Tool Changer Questions

[jevs]

I am retrofitting a Pratt & Whitney Tapemate C with a 7 tool tool changer. I am trying to determing if I need a PLC or if Mach 3 can do this without one. The changer is purely mechanical and does it by moving the Z axis up past the home switch (machining area) where a few things happen mechanically. Once the Z axis gets passed the home switch, there is then another long dog that hits another switch to tell the old controls that it is in the tool changing area. As this goes through this area, an arbor release hits on a cam and release the ball on the end of the BT-30 tool. Next there is a stationary rod that catches on what we call the turret assembly. This assembly is on a slide attached to the z-axis. When the stationary rod hits this portion, then the z-axis continues to travel up while the turret stays put. This basically pulls the tooling out of the arbor and clears it for rotation. After this is clear, then there is a rod that catches and pulls the turret assembly making it rotate one tool position. At the point that the rotation is complete another dog hits a micro switch that signifies to the machine that it is at the zero point of the tool change. At this point the machine would reverse the z-axis travel and the tool/turret would go back up into the arbor, and then the arm at the top would release tension and trap the BT 30 Tool and pull it tight in the arbor. The machine would continue down and then the tool change long dog would realease the micro switch and it would know the tool change operation is done. Then it would continue down until it hit the Z axis home position switch. Then it is ready to go with that tool.

So, basically there are 5 roller tipped micro switches and dogs that can make contact during a full travel of the Z axis.
2 of them are over travel limit switches. One at the bottom of the machining area and one if the machine should happen to get past the "zero point of tool change" dog.
1 is the z axis home position for the machining area of the z axis
1 is activated while the machine is in the tool changing area north of the home switch
1 is the zero point of the tool change telling the machine to reverse and come back down.

So, this is all done just by moving the z axis with some switches to let the old controls know where it's at. The dogs are adjustable as well as rod position on the turret assembly so you could fine tune the operation on the old controls.

My questions are as follows:
1) Do I need a PLC ?
2) Do I just you Z-axis coordinates to make this happen, or do I incorporate the switches (which may be safer?)
3) How will it keep track of what tool it is on and will it know after a power down and power up?
4) Can Mach take inputs from the switches and do anything with it, or will this be where I need a PLC to handle things?
5) I have not used Mach 3 yet and this is my first retrofit. I also have not had a CNC Machine before this one although I do have a manual mill and lathe.

This all may make no sense as it is hard to verbalize, so please ask questions. It is actually a very simple tool changer.

Here are pictures to help visualize all of this:
http://img831.imageshack.us/img831/6035/img0645o.jpg
http://img440.imageshack.us/img440/5930/img2668b.jpg
http://img291.imageshack.us/img291/6362/img2669f.jpg
http://img545.imageshack.us/img545/3009/img2674p.jpg
http://img146.imageshack.us/img146/4...eoperation.jpg
http://img255.imageshack.us/img255/7342/zaxisdogs.jpg

Extra Info not related to tool changer that you may like to know:
This machine was never used in production, it came out of Kansas University and they used it for training programming, so it is in very nice shape as you can see.
I am going to use AC servo motors and drives from Machmotion and their breakout board etc.
I am using a VFD on the spindle motor.
I was going to use the stock Fanuc DC servo motors, Rutex drives, Bob Campbell breakout board, Bob Campbell spindle motor controller, A custom wound transformer with an input of 220 VAC single phase and outputs of 80VAC and 40VAC going into rectifiers and large caps (Z axis has different motor specs than the X,Y) and a +/-5VDC +/-12VDC 24VDC power supply. I actually already have all this stuff mounted in the machine, but due to ease of making this project quick I am just going to go with the new proven Machmotion stuff to make my life easier. This will make it easier to single source support if I run into any issues. They are also only 50 miles from me if I should need something ASAP in the future. All of these other parts will be for sale if you're interested.

[ger21]

There's a video tutorial on a toolchange macro, and the macro itself can be downloaded.

ArtSoft USA - Videos

That might answer your question.

I think you can di it with just a macro, but I'm not positive.

[jevs]

I saw and watched that, but it seems like that is a macro for going to a certain XY position and picking up a tool and using an output to operate a draw bar, which is a quite a bit different than what mine does. I also have input switches that may need to be involved? How would I do this? If you accidentally travel past the zero tool change point it will rip the threads off the rotation rod (which I have to fix now as someone already did this).
Also, how can the macro keep track of which tool it's on and even remember it if power is shut off?

Thanks, I have a lot to learn.....

[ger21]

I don't know off the top of my head exactly how to do it. I don't know exactly how yours works, but can you home the Z, and then use machine coordinates to move to the proper positions? You can probably use all the switches, but it'll be more complicated.

As for the tool #, you can add a User DRO to the screen to keep track of the tool, and Mach3 will remember it when you shut it down and restart it.

I'd spens a little time getting familiar with macro's, then ask more specific questions on the Mach Yahoo group.

[jevs]

"I don't know off the top of my head exactly how to do it. I don't know exactly how yours works, but can you home the Z, and then use machine coordinates to move to the proper positions? You can probably use all the switches, but it'll be more complicated"

I don't see why I couldn't do this as long as Mach will let me go negative past the home position? Think of the Z axis like this as far as what occurs:

--- Over travel limit switch
|
--- Tool Change Zero switch (should never really go past this)
|
| Rotate To next tool
| ----------------------- Tool change occurs in this zone of z-axis movement
| Drop Turret-------------There is a long dog that keeps a limit switch on
|-------------------------as shown in the pictures in my first post
| Release draw bar
|
--- Home limit switch
|
|
|
|
| Machining area of Z axis
|
|
|
|
---Over travel limit switch


"As for the tool #, you can add a User DRO to the screen to keep track of the tool, and Mach3 will remember it when you shut it down and restart it."

This is good, I was hoping it would.

"I'd spens a little time getting familiar with macro's, then ask more specific questions on the Mach Yahoo group.[/QUOTE]

I will, I have not been sleeping this week as it is just trying to figure out what components to buy all over again. There are a couple used PLC's I found and that is why I need to know if I am going to even need one.

[ger21]

I don't see why I couldn't do this as long as Mach will let me go negative past the home position?

Yes, you can, as long as it's not set up as both a home and limit switch.

[jevs]

"Yes, you can, as long as it's not set up as both a home and limit switch."

The top of the z axis machining area will just be a home. The limit switch is up past the tool changing operation. Sounds like this won't be too bad.

I have been reading all day on the net and it pretty much seems I don't need a PLC. I have seen more complicated systems than mine running without one.

This one for example:
1987 Bridgeport Production Center Interact 412 to Mach3 Conversion