Messages

151

General Mach Discussion / Re: need help with steppers

« on: February 05, 2009, 12:52:00 PM »

If these are eight wire motors, then they have four windings, in the pairs that you know about. The red/yellow are one pair, next is blue /black, (these make up the A and C windings) then white/purple and brown /green (these make up the B and D windings).

The  A and C work together, and the B and D work together.

They can be wired up in series  i.e. red - yellow connected to blue - black -- then the red and black are connected to A and A+
The other pair white - purple connected to brown - green -- then the white and green are connected to B and B+.

5 wire motors have a common, these do not.

In this configuration they are wired in series, and take the least current (but only provide half the power). You can also connect red to blue, and yellow to black for A and A+, and white and brown, purple and green to B and B+. This is parrallel wiring which takes more current, but provides more power.

My motors are Ghekos, wired to 20 Ncm motors, but the Gheckos can provide up to 7 amps. My motors are rated at 2.5amp per winding. In series they take less that 2.5 amps, but in parrallel they take 4. In your case I would wire them in series. If your drives are current limited, it does not matter, but it is better to start small and work up. Try that and see what happens.

152

General Mach Discussion / Re: Constant Surface Speed.

« on: February 02, 2009, 08:28:50 AM »

Sorry SD this is an old post that has been brought forward.

Yes the 75 is the speed, but note that it is derived from the speed of the spindle and the diameter (or radius it is cutting at) This means it must be told where it is to start (see previous line).

The code Graham has included there works first time. The only problem was that I wanted to cut from the centre outwards - and I couldn't seem to get that to work the same way. I set the thing going as per Grahams program, have it travel in, the cut outward, and it worked perfectly. (up to the speed limit of that set of pulleys)

153

General Mach Discussion / Re: DigiSpeed-SD and CW CCW control

« on: February 01, 2009, 02:45:31 PM »

The reason is that as you power up, pins 8 and 9 are normally off.(There is no power connected)  In this position, this is ON (the pins on a PC are normally high in use (i.e. high is off). Therefore, if you connect the power to your relays before the computer is fired up this will happen.

The safest way (if you read your Mach blurb) is to turn on the PC and let it run up, select Mach 3, and when this is on the screen, then turn on your machine and accessories.

I must admit this is easier to preach then practice, although my VFD, an Omron, flashes an alert if both CW and CCW pins are on simultaneously.

154

General Mach Discussion / Re: Setting Tool Length

« on: February 01, 2009, 02:30:44 PM »

Ray - you ARE getting serious now.

Unfortunately each tool has only one setting, so for different jobs - well, you could enter the tool in the tool table in a number of different positions for different jobs, but that would be a lot of work.

What you really need is "HOME" switches - and you home the machine. Machine co-ordinates are 0.0.0 Zero all your program co-ordinates as well.

You now set all your tools with the machine in this position. Start with one - a length of rod - that is long enough to touch the top of your table. This is tool offset 0. All other tools are then set using that one, i.e. the z axis will have to be moved (normally down) to touch the same point. This gives you the offset of the tools. You dont actually need tool 0, you could just put a tool in and move the axis down until it touches the table.You do need some method of locating the tools in the same position each time. I start with the z axis at 0, then move the tool down until it touches my touch plate (a piece of copper clad). when it stops I look at the z axis readout then add the thickness of my coppr clad. Thats the easiest way to do it, I think.

You should now be able to put each tool in the holder, select the appropriate tool number, and do G0Z0 and the tool should move down and touch the table.

For your different fixtures, you vice etc, offsets are entered into your fixtures table. so that each different start point for your 0.0.0 position has its own fixture offset. (There are 255 to go at). This fixture is entered into the GCode program at the begining
(once all the preamble is finished). Enter, for example  G55 - G0X0Y0Z0 - M1

The sequence is then - home, enter the program, and run. The machine should automatically move the tool to the correct 0.0.0 position for that program, and stop and wait for you to check that all is well. Presscycle start again, and away you go.

This does seem a lot of work BUT you only do it once - even the offsets can be used more than once if you use, say, your vice for a number of different programs.

When it comes to running program it is childs play.

155

General Mach Discussion / Re: When Homing limit switches do not work...(?)

« on: February 01, 2009, 01:58:45 PM »

The answer is to wire all your switches up in series to one pin. Go from the pin to one switch (normally closed contacts) to the next switch and so on, and the last switch is connected either to your 0v connection or your 5 volt connection, depending on what your breakout board requires.

