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Messages - jimpinder

191
General Mach Discussion / Re: Homing Problem
« on: January 05, 2009, 01:29:45 AM »
The problem is that the computer works differently when homing or limiting.

When homing, it hits the switch, then backs off until contact is broken again (so the switch is not now live). When limiting, the machine hits the switch, stop - so the switch is still live. I do not understand what you mean when you say a proxy.

It seems to me that you are trying to do something that the software is not designed to do. It works ok for one axis, but the sequence of events and the  different possibilities with two axis are quite complcated.

As I remember it, you have the A axis slaved to the z axis, presumably driving opposite sides of the gantry. All you want to do is have both sides home together, so that they are square. You do not say how much out of square this gantry could be, I assume not a lot, and the problem is also, I assume, that even with one side of the gantry powered, the other side will move in sympathy anyway.

In such a position, I would set to and write a macro for what you want. You can do all the functions in Visual Basic, and just replace the Vis basic on the Set Home button.
The sequence would have to be something like this:-

1. Turn off the limit switches.
2. Start moving gantry towards switches
3. Monitor the limit switches.
4. When one is pressed, stop that side of the gantry and wait until the other hits it's switch.
5. Reverse out, monitor both switches.
5. When one opens, stop and wait for the other
6. Set DRO to zero.
7. Rest limit switches.

The problem is that there are so many combinations of switch settings while all this is taking place, that unles you write what you want, I do not think you will find that the Mach3 software will do it, without the odd hiccup now and again.

Jim




192
General Mach Discussion / Re: Reinstall Mach3 How To Do It Properly
« on: January 05, 2009, 01:01:32 AM »
Who has told you something has gone bad with Mach3 ?? - possibly someone who markets the Bob.

You must do a bit more detective work with a volt meter, before starting major re-boots. Having said that, you can install Mach3 again, without problems, but the only thing you would need to do is re-install the drivers.

However - more of that later.

The trouble with Bobs is that they interefere with the signals - in that they usually invert the voltage going to and from the computer. Lets start with the Z axis. There is a fault here - the led should be out, and light when you depress the switches, BUT at least it is working.

1. With the Bob connected to the computer, but not to the switches, check the outputs (i.e. the ones going to the computer) that correspond to the inputs from your switches and see what voltage they are - Ov of 5v. If you check the Z axis first and see what that is. then the X and the Y axis. They should all be the same. If not there is a problem with your Bob.

2. Go to Config/Ports and Pins/Inputs. First ensure that each input is enabled,and that all the Xs are shown on the same pin, all the Ys and all the Zs. check you have set the port number on them all, then check the active high/low.  If the voltage on the Z axis is +5 then you should see that the "Active Low" button is not ticked - i.e. the computer recognises a high signal as the switch being tripped. If the voltage input is 0v then you should see that "Active Low" is ticked - i.e. the computer recognises a 0v signal as the switch being activated. (This is the wrong way round for correct working, but we will make a simple alteration later). If you check that the X and Y axis and set the "Active Low" to the same as the Z axis, you should now find that all the leds are now llit on the diagnostics board.

3. Check the voltage at the input of your Bob board on your three pins. Get a small length of wire, and, if the voltage at the Bob is 0v, then fasten one end of the wire to your 5 volt supply on the Bob and touch other end of the wire on the input. The leds should go out. (If the voltage on the Bob input is normally 5v then fasten the wire to 0v and do the same, the leds should go out.

4. If the leds are working correctly at this stage, then the problem is with your wiring. The Z axis is correct, so, before fastening it up, check the voltage on the end of the wire going to the Bob. Your X and Y axis should be the same, and they all should alter when you switch the switches. If they do, fasten them up.

On your diagnostics page, you should now have all the leds lit. Pres the switches and they should go out.

5. To make the switches work correctly, now go back to Config/Ports and Pins/Input and reverse the settings on the "Active Low" column. This should put out the leds, and they should come back on when the switches activate.

A bit long winded, but you can probably do it quicker that reading it. I have numbered the points, if you have a problem tell us where the thing breaks down.

