In my case, I bought a lamp that came with a shade, so for my design I was able to measure the existing lampshade and adapt some of my measurements to match. You'll want to determine the diameter of the top and bottom of the lamp shade and the approximate height of your lampshade. 

The primary supports for my lampshade are the lower and upper circular supports. The bottom support will feature an inner circle that will rest over the lamp and under the light bulb. The upper support will be an open ring. Both supports will include notches that will give each fin of your lampshade a place to connect. 

During my design process, I tested 2 designs with 10 and 20 fins equally spaced around the lamp shade. I found that more fins made a more appealing lampshade for my purposes, as it allowed light to pass through while also obscuring the bulb directly. Altering the angle of your fins, increasing or descreasing the number of fins, etc will give you different results.

If you want to experiment but are concerned about wasting material, I recommend prototyping using cardboard. It is often similar in thickness to the 3mm stock and provides an inexpensive way to test ideas without using up all of your precious material!

If you want to make your own support design. I started by creating a circle the diameter of the bottom of my lampshade. I then made a 3mm x 15mm rectangle, which I rotated 45 degrees. Then, using the circle array tool, I made an array that copied and rotated the rectangle around the perimeter of my circle. To make the positioning and math easier, I used 0,0 for the origin of the rotation. This is the top, left corner of the work plane. I have included a photo of my array settings. The step of 18 was determined because 360 degrees divided by 20 fins is 18 degrees. If you want to increase or decrease your number of fins, divide 360 by your number of fins.

Once the array is complete, I create the inner diameter of the support. This width is up to you. For my support I reduced the size of the circle from 180 mm to 155mm. Then, selecting the 2 circles, I combined using the subtract at overlap tool. Then, I selected all shapes and combined using the select tool. If everything disappears, don't panic! Simply undo, then select the circular shape and send it to the back using the arrange tool. Copy and paste this shape, as it will give you your upper support!

Now, we'll add cross supports using rectangles to one of our circular shapes to complete the bottom support. I simply drag and drop a rectangle across the center of my shape, then copy and paste a new one. Rotate the new rectangle 90 degrees and center the 2 rectangles in the circle. Select all and combine. 

The last step is to build in a circular support that will rest on the lamp. I added a circle to the center of the bottom support and centered it. Then select the new circle and bottom support and combine. Add one more circle and center it. This circle should be sized to just go over the lightbulb base of your lamp. Mine was sized to 34 mm. Center this new circle, then combine and subtract at overlap.

You can design your fin to be any shape you would like. To make the basic structure, I use a rectangle and the vector drawing tool to create my curved elements. Then finishing the fin is as simple as combining the two shapes.

If you want to make your own fin, start b y creating a rectangle that is approximately the height of your measured shade. In my case, thats about 160mm. I make the rectangle relatively narrow, as the final shape's dimension will come from the vector drawing.

Selecting my vector drawing tool, I click to add nodes and create a path. Each node will add a point in the path where you can change the shape of your curve, so add as many or as few as you like, just be sure to overlap your rectangle and end your drawing where you started to close the shape.

Double click you finished shape. Each circle on your drawing can be double clicked, creating a curve. Drag the handles to increase or decrease the curve. You can also manipulate the path of the curve. 

Once you have a curved shape you like, simply select both shapes and combine using unite!

Using the provided design or your own, fire up the P2 and get to cutting!

Once you have everything cut out for your design, its time to consider how you will want to finish your lamp. 

I begin my sanding to remove any visible smoke or char marks on the supports and fins. This extra step can ensure a clean finish, especially if you'd like to finish your lamp with a simple clear coat.

I find that applying a stain or paint (if applied by brush) is more easily done before assembling. 

Once everything is sanded and prepped, assembly is pretty straight forward - simply insert the fins into the bottom and upper supports. If the I find that doing one fin at a time and connecting it to both the bottom and upper support is easiest. You can add supports that are aligned across from each other to give your shade a structure that makes adding additional supports easier. 

Depending on the fit of your material, now would also be a good time to apply glue if you choose to use it. This design should fit pretty snuggly if you are using a 3mm material, so be gentle. No one wants a broken support!

Once your lampshade is a assembled you can finish it with a simple clear coat. I tend to use a spray sealant, like Rustoleum Ultra Cover Clear Gloss, but you can use what ever your favorite finish is!