What are the Robocell shortcuts?


What are all of the Robocell shortcuts? is there a list somewhere?


There is just such a list, and special thanks to Moises Gonzalez for compiling it for us! There’s a picture below, or you can download it at the link below. The link will download a PDF with 4 per sheet so you can cut them up and pass them out to students to use in class.
reddownloadRobocell Shortcuts 4up     Continue Reading

Making the Physical Container on the CNC Mill

Sometimes you just have to see it to understand it. I know because I am a visual learner. So here it is: How to make the container from start to finish….. Physically speaking! From a block of Renshape to final product. No code  or 3D modelling at all!
If your looking for the Inventor tutorials for the container, look here: http://chrisandjimcim.com/how-do-i-make-a-container-in-inventor/
Lets start with the fixture:

  Then we can machine the base:

And now for the lid. It gets machined on the back side of the base!

Next we use a bandsaw to split the top from the base:

Want to manually face the part?  Here is how:

Last but not least…. How to put a surface on your container:

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Project Idea: USB Powered LED Sign

All files for this project are attached in a zip file at the link below. These files include:
  • 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
reddownloadUSB LED Sign Project CnJ


IntroductionSign night

After 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.

Parts List

The resistors are $0.05, the cable about $1.50 per end (cut the cable in half to make two!) and the LED’s about $0.50 each. That means the guts are only about $2.00 each!  Great deal, and your students will love how the LED’s fade through all the colors of the rainbow, and you will love how it does it automatically, because it is built into the chip!  NO PROGRAMMING or COSTLY MICROCONTROLLERS. Thanks AdaFruit! Video of how it works HERE.


  1. 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.
  2. 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″!
  3. When engraving the sign, the deeper the engraving, the better it looks. Invert the text and print on the back!
  4. Assemble the parts. Sign into base, wire through side, Hot glue the led into slot,  THEN solder!
  5. Solder the cathode, short leg of LED, to the 68Ω resistor.
  6. Solder the resistor to the BLACK wire of the USB cable.
  7. Solder the RED wire to the other side of the LED. Do NOT solder the green or white wires; do not even strip them!
  8. When soldering, you could use heat shrink tube to prevent short circuits.
  9. 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.
led sign bubbles
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How do I get my robot to work when I unplug my cortex from the computer?


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.

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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!


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)
1 Engraver 5000 15 0.025″
2 1/8″ End 5000 15 0.0625″
3 1/8″ Ball 5000 15 0.0625
4 1/4″ End 4750 18 0.125
5 1/4″ Ball 4750 18 0.125
6 3/8″ End 4500 20 0.125″
7 3/8″ Ball 4500 20 0.125″
8 1/2″ End 4250 20 0.125″
9    1/2″ Ball 4250 20 0.125″
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Get in touch

Jim Hanson

Chris Hurd


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