4-Axes Taig Micro Mill Computer Numerical Control (CNC) Conversion
Last updated on Saturday, September 03, 2011 08:21:53 AM Eastern US Time Zone

4-Axes CNC Micro Mill, Pre-CNC Baseline, Mach3 Interface, Involute Gears, Z-Offset Gage Animation, CNC Bench

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4-Axes CNC Micro Mill

Baseline configuration for the 4-axes, CNC-converted, Taig mill. A 25MB video of a circular pocket milled in machinable plastic.

There are different methods for measuring backlash. For the Taig mill, check the lead screw adjustable nuts for tightness.
The nuts that hold the couplers must also be snug but over tightening will damage the bearings. Sometimes, gently
tapping the coupler with a rubber mallet before tightening, helps. Loose couplers are a very common cause of
excessive backlash. Then, lubricate the lead screws, ways, & move the axes multiple times prior to the check.

For a CNC machine put a 0.0001" indicator in the spindle.
Using your controller, set the increment to 0.0001" & continue to “bump” it until you load the indicator 0.003”.
 Then reverse the motion & “bump” it 0.0001" increments in the opposite direction until the indicator reads 0.002”.
Count the total number of times you moved it 0.0001" to get the 0.002" reading & subtract 10.
The remaining number is your backlash in 0.0001”.

For a manual machine, turn the crank until it reads zero on the dial & zero the indicator.
Then reverse the crank until the indicator moves. Reading the dial will give you the backlash.

Pre-CNC Baseline

Pre-CNC Taig Mill with a DRO, ER-16 spindle & 12" travel table. The DRO has since been
removed for the addition of the CNC system. The X-axis lead screw motor was removed.

Mach3 Interface

Mach3 main screen showing among many other things, the DROs. Mach3 setup tutorial.

Mach3 ToolPath screen showing an involute gear design & its G-code.

Involute Gears

0.021" thick brass involute gears.

Involute gear animation.

A 4.000" height, Z-axis tool length setting gage (USA).

Z-Offset Gage Animation

Z-axis offset animation showing a ¾" end mill being set at 4.000" above the vise bed.

A 3.000" height offset gage.

An adjustable, brass, over-travel stop was added so the needle can only turn less than one revolution.
 Needle-based, Z-offset gages set the mill more quickly & accurately than illuminated or digital types.
All critical surfaces of the parts, including the round post ends, were precision surface ground for high accuracy.


Animation showing a 2.000" tool offset height being set on the Taig CNC Z-axis using the MPG in step mode.

Circular pocket.

Hexagonal pocket.

CNC Bench
 

Pre-CNC bench preparation (above). To reduce their exposure to swarf, the μATX computer, breakout board box, &
stepper motor controller are tucked up underneath the bench on a high shelf. The shelf has a 1.5-inch gap
 along the back for ventilation & cords. The bench's side & back have been closed off using ¾" particle board.
The board makes a sturdy mounting surface for the shelf brackets & further stiffens the bench.
The large hole for the wires is below the shelf surface in case any debris enters from the back.
 Steel anchors attach the bench to the cement wall. The (blue) wired WAN from the house router is to the left.

The MPG added an additional E-Stop. Its springy cord needed a strain relief clamp.
Both fans blow air outward. Have not seen any swarf on or inside of the electronics.
Everything is running at cool temperatures. Have since installed a green LED for the breakout box power.

The CPU, LCD, opto-isolation, safety charge pump, & pendant interfaces are protected by a computer monitored (RS232)
APC uninterruptable power supply (UPS) while the stepper motor control circuit is protected by a standard APC surge protector.

An upgraded APC Back-UPS ES 550 having computer monitoring software connected via a USB.

Rotate-to-unlock style E-Stops were installed to the left & right of the mill. The pendant has an E-Stop button, too.
A compact quartz halogen goose-neck magnetic-base lamp (manual) is attached to a metal plate screwed to the bench.
Stepper motor cable routings. To the right, they enter underneath the bench edge to reduce swarf entry.

4-Axes CNC Micro Mill, Pre-CNC Baseline, Mach3 Interface, Involute Gears, Z-Offset Gage Animation, CNC Bench