Why Build Excellent CAD Into Your Awesome CAM Product?

d for sure it's way above the head of any of Mark Wieber's clique of idiots .

r CNC Software which produces Mastercam. He worked for them for 8 years. As many know, I'm a very strong critic of Mastercam and the major reason why is they continue to refuse to do what their former head of software enginee ring wanted them to do.

ient can be found in this link and other links that branch off of it. This is the type of discussion that cannot be found anywhere else on the Interne t or in pay for play advertising based metalworking magazines like slow edd y works for.

, anywhere else. It's membership reads like a who's who of the CADCAM busin ess.

that pay for play CADCAM magazines are old school and aren't effective. Yo u will never find worthless ad copywriters like slow eddy in my LinkedIn gr oup. The reason for that should be obvious to anyone who is objective and t o those who take the time to understand the subject matter in this discussi on:

A few years ago I wrote a prelude to why you can't have powerful, efficient CAM, without making better use of geometry data. No matter what the cost, CAM doesn't use geometry data to the extent that it should use it:

I like my 2D cad that I use on my CNC-CadCam plasma machine - it imports math done in a spreadsheet. I can then export that and import that into my 3-D cad if wanted.

Martin

jon , you're a prick and every thing you post is bullshit . Your Linkedin group is bullshit too . Why don't you just die and save us all a lot of trouble?

Just tell us what you REALLY think.

Ahh! bet that feels good, got your little fix of degrading others.

Have you ever pondered why that is important to you?

What it does for your psyche to continuously degrade others.

I'm sure very occasionally you have some introspection, and you're shocked when you ask yourself, "Why do I do that".

Mikek

Does CNC make feeding a rack-tooth-shaped cutter across the synchronously rotating blank practical?

-jsw

A good thought, but the short answer is "no."

The problem with an incremental-stroke approach to generating gears is that it requires multiple storkes at very short intervals, as the blank rotates.

A hobber effectively does this by having multiple cutters displaced around a cylinder, and by rotating both the tool and the work to have a sequence of cutters entering the work at close intervals.

A Fellows gear shaper does it with a lot of tool strokes at brief intervals, as the gear blank rotates slowly.

There was a machine built by Gleason in the late '70s, called the G-Track, that used rack-type cutters as you describe. But there were dozens of them chained together. The chain moved continuously as the blank rotated, acting like a shaper with multiple "racks." Or you could think of the tool as something like a push broach, with one cutter quickly following the previous one.

The relationships are mechanically simple, so CNC only gives you one thing: quick-change versatility. You can set up for a different gear very quickly with CNC. But it doesn't simplify the geometry, except to replace one or both gear trains with some kind of servos. That's now most modern gear hobbers work. I haven't seen a gear shaper for 30 years, but I assume they've applied the same technology to them. CNC is a big setup-time saver, but that's about it.

So not worth pursuing.

The rack-tooth-shaped cutter would actually be a dressed surface grinder wheel, finishing one involute tooth space in a hardened form tool.

-jsw

I don't think so. Multi-tooth cutters, like racks of teeth, are advantageous in this context when multiple cutting teeth are engaged at the same time. With a normal-width helical gear, the rack wouldn't be a lot more effective than a single-point cutter.

I can't think of what advantage CNC would bring to it.

There are such things in industry, at least in the form of hobbers. Several machine tool and tooling companies make helical grinding wheels, which look like a gear hob without teeth, for doing that kind of finishing -- even roughing. The finishing wheels are usually a polyurethane-bonded, flexible wheel. You could make them at home.

Making gears, including making involute form tools, on a hobby basis is a great subject for creative thinking. I try not to dismiss ideas, but I've seen a lot of things tried by industry that didn't work out. The G-Track, for example, died because the cost of regrinding the rack-type toola, and disassembling and re-aslsembling the racks in the chain, was excessive.

You're probably aware that milling gears with form tools is mostly a repair/replacement operation. We did some of that in the job shop I was involved with in the mid-70s. It is not the way to go for precision gears or for production gear manufacturing. That's all generating with gear hobbers and gear shapers, or push- or pull broashing. Big internal ring gears, for example, like the ones used in automotive planetary gearsets, are mostly pull-broached. One tool can cost close to $100,000.

Everything I make is a repair or one-off. Yesterday evening I turned a

1/2-20 to 5/8-18 adapter bushing to use a larger hole saw on a smaller arbor that fits my 3/8" angle drill. The last gear I cut with a shop-ground tool bit was a new steering sector for my tractor.

-jsw

Same here.

That's pushing it. My only point there was to make clear that gears are not cut with form cutters, except as a last resort. They're almost always a compromise, although they'll usually work if you don't need extremely smooth conjugate action.

Right, and threads aren't single-pointed on an antique leather belt driven lathe, except by home hobbyists who haunt rec.crafts.metalworking.

-jsw

There's a difference. The drive method doesn't have any necessary affect on accuracy. And lots of bolts are single-point-turned, including the con-rod bolts for the Cosworth racing engines that we turned at Wasino -- an extreme example of demanding accuracy and quality.

Milled gears never have a perfect profile. Even if you're making the gear which is in the center of the cutter's range, the involute form is compromised from *that* to allow non-interference without undercutting, on gears cut near the largest end, and with a pressure angle that avoids loading the gear tips at the smallest end.

In other words, it's *never* geometrically correct.

Watch it bud , yer hittin' pretty close to home there ... though come to think of it that doesn't apply to me . My antique lathe is using an automotive serp belt for drive .

I like the leather belt drive. It disengages instantly when I thread right up to a shoulder, while the motor is still coasting down, and lets a bit dig in without much trouble, which I was glad of when reworking some solid copper truck starter terminals into current shunt bolts.

-jsw

Oh I'm using the original drive mechanism , just the belt has been replaced . I was using clipped belts from Logan , but kept pulling the clips out . At

40 bucks a pop for a new belt , I had my son the parts guy get me a serp belt of the correct length . I can actually stall the motor now if I try .

I set the belt loose enough that the motor can come up to speed if I forget to disengage the back gear lever after tightening a collet, and I can slip the spindle by tugging on the chuck key. Chucks are never difficult to unscrew.

-jsw

Flip it over, Terry. That'll relieve that little misstep. ;)

I seldom tighten the belt that much , no need to . I got really tired of having to regrind cutters because the belt slipped in a heavy cut and the cutter welded to the work . I've used this belt with both sides against the pulleys , not a whole lot of difference . -- Snag