Tool indexer

[blades]

So, I took a temporary detour while working on the 7 x 10 CNC project and decided to build a tool indexer.
I had to do something with the beautiful little NEMA 17 motor from the dead HF micro lathe fiasco.

This tool indexer will hold (4) 5/16" tools. Indexing will be controlled with a 3rd axis on the G540. The 4 center drill spots in the front of the tool block are not utilized. They were originally put in for another ratchet option, but changed my mind on that design.

Looking at the front of the tool block, it will index in a CW direction. A modified 3/8 ratchet will be mounted on the back of the motor, locking the tool block from rotating back CCW. I'm working on the assumption that the indexing program will rotate CW 52 steps, then CCW 2 steps to lock the rotation against the ratchet. Sounds good in my mind, anyway.

[eartaker]

Blades,

That is awesome I hope it works out. I like the ratchet idea.

[Fastest1]

Blades, nice work but I do have some questions. You intend to index by stepping 1 direction x amount of steps then back up onto the pawl by a few steps in reverse, correct? I think it would be best if the dro was reset to whatever the correct degrees of that tool holder is supposed to be. There will be steps lost when backing up onto the pawl, not hard on the stepper but necessary to insure the tool is the correct place. You state you are going to place the ratcheting mechanism on the back of the stepper, using the shaft of the stepper to secure the position of the tool? What will be responsible for holding, a grub screw or helical coupler. Seems like the stepper should control rotation and the ratchet should remove the load from the stepper and secure tool positioning. I would think the flex due to the leverage of the tool holder, tool and the stepper shaft will allow the tool to move under load. Btw wouldnt it be 92 steps forward and 2 reverse (I believe you were using steps in reference to degrees) for a 4 tool holder?

So, I took a temporary detour while working on the 7 x 10 CNC project and decided to build a tool indexer.
I had to do something with the beautiful little NEMA 17 motor from the dead HF micro lathe fiasco.

This tool indexer will hold (4) 5/16" tools. Indexing will be controlled with a 3rd axis on the G540. The 4 center drill spots in the front of the tool block are not utilized. They were originally put in for another ratchet option, but changed my mind on that design.

Looking at the front of the tool block, it will index in a CW direction. A modified 3/8 ratchet will be mounted on the back of the motor, locking the tool block from rotating back CCW. I'm working on the assumption that the indexing program will rotate CW 52 steps, then CCW 2 steps to lock the rotation against the ratchet. Sounds good in my mind, anyway.

[blades]

Thanks guys. Fastest, it's going to take some trial and error to get the programming right for the rotation. I hear what you're saying about programming the angle, but I don't have an encoder, so the program is ultimately going by step count anyway. The ratchet pawl has 72 teeth or 5 deg. per position. The stepper is 1.8 deg. per step, so in theory, I really shouldn't lose any steps if the ratchet is doing it's job. (BTW, I believe you have degrees confused with steps on your last comment, 50 steps = 90 deg.).

I will either press-fit the ratchet on the shaft, or use a set screw (I'd have to grind a flat on the back shaft). I'm not really a huge fan of press-fitting the ratchet wheen on the motor, so I'll probably try to find a carbide center drill to get through the case.

It's pretty obvious that this isn't going to be practical for heavy cuts, It's simply not built robust enough, although I expect it to perform decent on soft materials. I made it easy to take on/off, so it's no big deal to switch over to the standard tool holder if needed.

[Simon C]

That ratchet idear is genius, would luv to see a vid of this thing in action when its finished.

[awemawson]

Reversing onto your ratchet is a very similar idea to that used on the tool indexer of the Denford Orac lathe. They use a DC motor, drive it forwards counting pulses on a coarse optical encoder, and when just past the tool reverse the motor and leave it stalled running in reverse so it is pressed onto the ratchet. Cutting forces also press in that direction. I upgraded one a few years back, and made some electronics that did the reversing trick, then after 5 seconds halved the motor current as in the original design the motors overheated and fried themselves after a while!

[blades]

I'll definately post a vid of it when I'm done. I'll also update with more pics when I get the ratchet mounted.

[justin bowser]

Looks promising. I eagerly await your results as I have thinking about some sort of tool-change "turret" myself...

[blades]

Yeah, I was looking at a couple of different turret type options, and this one seemed the most do-able considering my limited resources (read, limited mill access).

[Fastest1]

Yes I was thinking in degrees. My Dyna lathe uses a 6 position tool changer and the stepper just stalls for a brief second when backing up just enough to insure contact with the stop. I have a tool changing macro provided by someone else. I havent used it as the lathe is in project status but it is getting closer.

[blades]

That's what I'll need, macros or canned cycles that can index 1, 2, or 3 positions.

[blades]

Ok, I ended up having some difficulty with the original ratchet setup. Concentricity of the ratchet, as well as problems trying to attach the ratchet head to the motor. The ratchet caused a bind in the rotation that I couldn't seem to resolve. Still wanting to utilize a ratchet, I decided to try something different.

I visited sdp-si.com for a shaftloc, as well as a 56 tooth timing belt for my X-axis (my original 55 tooth belt was bit short). I made a bracket that attaches to the round toolpost anchor in the cross slide, and modified a 1/2" Gearwrench. The result is silky-smooth rotation now.