Keyguard frames are used in two different ways – as a screen protector replacement or as a rigid frame for easily and quickly swapping keyguards or flipping up the keyguard.
Keyguard frames work in conjunction with a keyguard to fill the space of the case opening. The keyguard fits within the keyguard frame. The “mounting method” options apply to the keyguard frame (click on an image to enlarge it):
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| no mount | |
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| clip-on straps | shelf |
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| slide-in tabs | raised tabs |
The keyguard mounts within the frame using either snap-in tabs (for quickly inserting and swapping keyguards) or posts (for a flip-up keyguard) (click on an image to enlarge it):
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| snap-in tabs | posts |
Replacing a Screen Protector
Tablet cases often include screen protectors. Based on its name, you’d think the purpose of the screen protector is to protect the screen from scratches and breakage. However, most tablet screens are very resistant to scratches, and any force strong enough to crack an “unprotected” screen will probably crack a “screen protected” screen. What the screen protector is more effective at doing is preventing liquids that have dripped onto the case from reaching the electronics of the tablet inside. This is done by sealing a thin sheet of transparent plastic to a thick, rigid frame. The plastic sheet and frame act like a shallow bowl to hold any liquid dripped into it.
Screen protectors have long been the bane of keyguards because the opening in the screen protector’s frame is often only slightly larger than the tablet screen.
In order to expose as much of the screen as possible, the keyguard must have a very thin perimeter. This makes the keyguard more fragile and greatly limits the mounting options. The thin perimeter means there’s very little plastic for the attachment of micro-suction tape. The rigid frame means that you can’t wedge the keyguard into place. Finally, the clear plastic sheet is sealed to the frame, so you can’t insert slide-in tabs under the edge of the frame. You’d first have to break the seal on the screen protector and that would void any implied warranty offered by the case manufacturer.
We’re going to look at how we might replace the screen protector that came with your case with a 3D-printed version where you can control the size of the case opening so that your keyguard can have a thicker perimeter. And there might be additional benefits.
This method can also be used to create a screen protector for a case that didn’t come with one. Either the case came with a rigid frame that doesn’t have a transparent sheet of plastic attached, or the case has no rigid frame at all.
The idea described on this page came from Felice Flowers. She wondered if it would be possible to replace the screen protector with a 3D-printed version designed to accept a fitted keyguard. And would it be possible to attach a sheet of transparent plastic to the underside of the custom screen protector?
It turns out that you can – and the result is quite satisfactory.
The following example is for a particular case and screen protector combination. Your screen protector may be very different in its design and you may need to take a different approach all together.
Taking a close look at a commercial screen protector
A screen protector normally attaches to the face of the tablet with some retainer clips built into the underside of the rigid frame:
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Then the combination of screen protector and tablet slide into a rubbery case that protects the edges of the tablet if dropped.
There’s no way to replicate these clips reliably with a 3D-printed replacement so we’ll look at different methods to mount the keyguard frame to the tablet.
Determining the Overall Size of the Frame
The frame needs to fit within the same opening as the original screen protector. The most accurate way to get these measurements is to measure the original screen protector directly. The outer edge of the rigid frame should match the opening in the rubbery part of the case, which includes the curvature at the corners:
Place these measurements in the “height of opening in case”, width of opening in case”, and “case opening corner radius” fields of the “Tablet Case” section:
These will be the outer measurements for the keyguard frame.
Determining the Size of the Keyguard within the Frame
The size of the keyguard that will fit inside the frame is specified in the “Keyguard Frame Info” section. Specifically, the keyguard height, width, and corner radius values.
Let’s start with a sample keyguard we want to put into a frame. The size of this keyguard is determined by the values put into the “case opening” settings:
Note that the keyguard has a significant amount of plastic around the outside, so it will be a good candidate for a keyguard frame.
Begin by setting “have a keyguard frame” to “yes”:
The display will change to show your keyguard “cut” to fit inside the frame.
Specifically, it has been cut to the “keyguard size” measurements in the “Keyguard Frame Info” section:
The width is too small and the height is larger than it needs to be. Any increase in the width will take away from the frame. Similarly, any reduction in the height will be added to the frame.
Here’s what the frame looks like… First set “generate” in Keyguard Basics to “keyguard frame”:
Now the keyguard frame is displayed:
Clearly, the frame needs more plastic at the top and bottom so it will be helpful to take that plastic from the keyguard. It can also donate plastic to the keyguard on the left and right.
You could modify the keyguard size settings and toggle back and forth between displaying the keyguard and the frame, but there’s a more efficient way. You’ll take advantage of a Customizer “cheat code”.
With the frame displayed, find the “other tablet pixel sizes” option in the “Special Actions and Settings” section. The value is just a pair of square brackets:
Put the value “999” inside the brackets and press the Enter key:
The frame and the keyguard (in red) will both be shown:
Select View > top from the menu to look at the pair from above:
Because both the frame and the keyguard are displayed, you can change the keyguard size values and immediately see the effect on both components.
