Here's how the limit switches and DRO scale were arranged. The limit switches are at either end of the square section loominum extrusion and the home switch is on the side near the top of it. I've selected the same fetching yellow / brown shading for the "target" as the switches to make it easier to spot here. These Omron switches are inductive (eddy current) proximity sensors which work with almost any metallic target. However, they are less sensitive to non-magnetic targets so I have deliberately chosen to make my target from a piece of loominum angle extrusion. This cunning stunt relies on the detection distance being consequently shorter, leading to a marginally(?) more accurate / consistent detection position.
First, for no obvious reason, make up the bracket that locates the DRO reader head on the side of the yoke. I also need to make up some spacers to hold the DRO scale at the correct distance from the machine head. For this make up some spacers, using some nice mystery bronze or brass barstock:
Like this. I'll need to finesse the length later, so they are oversize for now.
The bracket goes in here between the reader head and the yoke:
And looks like this:
Or even better, like the top one in the next photo, otherwise I won't be able to get in to tighten the pinch bolt. There's plenty of movement on the DRO scale to accommodate a different position for the reader head, so this should work.
That'll do. Now drill some holes....
Getting there....
Pinch bolt in place. Looking good.
Make up some fatter spacers, as the originals didn't mate well with the DRO scale.
There you go:
Now over to the other side and fit the target piece for the 3 proximity switches. I put 2 diagonal holes in the yoke, one on either side of the pinch bolt to mount it on.
I've adjusted the target down a tad by bending it. Does the trick and reduces the distance between the home position and the +L (hard stop) switch. I want to lose as little Z axis movement as possible. It's about 2mm between the home position and +L limit switch operation.
Need to clean up the Leadshine stepper wiring and the switch wiring.
Take a note of the connections first:
It's not really the ideal wire to use (Cat5) but will have to do until I get something better.
Limit and home switches wired in properly through the cable glands, along with stepper connections:
Lid on.
I've done worse.
DRO in place and connected up:
Controller configuration:
Set the parameters for homing:
And the speed settings:
Final component dimensions:
Then connected up the stepper drive error output to the controller. Stalling the motor or forcing it out of position results in this error message, which stops the machine.
Knee power feed:
Next: Fit a motor feed to the knee. Knee mills aren't ideal for CNC conversion, as they have such limited Z axis movement. In turn this requires the knee to be set at the correct height to get best use of that movement. If you have about 100mm of travel (currently, in this setup), that has to cater for all your machining moves as well as any retract heights etc. These machines have a crank handle for raising and lowering the entire knee / saddle / table assembly but this can be pretty tedious work, with the risk of succumbing to terminal wanker's cramp.
I removed my Align 500X power feed from the table when I converted to CNC. On the face of it, I should be able to re-use it on the knee, as the basic drive unit is the same. However, there are some additional parts needed to complete the conversion, namely an extension shaft and a different bevel drive gear. I was unable to find drawings for the shaft on the internet and even if I did, there would be several hours work involved, including an internal 3/4" UNF thread and an internal keyway.
Here are a couple of Pootube vids to show what is involved in fitting the factory knee power feed:
There's a local company offering the Align 500 Z-axis kit for £299 at the moment. Seems like a good price, as mostly these come in around £350 or more, even on ebay. There's one on its way, even as we speak....
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