mill power table feed restoration cont'd

shouldn't it be the same
color as the column?

 This is the subject of today's blather; it's the motor drive electronics and housing for the mill's power table feed. -->

 It's defunct, demised, past-on, ceased to be, it's expired and gone to meet its maker.

 These controls were built - at least the electronics were - by a contract manufacturing shop, not Bridgeport themselves.  I'm not sure who made the cast aluminum housing.

 The original electronics weren't well-designed even for the time.  And, as usual, insufficient thought was given to heat rejection. The stock unit appears to have just one bad $10 SCR and it's still not worth my time to repair.

Old n Busted

<-- This is the stock drive electronics.  It wasn't terrible, but it wasn't good.  I guess they assumed every shop would have air conditioning and wouldn't have welders.

 I am replacing this with a modern motor drive (from Minarik) which is half the size and needs a quarter as much heat rejection because it uses newer devices with lower forward voltage drop.  I heat-sunk it to the back panel anyway, with silpad because that's who I am, and my shit doesn't break.  That's literally one of my mottos; don't build things that will break.

 

The New Hotness

 The outside of the housing is kinda grim.  Apparently whoever coated the housing, be they Bridgeport or bridge-dweller, did not know about acid etching primers for aluminum.  And so the paint kinda - fell off - over time, because it wasn't bonded to the aluminum, it was bonded to the (relatively loose) oxide layer.

 The good news is that this has been a solved problem for decades.  I used Rustoleum's "automotive" (I think they mean, for engine blocks) acid-etch primer for aluminum, stainless and mumble.  Then a few coats of conventional industrial enamel.

I used a rattlecan color called "Smoke Gray" because the 'Machinery Gray' (Rustoleum) that Bridgeport used only comes in gallon cans and I am not planning to repaint the whole mill.

notice where the round corners suddenly turn square?

 It feels good knowing you're doing a better job of something than the factory did.  My guess is that Bridgeport had little to do with the production of these, and here's why: the paint on the mill column is .045in thick!  I know this because former users hit the column with work that came loose and knocked chunks of the coating off.  The thickness is impressive.  (that's what he said)  I could measure the depth of the hole in the paint to the surface of the cast iron with a pair of calipers, that canyon's almost deep enough to have an echo. ;)

 I will put on several top coats, baking each in turn, and then I will use a sanding block with 200 grit waterproof paper with water to wet-sand the paint from the logo and from the "on" and "off" labels so they are bare metal.  That's the stock look and I think it's sharp.

 One weird thing I noticed is that the casting mold was modified from its original form, at the bottom rear of the exterior, where the round corners of the housing turn squarish right before meeting the rear.  That feature is not present on the top, and the mold marks there are less smooth than the rest of the casting.  This creates a little bump-out on the bottom rear of the housing for the drive mounting panel, which apparently turned out to be wider than originally planned.  I can easily imagine how that went down.

 And even tho it wasn't originally, and doesn't need to be now, this box will be nearly oil-tight (coolant spray tight by implication) when assembled.  The panel has a foam neoprene seal rather than an o-ring which is the only reason I say, "nearly".  The original cable glands appear to be re-usable, and will get some sealant on their threads... this time.  The new switch and pilot lamp will be oil-tight models, with a silicone rubber boot on the switch.

 Because that's how I roll.

More as it happens.

 ~≈{👁}≈~