Messages

341

Mach4 General Discussion / Re: Backlash not applied during manual JOG?

« on: January 20, 2016, 07:00:32 PM »

There needs to be a mention of what backlash comp can and can't do. Like a manual machinist it can take out the backlash that happens when an axis reverses. Like a manual machinist it can't allow you to climb mill no matter how careful it is. We had an acme screw Spindle Wizard knee mill that used a spring to turn a second nut slightly eliminating the backlash. It climb milled with no problem ever. The down side was that the considerable friction this introduced meant it was limited to 40 ipm.

342

General Mach Discussion / Re: Creating G-Code

« on: January 19, 2016, 10:26:54 PM »

Take a look at CamBam too. $150 and 40 sessions free before you buy. Software is the Personal in PC so you may find a program every raves about not to be to liking. I'm like that with Autocad, use it almost every day for 15 years and I still hate that program!  CamBam user forum is absolutely top notch too.

343

General Mach Discussion / Re: VFD Signal Issues

« on: January 14, 2016, 09:32:19 PM »

If the shielded cable to the spindle is attached to ground at the inverter end and to the spindle at the other end then you have two paths to ground, one through the cable and the other through the frame of the machine. This is called a ground loop. Since the motor is mounted to the frame you should leave the ground wire connected at the spindle and insulate it from ground at the Vfd end.

344

G-Code, CAD, and CAM discussions / Re: How can i use Mach3 to control a robotic arm?

« on: January 13, 2016, 02:59:53 PM »

I was not impressed by the video of a robot running Mach 3. If Mach 3 had the ability to calculate say a straight line move involving 6 axis and you simple programmed move A to B along this line then it would be feasible.  If you have the knowledge to do the calculations then you wouldn't need Mach 3 in the first place.  Clearly these solutions have been aound for a long time. In most cases you don't need real time processing power. You precalculate all the moves and stream a bunch of bits at whatever rate you want for each path. Memory is no longer a problem either. So think of a 16 bit word as 8 axis of step and direction. Build a spreadsheet with the kinematic equations and run it repeatedly calculating step and direction saving it as a stream of words out a parallel port right to the stepper or servo drives. Complex motion performed very quickly.

345

Show"N"Tell ( What you have made with your CNC machine.) / Re: Threading

« on: January 08, 2016, 06:55:09 PM »

Thread milling is often done from the bottom up. That way you aren't machining down into a pile of chips.

346

General Mach Discussion / Re: Taig Mill Questions

« on: January 03, 2016, 09:36:18 PM »

Sounds like your power supply isn't keeping up. Monitor the power supply voltage during a move with both axis. If it is a switcher it likely be the problem. A linear supply is actually better for driving steppers as they can handle brief overloads better and the large filter caps absorb the back emf better when motors decelerate.

347

General Mach Discussion / Mach 3 and a Stepper Spindle

« on: January 03, 2016, 10:03:55 AM »

I have Mach 3 running my homebuilt mill and I have added a HF lathe bed, headstock and tailstock ala Tormach . The headstock is driven by a large stepper motor with timing belt reduction and works fine as a 4th axis.  It reliably positions and runs the spindle at 600 rpm. However I'd like to be able to run it as a lathe with the stepper running continuously, as I have a Tormach QC Tool Post mounted behind the mill spindle.  However my set up is a Xulifeng USB motion card with 4 axis and supports only a pwm spindle.  Mach 3 supports a stepper or servo spindle using step and direction, however I can't see a way to make the outputs from Mach 3 use the 4th axis outputs of the Xuifeng card as the spindle.  Anyone know how I might do this?  Alternately I am thinking to add a pulse generator to generate spindle speeds and put an encoder on the spindle for threading.

At this point I am so close, and so far!

348

Mach4 General Discussion / Re: Backlash not applied during manual JOG?

« on: January 01, 2016, 11:13:15 PM »

I don't think any CNC applies backlash comp for manual moves. When you run a manual machine you always deal with the backlash by approaching a point always from the same direction or by cranking the other way by the backlash amount. In auto backlash comp occurs because the cnc knows to keep the tool on the path. There is no path when jogging, so know way to know what should be done.

349

Show"N"Tell ( Your Machines) / Re: I messed up with my new bench: EMF

« on: December 28, 2015, 07:49:17 AM »

Mogal,
I hate to say it but you have pretty much broken all the rules regarding electrical noise. First is non-metallic backplane, that doesn't provide a good ground plane. Second the signal cables should all be shielded cables. Third all components should be oriented so that signal and power wires can be routed away from each other. Mounting all 3 drives vertical would have helped routing, and then the heat sinks would work properly. Vertical heatsinks generate a flow of cooling air as warmed air rises. Experience will let you recognize a mistake, when you make it again.

350

General Mach Discussion / Re: limit swith vibration

« on: December 27, 2015, 03:10:11 PM »

You are of course right, but it is really difficult to build a switch with a long travel and accurate activation point. So they tend towards being one or the other, not both.