First we’ll reduce the value of “keyguard height” from 160 to 145 which will take plastic away from the keyguard and give it to the frame:
The display will immediately change to show the change:
That looks workable. Now change the “keyguard width” from 210 to 220:
The display now shows:
This will work, but first, let’s see what the keyguard and frame look like from a more appropriate angle. Set “keyguard display angle” in “Special Actions and Settings” to 45 degrees:
This is what the keyguard and frame combination looks like from that angle:
The “keyguard thickness” is 4 mm (in Keyguard Basics) while the “frame thickness” in “Keyguard Frame Info” is 5 mm. That causes the keyguard to be inset within the frame by 1 mm. If that isn’t appropriate, you can change either value. Note that the keyguard thickness isn’t allowed to exceed the keyguard frame thickness.
If everything looks good you will next Render and Export the keyguard and frame. But first you need to remove the keyguard from this view. To do that you’ll reset the Customizer “cheat code”. Unfortunately, there’s a bug in the Customizer that won’t let you simply delete the “999” from between the square brackets. Instead, you’ll replace the 999 with a “0”:
The keyguard disappears and you’re left with the frame:
Render the frame and Export the design as an STL.
Next, select “keyguard” again from the “generate” drop-down list and the keyguard will display:
Render and Export the keyguard design.
Mounting the Keyguard Frame
One way to fit the frame into the case opening is to put a shelf around the outside of the frame. Set “mounting method” to “Shelf” in the “Mounting Method” section:
You can control the thickness of the shelf and the depth of the shelf in the “Shelf Info” section of options. You can take these measurements directly from the screen protector that came with the case (“shelf thickness” shown below):
There are several other options for mounting your keyguard frame to the case: slide-in tabs, raised tabs, and clip-on straps – but among these, you’ll probably go with slide-in tabs.
Set “mounting method” back to “Slide-in Tabs” as the mounting method in the “Mounting Method” section. Use the settings in the “Slide-in Tabs Info” section to control where the tabs go, how wide they will be, how far apart they will be, and how thick they will be. In this example, we’ve put tabs only on the vertical sides. They’re 1 mm thick, 3 mm deep, and 96 mm wide. By setting the distance between them to a negative 10 mm, we can make them overlap and behave as a single tab:
Both the shelf and the wide, slide-in tabs provide a good amount of surface area for attaching a transparent sheet of plastic to the underside of the frame.
Now set “generate” back to “keyguard” and design your keyguard as you normally would based on the app and grid layouts.
Case Additions
You can put instructions into the “case_additions” data structure to add more plastic to the outside edge of your screen protector – or cut openings into the screen protector by putting instructions into the “case_openings” data structure.
One thing to note is that the 0,0 location is now in the lower right corner of the raised part of the screen protector:
This case has a small “crescent moon” cut-out for the home button. We want to fill in this space with plastic to protect the tablet as much as possible:
We’ve added the following instruction to the” case_additions” data structure:
Since we’re measuring relative to the lower left corner of the raised portion of the case opening protector, half-way up the left side is calculated as 127/2 = 63.5. (The case opening – and keyguard frame – is 127 mm high.)
This instruction has the following impact on the perimeter of the screen protector:
You can learn more about adding case additions and case openings by following their respective links.
The keyguard frame is now ready to print, and the transparent film is attached.
Attaching the Plastic Sheet
Most rigid plastic sheets will probably work, though you should avoid films that are intended for putting in a laser or inkjet printer. Such films have a coating to help the ink adhere, which reduces the transparency of the film. Here’s one transparent plastic sheet that will work.
The attachment of the keyguard frame to the plastic sheet needs to be waterproof or your screen protector won’t achieve it’s primary function. You could try using glues or silicon caulk, but spray adhesive works very well and is easier to apply.
Begin by putting masking tape around the keyguard opening in the frame. Avoid putting any tape on the underside of the frame.
When spraying the underside of the keyguard frame, try to spray directly downward rather than at an angle. That will limit the amount of adhesive that will get on the face of the frame.
While the adhesive is still tacky, turn the screen protector over, and set it onto the sheet of plastic. Place a book or other heavy item on top to ensure a good seal between the protector and the plastic sheet. Allow the adhesive to dry. When dry, you can remove the masking tape.
This video illustrates the process of mounting the screen protector to the plastic sheet:
Testing the Screen Protector
The following video follows a screen protector that has been assembled as described above and has had water (with a pink dye) poured onto its surface:
After 20 minutes, there is still no water leakage from around the edge of the screen protector. If you dump any liquid off of the screen protector within a few minutes of the accident, your tablet should be perfectly safe.
Preparing the Screen Protector for Mounting on the Tablet
Once you’re confident that the adhesive has dried, you can use scissors to cut along the edge of the screen protector to remove all the excess plastic sheeting.
It has to be possible to depress the Home button, so you’ll use a “sharp” utility knife to cut a circle in the plastic sheet around the Home button opening.
Our example screen protector doesn’t have any clips on the bottom so we’ll need to find a different way to mount the screen protector securely to the tablet. Micro-suction tape does this job very well.
