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Author Topic: BT30 spindle from scratch - with power drawbar and ATC of course  (Read 408364 times)

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Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #560 on: March 16, 2015, 09:37:04 PM »
I watched your video some more time(s) and now I can see the turret rotating very slightly as it cinches up on those teeth. If I knew what a hirth coupling was, it would have been clear from the git-go.  :-[ Now that I can see all those choppers, it makes total sense. Thanks for explaining.

You mentioned that the hydraulics were from a 'previous turret'. What was the motivation to build a new one? That is a very significant project to tackle, I would say.

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #561 on: March 16, 2015, 11:04:56 PM »
Ok kind of a long story.
Originally the lathe came with a 6 position turret at the rear and a 4 position toolpost at the front. Both were totally hydraulic so could only rotate one direction and also had to clamp at each position before unclamping and moving to the next etc etc.
 I then acquired a turret from a Bullard lathe, it too was totally hydraulic but I stripped off the hydraulic motor that rotated it and replaced with the motor and gearbox I am using still.
 So that meant I now had a lathe with 6 position turrets front and rear, Mach however wasn't that great with front and rear tools so I had to always edit my G Code to suit and add to that  I had to be very careful with new code to make sure I hadn't commanded a move where one or other of the turrets could smack into the stock or rather the tools such as drills smack into the stock.

 So next bright idea was to remove both turrets and make up a scratch built 12 position turret, it worked well for the most part but it was just a bit too cluttered, I would have preferred a 10 position turret but both the Curvic coupling from the Bullard turret and the Hirth from the original would not allow 10 positions due to the amount of teeth (48 on Hirth, 24 on Curvic) so it was 8 or 12 and I went for 12. That brought problems when using drills, boring bars  and normal turning tools, they were all too close and I had to be very careful not to crash a drill or boring bar into the chuck.

 So next idea was to go to an 8 position turret but make it a VDI turret so that the tools could be swapped in and out within seconds and be very repeatable, so that is where I am at now.
I also like a challenge and the VDI was defitately a bit more complex than the previous one I made ;)
I used the original turrets Hirth coupling and also the body/cylinder but I had to do quite a lot of modifications including adding thrust bearings internally and I likely would have been quicker and easier making one up from scratch.
Pics below of
1. Original setup (seen from back side of lathe)
2.  Bullard turret after I modified it
3. Scratch built turret
4. Latest, and likely the  last, turret.
« Last Edit: March 16, 2015, 11:11:39 PM by Hood »

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #562 on: March 17, 2015, 05:51:58 AM »
Now, that is quite a story. Well done. Very well done.

You may have been able to get 10 tools by having 6 on one 'half' (first 180 degrees) and 4 on the other and still used the 48 tooth coupling, however, The software to run such an arrangement would be complex and error prone and probably require a sensor or two to operate safely. Seems to me that 8 equally spaced tools with quick change holders is the bulletproof solution.

Just one more (compound) question if I may; presumably the turret is supported by a draw tube or shaft. Dies that shaft ride on bearings in the housing or on the hydraulic seals? It is a hardened piece from the original machine or did you design/build that part? Lastly, I note that the pulley does not shift in and out with the Turret. Is the shaft splined, keyed or slotted or is there a special slip joint and again was this recovered from the original machine or new design?

For a minute there, I thought you had posted a photo of a different machine, but it appears you built a full cover and painted it to match the machine. First class. Very nice!

OK, last, last question; there appear to be some kind of trapezoid shaped 'posts' sticking out of the turret surface that the tools attach to. Also I noted holes in the turret edge that look like there are screws or cams of some kind. Is this the quick change mechanism?  I can't tell from the photo how it works, but unlike an Aloris type piston, it would seem your arrangement must pull down as I see no tracks or dovetails to locate the toolholder.

