Messages

551

General Mach Discussion / Re: Spindle calibration, how I manage to get it working

« on: March 21, 2016, 06:35:08 AM »

Hi midyo

Spin: always a function of material and diameter. I have no trouble threading 7000-series Al or brass at 400 RPM on diameters up to 20 mm. To me, the limiting factors are sync distance and withdrawal speed. They might depend on your machine. Cut depth - not much, but always enough to actually 'cut'.

Yes, .062 is older than .066 or .067, but ...
.067 was only briefly available and was withdraw, afaik.
.066 is 'recommended' by the Artsoft web site, but users have had problems with it and most experienced users recommend dropping back to .062 . I suspect that whatever bug fixes they attempted with .066 made too many other things worse.
.063, .064, .065 - I don't think they were ever released.

Cheers
Roger

552

General Mach Discussion / Re: Spindle calibration, how I manage to get it working

« on: March 21, 2016, 04:30:28 AM »

I use Mach3 .062, an ESS, and a single Index pulse. I turn on spindle averaging in Mach.
I get quite good, even excellent, threading. But I do take small cuts so the load on the spindle drive is small.

Cheers
Roger

553

General Mach Discussion / Re: Spindle calibration, how I manage to get it working

« on: March 20, 2016, 05:02:21 PM »

Mach can control the spindle speed IF and only IF you are using the direct parallel port interface.
If you are using an external engine such as the SS, it cannot.

Mach does not 'calculate' the RPM: it just measures the Index pulses coming back.

Cheers
Roger

554

General Mach Discussion / Re: M3 M4 switching

« on: March 13, 2016, 11:14:40 PM »

Hi DB

There's one circuit diagram at the bottom of the first page. It works very well for me.

Cheers
Roger

555

General Mach Discussion / Re: M3 M4 switching

« on: March 13, 2016, 05:44:08 PM »

No, that's not quite correct. They mfr give specs for 240 VAC and 28VDC because they are two common voltages, but the relay can be happily used for a wide range of voltages, AC and DC. (28 VDC: over-voltage on 2 x 12V batteries.)

Yes, there is a difference in how contacts work. These are silver oxide / cadmium oxide, and they are designed for heavy currents. There is ALWAYS arcing when contacts are opened, and that's why the contacts use those materials. It's a bit hard to 'burn' an oxide surface, after all. Other switches and relays use gold-plated sufaces instead: gold is good for LOW-level SIGNALS, but not for power applications.

One of the advantages of using plug-in relays (ones using a socket) is that if there is ever a problem, you can pull out the doubtful relay and replace it with a new one. That is a lot smarter than soldering onto the terminals of the relay.

'Shorter lifespan' - debatable. If the relay is rated at 28 VDC & 10 A, but you use it at 48 VDC and 1 A, will it have a longer or shorter life? If you have the spindle motor howling away at full load and you open the relay, there will be some arcing - although the relay is designed to handle that. On the other hand, if you kill the supply down to 2 VDC & 0.5 A before turning the motor off, how much arcing?

In this day and age of modern semiconductors, it turns out that power relay technology is pretty good. Even a wall switch works pretty well.

Cheers
Roger

556

General Mach Discussion / Re: M3 M4 switching

« on: March 12, 2016, 03:42:39 PM »

I use a bunch of JQX-13F relays myself, on my 180 VDC spindle motors. They seem very reliable. I use 24 VDC coils, but that only is because I have a fair amount of 24V power available. I also use the sockets sold with the relays. Mine came from eBay, 22newcentury.

Cheers
Roger

557

General Mach Discussion / Re: M3 M4 switching

« on: March 11, 2016, 03:54:49 PM »

Hi DB

That cyclic variation - is there a feedback loop around the system? If it is not properly tuned it can sometimes cause some oscillation. The simplest solution in that case is to back off the P or gain term a whisker.

Cheers
Roger

558

General Mach Discussion / Re: M3 M4 switching

« on: March 10, 2016, 04:11:38 PM »

> It does have a teeny cyclic variation that affects threading at times.
Could you somehow just add mass to the spindle drive? That can be really effective.

Cheers
Roger

559

General Mach Discussion / Re: M3 M4 switching

« on: March 09, 2016, 03:59:42 PM »

Hi Dickybird

Sounds as though the KBCC is a good match for those motors. Useful information to spread around. And my experience has been that the KB drives have reasonable reliability too - maybe better than some Chinese VFDs. (However, one KB drive has failed on me.)

The arcane interface on the KBWT ... IS arcane imho. Yes, I know what the manual says, and I know what the front end circuitry actually looks like (because I managed to get part of the circuit diagram from KB). The problem is getting enough power out of the KB front end to power an optically-isolated interface **while keeping the response reasonably linear**. If you don't care about a somewhat non-linear behaviour it is much easier. OK, I was being fussy.

I must admit I had not searched on ebay for the KB SI interface. That might be easier, although my interface is reasonably simple NOW. It just took a bit of experiment on the bench - which was part of the fun after all.  :-)

Cheers
Roger

560

General Mach Discussion / Re: M3 M4 switching

« on: March 08, 2016, 05:27:26 PM »

Those old-school drives are OK if the motor is rated for an SCR drive, but they can make the motor hot if the motor is not designed for them. You get a LOT of 100 Hz or 120 Hz ripple on the power, and some of this comes through.

On the other hand, the more modern MOSFET drives like the KBWT-26 leave the motor a whole lot cooler and quieter - but I have to admit they can radiate interference half-way to the moon. KB should have put a LARGE dual-winding L-filter on the output.

Both designs seem to have somewhat arcane interfaces, which may be fine for manual controls but are a pain for CNC interfacing. The KBWT unit analog input controls are at -100 VDC!

Cheers
Roger