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- "4D Part" Using Your 3 Axis Mill -

Making a "4-D" part using a 2D System! Here's How!

Here is my FIRST "4th" axis project, well sort of :)! It's a candle (2x6") bought from Target and cut on my CNC machine! Amazing!
** Read Below for setup and pics! **

Setting up The Axis

The path is drawn in TurboCAD 2D, exported to Ace Converter for G-Code translation, and ran using CNCPro. Since I'm not quite sure how to run a "real" 4-D part I plugged the 4th axis, rotary in this case, into the Y axis driver. The 2-D drawing is essentially "wrapped" around the candle. I found through much experimentation (Scraps!), 3.50mm depth is max for the letters. Setup your Y-axis (rotary) so the machine thinks the total length of the axis is the circumference of the stock your using. It is very important to get this right or your work will not come out as drawn. Do this by changing the number of steps to the motor. For example, if the drawing made is 50mm in length then the stock you use should also be 50 mm in circumference. After your ready to go, make sure that jogging the machine 50mm means the stock turns ONCE and returns back to its original position (get this right). If this is not the case, change the number of steps to the motor until it works.

Radius Compensation

Why you can't cut too deep.

Since the machine is set up to cut on the circumference of the candle, when it plunges in the radius decreases so 1mm movement over is actually LESS with this new radius/circumference. Since CNCPro does not have "radius compensation" the machine does not know to decrease this movement over by that amount! For example, if a candle has a 15 mm radius, its circumference would be 93 (2·3.14·Radius). This same 1mm movement over at the 15 mm radius is not the same if the cutter is, lets say, 3.5 mm into the candle. The new radius is now 11.5 mm (15-3.5) and circumference is now 72.22 mm. To match the same 1mm movement at the surface the machine should now really move over only 0.76 mm! Since my program does not know this, the letters get slightly undercut.