[jasminder]

dear blades,
i have a simple solution to handle the flex of the shaft.
You don't need a ratchet even. the tool plate of your indexer will do the job.
you just need to mount a lever and spring for the design.
i don't know cad but i have used ms paint for some illustration. hope you get the idea from the pic.
i can bet that the shaft will not flex using this design.
thanks,
jasminder singh

(i am sorry i misunderstood you as blight, but both are bbs. You can see that i am loosing concentration after my marriage)

[blades]

I like it! I actually looked at doing something similar to your idea, but never thought it through all the way. If chatter becomes an issue, that's probably the first modification I will look at doing.
You're absolutely right about any small amount of flex from anywhere can and will affect cutting performance and finish.
I was a machinist for several years, then started doing tool design. I currently work for Toyota of North America doing dimensional confirmation (using portable CMM) of new body weld equipment for new model launches. I don't have a lot of free time to work on the lathe conversion, but I'm not in a big hurry to finish it.

Congratulations on your Marriage! Did you recently get married?

[jasminder]

I like it! I actually looked at doing something similar to your idea, but never thought it through all the way. If chatter becomes an issue, that's probably the first modification I will look at doing.
You're absolutely right about any small amount of flex from anywhere can and will affect cutting performance and finish.
I was a machinist for several years, then started doing tool design. I currently work for Toyota of North America doing dimensional confirmation (using portable CMM) of new body weld equipment for new model launches. I don't have a lot of free time to work on the lathe conversion, but I'm not in a big hurry to finish it.

Congratulations on your Marriage! Did you recently get married?

dear blades,
its really cool that you are working for toyota. I will be surprised if car companies keep their welded parts within microns as you said you use cmm for that measurements. i love cars also and want to build a convertible for myself or maybe convert a common sedan class to a cabriolet. But the sutuations are not the same after my marriage so it is just one of my dreams now.

i got married last year but feeing the changes now. For example, lack of time for personal tasks, lack of concentration and money in my pockets also. lol;
if you work for toyota then what you do of a lathe at your place. just for hobby or part time thing?

regards,
jasminder singh

[blades]

Hey Jasminder,

Sounds like the usual learning curve in a new marriage... things are different, priorities must be relearned or realigned, and money is prioritized differently, but you'll get used to it.

At Toyota, our new jig tolerance is +/- 0.3mm for all locators. This is a starting point, but the tooling gets adjusted as we do a series of quality builds of welded sub assemblies off the jigs. More adjustments are made based on laser scans done on the welded sub assemblies. After final adjustment of the jigs during the quality build process, we remeasure the jigs one last time to record their dimensional condition. That's so the jigs can be reset to their production condition in the event of a weld robot crash in the jig (it happens!).

My lathe is just a hobby, and I have very limited access to the machines at Toyota. I also like working on my cars & trucks. I'm picking up a new Tacoma 4x4 pickup next week, and I've already made and bought some custom parts for it.

What kind of lathe do you have, and what do you do with it? Would love to see pics of your lathe and tool indexer!

Regards,

Bill

[jasminder]

Hey Jasminder,

Sounds like the usual learning curve in a new marriage... things are different, priorities must be relearned or realigned, and money is prioritized differently, but you'll get used to it.

At Toyota, our new jig tolerance is +/- 0.3mm for all locators. This is a starting point, but the tooling gets adjusted as we do a series of quality builds of welded sub assemblies off the jigs. More adjustments are made based on laser scans done on the welded sub assemblies. After final adjustment of the jigs during the quality build process, we remeasure the jigs one last time to record their dimensional condition. That's so the jigs can be reset to their production condition in the event of a weld robot crash in the jig (it happens!).

My lathe is just a hobby, and I have very limited access to the machines at Toyota. I also like working on my cars & trucks. I'm picking up a new Tacoma 4x4 pickup next week, and I've already made and bought some custom parts for it.

What kind of lathe do you have, and what do you do with it? Would love to see pics of your lathe and tool indexer!

Regards,

Bill

dear bill,
nice to hear that. i have a scrap buiilt cnc lathe . i added lm guides, ball screws etc to it. Steppers are powerful enough for it.
But i was having tool chatter while using a parting tool. now i am going to replace the steel plate of my X with a casted one with double thickness. Hope it works better than before. today i noiticed that i am loosing my x offset while threading using mach. i don't know when it will start working in full swing. I resolve an issue and the second appears. Seems that i have not paid enough for it yet.

