Pendant


CNC Mill Pendant
I've had my mill running for a few months and have done several fun projects. I've really been enjoying the ability to simply make anything I can think up! One drawback has been using a keyboard while setting up and doing manual machining operations. So, I started thinking about putting together a pendant. My list of requirements were pretty small, an MPG (Multiple Pulse Generator), a few switches for setting the zero on the X, Y, and Z axis, an emergency stop button, and a button to start running a program. After looking for a while, it became clear that the MPG was going to be an expensive gizmo and that it would require an interface to make it talk to my controller. I ran into a thread on the CNCzone that talked about a new kit under development by Homann Designs. Click here to see the thread. Well, I decided that the kit of parts was nearly what I was going to end up sourcing on my own so a quick PayPal payment was sent to Australia. In a surprisingly short time a box arrived from down under which yielded some very nice quality parts. So, let build a pendant!

	My box contained parts as mentioned above and little else. So I sent an e-mail to Homann Designs support asking about the software and AutoCAD drawings mentioned in the thread. I received an e-mail back almost instantly with the requested files. I loaded the dxf file into BobCAD and picked the mounting holes and created g-code to drill them. The screen to the left is from Mach3 which I use to run my mill. The graphic in the upper right corner shows all the cutouts for the front of the pendant.
	I clamped a piece of scrap plywood in my vise. After drilling the mounting holes with a #31 drill bit, I screwed the case front to the plywood. Back to BobCAD to create the g-code for the cutouts in the case. Rather than drilling some holes and then routing the rest I used a 1/16" end mill for all the cutouts. For those building along at home I ran the EM at 1500 RPM, 6 IPM, 1/8" DOC (in two steps) using compressed air to keep the bit cool and clear the chips.
	Thirteen minutes later and the case is ready to insert parts! Have I mentioned that I love my mill?
	To mount the ModIO interface board into the case I just transferred the mounting holes to the case back and drilled them with a #32 drill on my drill press. If you look close you can see the laser cross hairs used to ensure the holes were accurate.
	The kit came with some nice PC board mounts that were predrilled. I tapped them for some 4-40 bolts.
	Here they are installed into the back of the case.
	I then installed the push button switches, rotary switches, LEDs, MPG, emergency stop button, and the LCD display. The supplied CAD drawing was impeccable. The only thing I changed was to leave out the holes for the anti-rotation pins on the rotary switches. I don't like the look of the exposed hole on the front panel. I could have dug in my spare parts and found a couple of knobs that would have hid the holes but this was the path of least resistance. Besides, what is the chance that I'll have three matching knobs anyway? Time invested so far, probably under an hour. At this point I'm playing with the knobs and making mill noises. My wife thinks I'm nuts.
	Next up was wiring the components in the pendant. This is classic PTP (point to point) wiring. The schematic supplied was clear and easy to read so wiring was commenced. I used masking tape flags to identify the wires since I had a limited choice of colors on hand. If you take your time and are methodical, this part will be behind you very soon. You can also see the nice strain relief provided for the pendant cable. It has a nice cable clamp internal as well as the spring to protect the cable.
	Here you see the completed wiring for the pendant. A few cable ties kept things manageable. Just don't look under the interface board... The hole for the strain relief is a 15/32" diameter and was biased to the bottom of the back of the case.
	I added a few extra connectors to my DIN rails and wired the other end of the pendant into the control enclosure. The cable in connected on the left side of the top block and the right side is wired to the power, ground, and serial connections elsewhere in the cabinet. Eventually I'll probably add another multi-pin connector to make the pendant removable so I can use it with my CNC router.
	I had to cut a new mounting hole in my control enclosure to mount a DB-9 connector for the serial cable. I probably spent as much time on this little detail as I did wiring the pendant.
	You can see why in this picture. Notice the wall immediately to the right of the enclosure, no clearance at all for working. A combination of a Dremel tool, small drill bits, and a file got the job done. Times like this almost justify the $$$ for a Greenlee punch.
	Here is the completed pendant, all wired and powered up. Next up is the installation and configuration of the software.