Jim Pinder

193
General Mach Discussion / Re: Spindle speed
« on: December 31, 2008, 10:13:33 AM »
I had trouble with my spindle control, which works on the PWM through a Digispeed to an Omron inverter. Probably much like yours.

The only way to check that Mach is putting out the correct PWM signal is to check the waveform with an oscilloscope, and try various speeds and see the waveform change.

If yours is a sudden fault, either your CNC4PC card has gone, but the other thing you might check is the pulley setting on Mach and the table of speeds for it.
As you probably know, you have to select a pulley, and write in the maximum and minimum speeds for that  pulley. Mach will not set speeds outside that setting.
Make sure they have not altered.


194
General Mach Discussion / Re: 2 Questions
« on: December 31, 2008, 05:14:04 AM »
Hood -

Yes, like you, my x axis homes between my front tool holder and my drill holder. Following your advice, all my drills are in holders and the tool offsets set so that selecting the tool, then Z0 and then X0 brings the tool to a position on the centreline and 5mm from the chuck.

I have done a similar thing with the cutting tools.

I finally decided on 5mm from the chuck as my Z0 because it allows a parting tool between it and the chuck, and it is an easy figure to remember when designing things.  Ball screws now - so had to go metric.

Bob -

Offsets for milling tools and diameter compensation have been covered many times, but the best one was by Graham Waterworth a few months ago, with diagrams as to which command to use depending on the way you were cutting. Try and look that up, becasue Graham is the man for that sort of thing.

I am not competant enough to advise, although - yes - you can use different sized cutters, and the same program, the compensation will automatically adjust for the width of the cutter. You have a problem with lead in and lead out.

I am wondering if it would be better just to design the star, using the bigger cutter, and writing the Code for the toolpath, then changing the tool and writing code for the toolpath to cut the sharp points, if you see what I mean, and make allowances in the code for the cutter width.

On your second query, your zeroing of the axis was not accurate, because the line you drew was outside the centre points of the bit so your actual 0.0 position is minus 1/16th on each axis, if you are lining up to the lines you drew.

I don't know how many stars you are cutting, but you can now see the benefit of "home" switches. If you can "home" your machine (and the actual position does not matter) then a simple offset G54 - G59 written into the program will always bring the table to the correct position for that program. You only have to set up once  ;D






195
I though that was the reason - I shall get an auto tool changer (eventually)

196
General Mach Discussion / Re: setting a permanent home point
« on: December 30, 2008, 09:54:53 AM »
There are several posts on the forum about this.

The machine keeps it's position in machine co-ordinates. These are displayed on the DRO's when the machine co-ordinates button is pressed and the led surround is lit.  In theory, the only way to zero the machine co-ordinates is to have homing switches and home the machine. However, when Mach was written, if you do not have home switches and they are not activated on the Ports and Pins, RefAll Home will zero them anywhere. You could, therefore, as Hood says, place your table in any position and home the machine co-ordinates. How accurate this would be depends on you.

The "home" position is probably no good for machining, and certainly will not be the start position of your GCode Program. For this you use offstes - G54 to G58 and then another 250 or so under G59 - plenty to go at.

The idea is that you wake up in the morning, and in a stupor, press the RefAllHome button. The machine then moves to it's "home" position. So the machine is now happy - it knows where it is. As Hood says, you cannot rely on it being in the same state as when you switched it off.

Having now woken up, for the first run, you then need to jog your table to the 0.0.0 position of your program. If you input G55 on the MDI line, then change to the program co-ordinates (by pressing the machine co-ordinates button - the led goes out) and zero each axis individually, then G55 is set to the start co-ordinates of your program. You can check this on Config/Fixtures. Run your program.

The next time, before you start, insert a G55 command in your GCode at the begining, followed by a G0 X0Y0Z0.

Start up, and "home" the machine. Run the program, and the first thing it will do is get the offset from the table, then move to the X0Y0Z0 position of the program, and then run the program.

The offset table is saved when you close down, and reactivated when you start up, so once set up, it can be used as many times as you want.

If your case, with a fixed position for your work piece, once "home" switches are fitted, the rest is easy.
As Hood says, optical switches are probably better than fixed mechanical switches. I use lasers shining onto detectors, and these are accurate to several 1/10ths of a thou, and have the advantage - if I accidentally overrun doing something manually, I don't plough through them.

