of the keyguard should be at least 3 mm wide for smaller tablets and at least 4 mm for larger tablets.
If you do something that violates this recommendation, keyguard.scad will warn you by putting “Issue” statements in the Console window.
The amount of plastic around the outside of your keyguard is most affected by the size of the opening in your case. If it fits very tightly to the screen you may end up with a keyguard that looks like this:
If you look in the Console window, you will see this:
You may say, “This doesn’t make sense. The side rails are wider than the top rail, so why these numbers?” If you look closely at the sides of the message bar opening, you’ll see that these rails are very thin:
In order to make the rail thicker here, you can increase the setting for “right edge compensation for tight cases” in the “Tablet Case” section:
Repeat for the left edge of the keyguard.
Now the Console window only shows one Issue:
There are several ways to address this last issue. You can add some space for a “non-existent” and non-exposed status bar or you can increase the value of “top edge compensation for tight cases”.
The goal is to eliminate all the issues that appear in the Console window.
Your final design should look very much like the final laser-cut keyguard:
If you want to check your keyguard design, and you have easy access to a 3D printer, this might be a good time to print it (at least the first two layers) and verify that it fits just like you want before you commit to laser-cutting a much more expensive acrylic version.
The next step to prepare your design is to transform the design into a single layer. To do that choose “first layer for SVG/DXF file” at the bottom of the “generate” pull-down in the “Keyguard Basics” section. It’s the second to last item:
It will take a while for keyguard.scad to figure out what the first layer looks like, but you’ll eventually see something like this:
You’re almost there… But first, clear out the contents of the Console window. You’re going to want to collect some information from that window in a minute and it helps to get rid of all the unnecessary content. Right click anywhere in the window and choose “Clear”:
Now choose Design > Render from the OpenSCAD menu (or press F6). The display will change to look like this:
This is the first layer (a 2D representation) and your design is ready to export and laser-cut, but first go to the Console window and right click. Choose “Save As”. Save the contents of the window as “settings.txt”.
Delivering Your Design To The Laser-Cutter
The next step is to export your design. If you’re doing your own laser-cutting, you already know what file format you need. Keyguard AT will want an SVG file. If you choose someone else they may want a different format. OpenSCAD supports one other 2D format – DXF. Choose File > Export and select the proper format for your design.
If someone other than you is cutting your keyguard, send them your design and include the “settings.txt” file that you saved earlier.
Having Keyguard AT Laser-Cut Your Keyguard
To have the folks at Keyguard AT laser-cut your keyguard design, go to the Design-Your-Own Keyguard page at their website.
- Choose “I will send you and SVG file” as the Design.
- Pick your preferred material. [Note: if you have the need, Keyguard AT can also CNC-mill keyguards from a sheet of polycarbonate that come with a lifetime guarantee and has the added benefit of a small chamfer around each opening and around the perimeter of the keyguard. The chamfer makes the keyguard much more comfortable to handle.]
- Optionally, add any special instructions – you’ll be sending an email message to them so you can include special instructions or questions in your email. Click on the Add to Cart button.
- Click on the Check Out button at the top of the page.
- Fill out the order form and place your order. [You may need to create an account if you don’t already have one.]
- Copy your order number from the confirmation page and create an email message with that order number as the subject line. [Alternatively, you can wait for your order confirmation email message and just reply to that.]
- Attach your SVG file and settings.txt file.
- Send the email message to sales@marblesoft.com
That’s it! Wait a few days and enjoy your laser-cut (or CNC-milled) keyguard when it arrives.
Putting It All Together
Note that the following video was created with an earlier version of keyguard.scad – before it was possible to independently add plastic to each of the four edges of the keyguard.
A Laser-cut Hybrid or Free-Form Keyguard?
Yes, it’s possible to create a Hybrid or Free-form keyguard design that can be laser-cut from acrylic. You can put instructions in the openings_and_additions.txt file and they will be included in your design.
You’ll have all the same limitations described above when it comes to features that rise above the surface of the keyguard, all openings will be limited to 90 degrees for their top, bottom, left and right slopes and you won’t be able to add engraved text to the top or bottom surface (after all, the laser can’t engrave the bottom side of the acrylic sheet and your design doesn’t have a “top” surface). If you want something engraved on the keyguard, you should provide that request separately to the person doing the cutting.
On the other hand, keyguard.scad won’t stop you from cutting openings of any shape or location on the keyguard. It also will support you in putting additions on the outside of the keyguard for cases with non-rectangular openings.
Finally, keyguard.scad isn’t smart enough to know whether one or more of your custom cuts or additions has resulted in a keyguard that can’t be laser-cut (or can be cut, but won’t be durable). So if someone else will be doing the laser cutting for you, verify that they can comfortably create a keyguard from your design. It’s one thing to 3D-print a keyguard that doesn’t work – you just change your design and print again. It’s a whole different thing to pay for a laser-cut keyguard that doesn’t work!