The next step was to export the solidworks object as a sterolithography file (STL). The STL file was imported into MeshCam, choosing the 4-axis option with 8 index positions. MeshCAM lets you create toolpaths from your 3D files quickly and easily. Meshcam generated G-code that would instruct the CNC machine to cut the entire object by indexing the rotary axis and using the regular X,Y and Z axis’ to position the endmill attached to the spindle. For my next experiment I’m going to try increasing the number of index positions by a much larger number.

Three Dimensional projectile created in Solidworks. Its size is .50 caliber and 1.5 inches in length.

In this MeshCam screenshot, the yellow lines indicate the 8 rotary axis positions between which the material is removed to create the object.

For my next rotary axis experiment I will try to optimize the cutting path by selecting a much larger number of indexes and cutting an object in aluminum.

Karl P. Williams

Using a 4th axis rotary table greatly reduces the amount of time and complexity that it takes to shape an object. Without a rotary table you must devise a registration system and are forced to reposition the object several times during the milling process. The precision that a rotary table provides also ensure uniformity and high quality in components.

I could have bought a cnc ready sherline rotary table but I decided that I’d rather get a table locally and build a stepper motor mount for it myself since half the fun is in the build. I decided to go with the Soba 4-inch rotary table (part# B2424) from Busy Bee tools down the highway in Mississauga. While I was there I also picked up the matching 4-jaw, 3 1/4-inch chuck (part# B2710) and Tailstock (part# B2424).

I wanted to design a mount that would let me return the table to its original state if desired. I used a CAD program to design the mount so that it could be dropped into place and secured with 4 set screws around the existing shaft collar.

The mount is 2-1/4 x 3 x 3 inches and constructed with 1/4-inch thick aluminum.  All 4 of the parts were milled on my Taig milling machine with the new controller and stepper motors. I’m always amazed at the amount of precision and accuracy of that taig mill! The rotary shaft is 10mm in diameter so I ended up drilling out two 3/8-inch shaft collars to 10mm. The shaft collars are used to take up the extra space since I wanted to leave the shaft at its original length. I used a 3/8-inch flex coupler drilled to 10mm, a rubber spider and 1/4-inch shaft flex coupler from Princess Auto to mate the rotary shaft to the stepper motor.

Rotary axis with 4-jaw chuck attached.

Stayed tuned for my next blog post where I’ll show the rotary axis in action attached to the Taig mill.

Karl P. Williams