Messages

7241

Mach4 General Discussion / Re: Lua

« on: January 07, 2017, 01:42:24 AM »

Hi dude1,
just having a look at your code. Note that you have numbered the entries in the signal table. Is it necessary?

This is from the default screen load script:

Code: [Select]

SigLib = {
[mc.OSIG_MACHINE_ENABLED] = function (state)
    machEnabled = state;
    ButtonEnable()
end,

[mc.ISIG_INPUT0] = function (state)
   
end,

[mc.ISIG_INPUT1] = function (state)
   -- if (state == 1) then   
--        CycleStart()
--    --else
--        --mc.mcCntlFeedHold (0)
--    end

end,
They are not numbered. The SigLib table can be searched by key and the key can be alphanumeric, a handy and powerful property in LUA.

The signal script can therefore be simplified, this is the default signal script:

Code: [Select]

if SigLib[sig] ~= nil then
    SigLib[sig](state);
end
This means that you don't have to use multiple IF statements, should sig be mentioned in your SigLib, ie a signal of interest, it returns non-nil and therefore
executes the function associated with that key with state as argument.

In fact LUA is a bit more crafty than that; if sig exists as a key in SigLib it returns the function entire, I think that property is called 'functions as first class values'.
Another extremely powerful and flexible property of LUA. In this instance of course we don't require the function but just that it exists, ie non-nil.
If you could be sure that EVERY possible sig is in the table then the script could be simplified even further:

Code: [Select]

SigLib(sig)(state);
This idea of bandying about a function, with all its statements, as simply as a single number is a real eye opener to me.

Craig

7242

Mach4 General Discussion / Re: Switching to Mach4 hobby from chilipeppr

« on: January 07, 2017, 12:18:36 AM »

Hi crchisholm,
I have recently switched to Mach4 after using Mach3 and Parallel Port for a few years. Welcome aboard.

As you've no doubt read Mach4 is fairly new and quite a step up in terms of potential than Mach3. Mach3 is very good and has
a strong following and will do for many years. Amongst the attractions of Mach3 is that it works well with a parallel port, in fact
the parallel port you might say is native to Mach3 and its free... The parallel port (PP) can be a bit cussed depending on your
computer and as a consequence a lot of users have migrated to an 'external motion controller' from about $100 and up.
Most controllers will also require a breakout board (BOB) with cheap Chinese examples for $20 and American/European ones for
$50 and more. A BOB is an amplifier/buffer to protect your computer and give you a convenient place to hook things up to. While
not strictly required they are a good idea.

Mach4 can be run with a PP but requires an extra licence $25. I haven't tried it but instead went to an external motion controller.
External motion controllers are more or less native to Mach4. The software plugin required for Mach4 is new so the choice of
manufacturers is somewhat limited. There are three manufacturers whom have excellent products and established reputations
who have Mach4 ready controllers for as little as $50 to $300. There are more expensive units as well with industrial capacity but
will make mincemeat of your budget.

In the first instance you don't need to spend anything. You can download Mach3 and Mach4 and experiment to your hearts content.
As to which choice...if you like tried and trued but somewhat buggy and in its sunset years Mach3 is good. If you want something
new and developing with potential to burn Mach4 is good.

As to whether you go PP or external controller...PP is cheap/free but can be quirky... external controllers modest priced but smooth
motion.

Sounds like you have almost made up your mind about a Geko driver, while there are (much) cheaper choices Geko has set the standard
that other have to measure up to.

Please don't take the following as a must but rather just the choices I made:
Mach4                             $200
Ethernet SmoothStepper    $180
Homan Designs BOB          $40
VistaCNC pendant              $160
I use rather specialised Vexta drivers for 5 phase steppers, nice but not cheap, don't go there unless you see the need.

Look thru some of the videos on the Artsoft site and Ytube and post your questions.

Craig

7243

Mach4 General Discussion / Re: Lua

« on: January 06, 2017, 01:25:58 AM »

Hi Craig,
no, I don't have any external buttons. I do use a pendant which has an MPG wheel and has all the functions of your panel
and some extras. It plugs in to the USB port, real breeze. Perhaps not as convenient as your panel but it works well.

