[SPEEDRE]

After setting home zero, zero, zero do I have to set the material position as zero, zero, zero and is it called machine co ordinate?
My trials run in the opposite direction from what I desired. Also, if the axis run true, regarding positive negative direction,
why does move contrary to the code?.

[Al_The_Man]

Machine coordinate position is set by G53 to G59.
The one set initially is G52, local coordinate setting to go back to.
Al.

[handlewanker]

Hi...... anybody correct me if I'm wrong.......the work position X and Y zero, be it the corner of the vice jaw or a piece of material clamped to the table, has a zero point ( G54 to G59 ) that you use to reference from once the spindle is positioned at the starting point for a vice and any different work piece.......this would be X0 Y0 and the offset of the cutter will then position the tool with the next G code symbol according to it's diam.........drills do not have a diam offset.

Home position X, Y and Z is at the table travel zero limit for all axes to move the spindle completely out of the way at the end of the job....G code G28..... in order to change cutters or jobs etc.

It is one fixed position that you know the spindle will go to when you code the program sequence with G28 and will move the spindle out of the way to that specific position always.........the work position does not have the Z zero set as this is set in Mach 3 for the particular tool length you are using and can be any Z setting if more than one tool is in a magazine, off machine rack or a tool changer.

A question I would ask.....would you first raise the Z axis above the job, before going to home, to make sure the cutter is out of the way of any clamps or walls of a cavity, as I think all three axes operate simultaneously when the G28 command is given.
Ian.

[daniellyall]

read this LinuxCNC Documentation Wiki: CoordinateSystems different system same stuff

[SPEEDRE]

O.K. That to me is Greek. I don't read code. I use Mach 3 and V Carve Pro Ver.4.6.
After I set the Z axis at zero, the left hand lower corner of the material, touching the material surface, raise the Z, no obstructions material taped to spoil board,
click the cycle button, the machine travels off in the opposite direction.
Instead of positive movement I get negative movement, what could be the problem here??????

[ger21]

Are your X and Y axis at zero when they are in the lower left corner, before starting?

[Superman]

After setting home zero, zero, zero do I have to set the material position as zero, zero, zero and is it called machine co ordinate?
My trials run in the opposite direction from what I desired. Also, if the axis run true, regarding positive negative direction,
why does move contrary to the code?.

Machine zero is where the machine is when ALL axis are homed
Work zero is the zero of the work-piece ( usually a corner of your stock material ) ( this is called up using the G54 G-code ) ( it stores the distance values form Machine zero to the Work-piece zero......it is not in your program, it may exist as the default )
( if G54 is X0,Y0,Z0 then your work origin IS the Machine zero, your CAD part should be placed according to this )

( Profile 1 )
( Mach2/3 Postprocessor )
N20G00G20G17G20G90G40G49G80 ( set rapid, check if m/c is set to inch, XY plane, check if inch...again, absolute, cancel cutter comp, cancel tool length, cancel canned cycle)
N30G70             ( not sure what G70 is ? )
N40T2M06           ( select T2, place it in the spindle)
N50G00G43Z0.7874H2 ( rapid, read H2 value, add to spindle length, goto Z0.787 above work zero)
N60S12000M03       (set rpm to 12000, start spindle CW)
N70G94             ( set feed per minute)
N80X0.0000Y0.0000F100.0 ( does your machine go to this position ?) 

G20 should be by itself on line N10 ( also doesn't need to be stated twice on N20 )
Check the control to see if G54 is actually set & is being used
What values are in the G54 (work offset page) ?
Dose the machine travel to N80 ?.......is the material placed in the same position on the table, as it is in Arcsoft ( from your NC file, the cutter is moving in the X+, Y+ area , you seem to be only cutting a maximum of 1/8"" deep into the material )

[handlewanker]

Hi........am I correct in saying that if you have set your machine's home position correctly, all you need to do when you are running a program that is compiled by a carving program....whatever..... like V Carve Pro etc is to place your material on a certain spot that is set in G54 etc?........the G54 offset value will give the co-ordinates to the carving program to know the starting point......the carving program will refer to the G54 position wherever it has been set for it's starting point.

If I hand write a G code program the home position is not needed for any reference as I already have the vice jaw position set at zero in G54 and any code....that I compile........ will be started from that point because I know where it is.

I realise that a program that is many thousands of lines and is CAM compiled would definitely need the home position for reference with a preset G54 position too.

My knowledge is that the home position is fixed....cast in stone for all time on the machine of your choice whereas the G54,,,,G59 position is set and reset for a vice or work pieces as the need be and is only relative to the home position if a CAM program is being run.

Am I right in saying that the CAM program will have a G54 in it and this will refer to the G54 position I have set in the Mach 3 tool register.........the CAM program does not know where the G54 position is.....that is my prerogative to set it for the job in hand.

Am I also right in saying that ALL CAM programs have a G54 etc line in them to get the starting point for the job......what happens if there is no G54 value set in Mach 3?
Ian.

[Superman]

Hi........am I correct in saying that if you have set your machine's home position correctly, all you need to do when you are running a program that is compiled by a carving program....whatever..... like V Carve Pro etc is to place your material on a certain spot that is set in G54 etc?........the G54 offset value will give the co-ordinates to the carving program to know the starting point......the carving program will refer to the G54 position wherever it has been set for it's starting point.

If I hand write a G code program the home position is not needed for any reference as I already have the vice jaw position set at zero in G54 and any code....that I compile........ will be started from that point because I know where it is.

I realise that a program that is many thousands of lines and is CAM compiled would definitely need the home position for reference with a preset G54 position too.

My knowledge is that the home position is fixed....cast in stone for all time on the machine of your choice whereas the G54,,,,G59 position is set and reset for a vice or work pieces as the need be and is only relative to the home position if a CAM program is being run.