You won’t be removing the screen protector from the tablet except very rarely, so you can feel free to add a generous amount of micro-suction tape. Tape should be applied to all four sides of the screen protector bottom.:
The transparent film is still in place on the tape in this photo.
This is a good time to clean the glass of the tablet – while you still have easy access.
Note that the micro-suction tape holds VERY well so position the screen protector very carefully as you make the attachment. Watch carefully as you mount the screen protector to the tablet – especially ensure that the camera is centered in the camera hole.
Another option is to use masking tape to hold the screen protector/keyguard frame to the tablet. You’ll need to add enough tape so you can wedge the pair into the case (which can be a struggle) without the two separating.
These small nylon pry bars can come in handy to work the shelf or tabs under the edge of the case opening!
Mounting the keyguard within the keyguard frame
By default your keyguard is mounted inside the keyguard frame by a set of snap-in tabs. Using this approach, you can easy swap between several keyguard layouts as you switch between different tablet apps. Under certain circumstances you may want to eliminate the snap-in tab from the top or bottom edges of the keyguard.
Alternatively, you can mount the keyguard using posts. Using this approach, you can swing the keyguard out of the way temporarily to interact with your keyguard in a way that would have otherwise been hindered by the keyguard.
Snap-in Tabs
Your keyguard will include snap-in tabs on all sides that “snap” into recesses on the inside edges of your keyguard frame. The tabs are designed to resist sliding the keyguard around on the tablet face, and to resist pulling the keyguard out.
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| snap-in tab on the outside edge of the keyguard | snap-in tab receiver on the inside edge of the keyguard frame |
You will need to pull the keyguard away from the edge of the keyguard frame slightly when inserting and removing the keyguard. You can follow the same process to easily swap keyguards designed to fit in the same frame.
If you have a keyguard design that doesn’t reach all the way to the top of the frame, you should set “snap in tab on top edge of keyguard” to “no” in the “Keyguard Frame Info” section. If you don’t, you’ll have a free-floating snap-in tab in your model that you’ll have to remove in your slicer or you’ll have printing problems.
Every 3D printer is different. Unless you’ve gone through a lot of work to tune your printer, it may under or overextrude plastic. If the keyguard is too difficult to squeeze into the keyguard frame or it’s too loose and slips out of the frame too easily, you can make small adjustments to the overall size of the keyguard. There are two sliders in the “Special Actions and Settings” section called “keyguard horizontal tightness of fit” and “keyguard vertical tightness of fit”. A value of 10 increases the horizontal or vertical size of the keyguard by 1 mm. A value of minus 15 decreases the size of the keyguard by 1.5 mm.
Posts
Mounting your keyguard to the frame with posts will allow you to flip the keyguard up and out of the way temporarily and then flip it back into place:
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This is controlled by two options that are also in the Keyguard Frame Info section.
If you set the “mount keyguard with” option to “posts”, your keyguard design will be modified automatically. It will be trimmed down at the top to the bottom of the upper command bar and a pair of posts will be added.
Slots for these posts will be created on the underside of the keyguard frame to accept these posts. The diameter of the posts and the diameter of the slots will match the thickness of the keyguard. If the keyguard and the keyguard frame have the same thickness, the slot will break through to the top surface of the frame. If that should happen, just increase the thickness of the frame or decrease the thickness of the keyguard:
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| 5 mm frame and 3 mm keyguard | 5 mm frame and 4 mm keyguard |
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| 5 mm frame and 5 mm keyguard | 6 mm frame and 5 mm keyguard |
The ease of rotating the keyguard within the frame will depend on the tightness of the fit between the posts and the slots. This is difficult to predict, given the large variance in different 3D-printers and slicer settings. If you don’t like the amount of force required to rotate the keyguard or if you’d like more friction to keep the keyguard up in the air, change the value of the “post tightness of fit” option. Larger values make the fit tighter, and lower values loosens the fit.
Splitting Your Keyguard Frame
You may find that you can’t fit the keyguard frame on your printer. In that case, you can split your keyguard frame into two parts by choosing “keyguard frame – split” from the “generate” pull-down in “Keyguard Basics”. The two parts will automatically be relocated to fit as tightly together as possible:
If you move the split line to the left or right, you may be able to use dovetails to split the keyguard and join the two parts more easily:
You set the location of the split and the type of split by setting the values of “split line location” and “split line type” in “Special Actions and Settings”.
The two parts of the keyguard frame will be arranged to accommodate the relative length of each part.
Mounting Your Keyguard Frame and Keyguard
Slide the screen protector and tablet into the case, add the keyguard, and test it out…
Repeating what I’ve said already… These small nylon pry bars can come in handy to work the shelf or tabs under the edge of the case opening!
Some Screen Protectors can’t be Replaced.
You may come across a case with a screen protector like this one:
The light blue screen protector of this case is critical to holding the entire case together by clipping to other parts of the case. As mentioned earlier, there’s no way to recreate these critical clips using 3D printing.