Messages

671

General Mach Discussion / Re: Macros

« on: April 27, 2008, 03:20:54 AM »

Yes - you are quite right - I don't know of any already written, unless someone has one they can post. I would perhaps search the forum, there are several sections, and see if any has what you want.

Look at the video tutorials on Scripting

You will need to learn a little of the Mach3 specific Visual Basic instructions, but yes, you can write a macro to "borrow" the touching bit, and then write to the relevant DRO's (or clear them) and move your tool to convenient position.

If you write one - how about posting it.

672

General Mach Discussion / Re: Noobish Question On Motors & Drivers

« on: April 27, 2008, 03:05:08 AM »

You might know a lot of this is you have been reading up on it.

Mach 3 puts out signals on the LPT1 - the old computer printer port. There are only 12 output lines and 5 input lines ( It is the input lines you might run short of) - so run through what you might need.

Each axis requires 2 wires (plus a return wire) to drive it, one wire drives the step, one wire drives the direction. If you have four axis you need eight wires etc. Don't just allow for three axis - most people eventually want a rotary table and other goodies.

Outputs must also drive things like the spindle control (normally three wires) coolant (one or two wires) axis enable wires (if required) one for each axis. etc.

Inputs are for limit switches, home switches, spindle speed, and any other switch you might want to put on your lathe like an "emergency stop" button or other safety device.

You can see that it is very easy to run out of wires, when your system gets a bit advanced - and you end up having to add other ports to your computer.

Many firms offer driver boards and breakout boards etc. A breakout board merely provides an easy way ( usually screw terminals) of connecting your bits and pieces to your computer. Many breakout boards have electronics on board to isolate signals and provide a 5 volt power supply for switches etc.

The disadvantage with a lot of breakout boards is that they are pre- wired and fixed in their applications - rather like painting by numbers - fine to get started with, but in the end, very limiting.

The Mach 3 admin boys are going ******** at the moment about a new interface board called a Smooth Stepper. This is a board that provides inputs and outputs (more than you need), it provides on board pulse engines to drive your axis, which means that your computer does not have to generate the pulses and can get on with calculating the job. I understand that it is opto-isolated , etc etc . The beauty about it is that it connects to your computer via a USB lead. I would recommend that you look at one of these ( if you are starting from scratch).

Whichever type of board you start with - you then need to interface this with your machine.

Geckos are good drives and I am pleased with mine - so I cannot crticise your choice. Use seperate drives - Do not get a single board that has breakout board and three drives all in one - if one goes faulty it all goes faulty. If you have seperate units you can change anything at will.

The output from your breakout/smooth stepper board will drive the Ghecko board directly. Mine require a 5 volt connection, a "step" connection and a "dir" connection to each board. The inputs to the Gecko are isolated from the rest of the board to protect the low voltage side of the system.

I have looked at the Grainger website and your choice of axis motor. I am at a bit of a loss. These appear to be a straight DC brushed motor, and there is no mention in the blurb of feedback for positioning, There is mention of a tacho - is this for positioning.

Mach 3 gives out step and direction signals. It is preprogrammed with the number of steps per inch of axis movement, so if you want to move one inch - it puts out say 60,000 pulses and says - "there you are - one inch". With steppers you hope the motor got all the pulses, but with servos (as I understand it) there is a measurement system either inside the motor, or external to,  which checks that your motor has gone the relevant distance. I do not see that system mentioned in the Grainger.

If you read the PDF file on the Gecko 320 it tells you how to wire them, and also about the feedback circuits. You can get external feedback circuits, but I thought that servo motors ( marketed as such) came with them ready installed integral to the motor. I would check the motors.

If you need any more - come back again.

673

General Mach Discussion / Re: Wrong feed rates after updating to Mach3 R3.039

« on: April 25, 2008, 04:40:56 AM »

Yes - you are quite right. On double axis moves, the axis with the longer travel will travel at the maximum set in motor tuning. The other axis will travel at whatever speed is necessary so the two finish simultaneously. It is the max speed times the tangent of the angle the cutter is describing.

I must admit I have no idea why the difference occurs on circles - with look ahead. One possible explanation is that once it has calculated the line, it stops calculating until that line is executed. With look ahead, with Constant Velocity on, the system is always calculating so that it can accelerate or decelerate the axis so the transition to the next line is smooth.

As a check try doing the circle cut again, once with the machine set to CV and again with it set to Absolute Stop and see if there is any difference.

674

General Mach Discussion / Re: Stepper motor setup questions

« on: April 24, 2008, 06:57:53 PM »

I have honestly no idea. I am an engineer and my applications are of a structured nature, that do not look like a sea on a choppy day.

Yes, the problem must be, for a CAM program, if it is tracing a complex curved surface, it only has a straight line it can draw. It cannot, by definition draw a parabola - they do not exist in GCode. It must, therefore draw a straight line, until that line strays out of pre-defined limits, then move the line and set off again. Again, by definition, the motors must stop at the end of the line, and start at the beginning of a new one.

You could try speeding up your computer - and putting additional RAM memory in is one of the best ways to do that. Also cut out all the programs, or processes that are running in the background. If your computer is dedicated, then you need the minimum number of processes running to support Windows.

As I say - I have heard that Smooth stepper also helps in this - perhaps someone else could comment.

675

General Mach Discussion / Re: I've Just Got My New VFD & New Motor Running But

« on: April 24, 2008, 04:21:23 PM »

In that case, check with a voltmeter the voltage your BOB is giving out to the VFD, both when jogging and when not.