Jim Pinder






197
Have you got the A axis set as linear or angular - see General Config. The only difference that I know it that is then responds to mm or inches, whereas in angular it only responds to your basic setting. In angular, the movement say from 350 to 20 could be in either direction, the long way or the short way.

This may or may not affect backlash - since I assume you have the backlash set for each axis - since how will the machine know which way to apply backlash if it can move in either direction.

198
General Mach Discussion / Re: UserDRO Alpha-Numeric input
« on: December 30, 2008, 04:39:33 AM »
Not that I know of - the DRO is supposed to emulate a Digital readout -  i.e. numbers. There should be no reason why it could not display letters, but I can only assume that they were only equipped with numbers and a full stop, the other characters will be ******

199
In "Turn" you do not use M6 to get the offsets.

The "T" command is of two parts   eg. T0101 (unlike "Mill" which is T +tool number)

The first 2 digits are the tool number from your tool table, the second two digits are the offests (also from the table) . Therefore you could have say tool 6 with offset 2. Don't ask me why, I don't know, but I assume this means that on an auto tool setter, you can select a tool number, and if all the offsets are the same, you can just use the same offset.

As Dave says, it works very well, I have a drill post mounted on my cross slide, for centre drilling - the x offset is common at 3.6267 inches. The other offset varies with the length of the drill, which I have set so that it arrives 0.05 inches from the work piece. The only difficulty is making sure there is nothing in the way, so after the T0404 or whatever, I do seperate G0Z0 and G0X0 to move it into position.

Reading your posts again - are you asking where to put the offsets - the answer is to enter your tools in the tool table, with the offsets.
It helps, of course, if you have a quick change fitting or similar, so all your offsets are fixed, once set.

You should be able to locate your X0Z0 position on your lathe, which is usually X0 - lathe centre and Z0 face of the workpiece (or perhaps the chuck face, which I use, because it is a permanent fixture). Set your most used tool to that position and then set the DRO's to zero. Enter this first tool with zero's as the offsets. Set your other tools to the same position and note the offsets on the DRO's and enter them into the table.

If you now choose a tool, using T0303 (or whatever) then G0X0Z0  should move all the tools to the same position.

If you have "home" switches fitted. You home the machine. A G54 offset  then brings the machine to your normal X0 Z0 position, and your tool table takes care of the offset for all the tools. You can then write your GCode programs from the same "position" every time.

Jim








200
General Mach Discussion / Re: manual tool change macro needed
« on: December 28, 2008, 06:09:32 AM »
The M6 tool change written for Mach (as it is) can do three things - see Config/General Config, top left hand corner.

It can (1) ignore the tool change, (2) stop the spindle and wait for a restart ( which allows you to change the tool etc) or (3) do a complete auto tool change program.

The first two options are programmed into Mach, but the third option can be altered.

It seems to me, however, that if you included a short instruction for the machine to move to your required position, then choose option (2) for the tool change (stop and wait for change manually etc), this would do the trick.

For this you need to write a small Macro - a visual basic program, which you can put in your GCode program, before the M6 instruction. There is a full explanation of this in the instructional videos, under "scripting"

The basic line for Vis Basic is

Code "G0 X0 Y0 Z0"
- if you write this in the Visual Basic editing window (under the operator menu) and save it as, say, M201, then every time you write M201 in your GCode program, Vis Basic will write an instruction G0 X0 Y0 Z0 to your machine. If this was followed by M6, then the spindle would stop and the machine wait for you to change the tool, and set the height.

You can also include in your Macro instructions to collect data from the DRO's before moving, and then return the machine to where it was, after Tool Change.

I think if you watch the video a few times, and do a little bit of experimenting with Vis Basic - i.e. try writing a Macro _ test it without tools in, and with the spindle off - and then come back if you are having a problem.

The difficulty is, as it says in the video, that everybody has a different requirement for a tool change.

I must admit that when I am milling, I usually use the (2) option - stop spindle an wait - jog the z axis up and change the tool, set the height again, and then carry on. It seems quicker to me than waiting for the machine to move about.