Messages

261

General Mach Discussion / Re: Plasma cutting with a MIG welder

« on: October 16, 2012, 10:22:22 AM »

You can't do that. A plasma cutter uses a high voltage to initiate the arc (about 300V open circuit voltage) and delivers a constant current. A MIG welder has a much lower open circuit voltage and is a constant voltage power supply.

262

General Mach Discussion / Re: Accuracy of Homing Devices? Pro's and Con's of Different Sensors

« on: October 15, 2012, 09:49:55 PM »

No matter what type of sensor or switch you use it will not be super accurate all by itself. For really accurate homing it is best to use a combination of a home sensor/switch and an index pulse on the axis motor itself. The home sensor/switch and the index pulse are seen at the same time the controller considers this 'home'. Since the index pulse is based on the angle of the axis motor itself it is very accurate.

I recently stumbled across this powerful statement and was wondering how one accomplishes "an index pulse on the axis motor itself" and if it's possible on a regular stepper motor without a shaft encoder.  I'm intrigued by this concept and would like to learn more.

Anyone have further info on the matter or links?

Thanks!

You must have an encoder on the motor for the described homing process to work. As Rich and Terry have said though on a typical machine tool really accurate homing does not mean a whole lot. Think of how you use a mill, you clamp a piece of stock on the table, indicate to the edges of the stock to set your part zero and then start machining. Having a super accurate home has no bearing on where your stock is. If you have a machine set up to run only one part, and if you never crash into the fixturing or otherwise disturb it than you might be able to home and then offset to your fixture. I bet most guys would still indicate to the fixture though to make sure nothing had happened to throw things off.

263

SmoothStepper USB / Re: Trouble with smooth stepper

« on: October 13, 2012, 12:47:26 PM »

I'm not sure about that Hood. I'll be talking to Greg today so I'll ask him

264

SmoothStepper USB / Re: Trouble with smooth stepper

« on: October 13, 2012, 12:06:47 PM »

A few stray pulses from a VFD will not effect the RPM reading much but could effect the threading timing. You can try adding some noise filtering to the index pulse in the SS config screen. You might also want to post this on the Warp9 forum so Greg from Warp9 will be sure to see it.

265

SmoothStepper USB / Re: Trouble with smooth stepper

« on: October 13, 2012, 10:59:00 AM »

Arch, I forgot that the newest SmoothStepper plug-in included the ability to use a standard encoder for the spindle. So using the A or B channel should work fine. Encoder signals can get swamped with noise from the spindle motor. I had this happen when I added a VFD and three phase motor to a piece of test equipment that was previously working fine. The noise from the motor/VFD was enough to confuse the National Instruments controller. The solution was to fit a differential encoder which was powered by an isolated power supply.

If you have access to an oscilloscope you can check the quality of the signal getting to the SmoothStepper. This will let you know if noise is an issue.

The other things to look for are how stable your spindle speed is and how much you are trying to cut in a single pass. You can start up the spindle and watch the RPM display in Mach while you apply some load. Is it easy to slow the spindle down? Then take a really light threading pass, just enough to scratch the surface. Does the pitch stay consistent?

266

SmoothStepper USB / Re: Trouble with smooth stepper

« on: October 12, 2012, 05:30:24 PM »

Mach expects one single pulse per revolution of the spindle, which is what the SmoothStepper also expects. You can try just using the Z from your encoder (which provides 1 pulse per revolution.)

267

SmoothStepper USB / Re: Newbie: issues regarding limits, e-stop and backlash comp

« on: October 10, 2012, 10:26:01 AM »

Start with a brand new profile. I've seen a corrupt profile do all sorts of strang things.

268

General Mach Discussion / Re: Mach3 R3.043.022 to R3.043.066 license stopped working.

« on: October 10, 2012, 10:24:07 AM »

I really hate hearing about people getting scammed. Unfortunately it happens all too often. I had a guy call me the other day that bought an imported 'high speed' spindle and it worked fine until you tried to get it to actually go to its highest advertised speed, it promptly burned up. He called the outfit that sells it and got the response, "why you want to go so fast?"

It sucks all the way around, for the guy who got scammed, for the guys at Mach, and for the guys running legit business who lost a sale to the scammers.

269

Promote and discuss your product / Special Gecko Stepper driver sale

« on: October 08, 2012, 12:28:34 PM »

I wanted to celebrate the fact that we are now carrying the full line of Gecko stepper drives. We already offer really, really good prices but I though we would sweeten the pot a little more by offering an additional 10% off our already low prices on Gecko drives.

When checking out use coupon code: GeckoSale , at checkout to receive the discount. This sale is in effect for the next 30 days. Please feel free to tell your friends about the sale and pass along the coupon code.

Thanks!

270

SmoothStepper USB / Re: Newbie: issues regarding limits, e-stop and backlash comp

« on: October 07, 2012, 07:35:46 PM »

OK, I was just confused by the reference to the G540. Anyhow, I've never seen the symptom you are describing. One thing I would do it not power the BOB by the USB port connection, use a small 5V power supply instead. If the BOB is putting out any noise on the 5V line and you are using the UBS power it could feed the noise back into your PC. Also many PCs cannot provide much current on the UBS ports so using an external power supply or powered USB hub for the SmoothStepper.

Second wire up only one switch and configure it as a single input (say X home) in Mach. How does the machine work with it set up as a home switch? If that works OK, change Mach so that switch is a single limit switch (say X++) and disable it as the home switch. How does this work?

The users manual for your Chinese BOB is so poorly written there is not telling how it actually works. Maybe the BOB asserts an EStop when a limit is seen. Since the BOB expects a lot of enable signals from Mach (to enable each stepper drive) maybe it disables all of the drives at once when a limit is hit which could cause a huge power supply spike.