Messages

7451

General Mach Discussion / Re: biggish servo spindle

« on: July 20, 2016, 04:46:38 AM »

Hi,
I bought a servo off ebay a while back 2.8kw at 3000 rpm. I cant find a drive to run it at least that I can afford.
This servo is quite old, mid 90's, but looks brand new. It is fitted with a resolver and restricts the choices for a drive.
I tried sensorless vector drive but am unimpressed.
I made the decision to build one, very much easier said than done. This hobby, or should I call it an obsession, requires
you learn all sorts of new stuff. If success is determined by what you learn along the way the this project is a boomer!

Looking around both new and secondhand there are plenty of servos to choose from and cheaply if secondhand. Drives
are a different kettle of fish altogether.

Amongst the bigger industrial drives it is quite common to separate the power supply from the inverter. It allows flexibility
to spec the supply to your existing regulations and whether you have your own onsite transformer.

There has been a big upsurge in VFD use in rural NZ for irrigation pumps. Now the power supply authorities are having
to demand farmers fit these units because of the degradation of the supply. They can be nearly as much as a VFD.

There is nothing to prevent you from running single phase but you will need a dedicated 32A or maybe even a 50A supply.
The power company will probably come down on you to fit a conditioning unit otherwise you will degrade your neighbours
supply. Additionally most servos above 2.2kw are rated for 400v line or 560v DC link. If you run such a servo from 230v line
it will not achieve rated speed. A PFC boost in a conditioning unit will overcome the problem but it will SUCK major current
and you going to have some BIG link capacitors.

Search for single to 3 phase converters but be warned they are expensive and you DON'T want junk because they blow
up. I've had several thru work, Chinese stuff and the proud owners are livid!

Craig

7452

General Mach Discussion / Re: Help Again

« on: July 02, 2016, 06:26:54 AM »

Hi,
when you zero XYZ does the current work offset reflect that? Can be seen on the 'offsets page'. Should
see also which workoffset is active, most commonly G54.
You may need to include a G54 command at the beginning of your part code.

Craig

7453

General Mach Discussion / Re: Hydraulic engine controled by mach3

« on: June 27, 2016, 03:51:26 AM »

Hi Nick,
quite so, the vast majority of steppers we use work that way and quite adequately mostly. Servos do require
a closed loop however and the only practical way to do that is with a servo drive with feedback.

Pablo's question was about a hydraulic motor with an encoder. Mach could quite easily read the encoder and
decide for instance whether the motor is required to rotate CW or CCW or within some deadzone not rotate at
all. The problem is how Mach could communicate to the motor or rather the electrovalves to achieve the rotation.

Mach's native communication is step/direction. Maybe you could use the direction signal to direct the sense of rotation.
That does not however give the motor enuf info as to when to stop so that it matches the commanded move.

Maybe you could write some code which controls the valves so that say one valve remains open until such time
as the encoder ticks equals the step ticks. The hydraulic motor could then achieve position control but not
velocity control. Linearly coordinated moves would not be possible even if two axes eventually ended up at
the right location. Maybe Pablo's application would accept that limitation.

The other way would require some sort of electronic drive which accepts step/direction and compares that internally
to the encoder, ie a feedback servo drive by any other name. I have seen references to hydraulic servos but never
read any of them. Apparently they were popular in the 50's and 60's when CNC was in its infancy. Pressbrakes and
benders must use some hydraulic system.... maybe Pablo can look in that direction for ideas.

Craig

7454

General Mach Discussion / Re: Is there a way to see where your origin is set when you load gcode?

« on: June 26, 2016, 03:49:50 AM »

Hi,
yes there is. If you go to the Home/Limits page of the Config menu there you can set the extents
of your table. If the Display Machine Boundries is checked on the Toolpath page then the table
extents will be displayed as a dotted line when you load a Gcode program.

Note that your part program may not be centered on your table but you can now jog so the 0,0 of your
part is centered within your table limits then zero x and y axes. A toolpath regen should then place the
toolpath of you part within the boundary of your table.

On the Diagnostics page you can see the machine coordinates of your part zero,the current work coordinates.
The Offsets page displays the same info.

Craig

7455

General Mach Discussion / Re: help with my VFD

« on: June 26, 2016, 03:06:58 AM »

Hi,
when I first got my VFD I couldn't get it to work either. It appeared to power up and so on but would
go into current overload when I tried to run my 24k spindle.

I had to read (and reread and reread...and understand) the manual. Turns out it was simple enuf,
as factory default it was set to a V/F curve of 240V at 60Hz, a very reasonable setting for a standard
induction motor but not for a high speed spindle.

To get it to work you will need the manual and to get the best you will have to know it backwards.
There are lots of settings over and above the most basic V/F ones and many of them affect the
rseponse of your spindle.

Craig

7456

General Mach Discussion / Re: Newbie - LPT/Setup Question - MDFly CV2501 CNC Breakout JCut-1325B-2 table

« on: June 17, 2016, 05:17:04 AM »

Hi,
we all have to start somewhere...
The config menu is next to file menu top left hand corner.
The different screens are in a row just underneath. The most often used ones when setting up as you are
MDI, that's manual data input, allows you to issue gcode commands and the diagnostics screen.
The driver test is found in the Mach3 folder on your HD. I have a shortcut on the desktop for it.
I rather doubt you want the internet on the PC running Mach3. In fact you don't really want ANYTHING
on the PC running Mach3. I don't have anything, that includes sound/video/internet/antivirus/firewall/network
I mean anything. The only other program that runs and not concurrently is notepad text editor. I have turned
off screen savers/watchdogs/powersavers and any other feature I don't use. The PC controlling my machine
is for controlling my machine and NOTHING else.
I have a second copy on my laptop for experimentation and all the CAD/CAM/viewers and all the usual apps
you find on a PC but it never goes near my controller PC, I transfer Gcode on a memory stick.
My machine despite being small is powerful as I have planetary gear reducers on the axes they produce
1500 lbf at/near to stall, easily enuf to injure. A crash can be VERY expensive, I've had a few...without injury
so far. I don't take any chances with my controller PC. I'm perhaps a little unusal in this regard but know
also that quite a few experienced Mach3 machinists are likewise.

