Messages

71

General Mach Discussion / Re: Big Power Amplifier

« on: December 17, 2010, 10:31:09 AM »

I have used Yaskawa drives and found them very easy to work with. they are easily configured for step/direction and come in a large array of sizes.

72

General Mach Discussion / Re: Has anyone replaced an Anilam M control with Mach 3 ???

« on: December 15, 2010, 04:58:08 PM »

You should understand before you start that Mach3 runs in openloop mode where the CNC you are used to runs in closed loop mode. What this means - MACH does not use feedback for posioning, it relies on the characterisics of stepper drives for posioning. The anilam control used the glass scales as feedback devices as part of the motion control function. As such you would have to have drives that can function in Step/Direction type control, and the scales would only function as Digital Readouts.

Mach3 is really a hobby level control with many great capabilities, The Anilam control was a commercial production control and the capability of higher percision ans speed. It is like comparing Apples and Pears. They are very similar and you can use them for similar uses, but there are times when you really need a Pear.

73

General Mach Discussion / Re: losing steps

« on: December 15, 2010, 04:49:15 PM »

Set the step pulse back to 9 and check you max speed. You want to test the drives at max speed when they are hot as that is the time when they are most likely to lose steps. Cool drives will generally allow a bit more current than will warm drives, so you could be a hair to fast on rapid moves.

74

General Mach Discussion / Re: Allen Bradley 8400 to Mach

« on: December 14, 2010, 02:20:04 PM »

Got any info on the drives? There are a few step to analog converters out there (not sure of the current models) or, of the drives can be configured for step/direction operation. Don't care about the CNC control, just the drives.

75

General Mach Discussion / Re: PLC With Analog Input

« on: November 30, 2010, 03:27:41 PM »

Looks like the 05 is not capable of floating point math.  I think I'll need that.  Looks like the 06 is it.

Foating point is not necesary for a THC. All you need really need is some way to get a scaled value in for the set point and compare it to the A2D and then make greaterthan/Less then descisions.

76

General Mach Discussion / Re: PLC With Analog Input

« on: November 30, 2010, 03:25:53 PM »

A voltage divider is not all that complex... The right combination of resistor of a high enough wattage and MAYBE a small cappacitor across the output side to filter it slightly. Then you have to program a little bit of deadband around your setpoint (2 to 5 counts out of 256) and it will behave pretty well. There may also be some averaging in the A2D circuit in the PLC to help with the noise. I have built a couple of PLC based THC and it does not have to be complex at all. Mostly you are looking at whether the arc voltage is greater or less than some reference value and then triggering the appropriate output for up or down.

Using MACH - you could send the Plasm Start signal to the PLC and then when the Initial height is set the PLC gets the Arc Transferred signal and sends it back to MACH. When MACH drops the Plasm Start signal then PLC turns off the plasma and waits for a second or 2 for the plasm to shutoff and then retracts for some preset time.

The main advantage of the PLC over the PIC is that you don't have to worry about the Real Time part of the process, the PLC does that itself. Also the programming might be a bit easier for someone else to understand because, while some try to disparage it, ladder logic is rather universal and thus easy to figure out.

I have had to figure out others ladder logic and been able to do major additions, the other option is STL and poorly written STL is a vile as poorly written assembler...

77

General Mach Discussion / Re: PLC With Analog Input

« on: November 29, 2010, 11:50:08 AM »

You should be able to control the THC with just the PLC. Yiou would need some communication between MACH and the THC so it would know when initial heaght has been set. Initial height can be set with just a timer, go down until the switch contact opens, raise for some amount of time, stop motion and tell MACH that the torch is in position. Another timer can be used to raise the torch when the THC run is turned off by MACH. The PLC will work for a THC with just about any type of motor - yiou could use a reversable AC motor, or a DC motor - you would have to use relays to control either - Pheonix contact made some small din rail mounted relay modules that worked real well. If you have 2 analog inputs you could use a potentiometer to set your arc voltage.

I have used an Omron CP1-H PLC to control a THC using stepper motors and it worked well. A stepper interface might work with the DL06, but there is a problem with most PLC's that they don't like the step commands changed while in a move. The Omron PLC has a nice workaround and lets the motion commands be changed on the fly.

Analog output could be used but unless you can program a proper deadband in the motor drive you will have to deal with creep in the THC when it should be sitting stationary.

I would think that it would be easier to treat the THC as a seperate component and not try to control the height with MACH because the  height doesn't have a good number as it is relative to what is happenenig between the torch and the plate.

78

General Mach Discussion / Re: Let's talk about brushless drives!

« on: November 22, 2010, 02:34:27 PM »

I have used Yaskawa/Omron branded drives and Mitsubishi Brand. Yaskawa and Omron are the same product, though Omron has a version that is Step/Direction Only.

The Omron drives were super easy to use if you used the default settings - 2000 steps per rev of the motor shaft - and had the added benefit that they have a switch dedicated to self tuning - don't have to change parameters to configure the tuning parameters. (had one setup with a large timing belt pulley that wanted to oscilate - flicked the switch and joged the axis a couple times and tuning was complete. Up to 800 watts will run on 220 Single Phase.

The Mitsubishi drives were similar, 1000 steps per rev. 

I liked the connectors on the Yaskawa/Omron drives better than I did the conections on the Mitsubishi motors. You will need to order cables as they come cut to length and terminated.

Seems like prices were in the $1200.00 and up range.


Might also look at Automation Direct though I have no experience withtheir product.

79

General Mach Discussion / Re: Plasma Table

« on: November 11, 2010, 02:16:00 PM »

I used to build Plasma/Oxy-fuel gantries and a rigid gantry to end truck will probably stay much more square as compared to an articulated one. The other factor to consider is that the more rigid your machine is, the better results you will have. Start out by making sure the machine is as square as possible when you assemble it and then the squaring routine will have as little work to do as possible. You don't want teh squaring routine to be trying to compensate for poor construction/assembly.

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General Mach Discussion / Re: For a new built machine, what would you change

« on: November 11, 2010, 02:08:21 PM »

Brushless servos - Yaskawa, Mitsubishi, Automation Direct and others make some really nice brushless servos with a stepper interface. Lots of speed, lots of torque and not a lot of heat. Price is a bit higher, but that is always the tradeoff- performance has its price.