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541

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 02:47:42 PM »

Could you not make up double width pots for such situations?
Hood

Now that's creative thinking!  I suppose you could indeed . . so long at the 'double wide' could get around the corners.

542

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 02:10:27 PM »

Steve
Heres a site that  gave me  ideas  when I was dreaming about how I was going to do mine, now I dont have to (assuming I buy the Chiron ) May give you some food for thought, I especially like the hinge down holders.
http://www.miksch.de/en/tool-changing-systems.html

Hood

Couple things, Hood;

First, thanks for the link. But a full half second for a tool change? Please . . . way to slow . .      OK seriously cool stuff. This is pretty much similar to what I have in mind . .  except on a whole different level.

Second, on their 'magazine', they seem to be linking individual tool 'pods' to each other rather than attaching them to a separate chain . .  interesting . .  and so much for the variable slot width  idea . . 

Third, since you won't need that old Beaver mill, you can just put it in a big box with a ribbon . . my address is . . . . .   

543

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 01:52:17 PM »

Steve,

Like Terry, I too question the real-world value of a super-fast toolchange time.  I can't imagine that it would save more than a few minutes per day at the cost of significantly increased complexity, and opportunity for disaster, due to higher speeds, and generally higher precision required.  I think you can quickly get to the point where doubling speed will take 10X the time and 2X the cost, to make it as reliable as a slower, simpler machine.

Re: the speed of a Geneva, this, too, I think is a bit of a red herring.  Perhaps a high-speed Geneva will always be a bit slower than a max-performance direct-driven mechanism, but I think the overall difference in toolchange time would still be small.  I'm running mine VERY conservatively, and it runs under a second per tool pocket.  So, even with a 24-tool carousel, max seek time would be 12 seconds.  I'm sure I could easily double that.  Beyond that point, you have to start worrying about the tools flying out as the thing moves.  The biggest job I ever did only used about 12 tools, and that one took hours to run, so an additional 3 minutes in seek time would be lost in the noise.

I'm not sure if our posts 'crossed in the mail' or if you misunderstood. My setup will not be 'super fast', just fast. And even that is a subjective term. I think the only number I mentioned was 5 seconds, but really I won't know what it will tolerate until it is running and I can push it to failure.  What I don't want is 20 second tool changes. Seconds add up when you are multiplying them by orders of magnitude. If you doubt that, just run Vectrix generated peck drilling code for 30 deep holes . . . .

Certainly doing a variable-tool-size chain-driven machine is quite do-able, but, again, at considerable cost in terms of complexity.  You'd have to not only program each tool length, but now the "pocket" width as well.  And, setting up a job will mean a fair amount of disassembly/re-assembly to move the tools to their required positions.  Or, have pre-configured slots of different sizes, but then you have to deal with mapping tool numbers so each tool lands in an appropriately-sized pocket.  My biggest tool is a 4" face mill, so I just sized all the pockets accordingly.

The jury is still out on this and I have not really thought it thru. Thanks for you observations. Every comment helps.

The idea probably falls apart without a smart servo drive that can find the tool spots on its own. I had in mind just a certain number of 'small' spots and 'wide' spots. You put your 4" face mill in an existing wide spot and your 1/4" drill in a 'small' spot. The only disassembly would be to alter the ratio of small to large to suit your typical jobs. The position of the tools can be defined as a distance from 'home' and could be calculated easily thus; 3 wide spots x 4" and 2 small slots x 3"; that tool is at 18". All you would need is a table of tool positions stored in the drive or the controller.

It would just be a way to shoehorn a couple more tools on a belt which may be all you need for a specific job. If I build in the capability, that doesn't mean it has to be used. Even if the slot width was variable, they could all be set the same, so no harm no foul . . . .  IF it turns out to be easy to implement. If it does result in a lot of complexity, then I would agree with you that it may not be worth the effort, but I don't know that yet. Certainly the tool postions could be completely random and be probed, but that is most likely over the doable-but-not-practical line.

The chain belt option is a definate, but variable spacing is just a discussion point at the moment.  

544

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 11:36:00 AM »

Certainly is an advantage to a double sided swing arm. I dought you will make fast tool changes with a single side arm . You have to get the old tool put it in the slot then rotate to the new tool and load it.

Certainly a valid point. I looked at a dual arm . . .  longingly . . .  salivating . .  however, while both arms work, they also both swing and a 360 degree sweep is required. A single arm requires only about 200 (approx). There just was no enough room for a full sweep and still be mounted on the mill head, so I had to choose.  

Super fast tool changes always add complexity to the tool changer.   Thinking out loud when the machine is running in auto what is the difference between 5 secs and 35 secs ??  It is no longer YOUR time being consumed with teh TC. You can be off drinking coffee(;-).

So . . .   is fast important or not important?   With my planned arrangement, there will not be anything approaching 'super fast', but as you point out, it will also not be super complex nor super expensive. So between a Smart Car and a Lamborghini, I'll be happy to end up with a Camaro . .  although actually I like the Challenger much better.

Making 30 parts in one hour instead of 25 parts would be significant enough for my purposes. I only have one product that I make a few hundred at a time.


