[krakenatwork]

Hi everyone.

I've been contemplating the purchase/build of a CNC mill since I went out of college in 1993 (graduated as a production tech; moved to computer sciences since)... but I didn't have the money, time, etc. I haven't touched a CNC for a long time and never built one. I bought a lathe/mill combo a couple of years ago to get back on track.

I did my homework though (lots of research on the net over a couple of years on and off), and at first I thought about modifying my Smithy 3-in-one (please, don't throw rocks at me! ) following this guy's experience, and I planned (what I think is) a good project using Gecko drives, PMDX breaker board, ANTEK power supply, nook ballscrews, Mach3, etc. The price tag is pretty hefty though.

I then pondered at the idea of having a dedicated mill; I then planned for an X3 conversion according to this other guy's pages which were quite helpful. The complete purchase of a grizzly/sieg/whatever plus all the parts is less than the cost of custom modding the Smithy and in the end it would have almost the same range of movements.

There are my plans:

Manuf.      Description                         #   un. cost    ref
Sieg        X3L	6X27 mill/drill		            1  1300 1300	https://www.machinetoolswarehouse.com/xcart/product.php?productid=16280&cat=308&page=1
Cncfusion	Small mill deluxe	 CNC kit premium ballscrews + CR G540 option
                                                1	959	959	    http://www.cncfusion.com/smallmill1.html
Gecko	    G540	CNC driver/breaker board	1	250	250	    http://kelinginc.net/GeckorDriver.html
Keling	    KL23H2100-35-4B	381oz Stepper	    2	49	98      http://kelinginc.net/NEMA23Motor.html
Keling	    KL34H295-43-8A	906oz Stepper	    1	99	99      http://kelinginc.net/NEMA34Motor.html
Keling	    KL-350-48	48VDC power supply	    1	50	50      http://kelinginc.net/SwitchingPowerSupply.html
Mach3	    Mach3	CNC software	            1	149	149     http://kelinginc.net/CNCController.html
CamBam	    CamBam + 	CAM software	        1	149	149     http://www.cambam.co.uk/shop/
        Other stuff; cable, e-stop, connectors  1	200	200     Grossly Overstimated
Optional: pendant
Ultimarc	I-PAC2	I-PAC2 usb keyboard controller
                                                1	39	39      http://www.ultimarc.com/ipac1.html
Ultimarc	U-TRAK+USB	U-TRAK USB trackball	1	93	93      http://www.ultimarc.com/trackball.html
        Box, switches & lights                  1	150	150     Grossly overstimated

I already use Alibre Design Express. Maybe not the best, but it works well for the price. This would be a hobby build; not a production machine. So all in all, what I'd like to know:

- Am I completely nuts? (did I miss a flagrant point somewhere)
- How would the Alibre/Cambam/Mach3 bundle work together? (I read they should work together; anybody could please confirm this?)

Since I can (and like to) read, if this has all been answered before, please don't shoot me in flames (I've been using the "search" buttons a lot with more or less luck for a long time) but instead please tell me what should I read to get the answers.

Thanks.

[krakenatwork]

Bump.

Uh. Have I opened the thread on the wrong forum? Should I post parts of this in other forums in CNCZone?

I'm open to suggestions; If I'm screwing all up I'd like to know, if I'm on the right track I'd like to know too.

[doorknob]

While I'm not sure that I can address your questions, I believe that most discussions of mills in that class show up in the Benchtop Machines category:

Benchtop Machines - CNCzone.com-The Largest Machinist Community on the net!

[krakenatwork]

Thanks doorknob!

I'll follow your advice and post there.

Bye!

While I'm not sure that I can address your questions, I believe that most discussions of mills in that class show up in the Benchtop Machines category:

Benchtop Machines - CNCzone.com-The Largest Machinist Community on the net!

[krakenatwork]

After a long time searching the 'net, reading around & letting the ideas sit, I came out with a new, hopefully cleaner, system. I chose a CNC4PC C11G breakout board (which seems popular and has a few very useful bells and whistles), a C16 optical limit switch board (and switches) and a C3 pulse generator, to be used as a spindle tachometer/index - I'd like to use the rigid tapping feature someday.

I followed Hoss's and Keling's adventures in CNCing, and opted for 570 oz-in 50V steppers for x, y and Z axis. They're 50V/5A motors and the G540 wouldn't quite do, so 3 G203V are in instead.

I don't know which power supply to get, though (input gladly appreciated): KL-5020: 50V/20A (overkill, higher cost but room left for a 4th axis), or the KL-600-48: 48V/12.5A (lower cost, but 3X5A steppers or 4X5A if I get there might be asking too much for this unit).

