Messages

1301

General Mach Discussion / Re: "Limit Switch Triggered"

« on: January 15, 2009, 04:58:47 PM »

Hood,

Your sketch is wrong!  You are showing the mill on the FLOOR!!   

1302

General Mach Discussion / Re: "Limit Switch Triggered"

« on: January 15, 2009, 03:52:31 PM »

It helps me to think in terms of the tool moving and not the table, or to imagine I am tiny and standing on the table so that I am 'still' and the tool is moving around.


My suggestion in this particular case is to split the difference and mount the mill on the wall instead of the ceiling. This way when you look at the table,  zero zero is the lower left corner . .  just like in a geometry text book. 

1303

General Mach Discussion / Re: Limit switch location on axis?

« on: January 13, 2009, 09:58:16 AM »

Mach has a feature called "soft limits" which slows and then stops the travel (based on your settings) before the limit is reached. That should serve to protect your machine, provided it is turned on of course.

A really nice aspect of this feature is that Mach will warn you if you are about to run a program that will exceed the limits . . . handy for a newbee like myself!

This raises an interesting question. If I have this right, Mach uses only one value for both accel and decel. If soft limits are turned off and the limit switch is tripped, does Mach still honor that value, or does it do an 'emergency' maximum decel?



As to cutting the power to the motors independent of Mach, wouldn't you then loose the ability to brake the motors? Certainly I would at least put a braking resistor on any normal PM DC motor, and cut that in when the power was disconnected by a relay. I don't know if steppers can be dynamically slowed. Anyone?

1304

General Mach Discussion / Re: "Limit Switch Triggered"

« on: January 13, 2009, 09:44:23 AM »

If you are having any trouble with the second Parallel port, that is a big red flag and you may have a conflict in the computer. Check to see if the two parallel ports are sharing and interrupt or have an address conflict. IBM defined these many moons ago, but add-in cards often come pre-configured as LPT3 (and LPT4 plus COM3 etc, if it is a multi card) or otherwise break the rules. It may be that you are chasing a problem in wiring that the PC itself is generating internally.

I can tell you from experience that bad, cheap or failing PC power supplied can make a horrific amount of noise. So much so in some cases that you can actually hear it in the motherboard speaker!

Use the task manager to check the CPU utilization. If it maxes out, it probably would not be a good thing with such a timing sensitve application as Mach. If another process is runing with a higher priority, it can suspend the lower programs. Also check to see if you have antivirus or a similar 'watcher' program running which could be intercepting the LPT1. Parrallel ports were often used for file transfer and networking at one time and it is possible that security software is monitoring it.

The only other though I had was based on my recent discovery that a wireless network adapter was making the whole CNC go nuts. False estops, false limits, and the steppers would suddenly stall for no reason. Unplugging the USB wireless adapter made ALL of the problems go away instantly.

Something else . . and this may be a stretch . . is if you are in an industrial area where some company has radio dispatched trucks. If you are getting slammed by a powerful transmitter, it would probably behave exactly like you are experiencing because it would all look fine until someone keyed the mike and it would just be an amazing coincidence if you happened to be looking at your scope at that moment.

I am still a newbee at this stuff, but still, I would put a spotlight on that PC as a possible suspect.

1305

General Mach Discussion / Re: Speed controller won't hold steady speed - where is the problem?

« on: January 12, 2009, 02:38:08 PM »

Ray,

I lost more than time. I also lost two $200 Minarik MM drives that immediately fried as soon as the C6 was connected and everything powered on. This is how I learned what an 'isolated' signal was. The CNC4PC document noted by sparkness is, and continues to be completely inadequate at explaining the issue. I informed both CNC4PC and the Minarik sales rep of my rather dramatic results the first time thru and neither mentioned the 'isolation' requirement. I got a new controller from CNC4PC and the Minarik sales rep sold me the identical drive again. Not surprisingly, I had the exact result the second time around. When I finally spoke to a support engineer at Minarik, his FIRST question was 'are you using an isolated control voltage'. I now have Minarik drives with control voltage isolation built into the drives.

Homann, on the other hand has big red warnings all over the place about mains potential voltages present in many drive's control circuits, and how NOT to hook things up. Had I gone with Homann to begin with, I probably would not have fried the drives . . which took out other components as well.  It remains the most expensive part of my learning curve thus far.

I did buy a Digispeed DC06 a couple months ago to replace the C6. I finally tried last weekend to hook it up. It worked for only a few minutes and then got locked on full speed. I may have done something wrong to kill it, but at this point I don't know. It is going back for repair. It did seem to have a steady output voltage while it was working, but while I was trying to configure MACH for it, the DC06 stopped responding so I never got to see if the motor would run steady. The output did seem steady while the thing was working briefly.

Peter responded immediately when I emailed him that the DC06 was kaput. I'll get it fixed and give the Digispeed another go before looking at the much more expensive PMDX product. I'm not going to mess with the C6 any further.

