Using free BlocksCAD software, you can program your designs with a Scratch-like interface.
Overview and Background
Summary: In this design challenge, students will solve the problem of misplaced keys by designing a key rack that could be mounted on a wall.
Lesson Objectives: This project will introduce user-centered design, and use blocks like difference, loops, and modules.
How do you attach your key rack to the wall?
When making an object that will be mounted to a wall by a nail or a screw, it is important to think about how many mounting points are needed to ensure that the object is mounted securely. When an object is mounted at a single point, it creates a potential pivot point. Consider a key rack mounted with a single nail. While the rack itself may balance, when a single set of keys is added, the weight of the keys rotates the rack, and it is off-kilter until balances by equal weight on the other side Figure 1). To avoid this problem, students can simply add additional mount holes (Figure 2). Depending on the number of rungs, students may want to add even more mount holes to help support the weight.
How many rungs will your key rack have?
The key rack should be customizable so that the user has the number of rungs they need. We will learn two possible methods to reuse code so students do not need to duplicate their code for each additional rung.
Lesson Plan and Activity
To make the backboard piece of the key rack, change the dimensions of a cube to fit the sizing you want. In order to add mount holes, you must use the difference block (found in Set Ops) and “subtract” a cylinder from the cube backboard. The following images show a sample the code and its render respectively.
The rungs can be made using the torus and sphere shapes along with the difference block. In order to get the rounded hook shape of a rung, use a torus shape and the difference block to remove half of the torus. Then add spheres to each end of the semi circle to help mount the rungs to the backboard and prevent the keys from falling off. The following images show the code and its render respectively.
Rather than copy-pasting and then translating the code for each rung, it is easier to create a module and then place it into a loop. To do this, take the code you used to make your rung and place it in a module.
Then place the module into a loop function, which will allow you to repeat the rung code for whatever sized key rack you would like, with enough space between rungs.
The loop index should be roughly the size of your key rack’s backboard. One rung every 20mm is a good distance between rungs. The following image is the render of the final product.
3D Printing your BlocksCAD Design:
Once you have finished coding your 3D model and are ready to 3D print, export your design as an STL file. This is done by clicking the "Generate STL" button on the render
window, which saves the .stl file into the downloads folder on the computer. The .stl version of the design can then be imported into MakerBot Desktop by clicking Add File, then select the STL file of your BlocksCAD model to add it to the build plate. The MakerBot Desktop program is a slicing program, which converts the file into gcode, which a 3D printer can use. The slicing program allows you to orient your model on a build plate change the size of the model, decide whether the model needs to be printed with supports, sets how thick the plastic outer walls are, as well as the infill percentage of the printed model, the temperature the model will be printed at, etc. In the case of the key rack, settings may be the pre-set quick settings including Standard Quality, no supports, layer height of .2mm, 10% infill, 2 shells, using MakerBot PLA, and an extruder temperature of 215 degrees Celsius.
Once you have modified the settings to your needs, the gcode (.makerbot) is sent to the MakerBot, where it can be printed.
The following images are the resulting 3D print of a 5-rung key rack.
Alternative key rack using the same principles:
1 device (computer, chromebook, ipad) per student
- 3d printing