Tuesday, December 11, 2012

Y-axis servo arrives! Damaged!

Mid-August 2012:

Did some digging on eBay to find myself a servo that is comparable to what is already installed on the mill, my primary concerns being torque and voltage. Like the Z and X servos I intend to drive the ballscrew directly (as in, no mechanical reduction). Be aware that if you go servo shopping on eBay there is an OVERWHELMING number and variety of servos on there. My first inclination was to find something approximately the same size as what is already on the mill, but I have since been told (warned?) that improvements in servo tech over the last 33 years since this mill was made have reduced the size and increased the torque of many of these motors, even in the same "style" as what I have on my mill (2- and 4- brush, brushed permanent magnet DC).

So I found this gem for $149 + $13 SH, says it will work in my voltage range (anticipating 70-80 volts, since the power supply is still not assembled yet), has encoder, 1500 oz-in of peak torque and I'm sold. Buy now, enter paypal password, eagerly await tracking number.

Then it shows up :(


As you can see, the end of the pin that holds the encoder wheel on is smashed from poor packaging, the pin itself is bent and encoder pins are all bent up. Another view:


I grumbled to the seller and got $25 back on it, hoping to repair the shaft and straighten the encoder pins and see what happens. I didn't take any photos of the shaft repair, but the encoder drive pin is actually just a piece of 3/16" round solid that was (poorly) machined down to 1/8" to fit the wheel center collet. I expected it to be pressed into the motor, but it was only glued in with some cheap epoxy. I applied some heat to the end of the pin and was able to pull it out with a pair of vice grips to take measurements and make a new one on the lathe, glue in place and reattach the encoder. Minor setback (hopefully) averted. We'll find out for sure when we attach a drive to that encoder.

Sunday, December 2, 2012

Y-axis servo mount

When I purchased the mill the Y-axis servo mount was all but missing. Someone had installed some sort of manual bearing mount that left the bearings unprotected and their handle setup didn't put the proper amount of pre-load on the bearings to keep the screw from shifting and throwing off the dial reading. Some requests on the practical machinist forums got me these pics of how the servo was mounted on other Lagun mills:

Lagun example brackets

And another:


And an up close shot of a third:

Photo  1

Photo  2

I went searching on eBay and turned up a pair of servo mounts that looked about right from a Precision Matthews brand knee mill.

$ KGrHqJHJEEE njyti9OBPsfm c U ~~60 57

$ KGrHqRHJEME m1WUt54BPsfm9nkf ~~60 57

These were a bit spendy ($325) but at least I was able to recoup some of it by selling the X-axis bracket I didn't need. Some grinding on one of the bolt holes and a few longer bolts and I was able to fit the Y-axis bracket to my mill:



Spindle ballscrew bearings and encoder mount

Late July 2012

Since almost every other bearing was in lousy shape I decided to pull the ballscrew bearings out of the head and replace them, and did some cleaning up while I was in there too.

View of the bottom bearing cap, before:


Pulled ballscrew out, decided to turn top end for a HEDS style encoder since 1/8" is a common (read: cheaper and more available) size for encoders. Shown here: a blurry photo of me indicating the screw to make sure I'm centered up on the lathe:


A much better image:


Shaft turned down:


Success! Encoder fits snugly!


After shot of ballscrew cap and bearing with some much-needed cleaning:




Boring updates and electrical work

June-July 2012

Maybe not the most glorious of updates, but I bought a hold down set from eBay and also dug up an automatic bijur luber that I had intended to use on an earlier mill. Both of these got mounted to the side of the mill.


Got the head fully reassembled with new bearings in the motor


Took apart the motor control button so I could make a diagram with wire codes


Another view:


Took off a bunch of old and cut wiring to get down to the minimum necessary to make the head run in forward and reverse


Labeling some wires in preparation:


Close up of rewired panel:


As Red Green would say, this is only temporary… unless it works.


Test bench set up. In the future there will be conduit for all wires and strain relief for the thick black power cord.


Doing all this wiring, I now have forward and reverse buttons working as well as a stop button for the spindle.

Varispeed Head Pt II

Around May 2012 While I bought many of the bearings from eBay and elsewhere, I purchased a new set of glacier sleeves and guides as well as a parts breakdown and manual from Carmen at Republic-Lagun HQ in Harbor City, California. Carmen is a good guy and has a lot of experience with old machines like mine.

I'm going to try to add dates to all entries from here on out so that other DIY'ers and experimenters can see about how long its taking me to get this project from basket case to functional again. Although I started this blog a couple weeks ago, I traded an automatic nonferrous saw for the mill + $300 cash in early March 2012. I started the rebuild with some seed money from the sale of my Amstar-Foxcon HVI 1/2 manual mill in April.


Added cleaned up sheaves to the back gear section of the varispeed head.


Started bolting pieces back together on the mill - this shows the back gear on the spindle head. It seemed like a much easier way to reassemble than reassembling the head then trying to lift that whole heavy assembly onto the splined driveshaft of the spindle.


Top belt cover on.


Side view


Chain and sheave movement assay in place on the front of the belt cover.


Spun motor shaft as I was getting excited about putting everything back together and realized I needed motor bearings too (face palm). So I pulled the motor apart, got bearing numbers to order more(6205Z x2) and went home with my pride hurt.


Motor-side sheave assembly.