Am I right in saying that the CAM program will have a G54 in it and this will refer to the G54 position I have set in the Mach 3 tool register.........the CAM program does not know where the G54 position is.....that is my prerogative to set it for the job in hand.

Am I also right in saying that ALL CAM programs have a G54 etc line in them to get the starting point for the job......what happens if there is no G54 value set in Mach 3?
Ian.

To give you a one word answer.........yes
- Mach is very similar to Fanuc...
Fanuc have a default setting of each family of G & M codes on start-up. This is why you state these codes at the beginning of every NC program....so the control is switched back to it's initial state......these you could call "Safety Codes"
( same would exist for a co-ordinate system, at least it should be stated at the beginning of each program )

so if you didn't state G54 in your NC program, it may be that the control resets back to that co-ordinate system.....it should show up on the status page as to what co-ordinate system is being used
( & you may have been using G54 since the beginning )

You are correct that the machine home is fixed.......PROVISIO.....it is reset EACH time you home the machine......in the ideal world, it would be the same point each time you home....
-- now think what could cause a "miss-home",... swarf around the limit switch, loose switch, may cause the axis trigger at the wrong position & preset the zero for that axis on the wrong "pulse"......suggest you only home it once (if possible )

G54 work offset holds the values from machine origin to the work origin ( ie M/C home in rear, L/H corner, Z at the highest point, then G54 should hold an X(+value), Y(-value), Z(-value)
- this allows you to program with a G54 in your program for one holding fixture, with the part origin stored in G54........you may need to have another job setup that interrupts, put a G55 in the program, set the G55 (work origin)

[daniellyall]

Writing a CNC Program – ManufacturingET.org

[Superman]

Well that beats trying to explain it........let someone else do it....:cheers:

[handlewanker]

Hi....read the tutorial......bit long winded and confusing to me.

What I gained from it was you have to set the starting point for G54 at the corner of the vice or work piece.........according to the tutorial you then write G54 as your co-ordinate starting point......or G55 if the starting point is another job etc.

The important bit is to, in the first instance, set the home co-ordinate point, and this is where I'm totally confused.

According to the Utube tutorial...I think by Paul Campbell...... for a mill, you move the table all the way to the right side and close to the column with the head all the way to the top.

When I did this on each axis the limit switch tripped out and every thing ground to a halt....totally dead still....all axes immovable.

The only way to get off the limit switch was to switch off the mill and hand wind the X axis back a bit off the limits, press reset and move the Y axis to the column....same result.....limit tripped......same for the Z axis.

Having done that I set the DRO's to zero ........must the M/C co-ordinate switch under the Mach 3 display screen be activated before or after I zero the DRO's?

The next bit is the tricky one.........when do I do the "refer all home" function and what does it actually do?

Sorry to be a bore......I know the home function needs to be done but not how the exact sequence comes about.
Ian.

[ger21]

Watch the Homing, Limits and Offsets video here:

ArtSoft USA - Video Tutorials

[handlewanker]

Hi....thanks for that.......I looked at that vid some time back but it didn't make sense as the guy waffled all over the place and fed info about things I knew nothing about and meant nothing to me at the time.....very confusing for this noob.

Now I'm a little bit more cluey....about 2% .......the homing is starting to come together....needs looking at over and over again until it's stamped on my memory prior to going outside and attacking the mill with gusto.....err... more confidence etc.
Ian.

[Al_The_Man]

Pic up the CNC programming book by Peter Smid!
Al.

[handlewanker]

Hi...thanks for the info, I already have a DVD on CNC Secrets Revealed etc, but the book would be handier as it's always available without having to fire up the computer every time, even though the DVD is in PDF form and can be printed out....my printer decided to go offline and needs to be "looked at".
Ian.
Edit.
Wow.....I'm in the wrong business.....the book aforementioned by P. Smidt sells for........wait for it......US$156 ....but it's post free......that translates to approx. A$200.....if I go for the same version on CD it sells for US$125.......I think I'll stay with the CNC Secrets Revealed DVD I have and give it a closer look as it does give the low down on programming once the fundamentals are learned and that's where I'm at......at the moment I'm on the starting blocks with my right foot on the pedals looking for a way to make the engine make more noise etc......getting there, thanks to the forum.

[daniellyall]

look up Amazon it's a bit cheaper

[handlewanker]

Thanks Dan.......I may have to.....the DVD I have on the subject is an all encompassing complete CNC tutorial guide to all aspects of CNC, but the important bit I needed.....specifically the method in detail to home the mill was not even discussed.

It is a typical approach by the experts that assume you are ready to make your first part and the machine is up and running etc........I needed to get to the start line, not off it and running.....that is the easy part as I have done a bit of G code programming and made the machine talk to me.

HOWEVER...........now that the Artsoft tutorial by Paul Campbell has been watched and listened to a number of times it's becoming clearer as to what is required.
Ian.

[daniellyall]

machine zero, home on a cnc machine, is a safe spot for the machine to be at, it should always be the same spot. it is as you have been told before front left with Z at it's max safe height ( it is with your machine) work Zero is where ever you wont it to be, but keep in mind you can not always use the same spot.
that is the hard part where to put work zero everything is driven from that.

but just get that book it will help and ask, not every one will be correct, but Ger21, Al the man, superman, Tweakie, Hood, hoss and there are a couple of other's listen to them, they have never put me wrong, they will correct you if you are wrong and are nice about it.

[Al_The_Man]

Wow.....I'm in the wrong business.....the book aforementioned by P. Smidt sells for........wait for it......US$156 ....

I always check out Abebooks clearing house for books, I have had them often with the CD unopened, for very cheap.
Al.