Messages

451

General Mach Discussion / Re: dying motor(s)?

« on: January 08, 2015, 09:58:19 PM »

On a stepper notchy is good smooth is bad. Notchy is because the permanent magnets line up with the poles on the stator. So a smooth stepper has probably gotten demagnetized. That happens if you drive them with too much current, or overheat them.

452

General Mach Discussion / Re: Fixture Save... questions?

« on: December 25, 2014, 07:22:27 PM »

Actually Fixture Save is intended to save the locations of multiple fixtures used typically to machine multiples of a part at different locations.  This elimininates needing to create g-code for each location.  So lets say you have 3 vises and you are making a large number of parts.  So you place stock in each vise, and the program machines one with the first tool.  A fixture change is called for vise 2 and you can rerun the same code to machine that part.  Call a fixture change and machine the piece in vise 3.  Change the tool, call fixture 1 again and machine the next step.

So unless this is the kind of machining you want to do you won't find many people using this.

453

Tangent Corner / Re: Motor question

« on: December 23, 2014, 07:19:27 AM »

The three wires to the motor are power to the motor. The controller board would have to have other wires or connectors to make connection to the rest of the machine, as well as wires to supply AC to the board. What you really need though is the wiring diagram for the machine it came out of. That would tell a lot.

454

Tangent Corner / Re: Motor question

« on: December 21, 2014, 08:05:11 PM »

Edit:
The voltage and hertz range is close enough it would probably work fine with any commercial inverter.

455

Tangent Corner / Re: Motor question

« on: December 21, 2014, 08:02:57 PM »

That is a 195 volt 3 phase motor and the controller is an inverter that puts out up to 310hz as the nameplate indicates.  So you have to use that inverter with it.  The question then becomes how is the inverter controlled?  It is likely that it uses digital inputs to select functions hard coded into the controller, not an analog signal from another controller which would have made it useful.  That is how the laundromat washers I have worked on did it.

456

General Mach Discussion / Re: Noise Problem on a large machine

« on: November 07, 2014, 06:42:43 PM »

One thing for sure, if an earth ground appears to fix your problem you haven't found the problem! I always consider this solution to be hocus pocus and possibly hiding a problem that could get you killed.  A large part of the problem is that electronic engineers don't seem to understand that electronic signal grounding and power grounding are completely different.  So they go looking for the mythical 'clean ground', which is what that earth ground is supposed to supply.  Nothing could be further from the truth.

In power grounding the purpose is to ensure that no two adjacent grounded points ever have a voltage difference that can kill.  Everything electrical leaks power to ground, all the time.  When things go bad, like a motor winding going to ground that 'leakage' may be thousands of amperes!  So by connecting everything together creating as many 'ground loops' as you possibly can you ensure that a very small voltage difference is all you see from that railing you have in one hand the handle you have in the other.

In electronic signal grounding you simply want no current flowing on the shielding because when done properly one one end is ever connected to ground.  Hence only the very small currents from signal leakage and induced currents through the air will ever flow through that shield. In order not to have ground loops you MUST check whether devices have ground connections to their cases. The single grounding point works only if no other device ties to ground through the frame of the machine.  If the ground point of the device is already grounded to the frame, insulate the shield from ground at that point, and make sure it is connected to the common ground point only back in the panel.

One reason your problem may happen when you turn the power off not on is because that is when the magnetic field in the contactor coil collapses and created a large back EMF.  You should have a suppressor on the coil in any event.  In the early days of digital meters I fried a few on contactor coils when I hit the stop button!

Opening the contactor to the VFD has a similar effect, an arc is drawn for an instant, and there is a large surge. I suspect the monitor is not going off on low voltage because it happens when you turn other devices off.  So that suggests it is going off due to seeing a high voltage when arcing or a load dump occurs.  I'd check your VGA cable to if it connects the shield to ground at both ends, because that is likely to be the case.

Hope you get your problem sorted quickly.

457

General Mach Discussion / Re: Dynamic feed rate - is it possible

« on: November 06, 2014, 09:12:14 AM »

CamBam has a 40 use trial for free.  Join the newsgroup, its excellent like this one.  You'll learn a lot even if you go with something else.

458

Building or Buying a Wood routing table.. Beginnners guide.. / Re: Working router table, options to increase travel speed ?

« on: November 02, 2014, 06:51:14 PM »

You don't say what voltage power supply you have, and what the drivers are rated for. It is the back EMF from the steppers that limit their torque.  If you can raise the drive voltage it makes a big difference. My steppers run on 68vdc powered by 80 volt rated drives. I can easily get 300 ipm with 5mm ball screws.

459

General Mach Discussion / Re: Dynamic feed rate - is it possible

« on: October 29, 2014, 08:34:25 PM »

So how exactly does Mach 3 know where the material is?  Leaving the material and moving faster is one thing, but how about if it were moving fast?  How far ahead would you have to make the speed transition?  This kind of thing can be done by high end Cam software where the program starts from a 3D model of the stock material and a 3D model of the part, plus a 3D model of the tool and a kinematic description of the machine so that it can calculate everything.  Not to mention you need data on the material, how it is fixtured, how rigid the cutter is etc.

CNC programming is always a tradeoff.  How many parts are you going to cut, and which costs more, cutting or programming. If you do lots of one-offs you will likely cut lots of air.  If you are doing lots of parts you will spend more time programming and less time cutting air. Get yourself a CAM program, even an inexpensive one like CamBam.  Then you can program a larger number of small operations that will result in less air cutting.  If you are programming by manually writing G-Code you are likely to cut lots of air as it takes a long time and as the complexity grows so do the errors.  This results in doing air cuts to test your program, losing most of what you might have gained.

460

General Mach Discussion / Re: Rotate Mill head

« on: October 24, 2014, 09:22:41 AM »

I need to do the same thing. I can rotate the head 90 degrees.  I think creating a new profile called Horizontal Mill is the way to go.  No need to think about a ton of potential gotchas, and if you are using a Cam program you won't have to worry about whether that posts properly too.