Home made ATC

[pstockley]

If anyone has been following my spindle design thread:

http://www.cnczone.com/forums/showth...083#post142083

I am in the process of designing a spindle with support for an automatic tool changer. One of my aims is to build a small mill (a little bigger than a Seig X3) utilizing one of these spindles. I also want to build a carousel ATC tool changer for the mill as it seems like it would be a fun project.

Does anyone have a details/pictures of commercial carousel tool changers? I have a few ideas but would like to see how professional units work.

[dpuch]

One of the simplist ideas I know of is a rack for your tools. The spindle moves over the tool needed. Then down and clamps the tool. It then pulls the tool sideways out of the rack.

No moving parts except the normal machine movments unless you add a guard to keep the tools clean.


A more sophisticated version replaces the fixed rack with a round one that rotates, but the rest is basically the same idea.

Sorry no pictures of these

Dale

[Karl_T]

Have you seen this one?

http://home.insightbb.com/~joevicar3/default.htm

Karl

[pstockley]

I like the rack of tools or carousel mounted on the table as it is simple. However, it is really only suited to bridge type mills. I have seen one on a conventional style mill but I don't like the idea of the long traverse required to pick up the tools. Also I am not too keen on all the tools zipping backwards and forwards. Plus you need some shielding with an automated door to stop coolant and chips getting on the tool holder tapers.

Karl, yes I have seen this and it is very ingenious but I feel overly complicated by the virtue of being totally mechanically actuated. The builder on his forum stated that it couldn't really be scaled up due to the weight of the tool holders. He also estimated it cost around $10,000 to develop because of the injection moulded parts!

[SMW Precision]

Originally Posted by pstockley If anyone has been following my spindle design thread: http://www.cnczone.com/forums/showth...083#post142083 I am in the process of designing a spindle with support for an automatic tool changer. One of my aims is to build a small mill (a little bigger than a Seig X3) utilizing one of these spindles. I also want to build a carousel ATC tool changer for the mill as it seems like it would be a fun project. Does anyone have a details/pictures of commercial carousel tool changers? I have a few ideas but would like to see how professional units work.

I keep having thoughts of a robotic arm for this task! It seems much simpler than a mechanical tool changer.

[JFettig]

Make a round rack with some sort of motor to spin it, sensors for each tool. The rack should be on rails with an air cylinder to push the rack out and retract it, make it stop dead under the spindle and set up switches to tell the machine/plc whats going on.

Really not too difficult to build, more difficult to get all the IO and programming right.

One of those things that would be very fun to build.

Jon

[WhiteTiger]

Hmmm... sounds like a fun project. Mind if I play too?

Few questions, just to get the feel of what you're after. How many tools do you want the thing to handle? What kind of machine is it going to be servicing? I'm getting the impression you'd prefer it to sit behind the work area and deliver just the one tool to the spindle?


Tiger

[pstockley]

Its for a small square column mill I am designing. The aim is to build a small but very robust/accurate mill (a little bigger than a Seig X3). Its mainly a project for fun and to see just how good a small mill I can make. I am not very impressed with the robustness of small mills on the market. I want an accurate/high speed mill for making relatively small but complex 3D model parts (IC and steam engines) mainly out of aluminum. I already have a Tormach CNC mill which will be fine for the bigger stuff.

Regarding the ATC, I have a basic design in my head for a carousel style changer that is mounted to the column. I plan on having capacity for 12 ISO25 tool holders. The rotary motion of carousel will be controlled by a small servo or stepper motor (probably geared down with timing pulleys). The linear motion to align the tool under the spindle will either be servo with ballscrew or pneumatic ram. This is all reasonably simple to envisage.

The spindle will feature the usual spring pack of belleville washers, compressed by a double acting pneumatic actuator. I will probably run this of a compressed air bottle I have at about 175 to 200psi.

It gets a bit more tricky designing the tool grippers in the carousel. From what I have found, most commercial changers use plastic grippers that have some flexure capability to spring over the holder and hold it in place. I may have a source for ISO 25 grippers which would simplify things a bit. Otherwise I would have to machine some out of a suitable plastic.

Now the really ticky bit comes in maintaining spindle and tool holder orientation so that the drive dogs line up. I could just use holders without drive dogs but I want to drill using the mill and I would think dogs are a necessity. So my current plans are as follows. The spindle will be driven by a 1000w AC servo. On tool change, the spindle will slow down to say 60rpm and the system will look for a tach signal from a tack mounted to the pulley. When the signal is received, the next phase will begin. About 180 degrees opposite the tach pickup will be a detent that engages into the spindle to lock it. Normally the detent will be sprung open. However, during the lockup phase the detent will try to engage (probably electromagnetically) and the spindle will turn very slowly. As soon as the detent engages, a microswitch will trigger a hardware halt on the servo controller (similar to eStop). The toolchange macro will detect this and the rest of the toolchange process will continue. After the old holder has been removed and the new one inserted, the detent will be disengaged and the estop on the spindle drive cleared and off we go. Sounds easy However, I hear enough about commercial units dropping tools to believe it will be very tricky to get running 100% reliably. However, I like a challenge!

[Ken_Shea]

pstockley,
Attached is file that shows the tool changer on my machine which is pretty much as you describe.

Ken

[pstockley]

Thanks ken, the pictures are very useful. I like the spring loaded tool holder clamps. What stops the holders from rotating so the slots don't line up with the dogs?

[Ken_Shea]

I tried to get that shot for you with the tool removed but the door shut too fast me to time a shot. I will try again the next time I have the mill operating.

In the meantime.......
You can see the beginning of a cross bar behind the tooling which the two tensioned fingers pivot on. This cross bar has a protruding tab that mates up to the tooling slots when locked in place.

The two fingers appear straight but are inside circular at the back.

Ken

[pstockley]

Thanks I get the idea.