A couple of ways to do it:
1) in the PLC script have a bunch of code that reads all of the inputs in turn and performs an action if it detects
    a button. The PLC script runs every 50ms or so.
2) use a signal script. In the 'help docs' look at 'Mach4 CNC Controller Lua Scripting Guide', section 3.2.4 Signal Script
    The method of building a table (in the screen load script) and having a series of functions in the signal script for
    each of the different buttons is probably the way to go.

Option 2 is by far the more computationally efficient method.

Have you got your machine running yet? No matter how fancy your control panel is you must have a debugged motion
controller and machine for it to control. At need you can run ALL your programs without a control panel, in fact the vast
majority of Mach4 installations run this way. With a touch screen you don't even have to have a physical panel.
1) Get your machine running with Mach4/ESS/MB2
2) Shag around with a panel to your hearts content, at least you'll still be able to get your moulds done in the mean time.

Craig

7244

General Mach Discussion / Re: Mach3 & G203v W/microstepping how to have DRO'S read in .00002" increments?

« on: January 05, 2017, 09:14:08 PM »

Hi,
your stepper torque is 900 oz per full step, between micro steps it is much, much less, theoretically 90 oz but in practice probably
half that.

Sound like your've got the gear so try it out, hey its only time any money.

Craig

7245

General Mach Discussion / Re: Mach3 & G203v W/microstepping how to have DRO'S read in .00002" increments?

« on: January 05, 2017, 08:47:14 PM »

Hi,
I use Vexta 5 phase steppers which corresponds to 0.72 degrees/full step. The drives have a half step option which due to the
quirkiness of 5 phase switching has slighty more torque than full steps. In addition these steppers are fitted with low backlash
planetary gearboxes of 10:1 ratio. The gearboxes are considerably more expensive than the steppers themselves and Vexta steppers
aren't cheap to start with.

I run them at full step and given the gear reduction that works out to 0.072 degrees per step and with a 5mm pitch ballscrew 1000 steps
per mm, 1um per step. The manufacturer of the gearboxes guaranties a maximum 3 minutes of arc backlash which corresponds to 0.7um.
No point the in going to half step if the known backlash is going to exceed the resolution. As it turns out I can't realistically measure the
backlash as the torsional flex of the coupler is about 4um. I describe my system as having 5um of 'lost motion' rather than backlash.
The steppers and gearboxes cost me $280 US each second hand and the drives nearly the same secondhand.

Obviously the gearboxes slow the rapids a lot, currently running 1200mm/min but the thrust of an axis is huge, 750kg thrust! Don't put your
finger in it!

If you seriously wish to achieve the sort of accuracy you want you're going to have to use harmonic drives. Look them up, they're really clever.
Typical minimum reduction is 50:1 with 100:1 being common. They don't have backlash but the manufacturers do specify 'lost motion', essentially
torsional flex, of 8-12 seconds of arc at rated torque, would have to use solid couplers and C1 or C3 grade ballscrews to get your result.
Going to make your rapids as slow as a wet week but you can't have everything.
The reason that not many people use them is cost, if you think planetaries are bad then harmonic drives are going to make you 'poo your pants'
even secondhand!

Craig

7246

General Mach Discussion / Re: Kress FME-1050-1 + Inverter?

« on: January 05, 2017, 03:17:38 PM »

Hi,
that's the combination I use and it works well. They too suffer from low torque and while they run at low speed often with
not enuf torque to be much good.

I have a German made 750W 24000 rpm unit which produces 0.3Nm of torque. At 6000 rpm it still only produces 0.3Nm torque
scarcely enuf to spin a 3mm tool when cutting steel. All of the high speed spindles suffer this problem.

Best approach is to determine the torque required to do the machining you want and work backwards. Say you want to be able
to cut steel in LIGHT cuts with a 6mm tool at 3000rpm  then you will need about 1Nm minimum. At 24000 rpm that works out to 2.5kW.
This means to get useful lowspeed torque you need a big spindle motor.

