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Messages - JG

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Certainly not your English TPS  -  that is vastly superior to my German :)   -  more likely to be my understanding.

I haven't yet tested this on my 'Real' system  -  it's on my simulation Office PC so no 'Hardware' attached  -  also it hasn't happened previously and I'm sure I've specified less than Z -71 in the past (I could well be mistaken though  :-\ ).

I will check the setting in the workshop system in the morning but I'd like to know how I can change the -29 to 0 -- as I've said I have no hardware attached so there surely must be a way to modify it.

That was quick TPS !!   

I've found the [Diagnostics] and see that Z has a work offset 0f -29  which makes absolute sense BUT  I can't find a way to change that to zero.  -   I can simply type '0' over the -29 but can't see a [Save] and the figure returns to -29 when I go back to the Program Run page.

I have to stop programming for the evening - I'm due to host a Zoom Quiz at 6:45  :)    -  I'll look in later though.

Progressing a little further, I'm now wanting to cut a circular 'pocket' - well the outside - and I'd like it to be 22mm deep.
The top of the work is at Z= -52 so starting a Z= -51 to provide a 'Z lead-in' so that there is no plunge entry, I'm using G2 with the Z parameter changing at each pass by 2mm I want to get down to Z = -74 but, in the simulation, I'm getting a [Soft Limits] error when Z is below -71  ???   

This is the program I'm simulating :
Code: [Select]
O0010  (Bore ready to Thread Mill 80 x 3.NC)

N10 (Author - JG  - 24 July 2020)
N20 (for Denford MicroRouter Compact under Mach3 V2)
N30 (Thread Milling 80 x 3mm    -   bore = 76.75 - R= 38.376)
N40 (T3 D=8 Flatt End Mill to remove centre)
N45 (T4 D=24.32 Thread Mill cutter)
N50 (units mm)
N60 (X & Y 0 in MACHINE centre)
        (X Min = -200, X Max +200)
        (Y Min = -100, Y Max = +100)
        (Z Max = 0 at top    Z Min = -100)

N100 G17 G21 G00          (set up XY Plane & Metric - fast traverse)
N110 X34.0762 Y0 Z-51    (move XY & Z     -    Determine Z by reference to work)
N120 S8000 M3                 (set spindle speed & start spindle)
N130 F3000                        (set feed rate  -  simulation )
N140 G2 I-34.0762 J0 Z-52    (cut Circle about 0,0 feeding Z 2mm)
N150 I-34.0762 J0 Z-54
N160 I-34.0762 J0 Z-56
N170 I-34.0762 J0 Z-58
N180 I-34.0762 J0 Z-60
N190 I-34.0762 J0 Z-62
N200 I-34.0762 J0 Z-64
N210 I-34.0762 J0 Z-66
N220 I-34.0762 J0 Z-68
N230 I-34.0762 J0 Z-70
N240 I-34.0762 J0 Z-71
N250 I-34.0762 J0
(N260 I-34.0762 J0)        (Cut flat bottom    NO Z change)

N1450 M05           (Turn spindle off)

N1500 G00 X0 Y0 Z0  (move tool at fast rate to 0 0 0)
N1510 M30           (Close Program)

The error appears if I set Z in N240 to -72   --   I would expect (in theory) to be able to go to -100, there will of course be other factors such as tool length that will preclude that, but I'm not setting a tool Nº which might confuse the issue anywhere.

A separate question  -  after each rotation (line of G-Code  N140 - N240) there is a tool 'dwell'; can this be eliminated so that the program simply runs a continuous cycle ?

Hi Paul,  I'm also very new to G-Code but my approach is to get an understanding of what G-Code does by writing short and very simple programs by hand to see EXACTLY what happens.

Over the past week I've learned a great deal by making silly errors and having them corrected by the other learned folk on the forum.

If you don't know what (say) G30 or G17 or G54 does then reading through a program generated by some CAM program is not likely to make a lot of sense.

That is fantastic news TPS  -  and tells me exactly what I wanted to know - without me causing a disaster by running a cutter into wood.

I can see now that by changing the radius I can control the amount of 'cut' applied when milling a thread and by specifying the Z distance I'm specifying the 'pitch'.   I was obviously over-thinking the whole issue by not having very specific details about what parameters needed to be passed using G33, G34 or G76.

It is now going to be worthwhile making the thread-milling cutter I've already designed.  :)

General Mach Discussion / Re: Cutting a Circle - Figures DO add up!
« on: July 23, 2020, 05:28:24 AM »
Success all round - see photo attached showing 88.75mm dia circle about the centre of my machine table.

I knew it had to be something simple but there are so many potential 'adjustments' available in Mach3 that without pointers from experienced users it can become a mysterious 'fog' and I am very grateful for the advice received.

Now to cut some wood !     

Oh....   before I do,  Graham,  in your code for a helical cut, can the feed in the Z axis be specified ?    ie. can it be controlled separately from the X Y feed so that a 'thread' could be specified using the pitch as the Z distance per revolution?

Thanks Graham & TPS  -  you have both helped immensely!

I've only run the codes on my 'simulation' system as yet but my next job is to go to the workshop system and test for 'real'. (I'll sharpen the pencil!)