Just a thought, (;-) TP
[/quote]

545

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 11:24:26 AM »

Heres a vid of the style on the Chiron.

Friggin' AWESOME!  Straight out of Star Wars. . . . .  I think I got some wood watching that vid . .  (not sure how that will translate internationally . .LOL!)

Anyway, given a 50k budget . . .  and a staff . .  I might be able to come up with something like that . . . . however, if I fall somewhere between that monster and Tormach I shall be well pleased.

546

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 11:20:50 AM »

Actually, no reason why a Geneva can't be used to move a belt just as well....

Geneva drive for a belt is doable, but lacks high speed random access, needing to stop at each position in sequence, including empty pods. With an intelligent drive such as the one described by Hood, you can simply command the drive to go to a spot and not have to track the position as you would with a Geneva.

I also wonder if it might be possible (in a practical sense), to have variable width tool 'slots' on a chain belt. i.e. why have the same real estate consumed for a 1/4" drill bit as a 6" face mill? I have not given this much thought yet, but if it is doable in some reasonable way, it could make the difference between getting 20 tools on getting 25 tools on the same belt.

547

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 10:36:06 AM »

I considered a "remote" carousel and transfer arm, but it seemed to get too complex too quickly.

Agreed. However, the goal of unlimited tools eliminates a moving storage device as a possibility. Moving a carousel is easy enough, as you correctly point out, but moving a 6 or 7 (or more) foot long chain belt and associated drive mechanism would be impossible by any practical method that I can think of. Another consideration on this aspect is the cover s for the tool storage. Since the arm moves up and down, I think I can sidestep needing an opening access door . . . .  hopefully . .  maybe . .  

My current carousel design is really quite simple, with only two air cylinders for actuation, also fully inter-locked.

how are you sensing a successful tool change

I'm using a Geneva driven by a simple gearmotor for tool selection.

Simple and effective for a carousel.  NG for the chain belt option, but a servo drive could be moved over with out much difficulty and the programming would not need to be significantly different . .  perhaps even handled by a config param.

With luck, I should have it working in another week or so.

A week!  Jeez, It will take me a week to figure out how this new coffee maker works . .  

548

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 10:22:54 AM »

On the topic of 'Any-Z-position-tool-changes', it has just occurred to me that if there is access in MACH to the tool table, the operator could enter the highest point on the workpiece stock and the ATC controller could raise the head to safe level for the commanded tool after checking the available Z travel. If the travel is exceeded, the machine could fault or suspend and wait for operator intervention.  

549

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 10:13:06 AM »

Sounds like it will be nice, are you having a dual sided arm or just using a single arm?
,
I am likely not going to have to bother getting the knee on the Beaver servo'd in preparation for a toolchanger,  now as I will likely be buying a Chiron FZ12 Mill shortly, going  to see it on Sunday so I can see if I reckon the motors I have will fit. Now they are fast, something under 1 second toolchanges.

Hood

Single arm mounted on the head. The swing is over 180 degrees making articulation rather complicated, so the arm will probably be servo powered. Expensive option, but one that also provides for accurate positioning and also for sensing jams, collisions, or empty tool pods.

The arm will raise and lower on a single linear slide via pneumatic cylinder. I am unsure at this point where to put the sensors for vertical movement.

I doubt there will be sub second tool changes, but 5 seconds would be great.

The tool change speed will be improved significantly in a configuration where the turret is carried on the mill head, but with a tool change possible at any Z position, special attention will need to be paid to tool clearance in the g-code to make sure there is room under the head for the new tool to swing in. Have not looked at that Gorilla yet.

550

General Mach Discussion / Re: BT30 spindle from scratch - with power drawbar and ATC of course

« on: September 21, 2012, 09:47:42 AM »

Update: I have settled on an arrangement for the ATC and completed the preliminary design.

So far, I have built one prototype tool storage 'pod' (for lack of a better term) for testing and while it works as expected, there *might* be a tendency for the release mechanism to jamb in the long term, so I have made some changes, adding to reliability but also to the cost, as is usually the case.
 
After reviewing a lot of existing ATC configurations, both DIY and commercial, I chose to not move the entire tool storage device and instead use a single swing arm to transfer tools from storage to the spindle. here are some design goals which are met with the design thus far:

1) safety - accommodate sensors at each step in the process for monitoring purposes.
2) configurable - choice of 6 tool turret or unlimited number of tools via chain belt
3) self contained - optionally the ATC (with turret only) can be mounted entirely on the mill head (credit to Hood for this goal),  
4) Tool tapers are completely covered and protected by the tool storage 'pods'.
5) positive mechanical retention of the tools in the storage device - no reliance on material spring - i.e. nylon 'fingers' or equiv.
6) tool release from storage pod is initiated by the swing arm 'claw', and then only after the claw has firm control of the tool.
7) fast - have not quantified this yet, but definitely not 10 to 20 seconds as typical DIY changers require.

Feedback always appreciated, especially if you have a favorite ATC arrangement and can cite the advantages. I will post a photo of the prototype storage pod a little later today perhaps.