Saturday, July 30, 2011

Installing The DRO

I walked into the shop this morning wondering what I should do for the next few hours. The to-do list is long but I was feeling a little lazy. I wanted to machine the nut mount for the leadscrew conversion to get that project out of the way. I also have the axles for Dennis which were long overdue. There is also the reorg of the shop to prepare for the arrival of the PD400. On one corner of the bench is the simple steam engine waving at me... Boy, I'm lost.

I finally settled down to install the DRO and work out the mounting to hang up the monitor on the window grill.

Lathe DRO
These are the parts that read the turns of the handwheel:

The DRO thrust collar was fastened to the back of the stepper motor using 2-part epoxy:

The thrust collar caused the setscrew on the handwheel to clamp too close to the edge of the shaft. Sherline's instruction is to drill and tap another #10-32 hole for the setscrew as close as possible to the plastic encoder gear.

I followed the instruction to do this by clamping a dowel pin to the handwheel using the existing setscrew. I do not have any 1/4" dowel pins around, and so had to make do with the 6mm dowel pin with some adjustments.

Job done for both handwheels:

You can see, from the existing setscrew hole, the end of the motor shaft:

The encoder housing was next. Quite an easy step:

I have a problem here; the encoder housing has the tendency to rotate when I turn the handwheel a bit faster. The instruction calls for a drop of super glue to mate the housing and the thrust collar should this happens. I'll do that as soon as I get myself some super glue.

The RPM sensor was mounted next, after I stick the decal on the pulley. Before applying the decal, I cleaned the pulley surface with adhesive removal to rid it of cutting fluid and oil. Didn't do a good job sticking the decal as it is slightly off centre.

I screwed up when fastening the sensor to the belt housing; it was a little too far in, causing the plastic arm of the sensor to pop up. The correction was easy - just relocate the sensor and fasten it with the self tapping screw on the belt housing.

With all the wiring work done, it was time to plug in the wires to the DRO.

The RPM sensor tested ok. I turned the speed control knob all the way up and it displayed top speed of slightly above 3000 rpm. This is in line with the number shown on the handheld tachometer I used sometime back. Sherline's advertised top speed is 2800 rpm.

The X axis tested ok but not the Z. I swap the encoder to see which is the culprit. It turned out to be the encoder I was using for the Z. I opened up the cover that house the wires of the encoder.

Strange things happened - it works with cover off!!! I screwed back the cover and it stopped working. This shows that 1 or few of the wires' exposed contacts came in contact with each other when the cover is pressing down on them. That's all I can do for this. No knowledge to work out a solution on my own or do further testing. I'll bring it back to Mike for a replacement.

This is a video showing the problem:
YouTube Video
There are 2 parts that are useless if you are installing the encoders to the back of stepper motors. I'll keep them unless someone wants to take them off me.

Some thoughts on the DRO kit. The plastic parts looks and feel flimsy. I'm a bit disappointed with its quality. I expected some harder plastic material being used. The handwheels felt stiff after the encoder housings were installed. Turning them will take quite some effort from now on... Sigh...

Mounting the LCD monitor
I bought the wall mounting bracket for LCD monitor hoping to modd it for use on the aluminum window grill. I wanted to fabricate a pair of brackets to allow the wall mount bracket to be fastened on them. Due to the messiness of the bench at the moment, I decided to just hang the LCD monitor using part of the hardwares provided with the wall mount for the time being.

This is how it looks:

Some space is now saved as I can have the small keyboard I've just bought on the Soigeneris controller box.

Oh, one more thing: I've now rolled up the blinds to free up the grills for use. To shield my machines from direct sunlight, I sticked 2 pieces of black cardboard bought from the neighborhood stationery shop to the glass panels, leaving the top uncovered to allow some natural light.

That's all for now.

- Posted using BlogPress from my iPhone


Anonymous said...

Wong, over the years( over 35) I have come to putting two thin shim washers between the handle and thrust plate on my sherlines. I have an assortment of shims for various size shafts and thicknesses.
I use two or three thousandths thick washers. This seems to relieve the friction and work as simple thrust bearings and the knob turns smoothly.


Wongster said...

Each set of handwheel did come with a thin washer with 1/4" ID. Putting that in made the whole setup tighter.
From my observation, the handwheels are rubbing on the encoder housing. Without the housing, the wheels turned smoothly.
Mike the distributor fixed the faulty sensor for me and I'll be mounting it back in my next session likely next week. On duty this coming Saturday and the following public holiday (Aug 9 is our National Day). Will try thining down the side of the encoder to see if that work.