My Cnc Conversion

[chevydyl]

Today I got my pc with mach3 to talk through my cnc breakout board to my allen bradley servo drives/motors, success I say. Next up is making the pulleys fit and custom motor mounts. Oh yeah, and 8 read a letter from my work saying we are all getting a cut in pay so the new set of ballscrews are off my shopping list for now. Gotta love oilfield work huh. I'm relatively safe being an operator as they still need me, just for alot less money.

 

[chevydyl]

Made an adaptor to fit the tiny 16t motor pulley to the motors 19mm shaft, I also bored the pulley for the screw to fit, the adaptor still has a couple ops left, the big pulley also has a few ops, I need to make a flanged bushing that will Bolt to the pulley and be keyed to the screw to ensure it rotates with no backlash. The drive ratio is 3:1, so I will have about 12lb-ft of torque on the screw. Also it has the ability to rapid at like 330ipm, not that a knee mill should be moving that fast but it could lol. The servos are 2.8hp/2kw from Allen Bradley. The tooth profile is Gates GT2, 5mm pitch, 15mm wide

 

[chevydyl]

Since my ball screws will arrive tomorrow, it was necessary to redo the pulley adapter, so I faced the hub off the pulley, and bored it to like .486, the motor shaft adapter was made much the same as the last one, the last one was for demonstration purpose only, two set screws will be torqued to the motors keyway, no actual key, broach a blind hole anyone? The pulley will be pinned at the face to the adapter, on the tangent of the two diameters. Then a shcs with a custom washer will keep the dowel pin in, and the pulley from being able to move. All the fit ups are pretty darn good, in the picture I haven't quite driven the pulley all the way on yet, but the pulley face and adapter face will be flush.

 

[chevydyl]

Ball screws....check.
Problems....check. lol
The issue is the x screw isn't quite long enough, on the float bearing side, the bearing journal isnt in the bearing, so I will make an extention, before anyone cackles about that, Prototrak actually makes screw extentions for oddball tables, like a 48inch screw on a 49inch table. I also had to machine a 32tpi bastard nut, screw has a .735 minor and .777 major for preload of the left bearings, I bored a .740 hole in some steel and started cutting threads until the screw fit, nice wiggle free fit Also the screw extention may be fruitless once the motor mounts arrive. I think it shifts the left bearing under the table a little, which would extend the right end of the screw where it needs to be....we will see. Any way here's a couple pics. Oh yeah, and when I turn the screws, that table moves, no detectable backlash, very happy for $500 ground screws, I got a major discount, they were new takeout screws off new machines, one an anilam the other an acu-rite

 

[chevydyl]

One more piece to the puzzle, these come off an older Bridgeport EZ-TRAK cnc machine, where Southwestern Industries made a ProtoTRAK control to bridgies specs, not my favorite flavor of motor mount style, the newer ProtoTRAK mounts look a little nicer, they kick the Y motor 40deg to the right, X mount is different looking also, little cleaner but for $300 shipped($40 priority, 2 boxes) they were all that I was able to find. Elrod machine wanted 965 plus shipping for JUST the castings and covers, these used ones at least include the correct 7204 AC bearings, and if I find that one pair is no Bueno I have a new pair, 30 bucks, SKF 7204 BECBP, retail 64 ea, so I did good on those too.

 

[chevydyl]

The motor brackets are installed, I need to turn a couple screw extensions for both screws, and a bearing bushing for the x screw. Then some motor spacer/adapters out of 1x4 alum sorry the shop and the machine is in complete disarray because of this step in my conversion. I can use the mill at this point but not accurately because the handles and dial don't fit without an extension

 

[Firestopper]

chevydyl, your servo conversion resembles the one on the Lagun. Looks like a fair amount of work too. Will you be using a Proto Trak and lastly 2 or 3 axis?
Looking good!

 

[chevydyl]

The motor mounts are from a bridgeport ez trak machine, I will be using a pc based controller, mach3, it's diy, 2 axis for now. The breakout board is a cnc4pc gem the C62 24volt, and I'm using allen bradley AC servos and drives. 1000w each. PLC type wiring terminal blocks.

 

[chevydyl]

Got the bearing bushing done last night, and started drawing out the screw extentions. Today the y axis belt and pulleys showed up, also yesterday I spent $20 on shcs for both motor mounts, I also have to do a little clearance work on the housings to clear the screw pulleys, Prototrak uses 44t driven pulleys and I got 48t, slightly larger diameter. Prototrak is 2.75:1 I'm using 3:1
Pulleys and belt were $70 from stock drive

 

[chevydyl]

Screw extention for x screw