On the Config/Ports and Pins/Inputs all the x y and z limts and homes are shown on the same pin. These are set up so that the normallly connected switches  normally hold the limits and homes OFF. i.e. on my machine I connect directly to the computer so my switches are connected to 0v and NOT active high on the ports and pins. The internal pull up resistor is overcome by the switches and the leds are  normally off. When activated, the line is no longer connected to 0v and the internal resistor pulls the pin up and switches it on.

As soon as any switch is activated, this breaks the connection and all pins show high - or activated. This doesn't matter - with a limit switch it is obvious which switch is activated from the position of the table, with a home switch, Mach is looking for the appropriate home switch anyway, and only reacts to that.

This has the added advantage, in that, if a wire comes off, or, as you say a switch becomes faulty, then it immediately trips the limits and your table will stop. You can find out which one it is by shorting them out in turn until you find the one that is activated.

As you probably know the state of all the input leds are shown on the diagnostics page

156

General Mach Discussion / Re: Mach3 and video card

« on: February 01, 2009, 01:40:35 PM »

WindowsXP has a driver in it to run a video camera through a usb port. Mach 3 puts crosshairs and other bits onto the image produced before it is displayed, so that you can use it with Mach.

I assume an integrated video card image will not be alterable with Mach3.

My video camera did not work with my laptop, that I was using for Mach.
Since I changed it for a desk top computer, it works first time. The driver for the video is part of windows.

157

General Mach Discussion / Re: Why does this radius not show up on my display?

« on: January 31, 2009, 06:03:27 AM »

You can magnify the display with the mouse. On mine you click the toolpath, and I use the wheel - perhaps this will show it up. If you look on the video tutorials it will show you how.

158

General Mach Discussion / Re: DigiSpeed-SD and CW CCW control

« on: January 31, 2009, 05:18:40 AM »

Vince -

As Peter said - that depends on your own particular motor control system. The Digispeed provide a voltage signal (usually 0 - 10v) to control the speed, as you seem to have sorted out.

The direction depends on what your own VFD demands.

Mine is an Omron and (as well as the voltage input for the speed) it reqiures two sets of wires connecting to give CW or CCW rotation. You can connect none, or either pair, but not both. Both is an error and will stop the Omron.

The standard instruction for CW rotation in GCode is M3, for CCW is M4 and off is M5. The M3 and M4 signal, as you say uses two output pins from Mach. I have used pins 8 and 9 to drive two 5v relays. (I actually made up a board with four relays, all driven by a Darlington array, so I could do the coolant as well) Darlington arrays are cheap (less than £1 for an eight unit array) and they run directly from your computer output. They are rated at 1/2 amp for each output, so plenty of meat there.

The advantage of using relays is that it means that your VFD is completely electrically isolated from you computer and other electronics, and as Peter says in his blurb with the Digispeed, sometimes the voltages are not to be trusted.

On the Mach screens, you need to untick the "disable spindle relays box" on the Config/Ports and Pins/Spindle Output page and assign M3 and M4 to outputs (usually 1 and 2.) On the Config/Ports and Pins/Outputs page, you then need to assign Outpus 1 and 2 to pin numbers, and enable them. Peter seems to have coped with this in the Digispeed, so you will have to read the blurb to see if they are active low or not.

I personally have used the PWM output from the Mach to control the Digispeed. My Digispeed could be altered to suit either. This comes out of Mach 3 on a pin specified on the "Step" output of the spindle motor drive. (The Dir" pin is ignored).

So - in a word, there is no simple way - it depends on what your VFD requires. Have a look at that first, and work your way back from there.

159

General Mach Discussion / Re: Problems with SPINDLE CW F5

« on: January 30, 2009, 06:22:32 AM »

I am using 1024set screen.

The "Spindle CW F5" button to which you refer seems to turn on the spindle clockwise. The  yellow led seems to continue to flsh. If you press it a second time, it turns off.

If you compare it with the "Spindle toggle" on the diagnostics page, this does the same, but the yellow led only flashes once.

The two yellow leds are, however not the same function. One is oem 11, the other code 813. 11 is Spindle CW (which I assume means clockwise) and 813 is spindle dwell.

I must report that mine turns the spindle off, and the led stops flashing.

160

General Mach Discussion / Re: Modifying my M3 macro for arc initiate - Plasma Application.

« on: January 30, 2009, 05:38:57 AM »

Unfortunately the machine cannot think, and therefore does not know whether you need the plasma arc initiated, or not - only you know that.

The solution is to use a different code when you need the arc, to when you move rapidly.  If you use G1 when cutting and G0 for a rapid, then you are there. Include the M3 start up routine in the code for the G1. I take it that it does not matter if the initiate arc code is used, even though the arc is already on.

You could also include the code for M5 (if that is what you are using), to shut down the code BEFORE a rapid move, to avoid cut where it is not wanted.

In that case, your job would be completely automatic.