Sorry for so many questions. It is a rather complex machine.
« Last Edit: March 17, 2015, 06:07:13 AM by simpson36 »

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #563 on: March 17, 2015, 08:08:53 AM »
Quote
You may have been able to get 10 tools by having 6 on one 'half' (first 180 degrees) and 4 on the other and still used the 48 tooth coupling,
I tried many designs,  to keep things as balanced as possible I had some designs with one position being 4 teeth apart and the next 7, but I was never truly happy with the design.
Quote
however, The software to run such an arrangement would be complex and error prone and probably require a sensor or two to operate safely.
It would not really have been a problem as I use the Indexing drive and thus would just have different encoder counts for each position, the actual M6 macro in Mach would have been exactly the same as I have now with the exception of 10 tools possible rather than 8.
Quote
Seems to me that 8 equally spaced tools with quick change holders is the bulletproof solution.
Yes seemed to me like the best solution but definitely not the easiest as the VDI setup requires fairly accurate positioning of the holes, especially the wedge ones in relation to the tool holder ones.

Quote
Just one more (compound) question if I may; presumably the turret is supported by a draw tube or shaft. Dies that shaft ride on bearings in the housing or on the hydraulic seals?
It is a shaft, see pic  below . It has a brass bush at the front (yellowish bit in the drawing) the rear just has a quad seal.
Quote
It is a hardened piece from the original machine or did you design/build that part?
It is from the original but is not hardened, just a decent quality alloy steel, probably EN24T or similar.
Quote
Lastly, I note that the pulley does not shift in and out with the Turret. Is the shaft splined, keyed or slotted or is there a special slip joint and again was this recovered from the original machine or new design?
I bought a length of splined shaft and a splined bush and fixed the splined shaft to the end of the turrets shaft with a socket capscrew, I also machined a flat on the end of the turret shaft and machined away the end of the splined shaft leaving a stub on one side so that the two shafts mated together and could not rotate.
The original turret was rotated by rack and pinion under hydraulic pressure so it did not need any thrust bearings. I had to recess the front of the piston section to fit a roller thrust and I also fitted one at the rear.
The piston itself is basically just a disc with two piston rings on the periphery and it  fits on the shaft and the shaft to piston is sealed with a quad ring.
 The piston itself does not rotate, it has a pin that fits into a hole in the turret housing (red circled in drawing) so it is just the shaft that rotates and the piston only slides back and forth.

I have also attached a screenshot of the splined shaft, splined bush and also the part I made up to activate the limits that tell whether it is clamped or unclamped. Also a pic of the back where you can see the limit switches. Prox's probably would have done just as well but I like my mechanical switches :)

Will answer your last question in another posting as I will have to get some screenshots as to how the VDI system works.
Hood
« Last Edit: March 17, 2015, 08:11:04 AM by Hood »

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #564 on: March 17, 2015, 08:51:50 AM »
Quote
OK, last, last question; there appear to be some kind of trapezoid shaped 'posts' sticking out of the turret surface that the tools attach to.

Think you may be meaning the blanking plugs, they are just used to cover the holes left when there is no tool in that position, stops crap getting in :) I was going to make some up out of delrin but WNT had a special on where they were only £5 each so I bought a few. They are just moulded plastic rather than machined but that is all that is needed. See pic below from WNT website showing a similar one.
Quote
Also I noted holes in the turret edge that look like there are screws or cams of some kind. Is this the quick change mechanism?

Yes that is the wedge, it is fitted into a hole that is at 20 degrees to the top of the tool holders slot. The wedge itself has a face milled at 20 degrees and then vee'd to mate with the vees in the tool holder. The centre of the hole for the wedge is 30mm in from the turret face and the central vee in the tool holders are 29.7mm from the face that contacts the turret plate. That means when you screw in the wedge it mates with the front of the teeth on the holder and forces it back into the face of the turret.

Normally VDI turrets are round rather than having flats on them. I do not have an accurate enough indexer, or rather I may do but was not willing to trust it's accuracy for this job ;) so I milled the OD edge so that the faces would provide the indexing and also the correct angle for the holes.

Hopefully the pics below will show how it all works.
Hood
« Last Edit: March 17, 2015, 11:33:08 AM by Chaoticone »

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #565 on: March 18, 2015, 10:52:55 AM »
Hood,

Well, I just transitioned from 'impressed' to 'amazed'.  :o  The video does not do justice to the complexity and ingenuity that went into this machine. Often the best solutions are evolutionary. The trick is to persevere thru the fails. Assess the performance gaps, re-design and have another go at it.

Plus, you  have anticipated and answered my next question already, so I'm all caught up!

However, as a follow up on the topic of 'indexing' drives:

It would not really have been a problem as I use the Indexing drive and thus would just have different encoder counts for each position, the actual M6 macro in Mach would have been exactly the same as I have now with the exception of 10 tools possible rather than 8.

