Tool changer (lathe)

[GuntisK]

Hi everyone! I have an old cnc lathe to rebuild. It has a turret that handle 6 tools. At the beginning I wanted to use EMC2, but then I change my mind because TCNC is more compatible with old system.
Could someone explain me how exactly automatic toolchanging can be done in TCNC? Did TOOL TURRET INDEX send a number of pulses of a tool? For example: when instruction M06 T4 is executed, there is a 4 pulses on TOOL TURRET INDEX pin or what? Need a help here.
Guntis

[The Blight]

There is only one pulse from TCNC. You can set how long this pulse is going to be though.

So if you want to change tool, you will either have to place the next tool to use on the upcomming slot, or write several M6 commands. I'm trying to place the next tool I'm using in the next slot. If thats not possible, I will just have to repeat the M6 command a couple times..

I have been toying with the idea of making a separat tool changing computer (just a microcontroller with LCD display and a simple keypad) which keeps track of what tool is to be used next and so indexes to this tool. My tool changer is already controlled by a microcontroller, so adding a feature like this should not be too hard.

[GuntisK]

Mmm! Thanks The Blight! So that signal just means: change to the next tool. I thought about using of a PLC here. Logic for that toolchange is this: PC gives a signal to change to Tn (n is a tool number), from another pin there goes PLC handshake signal that tell PLC to switch on a motor, instrumental disc is moving. Position is controlled by six magnetic reed switches, when there is the right tool for example T6, switch with the same number gives a log.1. to PLC, PLC gives a signal to reverse motor to lock instrumental disc, then the shaft press a microswitch, again the logical.1. signal goes to PLC input, PLC send signal to pin "PLC handshake sense". Tool is changed, everything is ok, TCNC can execute next line of program. This would be ideal for this purpose.

[The Blight]

Sounds good enough. I use stepper motors for my tool changer. The only problem with this system is that if one of the motors loose a couple steps, you can end up with a machine trying to take a cut that is not locked in place, or take a cut with the wrong tool.

I was thinking about another method on how to tell the controller what tool you want to use. Connect another axis output where you can write the tool number. On the controller for the ATC, you can check this line for which tool to use next. The bad side of this would be that you can't use the T word. In my eyes that would be too messy. I like a clean code, so I'm just setting it up to use the next tool in line.

[GuntisK]

I got an idea. You said that Your tool changer use a stepper motor. I know that in TCNC there can be set an axis which use angular positions so called A, B, C axis). For example we have 4 tools. 4 tools = 360 degree. So the stepper motor should rotate every 90 degrees to change to another tool. Just write a simple code in the line and You got it! At this moment it seems to be a simplest solution for this. Sad, that I cant use it in my system.

[The Blight]

I have set my changer up as a linear axis at the moment going from 1 to 4. I think I have set it as the Y axis (lathe), and if I type G00 Y1 it goes to tool pos. 1. First I have to release the locking pin, which is axis A. So G00 A1, G00 Y1, G00 A0 is a tool change. I just need to hook up the new microcontroller so that it takes care of the whole tool change with offsets for the locking pin and a home position sensor.

How does your tool changer work? Got any pictures?

[GuntisK]

Hi! Sorry for my late answer.
This one works exactly I explained in my previous post where I mentioned PLC- except is that there is used special electroautomatic control board instead of modern PLC. I found very interesting homepage where is explained how to build simple PIC based PLC : http://getok.net/plc2pic/index.php?next=index . Maybe it is worth to build one? Another idea is to change TCNC code in a way that TCNC gives in output a number of pulses equal to number of tool. T4 for example gives 4 pulses on some LPT pin. This would be more and more easier than it is now...
Aaa-and here are some photos:

[The Blight]

Looks like a nice project, and a beautiful cleanup so far.

That PLC circuit looks simple enough, and it should work just fine if you can hook it up. Do you know how to program in turbo pascal? If you get around to do some changes in TCNC, please share. I tried to get into programming pascal, but I gave up shortly after.

[GuntisK]

A good friend help me a lot in programming. Now we are trying to make TCNC multilingual (english, latvian and russian languages in one program, later maybe some other). If everything goes in a good way, then TCNC will became as a special OS for cnc machines. Of course I will share with the results. I must say many thanks to Dave Kowalczyk for this great program and his efforts to write it. It is really great and easy to use program.
The Blight- can You show a pictures of Your toolchanger?

[The Blight]

TCNC is really easy to use, and it has lots of functions. I think it's a great piece of software, and I don't think I will change. Dave has started working on it again it seems. I hope he fixes some of the bugs and adds a couple new features.

The ATC is for my mini lathe (which I also have built myself), and it's for taking light cuts. I have taken 2mm cuts in brass, and it doesn't complain. I get some vibrations when using a 2mm parting tool, but it does work.

[PEU]

wow, very nice ATC, I would like to have something like it for my Syil C6, do you know where can I find ready made ATC like the one you built?

[The Blight]

I think Enco have one, but I don't know how much it costs. There is lots of plans out there on how to make one. The problem is doing just that. I have heard some talk about using a rotary table to hold the tools. Might work if there is no slop in the system, or if you find a good locking system.