GearHeads Corner

After watching the tangential shaving you-tube video I think it's time to go past 2D gear cutting and into a 4th axis setup.  There are two basic types,  6x1 belt driven and 100x1 harmonic drive reduction.

I'm leaning toward the 6x1 drive but I worry it doesn't have enough resolution.

Suggestions anyone?  I just want to cut 75mm  or so simple involute gears.

Hi:

The 6:1 is probably fine, take a 2000 step motor and the resolution should easily be
enough for any gears..

Art

That sounds good to me, at least good enough to order one which I did.  Will report on my progress in case anyone else is thinking along the same lines.

Please do. I was looking at those last week wondering if I migth be better off with one. They do seem
to be well built and very well hobby sized...

Art

I got one in my 3040 mill package , its acceptable but the belt tensioner arrangement was badly made ,it needed modifying to make  re-tensioning even possible.  A 4 jaw chuck would be nice too but they are drilled for 3 jaw only , I'm not game to re-drill it yet

I use my Sherline CNC rotary tables and a Sherline stepper spindles for gear cutting/generating. The tables are 72:1 to the motor, which is a little slow, and the stepper spindles are 2:1 to the motor, which is a little low in resolution.

I've been wanting something in between, but I'll want something that I can use my tooling on. My tables and stepper heads can hold all my chucks, arbors, mandrels, face plates, etc.

I can boost the stepper spindles to 4:1 with another set of cogs, and if I get myself a new computer with more "steps", I get more speed out of the tables.

Between the two, I get what I need for now.

I've been experimenting with three nested rotary axes.

I see a couple on ebay that are 2 nested axis a 4th nd a 5th..that looks kinda interesting..
Bet I could cut a bevel then... :)
  The toolpaths would be a bitch to calculate, but itd be fun. Too bad there isnt enough of them
out there to make it feasable to do..

Art

I hand code bevel gear g-code in my sleep. Do you want it for a tapered mill or a straight mill?

Keep that thought, we can have an in depth discussion on Bevel Gcode when I hit the bevel recoding, Ive never been happy with my approach.. :)

Art

@JustinO, those must be interesting dreams.

Can you post some eBay links?  My eBay search-fu just isn't finding them.

Kirk

I thought these were cool..

http://www.ebay.com/itm/CNC-Rotary-Tabl ... 4d0b1662c8

Art

Kirk:
Search for this on Ebay:            4th axis engraving machine

Thanks!  I must have been having a bad search day.  The two axis version looks pretty interesting.

Kirk

Don't buy one of those Chinese 4/5th axis combos. The 5th axis has practically no torque even with a 380 oz in. 3.5A  direct drive motor.
They say they are for engraving and that is true. But engraving takes a lot less torque than for machining. They are worthless for machining.
I have been working on my Chinese 4/5 axis to up the torque for the 5th axis. I have been trying to make a hypocycloid gear head attachment but business has slowed the progress.
Here is a video of engraving the letters CNC on a dome using my 5 axis G540+1 control box.
http://www.youtube.com/watch?v=rF67CGlEVK4
If you skip past the 2 minute description of the control unit you can see the 4/5th axis as well as the XZ movements.
Pretty cool.
What is not showing is the machining of the dome/hemisphere. I actually had tohelp with my hand the C axis to rotate to prevent lost steps. So it wouldn't even cut soft pine.
The B axis could easily be increase in cutting force by adding a second ratio and the other thing to do is to mount the stepper motor on the outside for more travel in the B- direction.

My friend wrote the G code using and expensive Cad/Cam program. He had a lot of trouble getting the post processor working right.
We wanted to use Rainea's CNC_Tool_KIt  as a plugin to Gmax but his program was setup to use the spindle 4/5th axis and not the trunion type 4/5th.  He and I posted on their web site a few times to see if they would change the program but no one was interested. As I recall it is open source.

Dan Mauch

ArtF wrote: I see a couple on ebay that are 2 nested axis a 4th nd a 5th..that looks kinda interesting..
Bet I could cut a bevel then... :)
  The toolpaths would be a bitch to calculate, but itd be fun. Too bad there isnt enough of them
out there to make it feasable to do..

Art

SkyMoBot wrote: After watching the tangential shaving you-tube video I think it's time to go past 2D gear cutting and into a 4th axis setup.   There are two basic types,  6x1 belt driven and 100x1 harmonic drive reduction.

Do you have a link for a harmonic driven axis? Don't see any on eBay.

Dan