Messages

141

General Mach Discussion / Re: G31 Bug?

« on: February 19, 2009, 04:39:30 AM »

Ray - As far as I can see, G31 works on Program Co-ordinates only - in other words the number you put in the command refers to the program co-ordinate, not the machine co-ordinate, Perhaps you were looking at the Machine Co-ordinates when you did this.

142

General Mach Discussion / Re: dual arm control

« on: February 18, 2009, 01:44:17 PM »

If you are in London, have a look at the Arc Euro Trade website for details of their products - stepper motors and drivers. Mine are the 220 Ncm ones - fairly large to drive a metal turning lathe system. you could probably try the small ones, or the next up.

Bear in mind that gearing comes into focus here. If you are willing to sacrifice a little bit of speed, and gear down your motor then you can get away with smaller drives and smaller motors. Mine are geared down 60,000 to one, and could still manage 40 ins per minute. This sounds a lot, but the motors require 200 pulses to turn 1 rev, the drives multiply this by 10 micropulses (=2000), I have 3 to 1 gearing to drive my leadscrew, which turns 10 time to move the table 1 inch (i.e. 60,000 pulses). This means that my computer has to put out 60 pulses to move the table by 1 thousanth of an inch - accuracy is what I need, but I also get the power from the motors - more than enough to snap of 6 mm drills without even trying.

I would try the small motor, with the small driver, and maybe some sort of toothed belt driving the pen holder. Bearing in mind if you use a tooth belt system you can alter the various drive wheels very easily until you reach the ideal set up.

143

General Mach Discussion / Re: Looking for an alternate (small) video window

« on: February 18, 2009, 06:01:32 AM »

To go back to the original query - does your graphics card have dual output. Mine has, and so I could run another (small) display from the computer, on which I could program the video window. This wouldn't interfere with the Mach window.

144

General Mach Discussion / Re: dual arm control

« on: February 18, 2009, 05:50:22 AM »

Mach 3 is designed to do just that. It is normally used to control linear axis, not rotating ones.

You do not say how you are controlling these arms, but steppers motors would seem to be best for your system, they are cheap and reliable and drivers are available for them.

Mach 3 control these motors by putting out step pulses and direction pulses (i.e. two wires) to each driver card to move each axis. So make sure if you buy , that they work on pulses. (See Arc Euro Trade website under stepper motors and drivers for the general feel and a guide to prices) - if you are in America then I am quite sure some of our friends across there can advise you.

Control is by GCode programs. which simply move the cutter/tool/pen from where the machine is to where you want is to go with simple commands e.g. G0 X3.2 would move the pen from where-ever it is on the x axis, to position 3.2 (This can be millimeters or inches from your start point) Similar y commands moves the pen up and down the y axis, whilst z commands are normally to lift the tool/pen up and down off the work. Two axis on one line e.g. G0 X4.5 Y6.2 would move the pen in a straight (diagonal) line to the new co-ordinates. Mach 3 keep track of it's position at all times, and gives a digital read out of it.

The control of the other three axis is normally for complex machines for angled drilling or machining, but the majority of us poor relations just use the x,y,z

Get to it

145

General Mach Discussion / Re: Joystick cannot move axis when at softlimit

« on: February 08, 2009, 05:36:02 AM »

The limit is that - a limit - and beyond that disaster will happen. You shouldn't, as a matter of course, hit your limits.

I don't think you can configure the joystick to "back off" limits

146

General Mach Discussion / Re: mach3 problem

« on: February 08, 2009, 05:27:44 AM »

You need to set up your pulleys to reflect the speeds you are using.

Go to the pulleys on config. If you do not have pulleys, then set pulley 1 to cover the entire speed range of your motor - from 0 to x thousand RPM.

If you have a motor control system, then Mach will set the speed as accurately as it can - but if it is outside the limits for the pulley, it will only go to the maximum or minimum.

147

General Mach Discussion / Re: How do I tell Mach3 my CNC's table size?

« on: February 08, 2009, 05:21:00 AM »

I dont know whether it is time to go into the machine co-ordinates and program co-ordinates, but it ties in with your first question.

You have fitted switches - you don't say where - but I assume that these are combined limit and home switches. There is a difference. If they are acting as limit switches, then, once you have activated them, that should be that - the machine should go up to them and STOP (It has reached it's limit). So that is the first job. Get the switches active. Wire them up to LPTI (or your BOB) one at once, and configure them on Config/Ports and Pins/Inputs. When you have done this turn to the diagnostics page, and (leave the table out of the way) switch the switches manually. You should see the appropriate led light up. If it has already lit, then it is configuraed wrongly, and the active low/high needs changing. It you can't get it to light, then you must look to your BOB. I can't say any more, because a lot of Bobs invert the signal, and there are so many combinations, it is impossible to say, but the right combination of high or low common, low or hign input is there somewhere.

