Monday, March 20, 2017

Odds and Ends - Shop Edition

Saturday, I was able to get the oiling system for the CNC mill running despite the battery issues I talked about Thursday.  It didn't go as easily as expected.  I found a wall wart from an old Sound Blaster speaker system that was marked 12V at 4.2A.  Since the highest current I measured was 3.5-ish, I said, "hot diggity - I'm there".  Not quite.  The pump ran for a solid 4 or 5 minutes with oil never seen moving in the tubes.  Since the 35AH battery wasn't ready, it was on the CBA for the second discharge test, the only thing I had was my Gooloo jump starter.  The reason I picked this jump starter is that it has a 12V 10A output, enough to run my SHTF ham HF radio for hours.  That output ran the pump, so it's obvious that the basic system is OK, but the pump really sucks some serious current while it gets going and the current I read on the HF ammeter is a gross underestimate.

I have a spare PC ATX supply, as commenter matism suggested, and I pressed that into service.  Its 13 Amps is enough current, so it works to get the oil delivered from a dry start in about 4 minutes.  I need to build a case, to keep the power supply dry and add a few niceties like an on/off switch, but it will get the job done.  I don't plan to run the oil under the CNC control; just punch the switch every now and then. 

The 35 AH battery recovered nicely after a couple of cycles.  The first time, I tried to discharge it at C/10 rate (3.5 A) and it failed quickly.  The output was erratic on the CBA.  I lowered the discharge rate to 1.75 (half that or C/20) and ran the battery down to about 30% discharged, then recharged it on my new "good" charger.  The second time, it discharged at the C/10 rate and looked completely normal.  I discharged it to about one third remaining and recharged it. 

The biggest improvement is that the enclosure now closes thanks to some cheap magnets from eBay - 73 cents each including shipping.  I found a piece of half inch angle aluminum I salvaged out of something years ago, drilled some holes for mounting hardware and everything went together.
Closeup of one of the magnets and holders (the extra hole, upper right, is original - just happened to be there but was too high to be usable).
The drawback to these is that they will stop the doors from opening as far as I might need.  I find if I loosen the screws just a tiny bit, they'll stay attached to the extrusion but slide out of place if I want them to.  Perhaps I might improve that a bit with a bit of design and machining.

I took the opportunity to take the tweak I did to fix backlash on the Y-axis and try it on X.  I was able to reduce that from 0.013 to .003.  That's not as good as Y, which came out at .001, but I think it's usable; certainly for now.  That makes X, Y, Z, .003, .001 and .004 respectively. 

I'm working on the coolant system design now, and the option is either flood cooling with a couple of gallons of coolant and a sump pump, or something like the Fog Buster system.  Fog Busters are like mist cooling in that they spray a relatively tiny amount of cooling fluid, but in larger droplets than a mist.  I've read guys saying they have no drain and storage bucket under their mill at all with a mist cooler.  One user I read sprays a tiny amount of kerosene to cool aluminum.  I suppose that's not that different than using WD-40.  The professionals all seem to be using flood cooling, I'm just a bit concerned that this enclosure isn't an aquarium, and I need to do some testing before I'd feel comfortable spraying water around in there. 

Basically, though, it's a fully ready CNC system.  Which means I've been pondering what I might build for my first project on it.  Does this look familiar to you? 
I understand it's hard to visualize from one view, but it's supposed to be a 10/22 receiver with an integrated picatinny rail.  I know there are products like this out there, but what's the fun in that?


  1. Were you thinking 80%, or starting from scratch?

    1. From scratch. It would certainly be a good challenge to figure out all the fixturing and an order of operations. It's a complex little part to me.

    2. Having a lifetime of experience as a woodworker, making stuff from wood and sequencing operations is pretty easy.
      That was/is the hardest thing about metalworking, of which I have little knowledge. What to do, in what order. Feeds and speeds, that is a sort of by the book and look and listen to how the cut and machine is working. Knowing what operation to do first, so the part does not need to be moved and fixtured a jillion times- yikes. The other transition that was interesting is that in woodworking ,usually the material moves through a machine- metal working, mostly, the material is stationary and the machine moves. I guess it is good for the brain to learn new stuff. I just bought a Tig welder- steep new learning curve again! But to be able to glue metal together-how cool is that!

    3. Welding is on my list of things to learn, although it has been for long time. Lately, I've been talking about getting started with a friend via email.

      In addition to not wanting to change the fixture a bunch of times, I want to minimize my tool changes. The way I'm set up now, I have to find a new zero for all the cutters and that's tedious. There are electrical systems that find an edge and work out where "0.0000" is for all three axes, but what I'm reading is that they're not generally as accurate as they need to be.

      Just cutting the Picatinny rail ends up being hard. To cut the slots in the rail I need one bit; to cut the 45 degree tapers angles on the bottoms of the rail I need another cutter (or another fixture); to cut the vertical parts of the sides of the rails takes yet another fixture, and that's just getting started. An automatic tool changer and a k-buck in tool holders makes much of the tedious stuff much easier. Which is why companies use them.

      I've never tried a piece like this before and like I used to say about the pieces to build the mill itself, "every part is a puzzle". This is a hard puzzle to me.

  2. Glad to have been able to help twice with your oiling system - the pump and the power supply.