Messages

1121

General Mach Discussion / Re: online tutorials

« on: September 03, 2007, 01:14:19 PM »

I have downloaded the tutorials into a folder in "My documents/CNC tutorials". These can be copied onto a wand - I have just tried it with Turn Intro - which is 12 Kbytes.

What you must have is Shockwave Flash Player installed on your workshop computer.

Take the wand through to the workshop computer and download it

1122

General Mach Discussion / Re: Constant velocity

« on: September 03, 2007, 01:00:25 PM »

I am sorry - I do not understand your problem. I have just programmed my mill to cut windows in a miniature railway locomotive, each window had rounded corners off a straight as you have, and (as far as I could see) the machine cut the straight then went straight round the corner at the same speed.

I did not set any Constant velocity settings or anything. I used G3 as you have ( only I use X Y R instead of X Y I J ) no problem.

I did not think that constant velocity had anything to do with your axis motors, but it was to do with spindle speed on a lathe. As you cut into the work and the diameter reduces, the spindle speed increases to keep the cutting speed at a CONSTANT VELOCITY. I cannot see how you can apply constant velocity to a miller, since the feed rate will stay at what is set.

Am I wrong in this
 

1123

General Mach Discussion / Re: how to fit servo mottors?

« on: September 03, 2007, 12:38:05 PM »

why not just put bigger stepper motors on it ?

Mach 3 puts out pulses for direction and steps on two wires. If treated correctly it is accurate. Your problem seems to be that you are trying to do something outside the capability of your machine, not Mach3.

If you put servo motors on, you MUST then wire up the encoder be cause Mach 3 will Not know where it is unless you do. I find steppers very, very much more simple.

Arc Euro Trade in UK has some very big stepper motors that will easily power you machine - so you should find some in your country that will do the job.

1124

General Mach Discussion / Re: Lost Step on complex program

« on: September 03, 2007, 12:27:56 PM »

You seem to be confident that your machine is working accurately. So try this test.

Try moving the cutter round in a circle several times and see if the machine is correct after that. All positions on the circumference of a circle must be approximate (since PI has no finite end) and I am wondering if the approximations are always the same.

1125

General Mach Discussion / Re: Please recommend driving board

« on: September 03, 2007, 04:50:35 AM »

Yes - that looks like the big brother of the ones I have - a single and a double board.

I don't know whether to advise you to get one board - four axis, or two double boards. I don't know whether you are happy with all your eggs in one basket, so to speak.

The only problem with a 4 in 1 board, any fault at all means your whole machine is out of action. If you have seperate boards, you can still get some of the machine to work.

Mine is a lathe with a milling head. If one of my cards goes faulty, I can still run the lathe.

It is up to you, but mine certainly do the job !!

1126

General Mach Discussion / Re: Please recommend driving board

« on: September 02, 2007, 02:42:51 AM »

Stepmaster control  boards will run those motors - they are similar in spec to mine. There are suppliers on E-bay. You can get cards for one, two or three motors. They are adjustable for drive current, over voltage protection etc etc. You will have to adjust the wiring for the motors to make them bi-polar, but there is a diagram included with the board.

Mine worked straight from the box, and have performed faultlessly.

They interface directly with Mach 3.

1127

General Mach Discussion / Re: phase drive control

« on: September 02, 2007, 02:37:35 AM »

Yes, it is possible to drive stepper motors direct from a PC or a programmable PIC chip. I have done it myself on a PIC chip development board. You merely have to switch on  each segment of the motor in turn, in the correct order for forward or reverse. You will still need some interfacing for the electronics. Computers work on 3.5 or 6 volts - steppers (to be of any use in CNC) need 24 volts at least, plus a current of about 2.5amps.

You would then have to be fairly competant at programming (with a suitable program and knowledge of PC output ports) to get all the requisite functions of a stepper motor driver board.

I can't therefore, see why you would want to do it - unless you have a cheap, cheap supply of components and copper clad to use up. The time alone to design it would be more costly than the board is worth.

I consider the stepper boards as bought ( mine are from Stepmaster) to be good value. They are competantly built, faultless in operation, and three wires gives me all the control I need. The have overvoltage protection, adjustable current provision and various switches to use virtually any type of motor.

Mine cost about £30 per motor - three hours work each - 9 hours altogether. I couldn't build an interface in that time, let alone program the computer.

1128

General Mach Discussion / Re: Demo

« on: September 01, 2007, 04:05:31 AM »

You must have something wrong -

I only use the downloaded version - and everthing is fully functioning.

1129

General Mach Discussion / Re: phase drive control

« on: September 01, 2007, 04:03:53 AM »

Do you mean frequency control of a three phase AC motor for your spindle - or what ?

If that IS what you mean, then frequency control of a three phase electric motor means you can have seamless control of the motor speed from very slow to its maximum ( and a bit over maximum if you are lucky). Wiring is very simple, and with a modern single phase to three phase inverter merely involves connecting the motor to the controller.

The controller electronically changes the frequency of the output to control the motor. There are many different makes and models on the market, and probably many available second hand.

Mach3 can control them - if the inverter you choose has the electronics to do it - (NOT Mach3). Mine does not, but I can get M3,M4 and M5 without trouble and I am working on a servo control to control the speed.

The disadvantage is that at lower speeds, you do loose some torque, so if you do a lot of low speed work, a pulley system would still be of advantage, so you could still get maximum  torque at the spindle. My motor is twice the power of the original for this reason, and I haven't as yet resorted to a pulley change.

If you are NOT talking about this - ignore it !!!

1130

General Mach Discussion / Re: Cut Circle in metric

« on: August 31, 2007, 02:40:09 PM »

Hood

Yes - I am down in England (although my mother was Scottish and one of my sons lives in Kirriemuir, Angus). All the steel I buy is metric dimension, and I have been thinking of setting up the lathe in metric. The trouble is it is an imperial lathe, with all the dials (when I look at them) set in thou.

Perhaps I can go one step up, and use two versions of Mach3, one for metric work and one for imperial.

Does any body know the answer to offsets, when using metric or imperial ?


Jim