Messages

31

General Mach Discussion / Re: Myford Super 7 - adding ball screws

« on: September 07, 2012, 03:13:09 PM »

Take a look at this thread for info on how to make a zero-backlash nut out of acetal for a standard lead screw.

I used these methods to make a nut for the cross slide on my Clausing 5914 and it worked really well. It would have been very hard to replace that nut with a ballscrew nut as the space is limiited, you'll seen pictures of the nut I made towards the end of the thread.

http://bbs.homeshopmachinist.net/threads/43645-Making-Acetal-leadscrew-nuts-the-easy-way?highlight=acetal

Paul T.
www.springtest.com

32

General Mach Discussion / Re: Lathe CNC conversion 1334

« on: August 30, 2012, 04:16:20 PM »

I meant to add a little more on motor sizes.

For the cross screw I wanted a motor that wasn't too big so it wouldn't be too much in the way for manual use, I made a motor bracket that clamps on the cross screw bearing housing just behind the handle. The stock handle is still in the same place but the graduated dial got replaced by a timing belt pulley for the motor drive.

However I put graduated marks on this pulley so that for manual work I still have it as a reference.

The bracket is slotted for the motor so it only takes about 20 seconds to slack the drive belt so I can use the cross slide manually.

I used the larger 400 oz-in size 23 motor that is sold on Geckodrive.com for this, its a nice combination of pretty good power in a limited size. I geared it at 2:1.

For the Z I used a 1300 oz-in size 34 motor that AutomationDirect.com sells, their STP-MTRH-34127. I liked this motor as it has a low inductance for its size, I wanted this so I could run both motors on a 48 volt supply.

Both these motors will work well with GeckoDrive stepper drivers, I'm using the G201x ones.

I need to make some steel parts that need heavy drilling so that's why I went with a pretty strong motor on the Z (lead) screw, fortunately I don't need much power on the cross-slide so the smaller motor works fine.

The Z drive uses the threading nuts on the lead screw, which means its also very quick to release those nuts so I can use feed handle on the carriage for manual work.

I used needle bearing based thrust washers (McMaster.com) to get rid of all the end to end slop in the leadscrew itself and the threading nuts on machine were never used much so the backlash on Z is actually not too bad even just with this stock lead screw, its fine for the work I need to do.

Paul T.
www.springtest.com

33

General Mach Discussion / Re: Lathe CNC conversion 1334

« on: August 30, 2012, 03:59:42 PM »

I'd go to cnczone.com and take a look at lathe conversions there, there's a lot of well documented conversions there.

I used those examples to design the brackets for my 12" Clausing 5914, I liked a retro-fit there where the guy used the original lead screws which made it real easy to switch between manual and CNC modes, I need this as sometimes I need to make quick and dirty parts and the CNC parts I need to make are pretty simple so I can live without zero backlash lead screws.

However I'm making an acetal based non-zero backlash lead screw for the cross-slide screw and so far that's working out well.

If interested take a look at:

Its reallly cheap and pretty easy way to make a zero backlash leadscrew in very limited space, I could't fit a ballscrew nut in that stock location:

http://bbs.homeshopmachinist.net/threads/43645-Making-Acetal-leadscrew-nuts-the-easy-way/page15?highlight=acetal

Paul T.
www.springtest.com

34

General Mach Discussion / Re: Possible new project pending feedback on LazyCam software

« on: August 17, 2012, 05:37:43 PM »

SheetCAM would work very well for this type of machine. I use it heavily, its solid and is well supported.

35

General Mach Discussion / Re: kennametal .5" indexable mill cutter

« on: March 22, 2012, 05:44:34 PM »

Jonny, the only indexible endmills you'll be able to find at .5" and smaller usually only use one insert, I don't think they would work well for you. Most serious CNC shops don't move to an indexible endmill until they need 3/4" size or bigger, except for face milling.

For aluminum a 3 flute solid carbide endmill would be your best bet, I get good results with the ones from www.maritool.com .

Also, particularly on smaller machines, a 1/2" endmill is pretty big, you likely don't have the HP to make full use of that and carbide endmills don't last as long when they aren't run in their best range for their size. I'd stay at 3/8" or smaller when you can, with the added benefit that these endmills are cheaper.

You shouldn't be having problems with nicking the corners, are your speeds and feeds set correctly and are the chips get cleared?

Re-cutting of chips is something that will kill a carbide endmill.

Good luck-

Paul T.
www.power-t.com

36

General Mach Discussion / Re: Can Ipac only be used via ps2 with keygrabber?

« on: March 16, 2012, 11:47:47 AM »

TripleBlack, thanks for that info. I also had the noise problem on my original Ipac, putting a 0.1uf capacitor on each input to ground fixed it, they should just put those on the iPac in the first place, or a least have the holes on the board so its easier to put on those parts.

37

General Mach Discussion / Re: Can Ipac only be used via ps2 with keygrabber?

« on: March 14, 2012, 07:46:10 PM »

Don-

I'm also facing this problem. I bought a new Ipac2 and need to use KeyGrabber to program it.

But even on an XP machine using the PS2 port, I still get a CRC error.

Where you ever able to get your Ipac2 programmed from KeyGrabber, and if so how did you do it?

Thanks,

Paul T.

38

General Mach Discussion / Re: switch mode or linear?

« on: March 14, 2012, 06:05:59 PM »

I use a 800 watt 48 volt switching supply to power the 3 size 42 stepper motors on my BP clone mill.

I put a large cap on its output as I was concerned about too much voltage rise from the "back driving" of the supply that occurs when the motors are decelerating.

Its been working fine for over 6 years now. I don't believe that putting a large cap on a switcher will cause a huge input current inrush as most switchers have a maximum output current they liimit themselves to at high load, and while the cap charges the supply will be at this max current but its not a huge current spike, in my case its likely the current required to supply the 800 watts the supply is capable of generating.

I guess its possible that a really cheap switcher might have problems with a big cap but I doubt that any half decent switcher will have this problem.

Paul T.
www.power-t.com

39

General Mach Discussion / Re: Machine Limits without limit switches? to stop me crashing

« on: December 28, 2011, 12:50:38 PM »

To be fully candid, you can't really count on Mach's software based limits to keep you from hitting your physical end limits, there's just too many ways for those limits to get mis-set or ignored.

Its not that hard to put physical limit switches on your machine, take the time to do that, it will definetly pay in the long run.

Get lever switches that are normally closed and wire then in a loop from switch to switch. This way if any of your wiring or connections fail you know right away and failure doesn't disable your limit switch system. This is also the easiest limit system to setup and its simplicity has advantages.

Lever switches are cheap and easy to mount and get set up, just machine some small blocks that mount on the other surface that actuate the levers.

Paul T.

40

General Mach Discussion / Re: Off the shelf servo controller for Mach3

« on: July 27, 2010, 12:59:16 PM »

Servo motor's are pretty simple, as long as the encoder isn't flakey I'd be surprised your problems are coming from the motor, more likely its the servo drive and/or PC interface. If the encoders are flakey they can probably be replaced.

You may be able to keep your current servos and switch to Gecko servo drives and a breakout board like the ones from http://campbelldesigns.net/ or one of the serveral other breakout card vendors. I use a Campbell board and its worked well for me.

For the speeds you described steppers would work also, but it would be more expensive that way, and more work also to replace the motors. You'd also have to make sure your current supply voltage will work with the steppers you chose.

Paul T.