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

A friend was selling some 200 ounce/inch, 3.5 Amp stepper motors for a great price so I thought it was time to upgrade the taig cnc milling machine. With the old steppers installed, the machine was accurate but slow. Since the old controller couldn’t handle 3.5 amps I decided to upgrade that too. I found a 5 axis controller on ebay for a great price. This controller uses the Toshiba TB6560 stepper driver that can handle up to 36 VDC at 3.5 Amps. I wanted a board with at least 4 axis’ so that I could add a rotary axis to the mill but more about that in another post. I went to the local electronics supplier (Sayal elelctronics) and Parm set me up with a Hammond electronics 24 VAC, 10 Amp transformer (a local manufaturer). I picked up a bridge rectifier, large capacitor, switch, fuse, computer power cord socket and indicator light to complete the power supply. The entire conroller and power suppy were mounted in a computer case.

Transformer, bridge rectifier and capacitor.

Switch, fuse and power socket.

Mounted indicator light and switch.

TB6560 stepper controller board and 200 oz/inch stepper motor.

Power supply and controller mounted in a computer case.

Close-up of computer case.

After getting all of the stepper motors wired to the controller board it was time to start testing. I noticed that the motors started losing steps and stalling out at speeds greater than 20 inches per minutes. I hooked the oscilloscope up to the step line on one of the axis to see what was going on.  Instead of a nice square wave it looked more like a sawtooth because of the slow rise time. This is what was causing all the missed steps at higher speeds. The culprit was slow rise times of the optocouplers situated in the circuit between the parallel port and the drivers. An easy fix was to take the optocouplers out and jumper them with a wire. The parallel port is no longer isolated from the driver chips but that has never been an issue with my other drivers on different machines. The machine can now run easily at 40 inches per minute.

In this photograph, on the left, you can see the waveform of the slow rise time of the optocoupler. The waveform on the right shows  nice square waves generated after the optoisolators were jumpered. This makes a big difference considering that there are 8000 steps in one inch.

Karl P. Williams

This was a good project to master inkscape and gcode tools. There is a nice tutorial on how to render gears and then use the gcode tools plugin to create the gcode here: http://www.cnc-club.ru/forum/viewtopic.php?f=15&t=35&start=20

I started by using the gear rendering extension included with inkscape.

I launched the gcode tools when I was ready to create the gcode for my design. It took a bit of tweaking and experimentation but eventually I got some good gcode. I needed to set up a tool in the tool library as well as the preferences before creating the gcode. Note that you have to be in the ‘Path to Gcode’ tab for it actually do its thing.

Here’s what the tool path for the gcode looks like in the Mach3 tool path window.

I followed the same procedure to create the smaller gear that is attached to the stepper motor.

Karl Williams

Last weekend, on our way to Site3, Darin and I went to PlasticWorld in Toronto. After purchasing lots of great plastics we were discussing some of the cool things we could make, edge-lit displays being one of them. After googling the subject I came across one of the first applications using edge-lit displays; the Non Linear Systems digital voltmeter (DVM) produced in 1953. The NLS DVM is so interesting to watch that I want to create a similar display for a digital clock. I know that Darin also has an awesome project in the works dealing with a unique application of edge-lit displays.

Click through for more…

“The first NBS DVM used a new type of digital display based on stacks of edge-lit, engraved Lucite plates. Each stack (representing one digit) consisted of 11 plates arranged so that they recede from the viewer. Ten of the stacked plates have a numeral deeply engraved on it (digits 0 through 9). The eleventh plate has a decimal-point engraving. A small grain-of-wheat incandescent lamp located along the edge of each plate illuminates the associated plate from the edge. If the lamp is lit, its light travels down the plate, which acts as a light pipe. Eventually, the light strikes the plate’s engraved character. The deep groove of the engraving interrupts the light as it travels down the Lucite plate and scatters it towards the front of the instrument where an operator sees the engraved numeral light up.Each numeral display stack has 11 grain-of-wheat bulbs, so the 4-digit NLS DVM had 44 incandescent bulbs, plus two more for the plus and minus signs.”

NLS DVMs used a digital display built from stacked, engraved Lucite plates and small grain-of-wheat incandescent bulbs.

An NLS stacked lucite display.

A Cubic V-45 Digital voltmeter (circa 1960).

Now back to the experiment…
I started by designing each digit with a CAD program.

Each digit was engraved and cut with the Taig CNC milling machine. The line width of each numeral was 1/8-inch wide, leaving a slightly opaque area in between the edges.

When I stack more than 5 pieces together it gets hard to read the digit at the bottom of the stack with the additive effect of the opaque areas obscuring the lower digits.

For the next round of experiments I will engrave the numerals much thinner to negate the stacking problem.

More to come…
Karl Williams

Gus showing what a CAD part looks like in MasterCam.

Click through for more…

Simulating the toolpath before cutting the part on the milling machine.

Darin white decided to demonstrate that a part could be designed and cut using free software in less than 20 minutes. He used inkscape to design a part, exported it to .dxf and then used dxf2gcode to generate the gcode for the mill. A short time later his part was cut into a piece of foam! Kwartzlab rapid prototyping is becoming a reality.

Matt Bells shows his potentiometer controlled synthesizer circuit to the group.

Creating some very intersting sounds.