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Week 7. Computer-Controlled Machining

Group Assignment:

  • Complete your lab’s safety training
  • Test runout, alignment, fixturing, speeds, feeds, materials and toolpaths for your machine
  • Document your work to the group work page and reflect on your individual page what you learned

Tech Specs of ShopBot

This week, we utilized a ShopBot CNC machine to fabricate something big.

ShopBot router is a budget-friendly CNC tool for precision cutting and shaping. Controlled by a computer, it offers versatility in materials and opens up new creative possibilities. Easy to understand, affordable, and simple to maintain, it’s a valuable addition to any workshop.

Technical Information:

  • Standard tool accommodates sheet material up to 4’ x 8’ with cutting/machining depth (Z-axis) of 6 inches.
  • Table size approximately 6’ by 10’.
  • Step resolution is .0005” or better depending on gear ratio.
  • Positioning accuracy is +/-.005” or better (no load).
  • Positioning repeatability +/-.003” or better (no load).
  • Cutting accuracy is approximately +/-.015” for heavy cutting applications.
  • X, Y rapid positioning speeds (‘jogging’) up to 600” (standard)/1800” (alpha) per minute.
  • Z axis move speed up to 360” per minute.
  • ShopBot Control Software reads .sbp (OpenSBP) Part Files as well as standard Gcode and includes a .dxf converter which allows conversion of files from CAD programs such as TurboCAD, DesignCAD, AutoCAD, Corel Draw, and SignLab.

Safety Instructions for Using Your ShopBot:

  • Read Manuals and familiarize yourself with the tool’s operation and safety guidelines before use. Also, review manuals for any attached routers or spindles.
  • Get comfortable operating your ShopBot with the control software before activating the cutting tool.
  • Always turn off the router or power tool before loading materials or adjusting the tool’s position.
  • Secure the material to the work surface before cutting.
  • Avoid operating the machine when fatigued to maintain focus and safety.
  • Wear eye and ear protection during operation to safeguard against potential hazards.
  • Never leave the machine unattended while it’s running.
  • Contain dust particles properly to protect against airborne debris.
  • The spacebar on the computer keyboard serves as an emergency stop button during cutting. Additionally, locate and utilize the remote stop button for immediate halting of the tool’s motion.
  • Stay within easy reach of the computer keyboard or stop button during operation.
  • Wear sturdy, hard-toed shoes to protect your feet.
  • Wear an N95 mask to protect yourself from airborne particles.
  • Tie up long hair to prevent it from getting caught in machinery.
  • Always have another person present during operations for added safety.
  • Avoid placing any body part near the cutting path during operation.

ShopBot CNC Machining Processes

  • First, we make sure that the machine spindle runs smoothly and accurately without any excessive wobbling or vibrations.
  • We checked all axes of the CNC machine are properly aligned to get precise movements and accurate cuts.
  • Placed the material on the machine bed using clamps.
  • From the tool database, we selected the required tool and its default tool setups.
  • ShopBot CNC machines are capable of cutting a wide range of materials, but for now we used wood and based on that, tools and settings for wood cutting operation was set.
  • Now important setup is To create toolpaths for our ShopBot, we utilized VCarve to calculate the necessary toolpaths for the imported DXF file. This software allowed us to generate ShopBot part files (.sbp) for the ShopBot

Note For our CNC ShopBot project, we utilized 18mm thick plywood along with a 1/4 inch end mill featuring 2 flutes, with a diameter of 0.25 inches. The cutting parameters were set to a feedrate of 30 inches per minute and a spindle speed of 14000 rpm. These settings were chosen to achieve precise and efficient cutting of the plywood material.

Test Cut Strategies

For the test cut to assess the fitting, we employed dog bone fillets for the slots using VCarve software. Inside cutting operation type was selected for this purpose. Additionally, for the outer cutting of the main body intended to fit inside the hole, we considered the material thickness of 18mm plywood. While the result was acceptable, some filing was required to achieve a perfect fit.