Messages

11

Mach4 General Discussion / Mach4 (4.2.0.4284) Status Bar .... confused (wxLathe.set) ?

« on: August 12, 2019, 06:35:16 AM »

Mach4 (4.2.0.4284) Status Bar (wxLathe.set)

Any reason why G99 shows up twice on the current active status Bar??

When I change to G98, one of the G99's changes to G98, but the other remains at G99?

12

General Mach Discussion / Re: Mach3 plasma + THC 150 issue

« on: January 04, 2019, 04:14:03 AM »

Code: [Select]

N0120 Z3.0000
N0130 G28.1 Z3.00
N0140 G92 Z0.0
N0150 G00 Z0.0520
N0160 G92 Z0.0

With the above code you are setting you Z axis home location as the top of the material.

You are setting via G92 as Z0.0 ..... you should allow for the switch offset

The torch then moves 3mm above the top of the material (but again.... you've not allowed for your switch offset).

Code: [Select]

N0180 M03
Fires the torch

Code: [Select]

N0190 G04 P0.1
Waits 100milliseconds

Code: [Select]

N0200 G01 Z1.5000 F100.0
And then drops from (3mm to 1.5mm..... but again.... you've not allowed for your switch offset....)

To set your switch offset, get something like thin paper and place it below the torch.
Perform the G28.1 which will home the axis, and probably set it to 0.0
then jog the axis upwards 1 step at a time until you can slide the paper out from under the torch..... this is your switch offset height
Add that switch offset to your G92 X____ withing the post processor (it will probably be called "switch offset") ....... note that it will be negative (because when you perform G28.1 the torch will be homed BELOW the switch offset height)

So when you retract for the pierce it will retact 3mm + the switch offset.

13

General Mach Discussion / Re: Is this a "look ahead" problem?

« on: December 26, 2018, 11:39:36 AM »

I have not tested this myself but I have been told by a motion controller manufacturer (a few times) that has mach3+4 plugins for their motion controller that mach3 has a known issue that it can occasionally under certain circumstances exceed the defined acceleration setting by 6x during some motion planning to do with constant velocity sonbe careful increasing acceleration too much

14

General Mach Discussion / Re: Is this a "look ahead" problem?

« on: December 26, 2018, 08:12:56 AM »

What does you gcode look like?

Is it a load of linear moves (G01)
Or is it a mixture of linear and arc motion G01 + G02/G03
Constant velocity tries to attempt to maintain a constant velocity but there are limitations as to how constant velocity can actually be maintained.....  Think of it this way...

You're running down a road flat out. Can you change direction 90 degrees still running flat out..... Exactly 90 degrees!   If your flat out is walking probably, if your flat out is Usain Bolt probably not.

Ok option a..... Move slower so you can turn 90 degrees exactly..... Option b slow down so you can turn exactly 90 degrees.

Mach3 is not very good at defining what Constant Velocity actually is .....  what is the relationship of how slow is slow enough?  How much in advance of the junction or corner does it slow down?  Is it different for G01>>G01 or G01>G02/3 or G02/3 >> G02/3 or G02/3 >>G03/2 or G02/3 >> G01 motion?

Try to use the motion planner effectively by using linear motion where the move is linear and arc motion where the motion is an arc.  Use roughing cuts and finishing cuts.  Consider using exact stop with finishing cuts if precision is required.  That way the unknowns / undefined elements of the motion planner and constant velocity are removed or minimised.

Jerk or jolt is something slightly different and is to do with trapezoidal acceleration which all lower cost motion planners (mach3/mach4 etc) seem to do and is related to your machine setup of drive mechanism, microsteps etc.

15

General Mach Discussion / Re: Mach3 plasma + THC 150 issue

« on: December 26, 2018, 04:57:26 AM »

Have you read and setup the proma thc 150 according to the primary manual

There are a couple of settings within the primary that inhibit motion until the arc voltage has stabilised and also another that activates a delay to allow the voltage to stabilise

http://proma-elektronika.com/index.php/en/products/thc-torch-height-control/compact-thc-150

The proma is a VERY basic thc it can also be a bit slow especially if you are cutting thin material fast

I did not get on well with the proma but what I did was the following to get it to work ok for me

YMMV

In the proma set the following up
HYS (hysteresis) set to +/- 1V (its as good as you can get and the error is 2v which is about 1.2mm (1/16") approximately!
d-t (delay time) set to ~ 2 seconds.   What this does is when the proma detects the cutting arc voltage window (below H-U...see below) it waits the time delay before issuing an THCUP or THCDN signal.... It allows for an extra amount of stability once the voltage is detected.
H-U (high voltage) this is the transfer voltage detection limit (aka ARCOK signal).... What I did was set this to a lower voltage but slightly above the cutting voltage of my machine which was 160v.... This allowed for the the arc transfer to take place within the machine and for the voltage to stabilise.   The knock on effect was that the pierce hole would be slightly larger because the machine will not begin motion until the arcok signal is received (providing you have ticked the box under config>>>ports and pins>>> spindle >>>thc )