1306

General Mach Discussion / Re: Speed controller won't hold steady speed - where is the problem?

« on: January 12, 2009, 11:32:08 AM »

Peter: The C6 requires 12v. I am using an old PC power supply for both the 5v for the breakout and the 12 for relays and the C6. The 12V and 5v both read dead steady with the same analog volt meter that clearly showed the fluctuations in the C6 output.

Ray: I have not had any success so far with either of the C6 that I have. I have the same situation as you in that the problem is not consistent, but in my case it is not nearly as severe as you describe, but still not steady enough to be usefull.

I am using the C6 only for the relays and I control the spindle manually using a pot. It would be nice to be able to program increasing spindle speeds as multiple cuts reduce the diameter of a workpiece.

As a newbee, I don't have the experience to now if this is a solvable problem. What I don't like to do is chase my tail for a long while only to find out that the issue I am trying to fix is not fixable, so I was wondering if anyone is using the C6 with success.

Sparkness: I am not using a VFD. It is a PWM drive. The mystery is that the C6 output wavers even if there is no power to the PWM drive, so the problem cannot be RF from the drive . . AND the PWM drive works perfectly using a pot. Additionally, the C6 exibits the same behavior when it is connected to the breakout board with a very short piece of shielded cable and the output is measured doirectly off the output terminals of the C6, so I am perplexed as to where it might be getting interference from.

As a guess, I would put the wavering at about one second peak to peak, but I have not measured it.

TheC6 speed controller uses two voltages. The 5v comes off the breakout (supplied to the breakout by a PC power supply) and the 12v for the follow voltage comes from the same PC power supply directly to the C6. I've checked both and they seem steady on an analog volt meter. In both cases, the power ground is from the same source as the positive voltage. I don't understand what you mean by not sharing a common ground.

1307

General Mach Discussion / Speed controller won't hold steady speed - where is the problem?

« on: January 12, 2009, 03:13:41 AM »

I have two CNC4PC C6 speed controllers. Neither will hold a steady speed. Observing with an analog volt meter confirms the output voltage is fluctuating. I replaced the hook ups with shielded wire, but it didn't help.

Drive is a Minarik MM series which holds dead steady speed using a pot.

I am just curious if anyone is using this controller with success before I spend a lot of time trying to get it to work right if this is just a characteristic of the CNC4PC controller or Mach.

1308

General Mach Discussion / Re: X-Box 360 Controller and Spindle

« on: January 09, 2009, 06:39:30 AM »

Don't know if this will help, but I did the xbox360 controller setup thing and had trouble with it. I was using a wireless.

I've since discovered that RF screws up the steppers. My wireless network adapter was making the steppers go nuts, big time.

However, I did like the way you can control the machine with the xbox controller. I'm trying to snag a wired version off ebay. That should solve both the RF issue and any auto shut down caused by low batteries or whatever as the wired version is powered by the USB port.

1309

General Mach Discussion / Re: The Need For Speed. . . . At least for rapids

« on: January 07, 2009, 12:02:22 PM »

http://www.geckodrive.com/upload/Step_motor_basics.pdf

Quoting from that document, "The power supply voltage should be between 3 to 25 times the motor's rated voltage. If less than 3 times, the drive may not operate smoothly and motor heating is excessive if it is more than 25 times the motor's voltage."

Unless there is something I've missed (quite possible) higher voltage will not overcome the limitation imposed by the frequency, however, it would appear that low voltage definitely will prevent the motors from performing anywhere near where they should.

I am running both 4v and 2v steppers off a 36v supply and I can tell you there is a significant difference in the  . .  shall we say 'enthusiasm' of the drives.

In the case of Gecko, some have settable step size, but my 203v do not. As I understand it from Gecko's documentation, the drive's output starts at 10x and varies automatically up to full step depending on the speed the stepper is moving, but they always take a 10x input.

1310

General Mach Discussion / Re: CNC Gear Cutting

« on: January 07, 2009, 11:38:33 AM »

Interesting . .

Out of curiosity, I just did a few tests changing the increment value accuracy and the steps per degree setting to see the relationship.

My findings are that Mach sets the A axis to the nearest physical step, and that is what shows in the DRO. The nearest step is a physical necessity and showing that value in the DRO seems logical to me. However, internally it would seem that Mach is maintining the full accuracy of whatever increment is specified in the G-code, and uses that for calculations.

If that finding is correct, then Mach will automatically utilize the maximum accuracy your machine is capable of, provided you input enough decimal places in your increment.

To test this yourself, simply use a wizard to generate a 17 tooth gear. Then set the axis steps at 200 and then at 10,000. note the difference in the incremental DRO readings at each step setting. Yet in both cases, it ends at 360 without being commanded to do so, indicating that there is no accumulated error inside Mach (given the accuracy of the increment).