Would you sell parts that looked like this?

[Joe788]

Here's a topic from a different message board, where a guy paid a huge chunk of change for an intake manifold machined from SOLID. I don't know how many of these things they sell, but I know I would be embarrassed to even let my employees see a part that looks like this, let alone ship it out to the public. I guess there's a reason why polishing is so popular!

 

http://www.lateral-g.net/forums/showthread.php4?t=20460

[Guest CNC Apps Guy 1]

 

I look at stuff that way too Colin, I guess I'm not as sick as I thought.

 

Back to the subject at hand, their programmer needs to learn how to control his toolpaths a bit better. I see some residual cusps leftover - so not cool, but yeah, program that bad boy RIGHT and that a cool looking part right out of the machine. Those chatter marks on a prominent area are hideous to say the least.

 

JM2C

[Joe788]

quote:

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What concerns me more is not the lack of finishing on the builders part, but the horrible quality of the toolpaths he got.

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That's exactly what I was talking about. Do you see the random, horrible gouges and chatter spread about the part? There are some really, really bad toolpaths applied there.

[Guest CNC Apps Guy 1]

Wonder what CAM System he was using?

 

I can see Mastercam making some of those moves if you don't know how to control it.

[Joe788]

He'd mentioned in the past when it was first introduced, that there was over 100 hours of machining involved. Would be a fun part to put on a 25,000rpm 40hp Variaxis 630, or a 20,000rpm MAM72-63V.

 

There's a tremendous amount of programming in the complete assembly. The polished version is very, very impressive. I suppose if you have good, low cost polishing capabilities, there's no need to put too much attention to detail into the toolpaths.

 

[Joe788]

[Guest CNC Apps Guy 1]

quote:

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I suppose if you have good, low cost polishing capabilities, there's no need to put too much attention to detail into the toolpaths.

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That's heresy!

 

100 hours in the assembly, I can believe that doing it on a VMC. Michael Whitten programming a MAM-72 could get that down to less than 25 hours/assembly... well maybe 50 depending on tolerances but it woudl certainly look a helluva lot better I'd venture to say.

[Guest CNC Apps Guy 1]

Is Manuel Labor really cheaper than having the lights off, nobody around, and the machine making chips?

 

Uhhhhhhhhh, I don't think so.

 

I don;t care how good a port polisher is, he still will not match the consistency of CNC. Now, where the polisher's expertise comes into play, are the fine little tweeks to get that air flowing just right that you can't really program for.

 

On the roughness note, I saw some Allan Johnson and BAE heads with the flowline toolpath scallops left in... the only polishing was around the back of the valve guide. I think it's called that anyway.

 

On a sad note, Mikron killed THE ABSOLUTE BEST head machine on the planet... the Bostomatic Rotary A, Tilting B head machine. Perfect machine for the job. I like MAM's but the Bosto was a better setup for that kind of thing to be truthful.

 

JM2C

[Bruce Caulley]

Nowhere near 100 hrs in that on a HS 5 axis. And as for polishing, if there are any areas that need a bit of attention, an impregnated nylon brush would polish the part in the machine as well.

 

As a shop owner myself in the current climate, people=$$$=stress.

 

Bruce

[Chris Rizzo]

Even on the polished one it looks like about a .100 stepover in the intakes. How does that flow? pretty ghetto if you ask me. Then again this guy got what he wanted, but it sure shows what goes on behind the scenes. A blacksmith with a buffing wheel can do wonders I guess.

 

I believe a well machined part is a true work of art as-is. Polishing = lipstick on a pig.

[Joe788]

I agree 100% about the hand finishing deal. It's ALWAYS better to iron out a machining process that minimizes or eliminates hand finishing altogether. (As a testament to that, we don't even own a tumbler.)

 

But you have to look at it from that guy's point of view......If I had CAM software and equipment that spit out parts that ugly, I'd probably need a polishing department too!

[Guest CNC Apps Guy 1]

quote:

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I believe a well machined part is a true work of art as-is.

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I love mill marks - smooth and intentional ones anyway.

 

I love picking up a smooth part that has been machine deburred. No sharp edges, just smooth...

 

The turnkey I'm working on right now... that part os so smooth, I can't even get a picture of it. The camera won't focus. .00008 scallop height. Cycle time is not much of an issue they HAVE to look like jewelry AND the tolerances are pull your hair out tight! Profile Tolerance of .0011 in .060 thick Aluminum.

 

6 parts take about 8 hours to complete. A part that starts out as a billet 2.8 x 2.5 x 1.75

[Chris Rizzo]

come on James, I want to see something cool.

[Müřlıń®]

A couple hand made pads and I could polish that thing up in a couple hrs....

 

Seriously.....it's not as hard or time consuming as you might think...especially with Aluminum.

 

We hand polish high nickle alloy impressions to mirror finish with far worse finishes.

 

Those huge scallops will lay down in a couple seconds on Alu...

[Jack Neelands™]

Did a bunch of Harley parts in Brisbane out of alli and it took maybe 15 min with 120 grit on a pedestal belt sander and a buffer wheel with wax to bring it to a mirror finish...I was totally amazed on how fast we could polish these things.

 

You had to lay into it with the buffer wheel but you spent more time getting rid of the rainbows in it

[Joe788]

James, have you ever seen this head porting demo?

 

 

I saw the demo once at the Mazak factory in Kentucky about 5 years ago. The finish on the parts was pretty impressive. The machine is a bit of an overkill just for porting heads though.

[Guest CNC Apps Guy 1]

That's pretty much the way to do it if you want good heads. The major problem with "B-Axis Lathes" such as the integrex is thermal growth. Not a huge issue on something like this because the tolerances are NOT crazy tight, you've probably got ±.005 or so on position (not True Position) with tighter diameters but those features are easily comped.

 

The issue with thermal growth on these types of machine becomes evident when you're trying to hold ±.001 position (not True Position)or better. They just have trouble with that. It's an inherent problem with the machine design that so far noone has been able to truly overcome. Bostos did not suffer from this as the Head did not travel in X, Y, Z and B, only Z and B. MUCH less heat is generated in that scenario.

 

[ 05-01-2009, 01:39 PM: Message edited by: CNC Apps Guy 1 ]

[Steve Hattori]

I agree with James and all who think those toolpaths suck- that part should be much cleaner than it is right out of the machine. We make prototypes for one of the major motorcycles mfg, and they want zero hand-finishing done- the part has to look good as-machined.. regarding the inside port finishes, the scallopped bumpy finish is what they want because it flows better than a smooth finish. The small bumps help release the surface boundary layer and speed it up a bit. In fact, lately the porting tools are not spherical, they are hemisphere with a sharp break at "equator" line, so the scallops actually have a sharp edge showing in the opposite direction from flow. This helps mitigate reversion flow coming back out of the port after the valve closes...but the outer cosmetic finish on a part like that should be much nicer...

 

FWIW