Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Kristin D on August 21, 2008, 01:18:45 PM

Title: Basic initial setup question
Post by: Kristin D on August 21, 2008, 01:18:45 PM
I finally got my new leadscrews and steppers installed on my Taig mill, using a HobbyCNC Pro controller board w/205 Oz motors, got the motors tuned to provide the correct distance (duhh, after I realised that the controler was set for 8 microsteps). Now here is where I start getting confused between machine and work cordinates, I was able to write a bit of g-code to drill holes for the heatsink for my driver chips and was a little confused when I started out at the lower left corner and the machine moved to the lower right before starting! It worked out fine but I was not expecting the lower right as a start point, good thing I did a little "air cutting" first to see where it went.

Now I would like to activate the home/soft limits, I tried by entering 10" and zero for X with a .25 zone and it didn't seem to work at all (xml. attached) Do I need to edit the G28 box too? I still have not installed any physical home switches as I wanted to use the mill to make the brackets and am still between using micro-switches or optical slotted ones. Should I just wire a pushbutton and move the table with the jog keys to where I want home and fake it?

I ran one dxf through lazycam and it partly worked, I think I worked out why the circle was an elipse though as I didn't clean the dxf first. I am slowly finding all the little tweeks such as being able to direct enter to the DRO's and set scale (Is it obvious I didn't RTFM? got to take that to the printer and get it run off and bound).

Is there a way to zoom in on the toolpath window, all I see is a tiny flyspec in the center, no way to see what is going on.

Well that is enough of my rambling for now, sure I'll have dozens of more questions soon.

Kristin

Title: Re: Basic initial setup question
Post by: jimpinder on August 21, 2008, 02:07:58 PM
Machine co-ordinates - these are co-ordinates that Mach keeps track of so that it knows where it is. You cannot change these directly. If you press the Machine Co-ordinates button the button surround will light up. The DRO's are now displaying machine co-ordinates.

The only way to change these is with the "Ref All Home" button.  If you had your home switches connected (which you haven't) what you would see is the machine move in turn to each of the home switches, and stop there and the DRO would go to zero. The machine is now "homed" and Mach 3 knows where it is.

If you do not have switches, or they are not activated, then the DRO's will go to zero, without the table moving. (But that is not much use)

Program Co-ordinates - these are displayed when the Machine Co-ordinates button is pressed and the surround light goes off.
You can zero the program co-ordinates at any time by using the zero buttons. If you do this so that the Machine Co-ordinates and the Program co-ordinates bith display zero - then the difference will become obvious.

It is unlikely that the posittion in which your home switches are set is any use for machining components, and will almost certainly not be the position that your program calls 0.0.0. (for mills this is usually at the bottom lefthand corner of the workpiece, with the cutter resting on the top of the workpiece - BUT NOT ALWAYS SO). You must find out where your program thinks it is for position 0.0.0.

If you are displaying Program Co-ordinates, then jog the axis to the correct position to start your program - and zero the DRO's.
If you change to Machine Co-ordinates you will see that these have not changed. If you look in Config/Fixtures you will see that the default config G54 has changed and contains the co-ordinates that your Machine Co-ordinates are displaying. These are the offsets between Machine and Program Co-ordinates.

What does this mean -???

What this means is that (If you have the offset stored in one of the other offset slots - G55 to G58 and G59P7 to G59P255) if you zero the machine by "Ref All Home" then if you have the offset written into the program e.g. G55 then the machine will move to the correct position to start the program. All your programs can have different offsets if you need them (there are about 256 of them) or they can have the one offset if you always use the same work piece holder etc.

You can introduce other offsets into the program, and say run the program 3 or 4 times, using a different offset each time, and therefore cutting identical work in 3 or 4 different places. (My CNC man with a big machine does this quite often - He has 4 vices on the machine and puts work in each - the machine then cuts the same pattern at each of 4 places - it saves him changing the workpieces everytime.)

During all this your machine still keeps track of its movement in Machine Co-ordinates but the Program Co-ordinates display enables you and I to look at the DRO's and make sense of what we see - since it should at any particular line display the co-ordinates that line is in the process of cutting - or a position at which it is drilling etc - and we can compare this with the program immediately.

I'll now have a lok at the rest of your post.










Title: Re: Basic initial setup question
Post by: jimpinder on August 21, 2008, 02:18:47 PM
To set up your soft limits you need to "map" your table - so you need to set up a point to which you can return confidently - say the bottom left hand corner - with your cutter on the table. (This is only an example - and it can be anywhere - but should be repeatable, not necessarily to any great accuracy, but reasonablly so.) You are in fact making your own home position - and then "Ref All Home".

Your Machine Co-rds  DRO's will all go to zero.

Still watching the Machine Co-ordinates then jog your table to it's extremeties and make a note of the DRO reading - same with your z axis. Set your soft limits to these values (or just short of them) - in the machine set up units (ins or mm).