Craig

7457

General Mach Discussion / Re: Smooth movement while motor tuning, stall when jog

« on: June 16, 2016, 08:17:06 AM »

Hi,
hope this does not upset you.. but I want to ask that when you go back to the motor tuning page whether
the settings you had previously made are still there.
When I was learning this stuff I on too many occasions would forget to 'save axis settings' before moving on
and then scratch my head when the axis movement didn't appear to change. I mean how dumb can I get!
In more recent times I don't change those settings often if at all and if I did would still too often forget to
do so!

Craig

7458

General Mach Discussion / Re: Newbie - LPT/Setup Question - MDFly CV2501 CNC Breakout JCut-1325B-2 table

« on: June 16, 2016, 04:10:11 AM »

Hi,
don't know if any of this will help but then again it may...

I note that you have set the pulse rate to 75khz. You need a REALLY CLEAN LEAN PC to achieve that sort
of speed and unless there is a good reason to have such a high rate it won't make Mach run better but
worse. Another tip is that Mach resets its kernel speed at start up, ie change the speed, shut down Mach
and restart to see the change.

Have you run the Driver test. It is not an absolute test that the PP is producing pulses but is better than naught.
What sort of report does it give?.

Another issue which has caught a few over the years (no, not me I bloody swear!!!) is the charge pump. The charge
pump is on the BOB and it monitors the PP. If the PP stops producing pulses for any length of time it shuts itself
down. A sort of failsafe,'if no one is driving this bus then I'm going to stop'. I don't know whether your BOB has a
charge pump and whether it can be disabled, I don't bother with one but others do. The output from the PP
can be assigned (port and pin) on the outputs page of the port and pins page under config tab.

I don't see on the pic of the BOB whether it has LED's on the outputs. They are invaluable for diagnosing setup
problems. In absence of an LED you will have to use a multimeter to test each motor output. Go to the direction
output of an axis, x say. On the manual input screen of Mach issue a G1 x1 command. The direction output
will read high or low depending on your set up. Then issue a G1 x-1 command. The output should change state.
You can and probably will have to repeat this for for all direction outputs. Temporarily you can reassign step output
as a direction and use the same method to check the functionality of each of your motor outputs.

On the Mach diagnostics page you should be able to 'see' the operation of each of your limit switches. With the switch
closed the diagnostic LED might be lit (depending on assignment) and not lit when open.

These steps will allow you to establish whether Mach has control of the PP and that the BOB is capable of transmitting
the pulses. If all is well you are a lot closer to running motors.

Let us know how you make out.

Craig

7459

General Mach Discussion / Re: Question about encoders and missing steps, G540

« on: June 16, 2016, 03:25:27 AM »

Hi,
yes you do use ferrite rings as a coil. The ones I'm thinking of are commonly seen on the input wiring
of switch mode power supplies, computer power supplies and similar. They are primarily for EMI suppression.

I work repairing welders and see lots of them. Wouldn't mind betting you could find a whole bunch surplus
at just about any electronic repair outfit.

Commonly the wires are passed thru the hole a couple of times. The inductance goes up as the square of the no.
of turns so don't get too carried away, 3-4 turns will offer max suppression without distorting the pulses too much.
It is in fact better to have several cores along the length of cable with one or two turns than one core with 6 turns
say. What you're trying to achieve is to 'break' the cable into a number of shorter pieces that each piece becomes
a much less efficient anttena.

After I replied last night to your post I started thinking more about the board in the link you posted. I realise now
that it might work better than I had guessed. I assume it allows an encoder to be interfaced and monitored by Mach.
Mach could then signal an error should steps be lost. There have been a number of topics that discussed whether
Mach could 'close the loop' and auto correct. The majority of experienced users cnocluded no. That does not preclude
Mach from detecting an error or growing error from occurring. I have been a bit hasty in dismissing the board and the
idea on which it is based. My apologies.

Notwithstanding that it still seems better to find the reason for the error rather than just detecting it. From your description
the machine has worked well for some time so whats changed?. It could be as simple as a loose coupling or something.
Does the error occur on one axis only? If it were electrical noise you might expect it to affect more than one axis unless
one axis is more sensitive to noise, maybe proximity to anther cable.

Let us know how you get on.

Craig

7460

Mach3 under Vista / Re: Motor tuning,configuring for mm for plasma tabe

« on: June 15, 2016, 05:57:56 AM »

Hi,
don't know if this will help but probably won't hurt...
On the config tab there is a 'select native units' page. Make sure it is set to mm.
These are the units used to tune the motors.

You can still machine in inches if you wish but don't use this setting, use either
G20 or G21 codes.

Another tip is on the 'general configuration' page of the config tab is about middle of the screen
an initialisation string. It is a set of Gcodes that run each time Mach fires up. If you edit the
initialisation string to include G21 then you will always start in mm.
Incedently my machine would always start up with a federate of only 6mm/min, safe but really
slow until you MDI a more reasonable speed to set things up. I set up a F300 in the initialisation
string which gives me a more useful default start up federate.

Craig