In should not change.

Are the pin numbers on the BOB all pre - allocated - e.g. axis 1, axis 2 etc etc - and you have to set Ports and Pins to suit ??.

I can only think that you have the same pin allocated to the Spindle "step" and to an axis "step"  Without jogging the PWM (Pulse Wave Modulated) is OK.  If you can imagine a square wave of a fixed time interval, -  then on 0, all the wave is at 0, -  at 50%, half the wave is at 5v and half at 0v,  - at 100% the wave is at 5v all the time.

Step signals to axis motors are pulses, square wave with a fixed time span (depending on your time settings on Motor Tuning) - the frequency of the pulses depends on the speed of the jog.

If the two are combined, then the axis stepper pulse will turn off the PWM pulse for some of it's time,(the 0v pull down pulse being stronger than the +5v)  and so the converter on the BOB will translate this as a lower voltage.

A very detailed idea of what I think is wrong - but short of something actually being faulty, I can't see what else it can be.

676

General Mach Discussion / Re: Stepper motor setup questions

« on: April 24, 2008, 04:00:47 PM »

Mach 3 needs to calculate each move before it can start to run the steppers. If you are using a G2 or G3 code, this is one calculation. If, instead, your circle, or arc is compounded from many small straight lines, this is many small calculations for Mach to do. Mach is also, at the same time generating the drive pulses to drive the motors in a strict time sequence so that your many straight lines appear as a curve. It also, at the same time, calculates acceleration and deceleration times on CV to smooth the lines as well.

This is a well known problem and is the subject of quite a few posts.

There is a new board coming out, called Smooth Stepper to run from your USB output. This board has an on board pulse generator, which relieves Mach3 of a lot of calculation. It might be the answer to your problems.

In the meantime, try and use code which has as few lines as possible.

It gets even worse if you try Absolute Stop mode.

677

General Mach Discussion / Re: I've Just Got My New VFD & New Motor Running But

« on: April 24, 2008, 03:44:17 PM »

Yes - You need to use the PWM output from Mach3. If you look at Ports and Pins/Motor Outputs then if you look at the Spindle line, the PWM output is on the "step" pin. You can allocate this to what ever output pin you like.

The PWM needs to be converted into a voltage - and the best unit to do this is a Digispeed - (Australian). All you need is the cheap DC 01 board.

This takes the PWM siganl from Mach 3 on one side of the board. On the other side, three wires come from your VFD - a positive voltage, a ground 0volts and the input wire. Digispeed automatically converts the PWM signal to a voltage between 0v and the positive voltage, corresponding to the PWM signal.

The two halves of the Digispeed are electrically isolated from each other.

It is relatively simple to wire up.

678

General Mach Discussion / Re: I've Just Got My New VFD & New Motor Running But

« on: April 24, 2008, 02:38:51 PM »

I assume VFD is variable frequency drive controling the spindle motor.

I assume you have it control by the PWM output from Mach 3.

Is the answer is Yes - then NO. The spindle speed is not affected by jogging up and down.

I would check your Ports and Pins/Spindle configuration. The PWM signal is given out on the "step" pin. The direction pin should remain at 0. Set the Step Port at 1.

The only reason I can think of that the spindle speed drops by half is if your return wire from your VFD is perhaps another "step" wire, and the two signals are interfering with each other.

Check your configuration

679

General Mach Discussion / Re: Wrong feed rates after updating to Mach3 R3.039

« on: April 24, 2008, 02:27:13 PM »

The figures your are quoting for the speeds are axis speeds - not straight line distance speeds. Your X axis travels at 180 and your Y axis travels at 180.

If you look at your quoted figures, your cutter travels from pos X0Y50 to X150Y100 (X moves 150, Y moves50). Your compound speed - if you travel on both axis at 180 units per minute simultaneously is 1897.736659610 plus another 10 digits or so, which is what you were quoting. Actually, the time for the move from one position to the other would be just the same as the straight line move from X0 to X150.

This will be true for your other G0 move.

As for the G2 move, the F command will apply to the centre of the cutter - not the circumference - so therefore PI will will come into it somewhere.

680

General Mach Discussion / Re: Tangential control manualy?

« on: April 24, 2008, 04:20:28 AM »

The answer must be yes - although the actual "how" might be a bit more difficult.

However - if it is as simple as that, one thing I might try is -

Mount the laser parrallel to the saw blade. (And here I must assume) The blade has to be in line with the cut you are making.(and I assume it is the "a" axis). Zero the "a" axis i.e. put it parrallel to the work or what ever, then jog it to where you want it to go, using the laser as an alignment tool. You might not have to zero it - depending on the accuracy you need - and if you are satisfied that Mach has the proper current location in the DRO's

You could if you wanted greater accuracy, mount a detector where you wanted the beam to shine - I have them on my machine and it is accurate to less that 1/10th of a thou of an inch.

There must now be a reading on the "a" axis of the angle the blade is pointing.

Do a small Macro - a Visual Basic program to calculate the finishing position (X,Y) of the blade from it's present position (over a set distance) and away it goes. You would have to stop the cutter blade manually - unless the Macro knew what line to stop at (but then you would have to change the macro everytime)

The Macro could be accessed by a "button" on the Mach control panel, or even an external button.

As far as I can see that is the simplest method to implement, without having detectors to track the laser beam, and it takes longer to describe than do.

Basically you jog the "a" axis til it is pointing where you want it to go, press the button and away it goes.