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Topics - JG

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1
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.

2
General Mach Discussion / Simple radius cutting - isn't !
« on: July 19, 2020, 08:05:46 AM »
It all seems so simple when reading/watching various G-Code tutorials but the reality is far from 'simple'.

I had some issues when trying to cut a circle - well actually I was 'Drawing' a circle,  the 'simulation' in Mach3 using the standard layout I find difficult to read and changing that to show a larger image is fraught with many other issues needing a better knowledge of VB that I currently have. I found an easy solution though by making a spring loaded 'Pencil Holder' to use instead of a milling cutter and with that in place I have sussed what happens when you change the I & J  parameters.

Next I viewed a tutorial about simple radius profiling but no matter how I adjust the I & J parameters - to date I've only been able to 'draw' an outline with the corners reversed --  ie 'scalloped' instead of 'rounded' - see attached .PDF.

The program used is very basic :
Code: [Select]
%
O0000     (Radius test)
N100 G17 G21
N230 G00 X-100 Y50
N240 Z-27
N250 G01 Z-29 F250
N260 Y-70 F3000
N270 G02 X-80 Y-90 I0 J-20
N280 G01 X80
N290 G02 X90 Y-80 I10 J0
N300 G01 Y10
N310 G02 X50 Y50 I0 J40
N320 G01 X-100
N330 M05
N340 X200 Y100 Z0
N350 G40
N360 M30
%

I'm currently not too concerned about tool offsets - though I suspect that is the reason that the drawing produced has 'curves' instead of sharp points at each change of direction (witness the purple dashed line).   I would expect this code to follow the 'Red' Line so I'd be grateful if someone could point out what I'm missing.




3
General Mach Discussion / Are G33 & G76 supported in Mach3?
« on: July 17, 2020, 03:49:56 AM »
I'm investigating 'Thread Milling' but cannot find any details about the parameters I need to add after a G33 or G76 call. Using the [ G-Code ] button in Mach3, these codes are not listed so there are no 'hints' and I can't make head nor tail of what is supposed to happen after I select the 'Thread Milling' Wizard -- it simply shows me a new screen with Exit. Post Code, etc. along with a number of apparently editable dimensions which return to the initial state upon exit. The [ Post Code ] does not alter the 'No File Loaded' message.

Since I am looking to make 'large' (but short) threads  -  100 - 200mm dia and 2 - 4.5mm pitch  -  using a single point tool a 'Tap' is not an option  :)
I understand the complexity of threads needing a very specific feed rate in the Z axis which will not (necessarily) be the same as the feed rate in X & Y but cannot yet see any G-Code that will achieve that.
Any input appreciated!


4
General Mach Discussion / G82 Drilling Cycle
« on: July 13, 2020, 08:23:38 PM »
I do hope that this is the right place to beg a G-Code question - if not please advise, and maybe move to a more appropriate section.

I'm making a sacrificial table for my Denford into which I will be putting a grid of M4 threaded inserts.

This entails drilling a series of holes - all the same diameter and depth - so I've been reading the CNC Cookbook tutorial which tells me that the parameters needed for a G82 Drilling Cycle are :
  •   -  X-Y :  Co-ordinates
  •   -  Z :  Bottom of hole
  •   -  R : Retract position
  •   -  P : Dwell time
  •   -  F : Cutting Feed Rate
  •   -  L : Number of repeats
Now, I understand all of those but can't see where the distance between the holes is specified. I can see that the holes must be in a line - either on the X or Y axis and that a second/third (and so on) cycle would be needed to create a [grid] -  in my case this will be 50 x 40 (X - Y)

The holes will be less than two diameters deep so there is no reason to use G83
I've read the tutorial a number of times but cannot see any reference to the spacing --  what am I missing?

5
General Mach Discussion / Screen Editor ?
« on: July 13, 2020, 07:35:12 AM »
May be a silly question  - but I'll ask anyway :)
I see a response from 'Tweakie.CNC' to another post which mentions :
(Use the Screen Editor to add a VB button ....).
I've looked at all the options in the menus but can't see a listing for a Screen Editor  -  I have found a means by which I can modify the fonts used. If such exists, is it possible to modify (enlarge) the Table Display window ?   My screen is large and I also have a second monitor which I could expand on to as well.


6
General Mach Discussion / MDI G-Code not actioned
« on: July 13, 2020, 05:23:29 AM »
Hi - Very new to CadCam - been looking at Mach3 driving a Denford MicroRouter Compact for the past week and today cut my first slot(s) in 18mm Plywood to make a sacrificial table.

I haven't yet run a 'file' but I have been using the MDI and entering G-Code by hand which generally does exactly what I would expect but on occasion hitting [Enter] after typing the G-Code does nothing - not even displaying the command in the pop-up box - and at other times it does clear the line and show it in the pop-up but the command is not transferred to the Denford.

Even when that happens and I test that I can turn the spindle on it does action that and it also responds to [REF ALL HOME].

Once I [Esc] from the MDI Input I can use my hand controller to move the tool along X, Y or Z without problem but the manual G-Code entry still doesn't operate.

I've also made sure that there are no [Error] codes.

??? There must be something simple that I'm missing but look to the wisdom of the forum for guidance

TIA.

7
General Mach Discussion / How to generate G-code in Mach 3
« on: April 03, 2007, 06:56:23 PM »
It will no doubt be very obvious   -  once I've done it   -   but I've spent two days (well, part of) trying without success.

I can create .DXF, .WMF, HPGL or any of the supported bitmap format files using CorelDRAW but trying to create G-Code using LazyCam I find totally impossible.

I can get an outline of the object on the LazyCam screen when I import an HPGL file but all other vector formats report the file contains 'splines' which cannot be imported and then tells me that there is nothing to import.

When I do get an outline I can rotate it and move the origin but cannot see any 'button' to create the G-Code. Looking in the options or lazyCam  when I hit the G-Code button I see that there is a tick box for "Send file to Mach 3 when posted" but even with this 'ticked' on clicking the 'OK' button I get a 'File Creation error'.

I'm sure the collected wisdom here can point me to what I'm doing wrong.

JG


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