5C tailstock mock up:

Little better shot of the part:

Brand new integrated pneumatic caliper. Latest articulated verison on the right:

Lock and disc:

New belt drive setup:

FInally just some frames and various components:


I'll update this thread with the new tailstock and trunnion table progress and development continues on those projects.

Wow!

This was a fantastic thread! I have been looking for someone doing what you are doing for a long time now. And finally I found your clips on YouTube. From there I managed to find this thread by googling your nick.

It’s a long time since you last posed, so I’m assuming you have other things to attend to like most others. But like many others I hope you haven’t abandoned this project, and will return with an update and an even better setup!

You are able to do what most people, me included, are not so good at. Get things done and put to life. I must say your design really looks good, and you do know what it takes to get things to do what you want them to.

Anyway, I have an idea that your design could benefit from. I intend to do this when I make an attempt at building my own turning 4th axis as well.
It’s a design used on commercial lathes, so it’s a proven design. It’s also easy enough to get the parts needed.

The idea is to have an automatic gear changer. In your present design you have to loosen the motor and middle shaft assembly to change over the belt to change gear. What you could do is implement the design shown on Kirk Wallace’s page http://www.wallacecompany.com/cnc_lathe/HNC/about his Hardinge lathe conversion. He describes and show pictures of this design on his lathe. He then goes on to explain that the clutches should be easily obtained from car A/C units. As he mention the size on A/C clutches are sufficient for his sized lathe which is bigger than yours. But at the same time they aren’t so bit that it should be a problem. At least to me as my mill is somewhat bigger and I intend to put a 3-5 KW motor on my turning axis.

I hope you read this and take it in to consideration soon. I think it could be a great improvement on the design.

Then there is the encoder. I would like to get an absolute encoder on there with enough resolution to make it usable as a full 4th axis. And that require more resolution than the encoders you have on there now. The use of absolute encoders was founded in the idea that you don’t need to read them more often than the servo thread is run. And the resolution needed demands so high that turning at full speed would require MHz bandwidth if an incremental encoder was used.

I started a thread about wanting to build your design over at practicalmachinist. But they seemed most focused on telling me why not to do it, to get a millturn unit or farming the work out. That wasn’t my idea, and I tried to get them to understand that I’m doing it for the fun of it. But nobody seemed to think there is a point in doing this on a hobby basis.

That might also be why I haven’t found anyone at all except your attempt at doing this. I don’t se the big problem in doing it, and you have even proven there is none. Except for having to do all kind of hacking on Mach to get it to drive the whole thing that is. That is why I’m so glad I found your design and proof that it is in deed possible to do. And it works GREAT!

BTW, I REALLY like the clips where you show how to use a mill for shaping work. I hadn’t thought about doing things that way. But you have shown me that it’s both doable and works great! Thanks! Now I know it might be possible to do that hex bottom hole I need.

Thanks for the compliments. I do not have time for forums these days, but I can provide a few design tips that may prove useful if you intend to build your own machine. First, there will always be 'doom sayers' who will condemn any idea as unworkable or unnecessary . . usually because they have not been able to accomplish the same task. Some people demeaned the idea of this 4th axis, yet I cannot keep up with the demand for them. I am finishing the last three of another batch of 7 and when shipped in a week or so, that will be 14 units shipped so far this year. And there is a waitring list for more. So, do not be discouraged by the untalented who preach impossibility. Even the infamous R8 power drawbar and other 'impossible' projects are very doable.

That being said, every machine designer works to a spec and design criteria. Pretty much all things are doable, particularly in the realm of prototypes, but nobody will purchase a 4 million dollar mouse trap so cost is usually one of the criteria. Because of the pneumatic disk caliper and custom spindle drive pulley, this 4th axis is not an easy DIY project.
 
Note in the photo that there is no real estate available internally for additional components for an auto shifter mechanism. The spindle lock is a critical need and cannot be eliminated. In fact, the current model is even more crammed as it has a larger air cylinder which required the frame to be expanded slightly. Automatic shifting IS doable, but all features must be evaluated based on cost/benefit and there is also no 'room' in the pricing to add such a feature and remain affordable to the target market. Some challenges with your proposed scheme will be retaining a hollow 5C spindle, very high rotating mass and perhaps there would be consequences to having large electro magnets in close proximity to CNC equipment. I think syncronizers might be a reasonable alternative if automatic shifting is a requirement in your application. Note that on my 4th axis, you do not loosen the motor or the idler. Both are mounted on a moveable plate which is how the belts are changed/adjusted and the same belt is used for both high and low ranges. 