Most of the spindles you encounter on Ebay are 2pole (same as 1 pole pair per phase) and at 400Hz input synchronous speed
is 24000 rpm, they will spin a bit slower than this because of slip, which is after all how induction motors work, say 23000 rpm.
A 4pole motor (2 pole pair per phase) would spin at 12000 rpm with 400Hz input but twice the torque. If you had an inverter
that could produce 800Hz then you could get back up to 24000 rpm, assuming of course that the motor is rated for it, otherwise
you will explode the rotor. Downside is that an inverter like that is becoming quite specialised and expensive.

6pole motors can be had but are not common. 8pole can also be had which spin at 8000rpm @ 400Hz but with 4 times the torque and
are very useful but reasonably rare. The same company that I bought mine from do one which produces 8Nm torque but
power limited to 2.4kW for around $2500 US. I really REALLY want one but don't have that sort of money.

If you want good torque at low speeds ie metal cutting using a servo type motor is a good way to go, medium size servos, say
1kW are often rated to 3000 rpm is a torque of 3.2Nm. That enuf to cut steel in moderate cuts with a 10-12mm tool. Still
have to provide spindle/bearing and toolholding.

I bought a second hand servo of Ebay good for 14Nm up to 3000rpm for $300 US including shipping, a bargain. Downside is
I cant buy a drive for it, or least a drive I can afford. I'm making one. If I'd known just how complex a job that is I probably
wouldn't have started. Mind you I have had to learn ALOT about all sorts of things along the way so you can say that
this hobby is good for me. Not that I've even been good, and I'm not sure I want to start now!

Craig

7247

General Mach Discussion / Re: Kress FME-1050-1 + Inverter?

« on: January 05, 2017, 12:34:18 PM »

Hi,
you can control the speed of a universal motor by changing the input voltage but the input frequency stays the same,
ie 50 or 60 Hz depending on where in the world you are.

One way to do it is with an autotransformer widely called a variac. Downside is it has a knob on the front not electronic
control. Old school way of doing things but simple and reliable.

Another way is triac control, a bit like a light dimmer. Most light dimmers have a knob of the front as well but that knob
could be replaced, conceptually at least with a control voltage. Triacs are not the best choice for inductive loads, if the
inductance is to high they don't switch off to well.

For highly inductive loads anti-parallel SCRs are the way to go. They are as robust as each SCR even a $10 SCR can handle
20A or more. I'm not familiar with any particular commercial off the shelf product that would do the job. I made one
a while back for a customer who had an old (very old) school pin welder.

Whether you buy one or build one you may be disappointed tho. Just reducing the speed does not increase the torque so at
low speeds the spindle will have very low power and will be very easily stalled.

On the Kress there should be a makers plate and that could be used to make some pretty fair calculations as to how it might
work at low speeds. One problem to be aware of that the fan will also be slower than normal and the motor will run hot. In
some cases its necessary to provide a separate fan.

Craig

7248

Mach4 General Discussion / Re: Lua

« on: January 05, 2017, 08:11:24 AM »

G'day DTG,
that sort of thinking does my head in! Imagine axes spread over two controllers and you want to probe....would the probe be attached to one controller
or both...

My guess was that there will come a time when you can have multiple copies of M4 running on the same platform but running different machines, or
rather multiple threads, one for each machine but only one copy of M4 running. I'm a long way from coming to terms with just one active thread!

Craig

7249

Mach4 General Discussion / Re: Lua

« on: January 05, 2017, 07:41:20 AM »

Hi Craig,
just checked and Daz-The-Gaz confirms that only one motion controller can be active at once, however more
than one device can be active.

Thinking that your motion controller would be ESS with usual motors, limits, homes and Estop.

Your control panel hooks to the PoKeys.

Both would require an Ethernet connection but pretty sure you can arrange it so the IP addresses don't clash but
your PC would require two Ethernet ports.

I would in the first instance get the motion controller working and not worry about the panel until you've got the machine
running. Trying to get both going at once if your new to it is going to give you grief.

Craig

7250

Mach4 General Discussion / Re: Multiple controllers/devices

« on: January 05, 2017, 07:25:49 AM »

Hi DTG,
thanks for the reply. Mach4 gets cleverer every time I look.

Craig