I definitely want forward/reverse controlled from Mach3 - safely - so I already bought an used KBCC-125R, which has a 3/4hp resistor on it, I'd have to get a 1HP resistor to fit the 1HP motor on the GO704 (3/4HP for this unit is 0.015 ohm). I'll also need a few more thingies, like a small (1/2A) 12V power supply (for C11G's variable voltage output, used to control the speed on the KBCC-125R), a small 5V power supply in the 2-3A range (powering the C11G, C3 and C16 boards), a relay (I need 2 mechanical relays to control the 3 "directions": FWD, REV and BRAKE). The C11G's solid-state relay is not useable in DC circuits, so an external relay is needed. Of course, I'll need an emergency stop (already got 2 of these) and other things.

Below is the circuit I planned; I dunno if I could use pin 1 (as I won't use the solid-state relay), that'd let 2 outputs available for future use (e.g: 4th axis). Please let me know if I'm on the right track, or headed straight into a wall.

https://lh5.googleusercontent.com/-6.../bf-20-cnc.png

[krakenatwork]

After a long time searching the 'net, reading around & letting the ideas sit, I came out with a new, hopefully cleaner, system. I chose a CNC4PC C11G breakout board (which seems popular and has a few very useful bells and whistles), a CNC4PC C16 optical limit switch board (and switches) and a CNC4PC C3 pulse generator, to be used as a spindle tachometer/index - I'd like to use the rigid tapping feature someday.

By the way I tried updating a long-dead thread I started over a year ago (ok maybe 2 years ago), but since it wasn't in the proper forum, nobody seemed to even look at it. Sorry for double-posting, although this post is beefier than the other one.

I followed Hoss's and Keling's adventures in CNCing, and opted for 570 oz-in 50V steppers for x, y and Z axis. They're 50V/5A motors and the G540 wouldn't quite do, so 3 G203V are in instead.

I don't know which power supply to get, though (input gladly appreciated): KL-5020: 50V/20A (overkill, higher cost but room left for a 4th axis), or the KL-600-48: 48V/12.5A (lower cost, but 3X5A steppers or 4X5A if I get there might be asking too much for this unit).

I definitely want forward/reverse controlled from Mach3 - safely - so I already bought an used KBCC-125R, which has a 3/4hp resistor on it, I'd have to get a 1HP resistor to fit the 1HP motor on the GO704 (3/4HP for this unit is 0.015 ohm). I'll also need a few more thingies, like a small (1/2A) 12V power supply (for C11G's variable voltage output, used to control the speed on the KBCC-125R), a small 5V power supply in the 2-3A range (powering the C11G, C3 and C16 boards), a relay (I need 2 mechanical relays to control the 3 "directions": FWD, REV and BRAKE). The C11G's solid-state relay is not useable in DC circuits, so an external relay is needed. Of course, I'll need an emergency stop (already got 2 of these) and other things.

Since the GO704's motor doesn't show external leads to the field coil, I wonder if the KBCC-125R would work correctly (still has some reading to do) in "open-loop": Obviously no external field coil connection, I don't have an external tach connected to the KBCC either, although I'll have an electronic tach (CNC4PC C3 board) connected to the computer through the C11 board. I'll look at threadmill motors on fleebay just in case my motors pours the magic smoke out

I just read that I could/should also add the variable signal I send to P2 over to F- also, any comments?)

Below is the circuit I planned; I dunno if I could use pin 1 (as I won't use the solid-state relay), that'd let 2 outputs available for future use (e.g: 4th axis). Please let me know if I'm on the right track, or headed straight into a wall.

https://lh5.googleusercontent.com/-6.../bf-20-cnc.png

Thanks for the help.

[109jb]

Can't comment on most of the wiring because your components are different, but it is not recommended to daisy chain the power wires from the power supply to the stepper drivers. It is recommended to have a wire direct from PS to the driver for each driver installed.

[krakenatwork]

Thanks 109jb!

This is the logic wiring, your point is noted though. Anyway with the way I thought I'd build the control box, it was already headed that way. Now I'll make doubly certain :-)

Have I posted this in the proper forum? I just don't know where to post this kind of questions, I've been on other forums and people were quite more chattier; here I've got a hard time adjusting and making contacts.

Bye!

Bye!

[krakenatwork]

By the way, I looked at 7v/1000rpm or 50v/1000rpm DC tachs (the KBCC accepts both without too much trouble, other voltage range/rpm need a little bit of tinkering) and it looks like they're made of 100% pure unobtainium; even the smallest ones are in the 300$+ range on fleebay. (apart from one that I've seen that might work and sells for 155$ which I find quite steep for an used DC motor put in reverse)

I figured; it should be possible to hook up a PIC microcontroller to an optocoupler ("rpm sensor" built from a LED and a phototransistor), get the pulse rate, compute the output into a PWM duty cycle and filter the thing out; the result would be a DC voltage that could be hooked up to the KBCC's tach terminal, right?

