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General Mach Discussion / Bridgeport 2J Vari-Speed Head, Sensorless Vector Drive, Mach3, cheap tachometers

« on: December 07, 2015, 01:04:02 PM »

Hi I have a Hitachi WJ200 VFD hooked up via Modbus through RS485 to take advantage of SLV drive. I have a cheap $15 tachometer (AGPtek DT-2234C) that came with some reflective tape on the spindle. My vari speed crank is labeled up to 4000 RPM but stops doing anything past the 3600 RPM label, which turns out to be around ~3200 RPM @ 60hz, according to the cheap tachometer.

If I synchronize the head to the Mach3 at 1500 RPMs, then when I set Mach3 to 3000 RPMs the tach shows 2960 RPMs, and Mach3 @ 4000 RPMS -> 3950 reading. Is this considered acceptable? I tried going to Spindle Calibration page but couldn't find any documentation on it. It seems to be only for closed loop spindles.

A few other questions:

How accurate are these cheap digital tachs? They seem to be quite precise and consistent when I barely crank the variable head to adjust the RPMs manually.

Is there a difference between setting the Variable speed head lower and upping the frequency on the VFD to achieve the same RPMs versus setting the variable head at max? I don't think I would want to run it past 5000 RPMs anyway.


Thanks for your help!

2

General Mach Discussion / Intermittent problem connecting Mach3 to board

« on: November 29, 2015, 01:56:03 PM »

Hi folks. I've recently acquired a Bridgeport Series 1 w/ variable speed head converted to CNC. There wasn't much documentation on anything, but it appears I have 1200 oz-in Nema 34 motors (4-wire, part # 86HS114DF05D) connected to a 4-axis blue TB6560 board. I'm running latest Mach3 v3 through a PCI card for parallel. I metered some of the pins and they seem to be putting out 3.3V. With a lot of guesswork and googling, I finally figured out that the motor output pins are :

axis step dir
x 3 2
y 5 4
z 7 6

When I start the computer the motors always lock up. When I open up Mach3 sometimes it connects and motors stay locked up and I can jog, and sometimes it doesn't and motors unlock. When it doesn't, I change Z dir pin to 1, and then only Z- works jog and none of the others work. Then I change it back to 6 and then all of a sudden all of the other motors work again.

I've been playing with the output signals to try to figure out if I need to enable anything. I believe I had it at:

enable1 port 1 pin 14
enable2 port 1 pin 2
enable3 port 1 pin 6
output1 port 1 pin 9

But I don't think this can be right because pin 2 appears to be x dir.