Once the limit switches are fitted, configured and working, then you should be able to jog round your table and when the switches are hit, the table will stop. If you tick Auto Limits on the settings page (or something like that - I am away from my machine at the moment so can't check the proper name) then this will allow you to back off the switch.

Home switches work differently, although they are (in many cases) the same switch. Here the machine will travel (at reduced speed) until it hits the switch. It will back off until the switch opens again, then stop again. The DROs will automatically set to 0 (if you have the homing page configured that way) - end of story - there is nothing else you can do with homing - and you will see from the page, the speed and directions can be specified, so you can home to the most convenient point for you. Mach 3 automatically alters the program when reading a switch as home or limit.

Here is the rub - because with homing you are joining the "big boys". Homing sets your machine co-ordinates to zero. Machine co-ordinates  are those by which the machine keeps track of its-self. You cannot alter them, other than to home the axis.

If you press the Machine Co-ordinates button, and the led is lit, then the DROs are displaying machine co-ordinates, if you press the button again and the light goes out, you are viewing program co-ordinates. Program co-ordinates are the method you use to keep track of the machine, because it refers to your program.

Home the machine and check the machine co-ordinates (0.0.0). Press the button and view the program co-ordinates. These may also be 0.0.0. If they are not, then zero them by pressing the zero buttons at the side of the display. Your two systems are now together.

If you now jog you table to where you want the 0.0.0 to be for the program you are running, and when you get there zero the program co-ordinates, then if you check, the machine co-ordinates have not changed. The values displayed on the machine coordinates DRO's are the offset of YOUR 0.0.0 position, to the MACHINE 0.0.0 position, and if you now look at "Config/Fixtures" you will see that G54 reflects this. There are 255 offset slots to use. G54 is the default. If you copy these to G55 or G56 then you have YOUR 0.0.0 referenced.

You can now try for real - home your machine - from anywhere. Type in G55, followed by G0 X0 Y0 Z0 and the machine should now go to where you wanted your 0.0.0 position to be.

If you include G55 at the beginning of any programs, if you "home" your machine, then run, it will always start from exactly the same place.You will see that with 255 slots to go at, your can start your programs from anywhere on your table.

Hood mentioned about telling Mach 3 the size of your table - yes you can set soft limits, which will prevent the machine exceeding these. However there is no way you can tell Mach3 you have a 10 x 12 table or whatever. Mach 3 reads your program, and draws the limits on your toolpath display from your program, therefore you need to keep your program inside the limits. I can see, from your picture that you obviously have limits, from theconstruction of your machine, I on the other hand, can overlap my table, therefore the size is irrelevant.

That seems enough diatribe for a Sunday morning.


 

 

148

General Mach Discussion / Re: Radius comp in 4th rotary axis

« on: February 05, 2009, 01:50:10 PM »

It sounds an interesting problem, but I can't quite picture what your are trying to do.

Tool compensation is usually fixed to a linear axis, and Mach3 adds (or subtracts) the relevant distance from the one on the axis. I can't see how you can apply this to a rotary axis. Rotary axis rotate, I can't see where the radius comp comes in.

149

General Mach Discussion / Re: Stepper Motor Problem/Issue

« on: February 05, 2009, 01:41:22 PM »

The motor stalling will have led it to draw more power - is your Zylotex current limited. You are probably right, if you try a different motor on the same driver and that plays up, then the trouble is with the driver, not the motor. Try the "faulty" motor on a good driver and see what happens (you have probably done that while waiting for a reply)

150

General Mach Discussion / Re: Spindle Control HowTo Help

« on: February 05, 2009, 01:35:02 PM »

If all you are wanting is M3 (on) and M5 off, this is provided for in Mach 3. There are four outputs which are fairly general to most CNC and this is M3 M4 and the two coolant switches. I am away from my machine at the moment so I can't remember them and I am using someone elses lap top - but they are something like M6 and M7or M7 and M8.

Whatever - if you look at Conf1g/Ports and Pins/Spindles drive, you can allocate these functions to outputs (usually 1,2,3 and 4)
On Config/Port and Pins/Outputs you can allocate these outputs to pins. There are five available. If you are thinking of providing a variable speed signal as well that is your fifth output (using the standard LPT1 port)

I wired a small vero board circuit where the four outputs drive four relays, using a Darlington array chip. The Darlington array is an eight bit chip (on 18 pins) The inputs are 5 v positive, the output is 0v  at 1/2 amp per pin. A 0v (common) and +voltage (voltage of what you are driving) make up the other two pins. Outputs can be wired together to increase the current - more than adequate to drive relays (diodes are included in the chip).

I only use M3 and M4 at the moment, the coolant will have to wait and so I have two outputs spare that will still give output signals if I want to alllocate them.

I am sure you will be able to drive a relay with the capacity for your spindle drive if needed.