Messages

1021

General Mach Discussion / Re: Any help / suggestions please?

« on: October 10, 2016, 02:06:55 PM »

PS if your machine is in a garage/workshop consider putting in a good copper earth rod at least 6 foot long for the main PE that will calm it down that's what I have done even that we have a PME system

It's a fascinating subject for sure.

I am in a garage and was advised not to run an earth rod when i fitted the plasma table. We are PME and was advised it would not be good as the earth was exported from the house supply then it got technical

It all seems to work ok so i have not questioned it

1022

General Mach Discussion / Re: Can not increase motor velocity (65mm/min). Why?

« on: October 10, 2016, 01:58:35 PM »

....and the L297? ...and current limiting?

Well i presumed if the OP was smart enough to be using discrete drivers and other i.c's he would know the limits no?

Looks like 2A on the motor and the logic uses 5v as normal.

Data...
http://www.st.com/content/ccc/resource/technical/document/application_note/0a/84/39/6c/ae/9a/42/0a/CD00003803.pdf/files/CD00003803.pdf/jcr:content/translations/en.CD00003803.pdf

The ATX supply has a 12V output too, using that would help but will need different limit resistors etc.

1023

General Mach Discussion / Re: Any help / suggestions please?

« on: October 10, 2016, 09:51:43 AM »

I'm probably going out on a limb here and slightly disagreeing, ok maybe not disagreeing but raising a few points...

In theory the secondary 0v rails can be joined to chassis ground/supply earth quite happily - no current can flow between this link *unless* there is a path from the +ve supply rail back to the chassis ground somewhere - this should never happen.

Now, i say "in theory" because the chassis ground may possibly contain all sorts of nasty things like RF from a plasma supply, spikes from other sources and generally some noise. The level of this electrical muck can depend on how good or bad your supply earth is - if it is good then the muck gets drained rapidly to safety, if bad then it can raise the earth potential above where you think it should be for the duration.

Next - suppose I have my low voltage supplies floating - this is what you describe - "floating" because neither rail is grounded, and there is a short from +ve to chassis - what will happen? Nothing will happen apart from all the muck on the earth will now get injected into the +ve supply rail and forwards.

So, say i ground my 0v rail to chassis and there is a +ve short to chassis - what will happen now? It *should* blow the fuse alerting me to an issue, after tearing my hair out for a few hours or days trying to find out why it stopped

As you can see, grounding can be a nightmare and can cause issues if not done correctly, I am not saying that 0v should be grounded, especially when a PC is involved UNLESS there is 100% opto-isolation on all signals and the 5v rail is not being pulled outside the PC to power a BOB or the MP3 player etc

Its all about loops, interference, safety, shielding etc and sometimes - take a CNC plasma cutter, probably the worst case scenario, it can be a nightmare to get right.

My Bridgeport CNC conversion has multiple PSU's - one is grounded and powers the control signals into and out of the CSMIO controller, it needs to be grounded because i use a touch-plate which uses ground through the machine as a return path.

The other PSU is NOT grounded and only powers the CSMIO controller itself, this controller has fully isolated inputs and outputs so this lack of grounding ensures there no possible path for any muck to get into the controller. The PC will be grounded of course but it uses ethernet which is isolated so no loop there. The servo drives are grounded via the chassis (bolted down) and the AC supplies but internally who knows?

1024

General Mach Discussion / Re: Can not increase motor velocity (65mm/min). Why?

« on: October 10, 2016, 08:27:00 AM »

As Tweakie has said 5v is not going to do you any help here, what motors? Nema17, Nema23 ??

Even little Nema17's would need 12 or 24v minimum to get them moving with any load.

Nema23's maybe 24, 26, 48v depending on drive capability - it looks like the L298 can take up to 46v so i would go to 36v max to allow some headroom for overvolatge during deceleration.

Also try using the 1/10 idea for acceleration to start on - speed 65 acceleration 6.5 and so on, acceleration is the bit that takes its toll on current/voltage.

1025

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: October 09, 2016, 02:21:17 PM »

Thanks Hood, will test that.
 

Is there any indicator to look for to show things are or are not set right?

1026

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: October 09, 2016, 11:26:42 AM »

Great, will tweak the screen-set and try again.

Yes the vfd/motor setup seems well matched and didn't even notice the cut

I think the project is just about done now - checked the high-speed spindle setup again yesterday and that is all set now, needed a wiring change due to changing the vfd for the main spindle - the safety relays are different.

How do i verify if the encoder setup really is ready for rigid tapping?

1027

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: October 09, 2016, 10:00:21 AM »

Encoder gives spindle speed reading in Mill and also more importantly allows rigid tapping

If I recall for true spindle speed reading with the IP-A/S you need to make sure the Averaging is disabled in Ports and Pins.

Hood

Ok, I have spindle-speed averaging off, closed loop spindle control off, use spindle feedback in sync modes on.

There is no change in speed displayed, BUT does it need a certain DRO to view real speed?

The 2010 screen-set uses DRO 202 - "Overridden spindle speed" only - this just seems to show requested speed, i would expect an actual-speed display to show some variance when running??

Maybe it needs DRO 39 - true spindle speed instead - i can easily swap them over i guess if thats the one?

Did some more cutting today, just modifying my vise jaws for a job coming up, deliberately took some fairly heavy cuts on a 20mm tool down at 500rpm and the new drive setup didn't even notice

1028

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: October 08, 2016, 07:22:50 AM »

After hitting the problem with both G28 and G53 moves I switched to single block and stepped it, it triggered at the M6 command.

Next i pulled the M6macros out and it worked ok, a coffee and a sit-down with the macro open showed the problem. It was connected with the screen-set and the M6Start macro, a variable and DRO called "Clearance Plane" - this is used in the 2010 screen-set tool-change routines.

But as I cannot use them on the Bridgeport and do not need them due to the fixed length tooling, the already edited M6Start macro was still using the values and trying to send the Z to a position beyond home when triggered.

This is why the code always ran fine as a single-tool job - the first line in the M6Start skips the routine if the current tool = selected tool so the dodgy code was never hit

I have now edited the M6Start to remove all references to clearance planes, offsets etc and just issue a straight G53 G0 Z0 style home move.

The code i was struggling with has now been air-cut 6 times with 100% success.

Thanks for all the tips.


Now, back to "what is my encoder actually doing???"   

1029

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: October 08, 2016, 06:04:28 AM »

Thanks, i'll have a play with the pid values.
If running open-loop, do i need the encoder at all, can't remember now what function it performs ??

The code was just G28 G91 Z0.

I'll read the link later.

1030

General Mach Discussion / Re: Bridgeport Knee Mill Conversion?

« on: October 08, 2016, 05:37:06 AM »

got the encoder fitted, anyone know what settings i need to activate in the system to close the loop?

I tried activating the pid loop in mach and it makes the speed oscillate wildly so i turned that off again for the moment.

in the picture attached, i have now activated "Spindle DAC" as without it there was no speed control at all but is that enough, do i need more stuff set here?

Any tips?