My ebay $750 Retrofit non standard repairs

I have previously posted that I bought a Tree Mill Journeyman 300 off
ebay for $750. I plan to post my experiences in buying such a machine off
ebay, having it transported across country and retrofitting the controls in
the next few weeks so others can possibly share the knowledge to accomplish
a
similar project.
First of all, I have previously retrofitted a Tree Mill journeyman mill for
a customer that has a shop about 20 miles away. I was really impressed with
the excellent mechanical condition of his machine even though it probably
had
20,000 hours on it. In view of this and the fact that I was unable to locate
a suitable machine for sale at local machine shops, I turned to Ebay. Over a
period of 6 months I bid on several clean machine with working controls
similar or equal to a Bridgeport series 1 CNC. All of the machine sold for a
higher bid that I had been willing to pay. The one machine that I was the
high bidder was below the reserve price. I had budgeted $5000 for a good
machine in good condition with half way decent controls. Then I saw a Tree
Mill Journeyman 300 CNC vertical mill that looked good but it was being sold
as is because parts of the controls were missing. It turns out the cpu and
the crt were gone. I didn't want those anyway so I decided that for $750 and
some repair cost that I could end up with a very rigid machine with modern
controls once the retrofit was accomplish.
As I previously mentioned I use "oil eater to clean 30 years of oil off the
machine. The table top looked pristine after it was cleaned. The X axis had
about .001 backlash. The spindle with the Kwik switch 300 holder assembly
was in good shape. The Y axis was probably the reason the machine was sold.
The Y axis had .030 backlash. Disassembly of the Y axis ballscrew assembly
reveals that the ball nut flange was fractured completely just beyond the
flange but before the first ball groove. Since the material is hardened I
was pretty sure it could not be welded . I checked around and found I could
buy a new ballscrew and nut for that machine for $1500. Other replacement
ballscrews custom made would also run about $1300. Since the ballscrew and
ball nut were off the machine I chucked up the ballscrew in my lathe and
measured the end play. It was nearly zero!. Then I remembered that really
hard material like carbide is brazed onto tool holder. So I got out my
oxy-acetylene torch , removed the balls and ball nut from the ballscrew.
Cleaned the mating surfaces of the flange and ballnut, fluxed them and the
brazed the two ends back together. I reinstalled the balls and found that it
did turn smoothly. When I reinstalled it on the machine and reassembled the
thrust bearings I found the Y axis to be very stiff. So I took it apart
again and found that even thought he races on the thrust bearing looked ok
they weren't. So I replaced the two thrust bearing at a cost of $9.32 each.
It now turns very smoothly, easily and with about .0012 backlash which is
acceptable for my work.
While disassembling the Y axis I noted there was a BEI incremental
encoder mounted between the ballscrew and the servo motor. I removed it and
tested it. There was no output from channel A, B or the index. I called BEI
tech support and relayed what I had found. They asked me how much current it
drew. It was 70 MA. They told me that was too low and I would either have to
buy a new one for $400 or send it in for repairs and that repairs could cost
up to $200 if repairable. After thinking about it for a while I decided
that I could easily replace it with a US digital encoder for a lot less. But
I wanted to do a few more checks on the BEI encoder. I check quite a few
items and then realized that it must be the light source in the encoder. I
cut one of the leads and sure enough the encoder light source was open. I
assumed it was an IR LED. I removed it and noted that this little light was
only .125D and about .187L. I looked at the circuitry and was surprised to
see no dropping resistor or the LED. It was wired directly to the +5
terminal and ground. Upon closer examination I could see that there was a
portion of a filament inside the miniature bulb. It was an Incandescent
Lamp!.
I went through my catalogs and found that Chicago Miniature makes hundreds
of different incandescent miniature lamps some of which were 5 volts. I
then was able to find that Mouser electronics carried this replacement bulb
for $1.60 . I needed to order some other parts for various orders I had so I
went ahead and ordered it. When it arrived I installed it and powered it up.
I could see the light on and when I connected my scope I could see that all
the channels were working properly. These little lamps come with different
filaments so you can get them with 10,000 -40,000 hrs of life.
Failure analysis of the Y axis was probably caused by the encoder lamp
burning out. This most likely caused the Y axis to run uncontrollably into
the
column causing the Y axis servo amp to burnout, blow the fuse and fractured
the ball
nut flange.
The spindle motor is a 4.75HP PMDC motor with tachometer. It is 180VDC
and ran off a three phase controller. I didn't want to spend $600 for a
rotary phase converter or phase inverter. I bought a KB electronics 5HP DC
speed controller that has a manual speed control or will take a +/- analog
signal. It was pretty easy to install the KB speed controller and tested
just fine.

So the only remaining issues is that the spindle uses a bijur positive
displacement lube oil pump to lubricate the up and lower spindle bearings
and the quill. The sumps
needs cleaning and fresh lube oil installed. But I need to clean the sump
filter before I install the new oil.
I ordered a 3KVA isolation transformer for the power supply ( 170VDC ) and
have started the retrofit of the controls for the new CNCTeknix servo amps
that I will install. hope to make chips soon.
Dan

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