- All inventor part files: tweak to your heart’s content
- DWG Files to check tolerances
- STL files for a 3D Printer
- Laser files for the cover & Sign
- Various pictures to help with assembly
IntroductionAfter doing an expensive LED light up sign project last year (with a grant) with my CIM students, I was looking for a low cost alternative. In comes Scott Tobias, new CIM master teacher from Maryland. Thanks Scott for the great idea! You can make these signs for less than $3.00 apiece, depending on what you make the base out of. We 3D printed them at UK with an Affinia printer, as they were prototypes, but they could easily be CNC’d from Wax, Wood, or Renshape.
- Male A to Male A USB Cable: Amazon
- Color-changing 2 Leg LED Light: AdaFruit
- 68 ohm Resistor (100 will work): Anywhere
- 1/8″ Acrylic: Delvies
- Build the base. CNC or 3D print. Try to make sure that the LED comes in contact with the acrylic sign. Please see the enclosed Inventor Section view file for the dimensions and constraints. Also be sure to leave room in the base for all of the electronics.
- Design and build the sign. The more angles the better, as it will show off the light. Be sure to take into account the tolerance fit between the slot and the plastic. MEASURE the acrylic. It is NEVER really 0.125″!
- When engraving the sign, the deeper the engraving, the better it looks. Invert the text and print on the back!
- Assemble the parts. Sign into base, wire through side, Hot glue the led into slot, THEN solder!
- Solder the cathode, short leg of LED, to the 68Ω resistor.
- Solder the resistor to the BLACK wire of the USB cable.
- Solder the RED wire to the other side of the LED. Do NOT solder the green or white wires; do not even strip them!
- When soldering, you could use heat shrink tube to prevent short circuits.
- Insert the cover into the base. We cut the cover out of the same acrylic we made the sign out of, and just made it 0.005″ bigger in Inventor, and pressed it in. The hole in the bottom is there to pry it out if necessary.
Solution:Just change the setting you see in the picture here, and you will be all set! After you change this it will ask you to power cycle your cortex. Just turn it off and back on again, and it will run your program when it’s unplugged from your computer.
Question:What speeds and feeds do I use on wax or Renshape in my classroom? (spindle speeds in the attached picture are higher because they are for a machine with a 10K spindle!) Want to buy Renshape? Get it here: Freeman Supply I use the 450 because it is cheaper!
Solution:Great question! The short answer: Use the ones given as default in Autodesk HSM! They are there for a reason! The last version of EdgeCAM PLTW recommended uses defaults too! In reality, the wax and Renshape are very forgiving, and almost any spindle speed above 3500 and feed rate less than 20 should work. With that being said, be really careful with depth of cut….. Most teachers want to save time, so they max out the speeds and feeds on their small mills and then increase depth of cut… BE CAREFUL! Increasing depth of cut is very hard on the spindle bearings of a small milling machine, and can do damage! For more info on this see our lesson on tooling in the tutorials section HERE! I do however like to give my kids a list of speeds and feeds that I have come up with so that they can see and hear the difference with the different tools, especially when they write code by hand. Also, when you teach speeds and feeds for metals, they’ll wonder why it changes with the tool, but not for wax. Below are the speeds and feeds I use in my classroom on wax, butterboard, and Renshape 450. They are conservative, but I haven’t broken a tool with these in more than 5 years; and my bearings are still good in both 10+ year old machines in my classroom!
|#||Tool||Spindle Speed (rpm)||Feed Rate (ipm)||Depth of Cut(max)|