The reason your machine was doing unpredictable things is that it did not know where it was - or it thought it was somewhere ither than the place you thought it was.
Title: Re: Basic initial setup question
Post by: jimpinder on August 21, 2008, 02:21:52 PM
What you need to do - say re the toolpath window question - is look at the video tutorials, which are very good. You could (at one time) download them, I'm not sure if you still can, but they answer so many simple little questions, and quite a few you didn't think of.
Title: Re: Basic initial setup question
Post by: Kristin D on August 21, 2008, 02:43:39 PM
Jim,

Thanks again, who would have thought of shift and mouse to zoom the window, now off to try and set up the limits!

Kristin
Title: Re: Basic initial setup question
Post by: Kristin D on August 21, 2008, 05:27:31 PM
OK I have watched the flash video of homing,limits and offsets three times, on the second and third I went to the other machine and entered what I thought I needed, now it's telling me I am outside of the soft limits and can not invoke the setting. Here is what I did, I ran the Z up to 1/4" of the top, the X all the way plus and the Y all the way plus, measured with a rule to get the range entered 9.75 for X max, 4.25 Y max and 5.0 Z max. zeroed the axis and ran them to the other end by jogging (which should be 0,0 XYZ) then zeroed again in Machine cordinates. Moved the table and switched to program cordinates, and zeroed again. Must be missing something real simple here.

Kristin
Title: Re: Basic initial setup question
Post by: Hood on August 21, 2008, 05:51:00 PM
Ok heres what to do, jog so the tool is lower left of the table and Z is fully up and press Ref All button, that will set your machine coords to X0 Y0 Z0.
Now in Homing and limits enetr zero for X and Y min and Z Max. Values for X and Y Max and Z Min are the distance of your travel on each axis, however you need to remember that the Z will be a negative number so if for example you have a 5inch Z travel the Z min will be -5.

Hood
Title: Re: Basic initial setup question
Post by: Kristin D on August 21, 2008, 05:53:28 PM
 :D Another senior moment I suppose, I went back and put a (-) in front of the Z soft limit and it's somewhat working, just need to fine tune now, the steppers play a lovely little melody when slowing down at the limits.

Kristin
Title: Re: Basic initial setup question
Post by: Kristin D on August 21, 2008, 08:59:26 PM
OK,
I tried to run the roadrunner file, first it was cutting air then when I reset the z axis it said I was beyond the limits? Where do I start off with Z and in machine or program codinates do I either zero or ref to home. Slightly frustrating but I am sure it will all become clear soon.

Kristin ???
Title: Re: Basic initial setup question
Post by: edvaness on August 21, 2008, 11:45:47 PM
Kristin,
To run a job you set the Z zero at the top of your part. Program coordinates.

Ed V
Title: Re: Basic initial setup question
Post by: Hood on August 22, 2008, 02:30:06 AM
When you start Mach you will need to reference and because you dont have limits it means you need to jog so the tool is lower left and fully up, you then press Ref All. Once done load your G-Code and you will see the toolpath, now as you have SoftLimits set you can use the display button to show the table view rather than just the part view. You will notice there is now an area outlined the size of your table. As long as the work is within this area you will be ok but you may wish to get it more central by jogging the X and Y  then pressing the zero buttons at the side of their respective DROs, then regen and look again. Once you have that sorted then you move your Z down ntil it touches the top of the work and zero that, you are now set to start :)
Incidentally the Display button presed again witll take the view back to a work view.

Hood
Title: Re: Basic initial setup question
Post by: Kristin D on August 22, 2008, 04:37:32 PM
OK still a bit confused as to the axis, x+ should move the table left?
Y+ moves the table out?
Z+ moves up?
So I should bring the table full right and in and the z axis up to set machine coordinates, correct?
Then ref all home?
Then switch to work/program coordinates?
Then jog to where I want to start cutting.
Bring the z axis down to the workpiece.
zero the Z axis there.

Set soft limits on now or before?

Do I ref all home after I switch to program coordinates or not touch that again?

I think I have it in the right order but the machine either tries to ram the small cutting burr into the wood block I am abusing or stops with a soft limit. I know you have all answered this but it's spread over about three posts and for some reason my brain is skipping and I can't get this clear as a step by step process. Watching the video is not much better as he keeps saying Oops I forgot to set that and going back and forth.

Kristin

I know I am so close I am just missing one simple step here in the process.   
Title: Re: Basic initial setup question
Post by: Hood on August 22, 2008, 04:57:07 PM
OK still a bit confused as to the axis, x+ should move the table left?
Y+ moves the table out?
Z+ moves up?

It is easiest (for me anyway) to always think of the tool in relation to the work rather than the way the table is going. Having said that yes you are correct, table left and towards you are postive moves as is Z positive is up.