As you have a powermax45 it gives you a arcok output indicating transfer has taken place so I would use that and ignore (not use) the arkok from the proma.
I would set the H-U on the primary to about 150v because this will act like a kerf detect THCDN inhibit.  I would also consider playing around with d-t setting in the proma because if you do use the arcok from the hypertherm45 motion will begin when the hypertherm45 gives the arcok signal but the primary will not give the thcup/thcdn signals until both the detected voltage is below H-U AND d-t has elapsed.  So if you are cutting some thin material at 400ipm in 2 sec it would have travelled 12" (ish {depends on your acceleration settings as motion will go from zero to your cutting voltage)

The proma IS a very low cost THC do not expect brilliant TH control. THC offered by some other manufacturers offer a lot of other options.  Mach3 is now also very old plasma technology and many more plasma options are available so again don't expect brilliant finish...  It's like cars... Newer models offer developments in performace, efficency, and automation that you won't get from an older model that's development has stagnated and has not been updated for many years)

Good luck

16

Mach4 General Discussion / Re: G95 mill G99 lathe feed per revolution is it motion controller functn dependant?

« on: August 02, 2018, 12:34:15 PM »

Mach4 Mill, page 6, bottom, G94 Feed per Minute, G95 Feed per Revolution
http://www.machsupport.com/wp-content/uploads/2014/05/Mach4%20Mill%20GCode%20Manual.pdf

Mach4 Lathe, page 7 bottom, G98 Feed Per Minute, G99 Feed Per Revolution
http://www.machsupport.com/wp-content/uploads/2014/05/Mach4%20Lathe%20GCode%20Manual.pdf

different gcodes in mill and turn / lathe.

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Mach4 General Discussion / Re: G95 mill G99 lathe feed per revolution is it motion controller functn dependant?

« on: August 02, 2018, 09:19:43 AM »

Thanks Craig for your post + taking the time.

The discussion is over G95/G99 (feed per revolution) not G33/G76 (threading cycles)

from what I've read on various forums of misinformation is that G95/G99 can be done one of two ways broadlly.

The easy way (1) is:
No spindle speed feedback, and feedback is set (statically) based upon the programmed / commanded spindle speed (S*********x)
eg

Code: [Select]

G95 (feed per revolution)
X100 S10000 F0.01
which translates to 0.01 units / revolution X 10,000 revolutions / min = 100 units / min.

hence it would be exactly the same as specifying

Code: [Select]

G94 (feed per min)
X100 S10000 F100
There is no gain with this sort of implementation really except you get a little less calculation to perform than you would on a lathe for example or even maybe a mill where you may multiply the feed/rev X the no of cutter teeth to get your corrected feedrate.

The more difficult way (2):
With spindle feedback
This basically will slow down or speed up the feedrate based upon the ACTUAL spindle speed.

It does not adjust the spindle speed at all (forget PID loops).  All it does is dynamically, during the motion it will adjust the ACTUAL feedrate relative to the ACTUAL spindle speed.

The feedback does not need to be that great / fast given the change in spindle speed is likely to be small (its not going to go from 10,000 rpm to 1,000 rpm or you'll probably break the tool / its indicated that you've broken the tool).... but what it may do is go from 10,000 to 9 or 8,000 and then back up to 10,000 as PID kicks in (seperatly looped / controlled), and up to 11 or 12,000 when the cut becomes easy before PID kicks in to slow it down.

so when the spindle is doing 8,000 rpm, its a good time to backoff on the feedrate a little (- < 20% from the target feedrate) and when its doing 12,000 rpm it would be a good time to bump the feedrate up a little (+ < 20% from the target feedrate) to compensate for the cut load.

PID is normally programmed under no load conditions from my experience, so under load when the cutter begins to cut or when the load reduces when the cutter comes out of the cut or is doing a zig-zag pocket and not a contour the "P" + "D" (proportional + derivative (if used) factors) will be too low and the "I" (integral factor) will be too high.

I did ask Andy at Warp9 yesterday and was given this reponse

I talked with one of the Mach4 developers, and he said:
All we need is spindle feedback. Then Mach does it all. 

There are a few discussion threads on G95/G99, here is one
https://www.practicalmachinist.com/vb/cnc-machining/milling-using-feed-per-revolution-g95-good-265234/

Apparently G95 is the default setting for Mazak machining centers, never used one {or ever likely to}, but its interesting all he same, another way to skin that same cat

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Mach4 General Discussion / Re: G95 mill G99 lathe feed per revolution is it motion controller functn dependant?

« on: August 01, 2018, 03:27:12 PM »

Thanks for that, also trying to figure out if it needs to be enabled (coded) within the motion controller (like treading) of if mach4 gets the feedback and internally adjusts the feedrate before sending the motion out to the motion controller

19

Mach4 General Discussion / G95 mill G99 lathe feed per revolution is it motion controller functn dependant?

« on: August 01, 2018, 02:52:12 PM »

As per the title?

How does mach4 obtain the spindle speed?

Encoder feedback?

Single pulse per revolution trigger?
Thanks

Rob

20

Mach4 General Discussion / Re: Mach4 lathe / turning general state of development question

« on: July 31, 2018, 11:38:53 AM »

I've not started using them yet, but noticed that the Threading lists the pitch as 1/TPI

TPI is fine if you're imperial, but I'm from a land of metric threads....

(I was hoping to have a play with them at some point)