Please, can anybody here explain to me how does a CNC tool changer function?

How is a tool removed from the spindle and is changed to a different tool. The whole process mechanically wise.

I understand how it is controlled by Gcode.

Thanks :confused:

I think some use an indexer. I round thing similar to the revolver in a gun. A different tool in each section. The indexer moves around to select the tool, the machine moves to the indexer to pickup the tool. The machine has a mechanical gizmo to lock the tool in place.

I would love to build one for my machine. The trick is to automate the chuck somehow with a pnumatic cylinder or the like.

Eric

How is the tool removed from the spindle?

Does the spindle rotate to unscrew the collet? Snap off and on?

If your machine has a "real" machine tool spindle, it will have a taper socket for holding the tools. The rest of the spindle is hollow, or has a throuogh hole which will allow a drawbolt of some sort to pass through. This drawbolt can be actuated with an impact wrench, either electric, or air operated, to draw the tool tightly into the taper.

This is how the "Quickdraw" toolchanger works. It has a 24 tool chain carousel, with the tools standing on their threaded end in little pockets fastened to the carousel chain. This chain is indexed witha Geneva star-wheel indexing mechanism.

The electric impact wrench is run by a timer circuit which controls the on-time of the impact wrench. A short stroke air cylinder brings the impact wrench down onto the drawbolt, when the spindle is fully up at the top.

A two-finger claw arm grabs the toolholder by the flange out of the carousel, and then lifts it and swings 180 degrees to align the tool with the spindle. While the arm swings, the tool holder is also inverted so the the threaded end is up to fit into the spindle first.

It takes quite a bit of rigging to interface one of these units to your cnc controller. I've seen these units sell with old mills for $3000 or so on Ebay. I know that a factory refurbished Quickdraw can cost you $7500.00 This toolchanger is actually quite a fine piece of work. A bit dated perhaps, but it is still in use, and repairs are still available for it.

I believe the tool is held in the spindle by a pnuematic cylinder. The tool goes in the indexer,is released, the indexer rotates, and the machine picks up the next tool.

Eric

here is a pic I found of a indexer/changer

http://www.nacuttingsystems.com/asyst-tool-changer.jpg

Eric

Thanks Hu, I was hoping someone who knew what he was talikng about would step in...never mind me...:)

Eric

balsaman,

Thanks for the picture. I will very much appreciate if there are some more pictures in detail.

Thanks. :D

http://www.motionmaster.com/images/toolchanger.jpghttp://www.republiclaguncnc.com/vmc/Images/toolchanger.gif

I'm not sure how the real cnc's with the retention knob work. However, I would always want the tool to be retained in any event, should the power, or the air or hydraulic supply fail.

I think it most likely that the retention knob system must use some sort of a heavy spring (belleville washers) to retain the tool, and the tool change process must work against this, to release the tool.

I'd like to hear from someone who really knows, though.

Hu,

You hit the nail on the head.

They use a "stack" of Belleville washers on the draw bar. Then there is a large piston mounted above the draw bar and when a tool change is called, (auto or manual) it energizes the piston, which presses down on the draw bar, compressing the springs to release the pull stud. The pull stud fits into a socket with small steel balls. This socket is very similar to a quick release air fitting.

Simple as hell.:confused:

Long story short.....
When the spindle and head move over the chosen tool, a pneumatic cylinder actuates and opens the "fingers" in the spindle taper. The taper then drops down on the toolholder taper and when *contact* is made, the pneumatic cylinder actuates the other way and the "fingers" in the spindle taper grab the retention knob and "suck" the toolholder up into the spindle tightly. Then the tool carousel pulls the other tools away and the machine is then good to go. The whole time this is happening *most* cnc machines blow air through the spindle taper to keep chips and debris out of the spindle to keep the tolerance tight.
There is more to it than this but...
JD

I am into CNC. ATC has several different types of magazines. It depends on how quick the tool change needs to happen and how amany tools and the weight of the tool. Ultimately two tools needs to be intechanged within shortest possible time. IF you guys want to see several different types let me know, I will put a bunch of PIcs.

One of the replies was on the money on Holding. It is by fingers catching the retention Knob. Normally it is held by bellwell springs. It looks like a washer wiht abend. Noramlly they put a bunch of them together to create the movenment while knlocking it.

THe unlocking mechanism could be Hydraulic or pneumatic. Most cases it is Hydraulic, because of the pressure needed.

If you need more info on CNC check my site www.drmachines.com. THanks
Ven

Woody 5, what is you want to do make your own or figure out why your may not be working..

I see you are right up the 14 from me..

cadcam,

First of all, I would like to make my own ATC (automatic tool changer).

Before I do that, I need to know the inner working mechanism of the ATC available on the market to get the feel and come up with some ideas.

Ditto


"Too many ideas...not enough time"

cadcam,

http://www.drmachines.com. is it under construction? :(

http://www.drmachines.com/DesktopDefault.aspx

If you are using Netscape please use this link. Try using IE it will automatically resort to the above link, IE works beeter, since it is a DOTNET site.

Thanks
Ven

Woody I would say the Url was not complete. This not my site. But it looks as though Vencnczone has updated the link.

(First of all, I would like to make my own ATC (automatic tool changer). ) you can go on my website and look for SPE and contact Ryan over ther he would be able to give you some info as he is a Machine designer and builder. He used to work for Haas out in Oxnard.

He is based in Oxnard so it's not that far.

Hope this helps.