I've got a PIC programmer and a few PIC models lying around... It's the DC filter that bugs me; I haven't designed any analog circuits in ages. Last one was a speed control for an R/C car, about 20years ago.

[109jb]

Circular plate with holes mounted to spindle, optical sensor, one input on the BOB and you can have a tach on the computer screen. Otherwise, for the G0704, the stock tach I believe is almost completely electrically separate from the stock motor controller and it already reads a circular plate with holes mounted to the spindle using an optical sensor. I believe the only electrically common part with the motor controller is the switch which turns on both the tach and the motor controller.

[krakenatwork]

Hi JB.

Thanks again for your reply.

I'll be using a CNC4PC C3 tach/index to get the RPM on-screen (and hopefully to add rigid tapping ability to the mill).

I was referring to the KBCC's closed-loop regulation, which uses either a field coil with field wires available on the motor - not shunted to the armature like the G0704's motor - or an external tach connected to the reversing board and the F- connector on the KBCC, to help regulate the motor speed to within 1% of the commanded speed, so that, load or no load, the motor runs at the same speed. An external field coil would also help the low-end torque compared to a parallel-shunt motor, the KBCC would adjust the current in response to the motor load.

Can I run the KBCC in open-loop? that would make things a lot simpler.

Thanks.

[krakenatwork]

Ah-ha!

Finally found this thread where they say one can use a 24V DC motor (high quality, like Maxon motors). Found one for 35$ on fleebay, way better than fiddling around with my uncertain microelectronics or 150$ ready-made tachs.

[krakenatwork]

So as it goes, improved circuit, with charge pump enable for the KBCC and DC tach:

https://lh4.googleusercontent.com/-u...nc+-enable.png

[krakenatwork]

Improved diagram, with charge pump EN for the KBCC and DC tach:

graph on picasa

[krakenatwork]

Long time not updating this thread, I took the time to read much on the subject.

I bought a KBCC-125R and I'm about to buy a 7V/1000RPM DC tach for the controller feedback; this way I'll be able to safely get forward/reverse ability on the mill.

Please comment the diagram below:

https://lh4.googleusercontent.com/-u...nc+-enable.png

[krakenatwork]

Got a used SERVO TEK SA-757A-2 tach for a-bit-too-much on fleebay. It's a 7V/1000RPM so it's a direct matched with the KBCC-125R.

One thing solved. That way the motor will be regulated to within 1% of the requested RPM (by the KBCC, not by software that is), load or no load.

New diagram version w/DPDT tach reverser, as per KBCC's documentation.
https://lh6.googleusercontent.com/-F...nable-tach.png

Why are IMG tags not working in some threads?

[krakenatwork]

Added some missing wires (one can play the "7 differences" game with the previous diagram :-) ) and then changed some signals to prevent the need for one more channel.

https://lh4.googleusercontent.com/-7...ble-tach-2.png

Still wonder why the IMG tags are not working in this thread though...

Will I need a diode between the relay and the KBCC to prevent a (really transient) reverse polarity applied to the tach terminal? It's only a few milliamps, and at this motor's speed probably much less than 20V anyway. The KBCC's documentation isn't quite clear on this.

I'd be really glad to get somebody's help on these. Tried to search the forums, but the "search" feature often retuns links that are far off from the hit (esp. in the very long threads, spanning over 100 pages), so even if I have found some info on KBCCs, I think much remains to be found.

[krakenatwork]

Out of pure luck, while searching again for info on the KBCC's (serendipity rules!), I stumbled upon a thread by Hoss (well, it was in one of his threads and I think he was the one saying that) where he said the power supply has to be roughly able to push 2/3 the sum of all the stepper's current. Since I'll have 3X5A motors, that leaves :

(3*5+x)*2/3= 12.5 --> x=3.75amps

So that either leaves room for the times all motors would be pulling more amps, or space for a smaller 50V stepper for the 4th axis (can't find any on Keling, though, so I might end up having to buy another, lower voltage, PSU, stepper and gecko drive for the 4th axis.)

[krakenatwork]

Okay, so since the power supply required voltage is equal to the square root of the inductance in milihenrys times 32 (V=32*sqrt(L) ), a 50V stepper has an inductance of around 2.5 milihenrys.

Keling's KL23H2100-35-4B (3.5A/381oz/in) is in the ballpark for a 4th axis.

Formula taken from here: gecko

I've compared this computation with the specs of the KL32h2100-50-4b stepper, which I know it's a "50V" stepper.

I'll be leaving self-notes in this thread to help people searching for information to get a "one-stop shop".

[krakenatwork]

More info added to the schematic.

schematic on picasa

Still have to add the (optional) 4th axis on it though.

The only point that seems to be to resolve is twofold:

a) Is the tach inverting relay OK?
b) As an added safety, do I need to add a diode in the DC tach circuit?