Regards,
jasminder singh

[blades]

dear bill,
nice to hear that. i have a scrap buiilt cnc lathe . i added lm guides, ball screws etc to it. Steppers are powerful enough for it.
But i was having tool chatter while using a parting tool. now i am going to replace the steel plate of my X with a casted one with double thickness. Hope it works better than before. today i noiticed that i am loosing my x offset while threading using mach. i don't know when it will start working in full swing. I resolve an issue and the second appears. Seems that i have not paid enough for it yet.

Regards,
jasminder singh

Hey, this sounds famillar. I think I remember chatting with you some time ago about this, I remember you talking about your build with the LM guides. Sounds like you've gotten farther with that than I have with mine.
LOL, not paid enough for it yet. I understand that my friend!

[dang]

Great looking conversion. Someday i hope to CNC my Atlas lathe, and original conversions like this are encouraging. The ratchet backstop is fantastic, and although appearing quite utilitarian, that eyelet ballscrew holder may benefit from an upgrade. All good aside though.

[jasminder]

Hey, this sounds famillar. I think I remember chatting with you some time ago about this, I remember you talking about your build with the LM guides. Sounds like you've gotten farther with that than I have with mine.
LOL, not paid enough for it yet. I understand that my friend!

dear bill,
you have good memory. Yes, we have chat before about the tool chatter of my lathe (i was using linear bushings that time that were lately replaced with lm guides)
Here is my lathe running on youtube:
don't mind the indexing speed of the turret. That was kept slow for trouble shooting. Now the turret can index any tool in 3 seconds.
[nomedia="http://www.youtube.com/watch?v=cy0CxUtm840"]YouTube - C:\Documents and Settings\Administrator\Desktop\100_6190_flv.flv[/nomedia]

Now i am planning to replace the air cylinder of the turret with a solenoid.
i have to run an air compressor with the machine having 3hp motor on it. and the compressor gets very hot after couple of hours of run. So using a powerful solenoid will save power and space.
any help on building up a solenoid having 2 inch stroke and ~20kg holding power???
I am planning to build a mill with 12x12 machining area also. But that is future.
jasminder singh.

[doorknob]

Now i am planning to replace the air cylinder of the turret with a solenoid.
i have to run an air compressor with the machine having 3hp motor on it. and the compressor gets very hot after couple of hours of run. So using a powerful solenoid will save power and space.
any help on building up a solenoid having 2 inch stroke and ~20kg holding power???

Just a thought, as I have not actually done such a thing, but how about using a rotary solenoid driving a cam (or a set of cams on a common shaft) to get the desired stroke?

[jasminder]

Just a thought, as I have not actually done such a thing, but how about using a rotary solenoid driving a cam (or a set of cams on a common shaft) to get the desired stroke?

dear doorknob,
Rotary solenoid is no different than a stepper motor i guess. Then how about using a small dc or ac motor with worm gear to push the turret. Things will get complicated i think. I have already tried building a small solenoid using a pen cap and some wire arround it. it could pull a 3 inch nail into it and i could feel the attraction force on my hand. I am planning to build a bigger one using the same idea but this time using AC power 220V.
I have no clue about electromagnets so i am a little afraid.
maybe i should talk to my friend who makes commercial electromagnetic cluches for printing machines here in India.

thanks,
jasminder singh

[doorknob]

A possible advantage of a rotary solenoid over the use of yet another stepper motor or other motorized technique is that it can be actuated or disengaged with a simple on/off switch instead of requiring a more complicated motion control setup.

[jasminder]

A possible advantage of a rotary solenoid over the use of yet another stepper motor or other motorized technique is that it can be actuated or disengaged with a simple on/off switch instead of requiring a more complicated motion control setup.

dear doorknob,
seems to be a good idea. Any additional knowledge or links to a diy rotary solenoid (powerful enough) will be appreciated.
regards,
jasminder singh

[doorknob]

This is probably as good a place as any to get an overview:

Rotary Solenoids

They apparently can be had with fairly large torque values (but over a limited number of degrees of rotation).

I have seen them offered for sale through several surplus dealers, but I don't have any specific sources to recommend (and I'm not sure what might be available in your corner of the globe).

You can usually find an assortment of them on eBay, for example. I never really had any application in mind for them, so I haven't paid much attention when I have seen them, but maybe this will turn out to be a good one to use them for.