I recall that you are using Allan-Bradley and those guys have both 'universal' input and also positioning in the same drive. Is that correct?  With Mitsubishi, you have to buy different drives and Yaskawa has 'motion controller' to pair with their drives. I have one of the Yaskawa controllers that I purchased with the idea of running an ATC carousel or chain with differently spaced 'tool spots', but I have not had time to mess with it.  Also, I have in-house at the moment a customer's new Sigma5 Yaskawa motor and drive in 3kw size and it is uber impressive. The motor is about half the size of my 3.6kw Mitsu and it's fast!

As you know, the manuals on these things are just huge and I have not looked at what the new Yaskawas have to offer (beyond what I needed for the task at hand), but I am leaning toward the Allan-Bradley since from your description, it would be more or less 'universal'.

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #566 on: March 18, 2015, 02:03:31 PM »
The ingenuity of the VDI system has nothing to do with me, it was the German Engineers Society :)

The Allen Bradley DSD drives come in a few versions, there is the standard model which can accept Stp/Dir and/or Analogue commands and then there is the Indexing version which can, in addition to that, do Indexing.
The standard drive would have a designation something like
DSD-020
The Indexing drive would be
DSD-020X

There is also a Sercos version which you can disable the Sercos via the Ultraware Software and doing that turns it into an Indexing drive. The model number for them has a SE on the end, so something like DSD-020SE.
There are also 2 versions that support device net, they too can be used as normal drives but only the Indexing version of it can do Indexing.

How the Indexing works in the AB drives is you assign up to 6 Inputs and depending on which Input combination is active you can have up to 64 different Index positions set. You can configure the RPM, Accel, Decel, Position etc for each Index.
Below is a screenshot showing a few of the Index setups in my Turrets drive.

Hood

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #567 on: March 19, 2015, 06:16:39 AM »
The ingenuity of the VDI system has nothing to do with me, it was the German Engineers Society :)

The VDI system deserves its own Kudos, no doubt, but then again, a lot of engineering also goes into a harmonic drive, and the designers of that component deserve their kudos in turn, however, it is still a component and can be used in a good design or a bad design. It appears to me that you reclaimed some components and methods from a previous machine, but that monster sitting on your lathe is a Hood design. Integrating all of those pieces together and adding a slip joint and servo control is not a trivial task. Nor was the machining of those tool holders.

I will add that the logic and methodical movement thru the evolution of the machine design is classic prototype engineering. Regardless of where the components came from, the overall machine is an achievement. That's my view.  8)

  

How the Indexing works in the AB drives is you assign up to 6 Inputs and depending on which Input combination is active you can have up to 64 different Index positions set. You can configure the RPM, Accel, Decel, Position etc for each Index.
Below is a screenshot showing a few of the Index setups in my Turrets drive.

Hood

I don't think it gets any better than that. .  Sigma5 has some kind of indexing capability, but I have not had time to dig into that encyclopedia of a manual yet. The Signma5 would be an expensive alternative, in any case, so I'll start poking around for an A/B drive using the data you have provided.


Question: is there a provision for fine adjustment, per tool, to bring the cutting edge to center for say the parting tool??


« Last Edit: March 19, 2015, 06:19:36 AM by simpson36 »

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #568 on: March 19, 2015, 08:15:05 AM »
You can get height adjustable holders for the parting tools, see pic.
Theoretically there should be no need for height adjustment as the hole for the holder fitting into should be exactly on centre. The holders themselves should also be exactly on centre for the drill/boring bar holders and the normal tool holders should have their face either 20mm below or 20mm above centre.

That is of course the theory ;) we all know that the square section tools can be off a wee bit so I just pack them up with brass shim. I have made a holder for setting tools up and have it so I can set the height as well as setting a rough length. That way I can command an offset for a known tool and then just take a cut and then I am able to set the offset for the new tool.
Pic of the setting block below.

The parting tool I use is just the normal block/blade type so I can just shim to suit and do not need the type as mentioned earlier.

Hood

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #569 on: March 19, 2015, 08:22:09 AM »
Oh and I never made the tool holders, bought most from eBay at a good price and only had to buy a couple new, even then the price of them has dropped massively in the last few years.

Hood