You are quite correct in that integrating the unique capabilities of a combined lathe/indexer into Mach3 (or others) is the largest challenge. Lastly a comment on encoders; the motor you see in the above posting is a 400 watt  Mitsubishi industrial AC servo with an absolute encoder of over 100,000 counts. That motor has been replaced now by a 75-0watt version and I have acquired three of the current Mitsubishi J3 series for my new mill. That series has 262,000 pulses per rev absolute encoders. However, in practical terms, Mach3 cannot utilize an absolute encoder in a useful way and a typical 2000 line (8000 in quadrature) encoder is completely adequate for most indexing.
Good luck in your project and please do post a link to a build thread if you start one somewhere.

Videos showing the new tailstock and trunnion table:

Tail stock is finally completed. It has the original planned features as well as some new features. The ball bearing supported hollow 5C spindle is probably the largest difference between this tails stock and any other. The version shown in the video is the first prototype whick has now been sold and the latest version is similar, but the leadscrew redundancy has been removed and a new adjustable drag and spindle lock have been added. Some new videos of that version will be added soon.

http://www.youtube.com/watch?v=DJXg1u4D3Y0
Some testing of the new tail stock:
http://www.youtube.com/watch?v=yM06Ro7y_oUhttp://www.youtube.com/watch?v=K4rziDNTu5A
And finally the first tests of the trunnion table:
http://www.youtube.com/watch?v=itJqDwl7X2o

More videos:
Use 4th axis for sharpening
http://www.youtube.com/watch?v=Y3PIdnNwsAg

Internal shaving of keyways
http://www.youtube.com/watch?v=Nnfcc2fqeTA

Major bench mill upgrade phase 1 table
http://www.youtube.com/watch?v=HTQ7u3pcdYs

Major bench mill upgrade phase 2 column and head
http://www.youtube.com/watch?v=QsuJgCCPSl0

Amazing work there on your new mill, Steve!

I have been thinking of using a 4th axis as a tool grinder for some time now. Nice to see you actually doing it and getting good results. Gives good motivation.

You're videos are very professionally made as always and a pleasure to watch. Thanks for showing!

Dan

Some pics of the latest tail stock. Redesigned to eliminate positioning redundancy and to add spindle grag/lock mechanism.

It looks like the tail stock is about 5" wide?  This could work on an X2.

To use this on a mini mill you really do not need the lock or break.  But you would need to figure out a belt and motor.  I have also though of using a X2 spindle box and remove the gears then mount a pulley on the back with a belt and motor.  Problem is that I do not have the equipment to mod the parts.

http://littlemachineshop.com/products/product_view.php?ProductID=1906&category=-269978449

Issue with any of the existing Phase II style tables that are retro fitted with a stepper motor is the backlash is difficult to control if you put any real hours on them.

The tailstock frame is only 4" wide. In the case of using the tail stock as a 'mini' 4th axis, there would be no need for the rails and therefor, the base could be 4" wide and bolted down from the front and back like the 4th axis base.

I would not consider using a mill spindle because you are going to have R8 or MT which are not good choices for a 4th axis. These are designed to hold cutting tools, not workpieces. 5C is better because you can pass stock thru it and also there are an amazing array of collets available for 5C, including square and hex, as well as 5C mounted chucks.

There is a fundamental difference between a motorized rotary table and my 4th axis in that a rotary table is strictly for indexing. It cannot rotate any where near fats enough to do turning. With a 5C spindle sitting on ballbearings and a tooth belt drive, you have indexing and also turning in the same device.

A paradox inherent in this chameleon is that to get speed useable for turning, you need a servo motor and servo motors, while vastly more powerful and faster than steppers, do not hold as well. that is the reason for the spindle lock.

I agree the 5C system is superior.  The main purpose I would see for using a 4th axis on a mini mill is for indexing.  Most people using a mini mill are cutting light materials such as wax, plastics, brass, etc.  

I would forgo the servo for a stepper. Steppers are much more compatible with small home systems.  The addition of the belt I assume fixes the back lash issue by eliminating any and increases the positioning speed.