Linkage question on from carriage to Headstock spindle

[Brian Weick]

I am in the midst of trying to figure out how to do this. I would like to have the headstock spindle (linked ) to the carriage on the bed. I was sent an E-mail from a member of OWWM and had mentioned cnc-ing this lathe. My thinking is this: If I can get 2 servo motors linked together through processing unit for both and manipulate that through software I think the possibilities are almost limitless.
Are any of you familiar with servo motors/processing units and software as far as cnc conversions. I know this can be done but my problem is i don't know what I am looking for and am not educated in this area, as far as what power to look for in a servo motor, what processing unit would work. I have an X axis (headstock) and a Y axis (carriage) I also could add a third probably to the in-feed to the material Z axis (cutting tool or router.
I can have my machinist make the necessary parts- that is not the problem, what is , is where to go? I originally was going to do this mechanically linked , and may still have to do that , but this idea has sparked my interest.
If any of you have any knowledge about this I would really appreciate any feedback you can give me, at least I will have a place to start.
thank you,:confused:
Brian

[Brian Weick]

I received this From a fellow Woodworker with his approval I am posting this to get additional information from others to add to this or any other ideas.

Hi Brian...

This problem is neither simple nor absolute. You can do this one of two ways... pure mechanical or a combination of mechanical and electrical solutions.

The best way to understand this is to look at an older milling machine with helical capability. On these, there were change gear boxes attached to the end of the main table that engaged the main X axis lead screw. If you know the pitch and lead of the helical movement, you select the X feed rate and the appropriate change gears. Then, a PTO shaft interfaces with your dividing head and allows the machine to cut a helical pattern. This would be something like a drill bit or helical gear in the metal world or in your case, a barley twist, etc. This system was completely mechanical.

The next step up is to add some electrical parts. E has lots of these. Namely Allan Bradley encoders and stop switches, etc. First of all, your going to need to add a shaft encoder to your head stock lathe quill shaft. The encoders can go very slow or very fast... at least faster than your lathe is able to turn. These are electrical gizmo's that will output a digital word representing the absolute position of the lathe head stock shaft at any given point in time. For example, if the word output is only 8 bits, then you will have 255 positions representing a circle which has 360 degrees. To get 1 degree resolution, you need more bits. So the next step up may be two words or 16 bits. This will give you about 64,000 positions. Divide 360 degrees by 64000 and your dealing with incredible accuracy. These encoders are heavy duty and designed to take cutting lubricants and other abuse.

Then you need a way of knowing where your router is at any given time along the bed. You also need a way of moving the carriage. One easy way to do this is to add a stepper motor to the carriage. A DC motor will also work but the stepper can give more control later on. This can be added on top of the existing shaft with the hand crank then sticking out the top of this solution or you can add a second drive gear to the rack and mount the motor off to the right side of the carriage skirt. If you use the existing drive gear and shaft, you may need to add some form of in line clutch to the hand operated crank so you can still use the lathe manually or electrically.

For control your going to need some computer stuff. First of all, you need software. Since this has never been done before more or less and since your watching your pocket book, you need to log onto the GNU CAD site for EMC software. EMC is a CNC GNU program that runs under the Linux operating system. Its free. The government developed this and its part of GNU so the source is open and the cost is nothing but your time to download and tinker with it. Your going to need a computer. Buy an obsolete computer for parts and get the best one you can afford. This application will work with a Pentium running at 200 MHZ. Folks are throwing these away! If you can find one at say 1 GHZ, cool.

The mother board, hard drive, power supply etc. needs to be moved to a metal box. A large Hoffman electrical enclosure will work here with some cutting and fitting.

In a nutshell, the computer watches the encoder output of the shaft. If you have a stepper motor up there too, you can disengage the main motor and run the shaft off a powerful stepper motor at something like 5 or 10 RPM, etc. Often steppers also have built in encoders too. Then the software will issue automatic commands to the stepper motor driving the carriage and move it in sync with the headstock. A stepper can position a shaft to any angle. If a series of sequential movement commands are issued, the stepper can actually rotate like a normal motor. Speed up the issuance of these commands and the stepper runs faster. Likewise, slow down the issuance of these commands and the stepper slows down or stops.

The above scribbles and diatribes represent the basics of two ways to do this. Please understand that the Oliver pattern lathe was not designed per say to do this but is actually the best host machine to get this task done. I myself am looking for a box head oliver and have come close twice but gotten screwed by dealers. In your case, an auto feeding carriage was used to simply the making of precise cylinders for pattern shop use. Syncing the carriage to the headstock was never the intent. This was done with a bull gear and belt drive running a long lead screw which was then engaged by the carriage via a half nut. On the newer box heads, this movement was done by using a motor attached to the rack via a rack engage gear. Similar in ways to what I just described.

Here is a photo of a very rare box head that I almost got (attached photo). I was going to trade a maka mortiser for this machine but wound up having to keep the maka to finish a cabinet job that was worth a lot of money in both cash and possible penalties. So I lost out on this one and I am kicking myself for it. But you can see how the carriage drive was done on these newer lathes.

Dev,


Dev really did a great job with what I need ~ If any of you have additional information please feel free to add to this. I am looking for as much information as possible to achieve this -
Thank you:)
Brian

[Dennis Ford]

I have built a small cnc router. I used stepper motors, servo motors are a step up (both in speed and in cost). Check out cnczone.com, they have a lot of information on this stuff. ;)

[Brian Weick]

I have built a small cnc router. I used stepper motors, servo motors are a step up (both in speed and in cost). Check out cnczone.com, they have a lot of information on this stuff. ;)

Thank You,
I will check that site out.
Brian

[Brian Weick]

Nice sight- found the Stepper3 company and they have set me up - quite pricey $3200.00 but it is going to work like a swiss watch. this is what they came up with:

1) Qty 1 - S3CAB1 2 Axis Motion Control Cabinet
2) Qty 2 - S34HT1700 1700 Oz-In Stepper motors @ 250.00 Ea - Sub total
3) Qty 1 - Mach3 CNC Software
4) Qty 1 - BobCAD V21.5.3
( significant factory discount being offered on the BobCAD software )
5) Qty 1 - Spridle Encoder


The most expensive parts are the s3cab1 Axis motion control cabinet and the Bob-cad v21.5.3 software that alone is $2400.00 , the only thing I am questioning at the moment is the Bob-cad software? it is a 3 Axis software program - I will have a 2 Axis system? any thoughts?
Brian

[Paul Engle]

You could buy a traverse ( cross feed ) tool rest and convert for the 3rd axis add another servo to run it in and out , add sensor to index it to the soft ware and the up down / side to side .... and bob's your uncle.....cheap cross feed is less the 200$ , see one at HF, good drilling table will have one usually about 5-7 inches l/r and 4-6 inches in/out.

[Brian Weick]

Are you saying to cannibalize some equipment- not sure where you are going with this?
Brian