Messages

5871

General Mach Discussion / Re: Alright fellow campers...a frankenstein moment!!

« on: November 17, 2017, 05:01:32 PM »

Hi Rich,
yes they do look better than most.

I am coming to the same conclusion as you, 'don't get involved supporting junk'. I got rather short with another poster where he refused to consider a G540
as opposed to the rubbish BoB that we'd already wasted so much time on. He'd bought the whole machine second hand for $200 so even if he stumped
up for a G540 he would still be well ahead. He was rather curt with me, which I understand nor even blame him. The upshot is that if I don't try to support
those types then I wont get the grief either.

Bottom line, if someone buys Chinese junk without doing any research, don't expect any help from me.

Craig

5872

General Mach Discussion / Re: Need help/advice

« on: November 17, 2017, 04:05:22 PM »

Hi,
the only Bridgeport I've really had anything to do with is an Indian made copy of a series 1 I think. Its got a lot of backlash too, the yoke is badly worn.

The yoke is a big lump of brass with two machined ACME threads at right angles to each other for the X and Y lead screws. Its expensive to buy, really hard to
get at an replace. The separation between the axis screws is not that much greater than the diameter of the screws. To make a yoke with ball nuts (with their
much larger diameter) and so retain the existing screw locations is a challenge.

A conversion kit is despite the cost likely the best way to proceed.

A rolled screw will lose you considerable accuracy.

If you can't afford ground screws you might be better off buying another yoke and repairing what you have got. Even worn OEM lead screws are probably better
than rolled screws.

BoschRexroth do a line of ballscrews where they are rolled but subsequently ground. Still not the accuracy of C5 or better ground screws but better than C7 rolled
screws at an intermediate price.

Craig

5873

General Mach Discussion / Re: Need help/advice

« on: November 17, 2017, 03:35:34 PM »

Hi,
ballcrews are the right solution for backlash. Components for Bridgeports are readily available but they will cost many hundreds if not thousands of dollars
if you buy components specifically intended for Bridgeports.

You can buy cheaper secondhand off Ebay but will have to modify/machine to have them fit your machine. If you have a good lathe and the confidence to use it
it can be done.

Be aware of the difference between ROLLED ballscrews and GROUND ballscrews. Rolled screws a cheap and pretty damn good, say $200 for a largish one, the same size
but ground try $2000 or more....very very good but really expensive.

Craig

5874

General Mach Discussion / Re: VFD Noise

« on: November 17, 2017, 03:22:39 PM »

Hi,
yes you are advised to separate your VFD wiring from signal wiring. This is a strategy to reduce RADIATED interference but does not address CONDUCTED interference.

You say that you have your VFD in separate 230V outlets but what degree of electrical separation is there between the outlets?

In New Zealand at the current time in the province in which I live there has been a major upsurge in agricultural irrigation much powered by multi hundred kW
VFD pumps. The electrical noise which is reflected into the power grid is causing major issues. The local power companies are having to insist that line reactors and
filters be used. The farmers hate it, line reactors and filters can cost tens of thousands dollars.

Small VFDs such as we use are not likely to come under official scrutiny but they do 'pollute' the electrical supply in their vicinity. My suggestion relates to the fact
that many hobbyist CNCers pollute their own power supply and then wonder that their sensitive electronic systems go cranky.

Try running your VFD, or alternately your machine controller/PC, from an extension lead well separated (physically an electrically) from the other.

I have given similar advice to others and about half have found that it solved the problem. Some have gone on to buy line reactors per VFD manufacturers recomendations
to achieve a permanent solution.

Conducted electrical interference is often overlooked. You could spend many hours and dollars trying to stop radiated interference and achieve nothing. Try the conducted
noise experiments until you are 100% positive that it is not the fault before trying the radiated noise reduction strategies.

Craig

5875

General Mach Discussion / Re: Gear Reduction question.

« on: November 17, 2017, 01:11:32 PM »

Hi,
don't know if you've had much to do with AC servos but almost all of the offer 'torque mode' usually with analogue input.

You dial up 8V and the servo will produce 8/10 x 11.5 (Rated torque)=9.2Nm through your reduction and screw to give 1.3 t say. Doesn't matter if it
stalls it still produces the force that you wanted. If you want more force....turn up the knob a bit more.

Caig

5876

General Mach Discussion / Re: Gear Reduction question.

« on: November 17, 2017, 12:58:40 PM »

Hi,
best rated torque for 80mm frame (34 size) DMM servo is 2.4 Nm, not enough.

The 11.5 Nm (rated) DMM is 130mm frame, quite a bit bigger.

Large torque requires a large rotor diameter...

Craig

5877

General Mach Discussion / Re: VFD Noise

« on: November 17, 2017, 12:34:03 PM »

Hi,
electrical noise is both radiated and conducted. The high frequency currents in the VFD output are very likely to be radiated to other circuits.
The electrical demand of the VFD will induce voltage fluctuations on the 230V input an can be conducted into other power supplies/devices.

As an experiment try plugging in your VFD into a separate socket to your PC and machine supplies.

Craig

5878

General Mach Discussion / Re: converting from PDMX 411 to ESS and using g540

« on: November 17, 2017, 12:15:38 PM »

Hi,
if the G540 is plugged into port 1 of the ESS then pin 10 of he G540is connected to pin 10 of the ESS, pin12 of the G540 is connected to pin2 of the ESS.
When I say 'connected' I actually mean buffered. So an input on pins 10 or 12 will be amplified and hooked to the ESS pins.

Mach4 recognizes the signal but YOU have to tell it what to do with it....ergo those few lines of code.

Craig

5879

General Mach Discussion / Re: Gear Reduction question.

« on: November 17, 2017, 12:00:43 PM »

Hi,
those CP servos are good for 500 oz.in if you expect to run them at their peak torque they will fault out within seconds.

Fundemental fact about motors: torque s proportional to current. Therefore to run those servos at three times rated torque (1500 oz.in) will require three times
rated current.....and that level of current might be sustained for 10 seconds but not much more.

Those DMM servos require Step/Dir signals only, they have their own 230V power supply, they require less of your controller than the CPs. Don't see that you should
have to do anything to your controller at all.

Craig

5880

General Mach Discussion / Re: Alright fellow campers...a frankenstein moment!!

« on: November 17, 2017, 11:40:49 AM »

Hi,
just put a capacitor between Dir+ and Dir- and another between Puls+ and Puls-

Craig