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Author Topic: BT30 spindle from scratch - with power drawbar and ATC of course  (Read 400513 times)

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Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #110 on: September 09, 2012, 05:48:50 PM »
Will this thing make coffee in the morning as well(;-).

No, but there is a Margarita adapter for the ATC.  :D

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Have you considered just adding the turret mechanism to the spindle housing and just index the spindle then relock the turret solid each tool change. You could add the index slots to the spindle housing then use the Power draw bar to lift the turret off the slots then use the spindle motor to rotate the turret then release the power draw bar to engage the slots again to lock it down.

When you say spindle 'housing' I think you mean the spindle itself? If so, then yes, attaching to the spindle nose may be the way to go. I really wanted to avoid having the spindle stick down past the bottom surface of the head, but that may be what I'll need to do.

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That way you do not need a huge servo OR brake mechanism JUST to hold the turret in position

 
You have a knack for making suggestions right AFTER I have finished building something . .   :(  However, notching would not be adequate for the spindle because fine adjustments are needed for the tools. Something that is extremely cool is to cut up to a shoulder in one direction and then just rotate the tool and cut up to another shoulder in the opposite direction. Saves a tool change! But the rotation is not exactly 180 degrees, hence notching would be an impediment. Besides that, I have already added a substantial rotor (see photos) and will use one of the 4th axis calipers with it. You can't move the 4th axis spindle or the mill spindle when locked, trust me on this.

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When NOT in lathe mode the spindle then uses a standard BT30/40 tool holder.  IF you are going to move up to 40 you might want to consider Cat40 as they are more common in the used market than BTs.

The jury is still out on this question. I'm working on other stuff right now so I will revisit this question later and consider all suggestions. I have completed the PDB design. Quite unique I will say . . extremely compact. It mounts on the head, so I will need to mock up a head to do any testing. Hood expressed that he liked that on his mill a lot of stuff follows the head around, I have that as a design goal.  We shall see.

Incidentally, 'your' bearing retainer has come in handy as a leg up on incorporating an oil seal.  SKF has some contact seals good for about 7k RPM, so I am going to use that instead of the labyrinth with the current bearing because I do quite a lot of grinding. I have added a positive pressure purge to the housing already, but that can just be plugged. The labyrinth and purge is still necessary for high RPM with the precision bearings though, so it is good to have also.

Spindle lock rotor:



Online BR549

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #111 on: September 09, 2012, 06:33:11 PM »
To adjust the toolpoint on center you always have the Y axis available to adjust it.

Just a thought, (;-) TP

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #112 on: September 12, 2012, 02:49:57 PM »
Drawbar Actuator is completed. Met and actually far exceeded all design goals.

Specs:

Travel:  .25"  (selectable)

Working Downforce @ 100psi with .25" travel: 5,281lbs  (in service, this will be adjusted down to about 1,500lbs via pressure reg)

Max Downforce: 9,127lbs

Apply time: < 1 sec            (configurable via tubing size or orifice, can be almost instantaneous, but imposes shock load)
Retract time: approx 2 sec  (configurable as above, soft retract is intentional to limit shock load)
Electric Solenoid operated positive mechanical lockout. Actuator cannot release drawbar unless solenoid is activated first to withdraw mechanical interference.

Currently presses against spindle bearings (top bearing if pre-loaded). Can be installed in a floating configuration and forked to whatever is available on the spindle for zero bearing load. This actuator generates nearly zero shock load so bearing loads would be the compressed spring force only.

Overall dimensions installed orientation:

Length 9.35"
Width 4.56"       (solenoid adds approx .65" to this dim on one side)
Height  4.49"

« Last Edit: September 12, 2012, 03:07:29 PM by simpson36 »
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #113 on: September 12, 2012, 02:59:56 PM »
Steve,

I guess that should be enough force.  :-)

So.....  I'm guessing you have a two-stack 4" cylinder, generating about 2500#, with a 1:2 cam arrangement pivoting on the shaft in the lower RH corner of the photo?

I'm curious why the release is so slow?  Is it a single-acting cylinder, and that's just the bleed-down time?
Regards,
Ray L.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #114 on: September 12, 2012, 03:15:33 PM »
Steve,

I guess that should be enough force.  :-)

So.....  I'm guessing you have a two-stack 4" cylinder, generating about 2500#, with a 1:2 cam arrangement pivoting on the shaft in the lower RH corner of the photo?

Close. Two stack 3", 4:1, no pivot.

Compactness was a design goal. Actually, I did three complete designs using different methodology and selected this one as the best all around.

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I'm curious why the release is so slow?  Is it a single-acting cylinder, and that's just the bleed-down time?
Double acting. I added an edit to explain that this is configurable and I have it set conservatively. Essentially instant speed is available, but the cost might be high, so other than torture testing, I will want to run it as gently as is practical in actual service. I have a restrictor on the exhaust.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #115 on: September 12, 2012, 03:21:33 PM »
I guess that should be enough force.  :-)

Some pretty outrageous drawbar force numbers have been batted about for the big mills. It is hard to know what the facts are because the 'specs' never come with any references, but in any case, I am not developing these machines just for benchtop mills. Everything can be used in 24/7 production shop floor. The actuator can easily push 5k with a 2:1 safety factor. There is an intentional (and easily replaceable) weak link that fails just under 10k (hence the max force spec).

Online BR549

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #116 on: September 13, 2012, 02:01:21 PM »
Ok you have my curiousity up. IF the cylinder is 90 deg to the pushrod how do you actuate it without a pivot??  What is the pin in the picture for??

I can think of a few ways but just curious as to what you picked.

(;-) TP

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #117 on: September 15, 2012, 09:43:08 AM »
Spindle completed. Actuator completed except for lockout solenoid which is on order.

I made up a test rig from scrap that duplicates part of the future head. The initial test was added to the previous fragment. and can be seen here. If you already say the first fragment, skip to 00:40 sec.

That wraps up the spindle and PDB. The ATC is next, but I have had some other stuff come up so it will be a while before I can resume this project.

A big THANK YOU to all who participated in this thread.   :) :-*


www.thecubestudio.com/BT30SpindleProject/BT30SpindleTestRig.wmv

Online BR549

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #118 on: September 15, 2012, 11:09:54 AM »
Excellant Job Steve you make us proud (;-).

(;-) TP

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #119 on: September 15, 2012, 01:33:04 PM »
Looks like its going to be the dogs danglers :)

Hood