Gears...

[precisionmetal]

Hello all,

New to this forum. I'm in California, and my passion (as well as job part of the time) is wire edm work. Specifically, I enjoy developing and cutting gears via wire edm. Solving gear-related design problems or reverse engineering replacement gears is my forte. Needless to say, I also cut many things via wire edm that have nothing to do with gears at all.

Am always happy to help if I can provide anyone with geometry, CAD models, or anything else pertaining to gears.

A few photos of some fun stuff:

Photos 1 and 2 are of a 34 tooth 140 DP 20° PA gear, with a 9 tooth 80 DP 45° PA internal spline. This gear was cut from solid carbide.

Photo 3 is a 40 DP 20° PA pinion which was cut complete including the D-shaped bore from heat treated 440C.

Photo 4 is 2 Module 20° PA gear that was a replacement for a broken gear in an Italian-made wine bottle corking machine.

Photo 5 is 64 DP 20° PA ring gear cut from heat treated 15-5 stainless for a prototype planetary gear set in a small robotic vehicle.

Pete

 

[Powder keg]

Nice work Pete!!! I've built a couple of gears. My 1935 LeBlond was missing a few teeth. The small one was fun. It had about a 5/8" 6 spline in the middle and the OD on the gear was about 1.125" if I remember right.

Thanks for sharing)

 

[ChooChooMike]

Those are some complex EDM calculations - very nice :bow:

A warm welcome to HMEM Pete !!

Mike

 

[John S]

Pete,
What gear software do you use ?

John S.

 

[precisionmetal]

Thanks for the welcome here!

John,

I use a few different programs when creating a gear profile -- most everything (other than a CAD and a CAM program) is custom written.

 

[vlmarshall]

Great stuff. I keep wishing for a wire EDM at work... no luck yet. ;D

 

[doc1955]

Welcome
I'm pretty new here too. I have enjoyed setting back reading and taking note. Where I work we do very little with gear cutting I have done a few but not that small. I'm very impressed. We have a wire edm here we had a sinker edm but have gotten rid of it.
Do you work with cad now?
If so which cad system do you use? I use to work in the tooling shop but now work as a tool design engineer. I use NX6 and CATIA V5 and also FeatureCam or now known as DelCam.

 

[1hand]

Real nice Pete. Kinda gives me a headache trying to imagine working with stuff that small. Welcome. th_wav

 

[precisionmetal]

Doc,

I've used a number of different CAD apps, but have to say that anything by Ashlar is probably my favorite.

Of course there is always the old saying: "What's the best CAD program in the world? ..... the one you're most familiar with!". ;D


1Hand,

I enjoy making small parts, I admit. I have yet to really push the limits on size -- I think I might be able to go to 200 DP on gears, but may have to have the moon in the right position before I can pull that off! The small gear above (first two photos) was cut using 70 micron wire (.0028"). That's already 30% smaller than my machine is rated for, but with a bit of tweaking I've had some pretty good success with that size wire. I've actually run 50 micron wire in my machine before, but it will take more work to get that to run reliably. The tension and power settings get so low with wire that small that everything has to be "babied" to pull it off.

Here's another small part I made (I think I made about 25 of these). Looks simple... but this customer required every dimension to be ±.0001". I had the material centerless ground to ±.000050", then sliced off the "discs" in the wire machine. Then wire cut a fixture right in place and never moved anything -- inserted the blanks and cut them.

Fun stuff!

But I have to say that some of the model engines I've seen on this site make anything like this look trivial. There are some phenomenally talented people here, and I'm really enjoying going through some of the posts and reading about what's been built.

 

[doc1955]

You are right with the saying I've heard that before. The reason I was asking is I usually attend except for this year the Seimens UG users groop meetings and though maybe by chance you used UG and attended also. Year before last it was in LongBeach CA matter fact 2 years in a row. Last year it was in Nashville and next year again in Nashville.
Anyway I'm totally amazed we run .005 wire dia. I don't believe we run any other dia.
I've never got to run the wire edm machine but have designed several holding fixtures for them.

Simply impressive!

 

[precisionmetal]

Aha,

No... not a UG user.

You'll have to jump in there and play with the wire machine if you get a chance!

 

[Deferr]

WOW! I am amazed by this.

 

[BillC.]

140 dp? Where's my microscope?

Wire edm's are the greatest invention in machine work ever! The only method that rivals it is electron beam wire fed fabrication - but when finished the part still needs to be finish machined.

Good stuff!!

Bill C.

 

[precisionmetal]

More gears...

Cut these for a buddy who is working on a ¼-scale engine project. Crank gear (the small one), 2 cam gears, 2 idler gears and 1 magneto gear. The two 1/16" holes in the cam gears are for driving the cam (only one hole will be used). He wasn't sure yet whether he wanted the drive hole on a tooth, or on a gullet, so I put in one of each. Those gears have 40 teeth, so the drive holes are 175.5° apart. The crank gear has a .250" bore with a 1/16" key. Since it wasn't possible to put a keyway in the gear, I just integrated the key into the part.

Gears are 64DP 20°, with the tooth thickness reduced about .0007" from standard in order to give each "pair" about .0015" total backlash. Material is A-2, heat treated to 55Rc.

 

[Powder keg]

Those sure are nice!

 

[cfellows]

How long does it take to make one of those gears with EDM?

Chuck

 

[precisionmetal]

Chuck,

The larger gears (40 teeth, .625" PD) took about 55 minutes each.

That includes wire cutting all 3 holes (.1250" in the center and the two .0625" holes), and then the gear.

I took 3 passes on the holes because I wanted plus/minus .0001" or less. The outside of the gear was done in one cut.

Pete

 

[vlmarshall]

What's the average amount of overburn with .0028" wire in a finish cut?

 

[precisionmetal]

Vernon,

On a finish cut (i.e. the last of a few trim cuts), the overburn will be near zero... maybe 50 millionths at the most. Or to put it another way, on the final trim pass the "offset" will essentially be the radius of the wire, or maybe 50 millionths over.

On a single pass cut, overburn will generally be around 25%-35% of the diameter of the wire. In other words, if one were using .010" wire and cut straight through a piece of 1" thick plate, the width of the cut would be around .013" or just over.

Is that the question you were asking?

 

[vlmarshall]

Vernon,

On a finish cut (i.e. the last of a few trim cuts), the overburn will be near zero... maybe 50 millionths at the most. Or to put it another way, on the final trim pass the "offset" will essentially be the radius of the wire, or maybe 50 millionths over.

On a single pass cut, overburn will generally be around 25%-35% of the diameter of the wire. In other words, if one were using .010" wire and cut straight through a piece of 1" thick plate, the width of the cut would be around .013" or just over.

Is that the question you were asking?

Yes, that's exactly what I was wondering, thank you!