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Offline Kristin D

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Basic initial setup question
« 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

Offline jimpinder

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Re: Basic initial setup question
« Reply #1 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.










Not me driving the engine - I'm better looking.

Offline jimpinder

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Re: Basic initial setup question
« Reply #2 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.
Not me driving the engine - I'm better looking.

Offline jimpinder

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Re: Basic initial setup question
« Reply #3 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.
Not me driving the engine - I'm better looking.

Offline Kristin D

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Re: Basic initial setup question
« Reply #4 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

Offline Kristin D

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Re: Basic initial setup question
« Reply #5 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

Offline Hood

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Re: Basic initial setup question
« Reply #6 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

Offline Kristin D

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Re: Basic initial setup question
« Reply #7 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

Offline Kristin D

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Re: Basic initial setup question
« Reply #8 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 ???
Re: Basic initial setup question
« Reply #9 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
Ed VanEss