So I should bring the table full right and in and the z axis up to set machine coordinates, correct? Yes thats correct
Then ref all home? Yes
Then switch to work/program coordinates? you dont have to be in machine coords to home, only if you want to check or be in them for any other reason, if you are in machine coords then yes change to work
Then jog to where I want to start cutting.Yes and remember to zero these axis
Bring the z axis down to the workpiece. Yes
zero the Z axis there.Yes

Set soft limits on now or before?  Softlimits can be left enabled at all times, if Mach wont let you then you have them set wrong,

Do I ref all home after I switch to program coordinates or not touch that again? Only time you need to Referece is when you start Mach or if for some reason you have lost position,eg E-Stop or crashed the tool and lost steps


Hood
Title: Re: Basic initial setup question
Post by: Kristin D on August 22, 2008, 05:00:56 PM
Hood,

Thanks I am off the the other room with a printout of your answer so I can follow step by step, I let you know in a bit if I had any luck with this. As every computer user knows GIGO.

Kristin
Title: Re: Basic initial setup question
Post by: Kristin D on August 22, 2008, 05:06:56 PM
Sucess at last, worked perfect once I got out of the way and sorted out not pressing the wrong buttons when trying to set up!

Back to abuse my bit of 2x4 wood again! :o

Kristn ;D
Title: Re: Basic initial setup question
Post by: Hood on August 22, 2008, 05:17:43 PM
LOL
 It will soon become second nature and you wont even need to think about what you are doing :)

Hood
Title: Re: Basic initial setup question
Post by: Kristin D on August 22, 2008, 07:23:33 PM
OK when I try to cut a circle with either lazycam generated or using g12 (g12 I .25 f3 for example) I end up with an oval, checked that all the motors are set to the same steps per, I entered this in the midi box and that's what I get?
attached is my current xml file. Oh the cutter returns to the same position so I don't think I am loosing steps, very odd>  :o

Kristin
Title: Re: Basic initial setup question
Post by: Hood on August 22, 2008, 07:34:00 PM
backlash?

Hood
Title: Re: Basic initial setup question
Post by: Kristin D on August 22, 2008, 07:56:16 PM
Hood, good answer, I need to check but since it's all new leadscrews with adjustable nuts, and the oval is like 1.5:1 off I can't really see that as the problem. I cut a .25" radius and its .5 side to side but .375 top to bottom, that has to be way more than backlash. It looks like it's stopping Y movement and just running X across the top and bottom. Looks good on the tool path.

I would think it was loosing steps but I am taking a light cut, slow and the dang tool keeps returning to the same start position. Perplexing.

Kristin
Title: Re: Basic initial setup question
Post by: Kristin D on August 22, 2008, 08:08:06 PM
Acck! it is backlash seems something came loose and I can see the shaft moving in and out before it moves the table :-[
Time to pull it apart and tighten the offending part!
Kristin
Title: Re: Basic initial setup question
Post by: Hood on August 22, 2008, 08:19:51 PM
LOL oh well at least you know now :)

Hood
Title: Re: Basic initial setup question
Post by: Kristin D on August 24, 2008, 08:42:19 PM
OK here is another question, I have a cast aluminum tray about the size of my mill table I have been milling it as a tooling plate (10-32 holes on 1/2"  centers) with the attached G-code (crude beginer stuff) now before I unbolt it is there a routine to sweep the whole plate with a 1/2" end mill to smooth out the surface, it's 9.5" in the x direction and 3.75" Y. It would be cool if someone could explain the function of the code as I can see this going on once more as I am planning on buying a piece of 1/2" 6061-t6 next time I order metal stock and remake this. I can see the need to do this type of operation over and over again and just can't seem to find the examples of g-code for it.

Kristin
Title: Re: Basic initial setup question
Post by: Hood on August 24, 2008, 08:50:27 PM
Not just use the surface wizard?
Hood
Title: Re: Basic initial setup question
Post by: Kristin D on August 24, 2008, 09:18:08 PM
How do I do that most of the NFW Wizzards are not avalable to me!

Title: Re: Basic initial setup question
Post by: edvaness on August 24, 2008, 10:19:50 PM
Kristen,
 enclosed a program to face your plate. It will go to 10.25 in x and 4.25 in y.
Make sure you have enough travel. XOYO IS LOWER LEFT CORNER.
Use .500 end mill. touch off top of your plate for Z0. Machine will rapid to x 10.250, right hand corner
and feed down to -.010. If doesn't clean up,lower your Z and cut again
NOT RESPONSIBLE FOR CRASHES :o.
 
Ed V.
Title: Re: Basic initial setup question
Post by: Hood on August 25, 2008, 02:49:57 AM
Kristin
 there are lots of wizards available if you click the "Load Wizards" button rather than the NFS Wizards.
Hood