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Author Topic: BT30 spindle from scratch - with power drawbar and ATC of course  (Read 411882 times)

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Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #460 on: January 24, 2013, 08:31:59 AM »
OK, here we go . .  finally.
Air cylinder speed is a topic, so I'll start with some mods to the arm raise/lower actuator cylinder. When I removed the restrictor, I found it actually did not move as fast as I wanted, so I had to take it apart and drill the air passages a bit larger and use 1/4" tubing. Fortunately there are 1/4" tube x 1/8" NPT fittings so I di not have to drill and re-tap the ports. It's plenty perky now.

Not so exiting photo here (don't worry it gets a lot better in the next couple posts):

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #461 on: January 24, 2013, 08:44:51 AM »
I'm going to back track a bit now. I don't think I covered this well, and there are questions so here is the story on the 'big spring'. The photos are self explanatory for the most part. The spring is held at center by the washers above and below the spring. The smooth bore for the spring pocket is to allow the spring retention washers to slide smoothly. The spring itself does not rely on the bore for centering. In fact is does not touch the bore at all:

 Belleville chafing problem is evident on the first photo. The bar gets an initial compression and is retained by a snap ring in the top of the spring pocket. This has a side benefit in preventing the bar from extending up and pressing against the actuator when there is not tool int eh spindle nose.






Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #462 on: January 24, 2013, 08:49:56 AM »
A detail I don't think I covered previously. If I did, then sorry for repetition here:

What I consider to be THE most important part of the whole device is this little guy. The pin is hardened steel and rides in a hardened die bushing in the drawbar actuator. This pin protrudes from the bushing and provided a positive mechanical interference with the actuator's operation. In other words, the spindle CANNOT release a tool unless this solenoid is first activated removing the interference. The actuator has some serious Kahunas, so the hardened components used here are so that the interlock can get more than one use.  :P

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #463 on: January 24, 2013, 09:06:17 AM »
I think that to run higher than about 8k to 10k, it would be advantageous to have an extremely rigid spindle. This will be much more resistant to harmonics. I made a spindle  using A6 tool steel. Properly hardened and tempered and fully ground, it will undergo torture testing in my InTurn™ 4th axis. Obviously, I will not be running the 4th axis at 15K RPM, but it is a brute and quite capable of testing the strength and rigidity of the new spindle. Once I am confident of its performance, I will make a similar one for the upcoming high speed BT30.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #464 on: January 24, 2013, 09:15:44 AM »
OK, moving on to some chunky parts;

The bottom of the new head is a 1" thick chunk of pre-ground mild steel (probably A36). Initially, the new head will be bolted together and I may take it down and weld it up at a later time after all adjustment, mods, tweaks, etc are completed. The sides are also steel plate with the ATC side being 1/2" thick and the InTurn™ side being 1" thick. The entire head and ATC will be assembled on a test stand that I made up in order to work on the thing safely until the new mill column is ready. I am having a very tough time deciding what to use for the column, but that's another story.

Hanging at the top of the test stand is the head's upper mount. The lower mount is the base in the first photo. The soda can is just fore scale . . I did not make that part.  ;)


Offline BR549

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #465 on: January 24, 2013, 09:35:38 AM »
Steve for the column you may want to consider 6" Square X .500 wall 4130 tubing.

(;-) TP

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #466 on: January 24, 2013, 09:40:23 AM »
Moving on the everyone's favorite, the  <dun...duuuun>  CLAW.

Hope you are paying attention Ray, 'cause here come the sensors.

There are a bunch of things to keep tabs on with this crazy thing and some relief comes in the form of 'position reached' signals available from the servo drives. All positioning of the arm and the carousel will rely on those signal from he drives and will serve as 'sensors' for that part of the sequence.

Things that are monitored in the following photos are:

1) is the CLAW open?
2) is the CLAW closed?   (same sensor, but a different event)
3) is the interlock in place?
4) is the interlock retracted?    (same deal)

For continuity, I'll mention these as well although they will be in the next post along with the new spindle lock
5) is the spindle lock engaged?
6) is the spindle lock released?  (seems redundant, but some events need two separate sensors to monitor each state)

The first photo is the overview. The second is self explanatory and shows the switch that 'watches' the claw closure.

The last two show the switch that looks at the solenoid. This was a little more complicated in that I had to make the specialty shaped plunger from scratch and add a small rod that extends outside the solenoid case and activates the switch. These particular solenoids do not come with a spring extender so I have to add that internally to both this solenoid and the drawbar interlock solenoid.

The solenoids and the switches are sealed, but I think that I shall still put a cover over the whole works on the arm to keep junk from interfering with the workings. There are a million nooks and crannies that all need to stay relatively clean. 




Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #467 on: January 24, 2013, 09:54:56 AM »
Steve for the column you may want to consider 6" Square X .500 wall 4130 tubing.

(;-) TP


I am considering 8" square x .5" wall or 6" x 10" rectangular x .5" wall. While it does not seem so intuitively, the tortion characteristics are the same. Either of these sizes can ship UPS in a three foot length. I really want 12" square, but the shipping is truck and just stupid expensive. A local steel yard here can get is without hitting me with the shipping, but they require that I purchase the entire 21 foot piece at something well over $1,000. They will cut it up for me though, so that's in the plus column.

Really I want cast iron. Grey cast iron has something like 30 times (from memory) the damping of steel. An important consideration. Note that only Grey iron has this characteristic, not ALL cast iron. I am thinking about using the column from one of those small el-cheapo off shore knee mills.  They are all over the place and cheap. There is one locally on Craigs list for $1,000 and I think I could get it a lot cheaper than that even.  The irony of it would be if they don't use Grey iron.  Its for sure they do not use mehanite. It might actually be better to use the steel tubing and fill it.  I just have not made up my mind on that yet. 

One thing I have decided on is the table. I have a 42" x 9" Bridgeport mill table on its way. 'Previously Owned' of course, and hopefully useable as is. Paid $500 with ship, but if I have to have it ground or otherwise tinkered with , that cost could easily double.
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #468 on: January 24, 2013, 10:00:01 AM »
Steve,

"The soda can is just fore scale . . I did not make that part." - I was REALLY impressed, until I read that....  :-)

You've been busy!  All looking really good!

On the airflow control - look at automotive idle air control valves.  I'm not sure what the airflow range is, but the functionality is exactly what you need, and they're pretty cheap.  I suspect they could be modified for lower flow, if necessary.

Those are nice little solenoids you're using.  Where do you get those?  What do they cost?  I'll probably need some on the new 12-tool fixed carousel ATC I'm designing for my new machine.  All the ones I've found so far are stupid expensive.

Regards,
Ray L.
Regards,
Ray L.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #469 on: January 24, 2013, 10:02:27 AM »
Another detail and then on to more cool stuff.

The seemingly obvious requirement of a counterbalance for the swing arm did not occur to me until the whole mechanism tried to jump off the bench during the initial testing.

So the counter balance is bolted on for now. The smaller round weight is for adjustment and I made up a few in different sizes from scrap. Should help considerably. I may make up an entire new arm once the prototyping is completed, of I may just weld the counterbalance to the arm . . .  or not . .   :-\