Vacuum Failure on an otherwise lovely project

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Vacuum Failure on an otherwise lovely project

Postby Rcnewcomb » Tue Oct 20, 2009 3:08 am

It was going along so nicely. The first pass was (almost) done with a 1/2" ballnose. It was 90% complete when the vacuum let go due to too many holes in the pine.

If it had worked then it would have been:
Material: Pine 47.5x9.25x0.75
Pass 1: 1/2" ballnose at 10% stepover @ 6ips, 72 minutes
Pass 2: 1/8" ballnose at 8% stepover @ 6ips, 85 minutes - dog & pheasants only

DC01.jpg
It was going so nicely...


When vacuum doesn't suck it really sucks.
VacuumOops1.jpg
Oops!

simpsons-the-doh-4900579.jpg
DOH!
- Randall Newcomb
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Re: Vacuum Failure on an otherwise lovely project

Postby moto633 » Tue Oct 20, 2009 3:11 am

Take it over to that miter saw in the background and trim it off! :D
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Re: Vacuum Failure on an otherwise lovely project

Postby Phil » Tue Oct 20, 2009 1:11 pm

Been there. I keep a few of my bloopers on hand to remind me of things that went wrong.
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Re: Vacuum Failure on an otherwise lovely project

Postby gravirozo » Tue Oct 20, 2009 3:58 pm

hello


randall, i think for a display in your shop, it still pretty good... at least the hours are not wasted time... of course with some fix as others suggested...


thanks
viktor
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Re: Vacuum Failure on an otherwise lovely project

Postby Rcnewcomb » Tue Oct 20, 2009 6:05 pm

I'll hang it in the shop as a reminder to fill in worm/nail holes in wood before putting something on the vacuum table.
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Re: Vacuum Failure on an otherwise lovely project

Postby tmerrill » Tue Oct 20, 2009 8:29 pm

Randall,

I normally don't like pine, but that is some pretty wood!

I didn't realize those holes would be enough for you to loose vacuum.

Tim
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Re: Vacuum Failure on an otherwise lovely project

Postby buck4 » Tue Oct 20, 2009 11:46 pm

Randall,
Do you always cut at 6ips, that seems pretty fast. 30ft/min, wow!! Your spindle most be at 40 thou plus rpm's. Sorry I got to believe, that the vacuum did let go, by cutting too much too fast.
Buck
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Re: Vacuum Failure on an otherwise lovely project

Postby Rcnewcomb » Wed Oct 21, 2009 2:43 am

Do you always cut at 6ips
Yes, that is my standard feed rate, though the Z movement means I rarely get up to that speed. Usually the vacuum has no problem. At 10% stepover I'm only removing 0.05" per pass with the 1/2" ballnose.
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Re: Vacuum Failure on an otherwise lovely project

Postby gravirozo » Wed Oct 21, 2009 3:25 am

hello

most possible, the board cupped up... as i can see there was removed about 60-70 percent of the board thickness...
and the vac could hold down on the beginning because the board was "straight" and by removed material some stress raised in the wood... and the vacum that was enough on the beginning, already was not sufficient... some thicker board able to pull nail out...


thanks
viktor
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Re: Vacuum Failure on an otherwise lovely project

Postby kilrabit » Wed Oct 21, 2009 11:53 am

Randal,

What are you using for the Z feed rate, and are you using the CV mode? I made a few of the mountain sheep mantels 6 feet and 8 feet long, I used the dish to help eliminate the destressing of the wood. I used 2 inch quarter sawn white oak, and left a depth of .750 in the deepest place of the stock, it still moved about 1/8 of an inch in two directions when I unclamped it, and I used 5 sets of linear clamps to hold it down.
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Re: Vacuum Failure on an otherwise lovely project

Postby Rcnewcomb » Wed Oct 21, 2009 4:20 pm

What are you using for the Z feed rate
6 ips as well

and are you using the CV mode?
I'm not running Mach, I'm using the Shopbot control software with default ramp rates. I plan of doing some tweeking but we have had consistently good results with these settings for the past few years.

I used 2 inch quarter sawn white oak, and left a depth of .750 in the deepest place of the stock
That would have worked much better. I love carving quarter sawn white oak, and leaving 0.75 would have improved stability.

I think Viktor is correct that the combination of holes in the board and the cupping caused by removing so much material were the root causes of the vacuum failure.

But now I know for sure....
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Re: Vacuum Failure on an otherwise lovely project

Postby Dropout » Mon Dec 14, 2009 1:35 am

We do a fair amount of work with pine and find that the easiest thing to do is screw it to a piece of melamine before we put it on the vacumm table.
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Re: Vacuum Failure on an otherwise lovely project

Postby Dublinman » Mon Feb 22, 2010 5:20 pm

I couldnt endure listening to a vac for the amount of time a 3D carving would take. I would use screw down clamps or t track.
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Re: Vacuum Failure on an otherwise lovely project

Postby Rcnewcomb » Mon Feb 22, 2010 7:50 pm

Well, we can't hear the vacuum above the noise of the router.

Some day we'll have a spindle....
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Re: Vacuum Failure on an otherwise lovely project

Postby backyard_cnc » Wed Feb 27, 2013 1:00 am

I sometimes reduce the chance of movement by pinning stock to the table with 23gauge pins I shoot in with an air nailer. 23 gauge pins hold well yet are so thin that if you machine threw one it shouldn,t damage the router bit. The stock is easily pryed off the table.

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