ATC Info

[RJS100]

I am in the initial stages of considering if I want to build an ATC for my 3 axis converted mill. I know very little about them and have never used one so I am looking for any info I can find on how to integrate an automatic tool changer with Acorn or any examples of what others may have done.

Let me know your thoughts... Richard

[Chaz]

Loads of info about this if you search. What type of ATC? Umbrella / Fixed etc? Acorn can cater for most out the box and/or with some effort to customise.

[Ken Rychlik]

The biggest challenge is figuring out the mechanical part of what type of rack or carousel will work with the spindle you have or purchase. The Acorn programming, and macros will be the easy part with plenty of help here.
There normally will be some air lines, and air solenoids, controlled by relays. If you look at the whole thing it can seem hard, but just look at one wire and one part at a time.

[RJS100]

Thanks guys. I am interested in some sort of carousel type ATC. I have not located any Centroid setup information to better understand what kind of variables Centroid communicates to/from ATC's. Any information would be great.

[cncsnw]

You can make a Centroid control work with almost any type of ATC design. It just requires appropriate PLC and macro programming.

If you want a "path of least resistance" to making a sliding-carousel ATC work, it would be roughly this:
1) Carousel rotation via reversible motor controlled by PLC relays. The motor must stop promptly when switched off. Include a brake if necessary.
2) The motor should drive the carousel with a Geneva cam, so that the precise motor stopping position is not critical.
3) Carousel rotation feedback should be via a sensor that detects rotation of the Geneva cam: e.g. closed when aligned with a tool position, and open when in transit between tool positions.
4) The carousel should slide in (under the spindle) and out (out of the way) using a pneumatic cylinder. The cylinder should be controlled with a 3-position 2-coil solenoid valve: power one coil to advance the carousel; power the other coil to retract the carousel; with neither coil powered, the carousel is not driven in either direction.
5) Carousel advanced/retracted feedback should be via two switches or sensors: one that closes when the carousel is fully advanced under the spindle; and one that closes when the carousel is fully retracted out of the way. Typically these are magnetic reed switches clamped to the cylinder.
6) Drawbar release should be via a single-coil spring-return air solenoid. Power on to unclamp the drawbar.
7) Tool unclamped/clamped feedback should be via two switches or sensors: one that closes when the drawbar is fully unclamped (okay to pull tool out of the taper); and one that closes when the drawbar is fully clamped (okay to run the spindle).
8) Use Z axis up/down movement to move the spindle up off of the old tool (once the carousel is advanced) and to move the spindle down onto the new tool (after the carousel has rotated to the new position). It is not necessary to make the carousel assembly move down and up.
9) If your spindle has drive keys, and so requires orientation prior to a tool change, then use a closed-loop VFD with orient capability. This, of course, requires a spindle encoder that turns 1:1 with the spindle, wired to an orient card in the VFD. The VFD should accept an Orient command from the PLC, and should provide an Orient-Complete signal to the PLC. If your spindle does not have drive keys, and there is no preferred orientation when the tool holders go in the carousel, then you can omit this part.

If you build an ATC that has those features, then chances are good that you can use a factory-supplied "umbrella" ATC program and macros with little or no modification.

[RJS100]

Thanks. That is a lot of info. Really appreciated! I will keep these ideas in mind when I am looking at various designs.

[RJS100]

Hello CNCSNW,
Thanks again for your thorough explanation. I have been reviewing carefully and have a few questions:

1. I found someone that sells plans for a tool changer that seems to check all of the boxes that you noted. I have not purchased the plans yet, but here are a few images of the finished ATC https://fabrication-arc.com/products/g0 ... 6046788698

2. I have virtually no PLC programming experience and very limited macro experience. Your last comment "If you build an ATC that has those features, then chances are good that you can use a factory-supplied "umbrella" ATC program and macros with little or no modification". Are you saying that there are Centroid ATC programs and macros that are available?

3. I see from your explanation that CNC12 uninitiates the tool change, synchronizes the steps, but don't you need another processor to drive the stepper motor that turns the carousel?

4. Lastly, you mentioned the importance of a Geneva cam for definitive carousel positioning. I will confirm that the above design incorporates this when I buy the plans, but was curious why you think this is crucial. I saw an atypical overly simplistic design that does not use the cam. Just curious what the downside if this is. Here is a quick video:




Please let me know your thoughts.

Best... Richard

[suntravel]

With a Genova cam you will not need an extra axis for the umbrella, but it can be done with a rotating axis also.



Uwe

[RJS100]

Thanks Uwe. I am familiar with the video you posted, which clearly describes the sensors, inputs etc. used to coordinate the tool change, but I do not understand how the Geneva cam eliminates the need for an additional axis.

[suntravel]

Thanks Uwe. I am familiar with the video you posted, which clearly describes the sensors, inputs etc. used to coordinate the tool change, but I do not understand how the Geneva cam eliminates the need for an additional axis.

With a Genova cam you get perfect position with one turn of the motor, that not needs to stop precisely, a simple DC motor an a sensor to stop is sufficient. That was used on mechanical machines for decades.

If you want to have a 4th axis on acorn for machining, use Genova, if you only want 3 axis, use the 4th axis for the toolchanger, because it is easy to build.

Or swap to Acorn Six for 5 axis machining and one axis for a toolchanger

Uwe