[NEATman]

How about a windshield wiper motor from a car?
They are high torque due to the worm gear drive, and they usually have a electrical switch that will return them to the same location when the power is turned off. Think of how the wipers always finish a stroke when you turn them off. This is due to a copper plate mounted to the plastic worm wheel with a spring loaded contact. This copper plate has a section cut out to interrupt the circuit and stop the motor at the same rotation each time at the "Insulated Segment" show in the attached pic. If you modify the copper plate to have four "off" points, which should be as easy as cutting slots in the copper plate, then you could simply pulse an "on" circuit momentarily to run the motor until the copper plate would then power the motor to the next station, where it would shut off on it's own. If you then add the ratchet idea to the mix, it would work even better.

If you wire in a DPDT relay, such that there is low current always on driving the motor backwards into the ratchet tooth, then when you want to change tools, you energize the relay the opposite way momentarily. The motor would then turn to the next position, and stop on its own, then the relay would de-energize back to its normally closed state, and the motor would reverse to the next tooth on the ratchet.

As posted earlier, I think this is very similar to how it is done on an Emco lathe, just with inexpensive readily available parts. Heck, you could even get a relay panel from a car and use that to control the motor...

Keith

[blades]

Jasminder, I really like your rotary changer! Nice and heavy duty. I was wondering why it's necessary to run the air compressor constantly, since (presumably) the only time the cylinder requires air is when pushing the tool changer out? Seems like even a small air holding tank should provide the required air for many tool change cycles.

This discussion has become very interesting! With the ideas turning to solenoids, another low-voltage requirement would be either an automotive A/C compressor solenoid or an electric PTO clutch from a riding lawn mower. Either of these applications require a LOT of holding force. I picked up a nearly-new clutch similar to this one for cheap (like $25 off ebay) for a project several years ago.
Lawn mower PTO clutch shown



I need to figure out the canned cycle I will need to index the stepper motor because in using manual jog, when traveling CCW back against the ratchet, the motor basically "bounces" off the ratchet stop with power applied. I need to find out if it will lock in against the ratchet more stable, without the bouncing.

dang: good catch on the eyelet screw holder (belongs in the hall-of-shame on my conversion )
It's not actually a ball screw, it's a 3/8-10 ACME screw. Because of the relatively short "working" section of the screw, the only purpose of the eyelet & nylon spacer is to control screw "whip" during high-speed moves or jogs. I have considered cutting a bit over 3" off the length of the screw, so that the ACME nut would basically drive off the end of the screw at the extent of travel closest to the chuck. Sort of a poor-man's overtravel protection method. With the screw that much shorter, it would eliminate the need for the eyelet.

[fragger6662000]

has anyone thought of using a rotary table?

on a 7" lathe it might be a bit tight.

£100 for the table £40 for the stepper and only limited to the number of tools is the fixture you don't need have any lockers as it is a worm drive and should be stiff enough to take the strain.

i thought of using this one i converted to use on my mill.

in a spin

[blades]

I think a small rotary table (assuming it would actually fit) would be a really excellent idea, as it easily lends itself to that sort of application. Another plus about using that would be the ability to easily tweak in the height location of the toolbit (assuming it were mounted vertically). Even a small stepper should have sufficient holding torque to hold the worm gear from back-driving when under cutting pressure.

[hoss2006]

I think a small rotary table (assuming it would actually fit) would be a really excellent idea, as it easily lends itself to that sort of application. Another plus about using that would be the ability to easily tweak in the height location of the toolbit (assuming it were mounted vertically). Even a small stepper should have sufficient holding torque to hold the worm gear from back-driving when under cutting pressure.

Heres one.
[nomedia="http://www.youtube.com/watch?v=0MrSH8LMKGM"]YouTube - Homebuilt Lathe Automatic Tool Changer[/nomedia]
Hoss

[Simon C]

Theres some realy intresting ideas being thrown around in this thread.

Blades, could you tell me what the O.D and width is of those PTO solenoids? i realy like that idea.


Theres a realy nice home built toolchanger here http://www.issintl-inc.com/latheturret/ but im not sure how well it would work if it was directly scaled down smallenough to fit on our mini lathes.


regards
Simon

[blades]

Simon,

They vary, but in general they are approx 4" dia. x about 1" wide. The only down-side I can think of regarding the PTO clutch is that it's magnetic, and of course you know what that means in terms of chips, that's not a battle I would want to fight.
I'm not real fond of the idea of a a pneumatic engage-disengage mechanism on a tool turret, because you're introducing another type of power requirement that has no other application on the lathe. I'm sure it works fine, that's just me.

BTW Simon, did you attend the Royal Wedding? Looks like it was pretty amazing.