Part II: retrofit of an Emco Compact 5 CNC lathe

This is a delayed follow up to the post on disassembling an Emco Compact 5 CNC (http://coltpython.blogspot.com/2009/10/part-i-retrofit-of-emco-compact-5-cnc.html) on putting the machine back together with new bearings, motors, etc. I did this a month or so ago; hopefully this doesn't leave out anything important.

Note: this writing is *way* too detailed for a real machinist. It includes a bunch of very basic steps since that's the level I'm at.

It's currently at around 80%: motors in, everything turns, but still have:

1. hook up limit switches, the motor, the shutoff switch, and the RPM encoder to the gecko g540.
2. do something about the cosmetics: I ripped out a bunch of the stock electronics, leaving empty holes. These will suck up dust and junk, so need to decide what to do.

It's largely straightforward to put things back together.  The two tricky things are:

1. getting the optical encoder to not drag as the spindle turns. It turns out you have to bolt the lathe in and push/pull it back and forth so that the sheet metal of the housing torques until the drag stops. I kept disassembling the spindle head (and trying to seat the flywheel assembly deeper) in a misguided belief that these were the problems.
2. You probably 't just bolt the motors right on and go --- you need to make sure the tension is sufficient. So push the motors away from the timing belt wheel until the belt is tight and then tighten the bolts.

Finally, I still cant' get mach 3 to run reliably on windows XP on a Thinkpad T61 laptop, but this seems to be a known problem.

OK: first things first, getting the new 6006-ZZ class 3 bearings into the headstock. This likely made little difference, but I put them in the freezer to hopefully make it a bit easier --- it was suggested I use dry ice, but I was too lazy.

One thing I'm disappointed about is that the headstock is aluminum, which seems kind of cheap given the general quality of emco stuff. Maybe worth redoing in steel at some point? In any case, here's the headstock and bearings (in a few freezer bags to eliminate moisture):


One slightly confusing asymmetry is that the number of pieces is different in the front and the back. Front has just a bearing and a ring:


Back has bearing, wave washer and ring:


This can lead to a bit of panic when you disassemble (at least for me) where you disassemble and think you lost something in all the excitement.

Putting in one of the bearings: we use a flat piece of wood to give contact and minimize chance of dents:


Next is putting in the spindle. Here's the spindle from a real lathe (a Hardinge/Cataract) for comparision. As you can see, not much of one:


The spindle is a tight fit, but if it requires a lot of force, the bearing is probably not seated:


We put the pulley, etc on and then lock it in with the ring:


Now time to bolt on the motor:


Note that you can't tighten the bolts here down until you adjust the belt tension. The small hole in the pulley is provided so you can tighten the bolt behind it:


Time to put the felts back on the cross slide:


And then bolt it back to the bed using the plastic (yeah, I know) supports. Note: you don't want these too tight or the bed won't be able to move!


Now we bolt the top to it:


And, in the interests of full disclosure, at this point I discovered I left a bushing off of the spindle. ARGH!!!!




So we use the pulley puller to pull off the pulley and on it goes.


The new nema23 motors I have don't have holes in them for the pulleys that came with the emco. So we use a small proxxon drill press to drill a hole in from the flat part of the motor spindle to the back. Starting (note: during the actual drilling there was support on the spindle to avoid bending anything):


After:


And banging the pin in using a bench block:


In good news, they bolted right on:


At this point we get to the most annoying issue: when you turn the spindle, the optical encoder on the machine (the part with the cable in the photo) would rub no matter what we did. It seemed that the spindle was off center (which it wasn't):


First problem is that you need to bolt the housing to the lathe body:


Second thing is you need to push/pull the lathe bed back and forth, spinning the spindle til it stops rubbing. Then bolt everything down to keep it in this configuration. I am not a big fan of this design methodology. I much prefer things that when in their right configuration are, in fact, in their correct configuration. Having to bend things about is too ghetto.

In any case, success, so we move on.

A bit of adjusting of the cross slide since it was too loose and wobbled back and forth:




Now just have to bolt on the top part:


Clearly something has to be done about all the holes from missing electronics:


And here's everything bolted up. One step you didn't see was adjusting the belt tension on the motors: loosen bolts, push the motor away from the belt pulley and tighten.