Graham - your solution did work but I had to click [ Yes ] when asked to over-ride the soft limits.

TPS  -  you hit the nail firmly on the head!   -   I had assumed that IJK were incremental since I had seen that as the default so hadn't checked, but yes, it was set to absolute and once that was corrected the table display immediately changed.  ;D      I didn't really need to run the code (but I did) and of course the figures fell into line.

This probably also solves the seemingly erratic behaviour I'm seeing in another test of plotting a rectangle with 3 differently curved corners.      I'll let you know.

Thanks for the input Graham but your code produces exactly the same result as mine does   (I'm ignoring the helical for now).

To run it of course I had to modify the Z figures since my system has a Z max of 0 so Z5 and Z1 are both 'soft limit' errors.

Running a simulation and watching the X & Y DROs I see that the max X gets to 44.375 (as you would expect but the Min X goes to -133.125. Similarly the Max and Min Y go to + & - 88.75. From those figures I determine that with an 8mm cutter the diameter of the circle produced would be either 88.75+88.7+8  or  133.125+44.375+8  - both of which amount to 185.5   not the 88.75 ( 96.75-8 ) that I would expect from using a 44.375 offset.

To further check that I'm not ready for the asylum  :)     I've done a 'real life' test using my [Pencil] tool and produced a real plot - including marking the X0 Y0 position - see attached photo - you'll see that the ruler indicates about 177.5 dia and the line is just over 1 mm  wide  (that's due to the marginally off-centre sharpening of the pencil)  which further confuses the issue as it seems to be 8mm smaller than the simulation plot indicates   ???

Incidentally - I now know why I got the 'R or IJK missing' error - the way I'd added that line meant that G2 was still in operation and I should have issued a G1  :-[    but at least I've learned that today !!

In case you'd like to check that I haven't applied any pertinent changes to what you provided, here is the latest program which produced the plot :

Code: [Select]
G21 G40 G00 G99 G17

N1 (Pencil)
G54 G00 G90 G43 X0 Y0 Z0 T3 S3000 M3

G01 X44.375 F500.
G02 I-44.375
G01 Z-34.5
G02 I-44.375
G00 X0 Y0
The second pass using Z-34.5 just presses the pencil down a little harder.

General Mach Discussion / Cutting a Circle - Figures don't add up!
« on: July 22, 2020, 11:42:32 AM »
Trying to get my head around G2 arc cutting, but the simulation shows that the circle diameter is not as designed.
Using an 8mm dia cutter - and therefore allowing a 4mm adjustment to the radius - the simulation shows that rather than cutting a 96.75mm dia pocket it will cut a 185.5mm dia ??? ?  whose radius is 92.75 --  so it's not even cutting 'double size'.

This is the code :
Code: [Select]
O0000  (Bore large shallow hole.NC)

N10 (Author - JG  - 22 July 2020)
N20 (for Denford MicroRouter Compact under Mach3 V2)
N30 (Thread Milling Ø100 x 3mm    -   bore = 96.75 - R= 48.375)
N40 ()
N45 (T3 D=8  Flat end-mill)
N50 (units mm)
N60 (X & Y 0 in MACHINE centre)
        (X min = -200, X max +200)
        (Y min = -100, Y Max = +100)
        (Z 0 at top)

N100 G17 G21 G00                   (set up XY Plane & Metric - fast traverse)
N110 X44.375 Y0 Z-50              (move XY & Z  Determine Z by reference to work)
N120 S8000 M3                         (set spindle speed & start spindle)
N130 F100 Z-52                        (set feed rate & plunge into work 2mm)
N140 F200 G2 I-44.375 J0        (set feed rate, cut Circle about 0,0)
(N150 F100 Z-54)                     (set feed rate & plunge into work 2mm)
(N160 F200 G2 I-44.375 J0)     (set feed rate, cut Circle about 0,0)

N1450 M05                               (Turn spindle off)

N1500 G00 X0 Y0 Z0                (move tool at fast rate to 0 0 0)
N1510 M30                              (Close Program)
I've included all comments/annotations rather than just the working lines in case there is something that I simply have wrong in the basic understanding.

Lines N150 and N160 are commented out because, with them in, Mach3 complained that "R or IJK are all missing from N150" - which I also don't understand - I would expect to take the first cut then reduce the feed for a further 'plunge' and then do a second cut (where I & J would be specified).  Ultimately there would be more cuts depending upon how deep I want the hole to be.

In the light of the Mach3 error message, can anyone suggest how the Z parameter can be specified in the same block as G2 and therefore create a helical cut getting deeper with each 'turn' and if such is possible how would the final depth the specified.

In case anyone thinks that the feeds and speeds are in error I should say that this would be cutting a hardwood such as Ash, Elm, Teak, Walnut  --  etc.

General Mach Discussion / Re: Simple radius cutting - isn't !
« on: July 21, 2020, 08:16:40 PM »
That sorted it Graham, well, at least as far as letting me run a simulation --- and I can see how a 90º arc would be a gentle lead-in to avoid a 'slam-dunk' into the pocket giving a better finish.

I'll see if I can do something similar on my workshop machine in the morning by getting it to draw the path but I'll naturally have to modify the Z figures since that machine has Z0 to Z-100 as the soft limits.

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