# CNC Spoil Board



## Leo G (May 12, 2005)

Found this on WoodWeb and if you guys are not using it I think it is a really good and efficient idea.



http://www.woodweb.com/cgi-bin/forums/cnc.pl?read=651901



> Let's look at the extremes.
> First, picture a very thin spoilboard. It lets a lot of air pass through it quickly. It doesn’t allow a hard vacuum to build under the board so you don't get any pressure holding your parts down. It still works pretty good if the entire surface of your table is covered with melamine, but as soon as you cut through you get a rush of air equalizing the pressure below and soon the vacuum can't keep up no matter how big it is.
> Now picture a very thick and dense spoilboard. No air flows through it, and so no pressure holds the work down. The pump is creating a hard vacuum below the spoilboard, but it is all held in by the very dense and thick spoilboard. A very small pump will evacuate the plenum below the table, but no holding power.
> Real life is a balance between these extremes.
> ...


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## Leo G (May 12, 2005)

Bump, now that Gus is on the board


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## Bergstrom (Mar 14, 2009)

His method has merit but it seems like a lot of screwing around for something that only needs replacing every 4-6 months. I agree about the high air flow on the thin spoil board and because of it I would never run it down much below 1/2" 

For small part machining (such as fluting) I would just screw the part to a larger base and rarely had any issues.

ps Gorilla tape (or any other) works well for edge sealing...keep the poly in the finish room where it belongs


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## Bergstrom (Mar 14, 2009)

You would think with all of your saddle time with CV the typing speed would've picked up...why you gotta make me wait so long. I need to get to bed :laughing:


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## Gus Dering (Oct 14, 2008)

I'm interested in the Tarpon. Have not heard of it and google did little for me.

We find that 3/4 mdf is too thick and loose more small parts than starting with 1/2" and take it right down to 5/16" or so.

We lose small parts when we need to surface the spoils board for more than any other reason. All the little troughs from the previously outlined parts creates a lot of vacuum lose.

I do find a lot of logic in the concept of losing more vacuum through the kerfs as the sb gets thinner. I have not considered that before. And it has not been my experience either. I think the matrix of your phenolic top may have a lot to do with that. Ours has quite the grid to deliver vacuum to the bottom of the sb as much as possible. 

I just have not experimented with anything other than mdf.


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## Gus Dering (Oct 14, 2008)

Bergstrom said:


> You would think with all of your saddle time with CV the typing speed would've picked up...why you gotta make me wait so long. I need to get to bed :laughing:


sorry I was multi tasking. I had to see a man about a horse. And downloaded some material.:whistling


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## Bergstrom (Mar 14, 2009)

How deep are these troughs that you speak of?


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## Gus Dering (Oct 14, 2008)

.005


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## Bergstrom (Mar 14, 2009)

Can you catch your finger nail on them?


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## Gus Dering (Oct 14, 2008)

Yes, but I have false nails


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## TimelessQuality (Sep 23, 2007)

Gus Dering said:


> Yes, but I have false nails


roflmao:laughing::laughing:


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## Gus Dering (Oct 14, 2008)

Who is typing slow now?


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## Bergstrom (Mar 14, 2009)

Try dialing in your cutter a little tighter. I assume you are using a comp bit of some fashion. Try to get it set so the only way you can tell a pass has been made is that the mdf looks a little burnished. The little troughs are causing you to lose a lot of vacuum. How often are you resurfacing the spoilboard? 

My wife is pissed at me....I gotta go TO BE CONTINUED :shutup:


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## Bergstrom (Mar 14, 2009)

Gus Dering said:


> Who is typing slow now?


Who's multi-tasking now :thumbup:


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## Gus Dering (Oct 14, 2008)

Bergstrom said:


> Try dialing in your cutter a little tighter. I assume you are using a comp bit of some fashion. Try to get it set so the only way you can tell a pass has been made is that the mdf looks a little burnished. The little troughs are causing you to lose a lot of vacuum. How often are you resurfacing the spoilboard?
> 
> *My wife is pissed at me....I gotta go* TO BE CONTINUED :shutup:


Now there is something I understand.:laughing:

I'll give that a try tomorrow.


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## Bergstrom (Mar 14, 2009)

Gus Dering said:


> Now there is something I understand.:laughing:
> 
> I'll give that a try tomorrow.


Pissing off your wife or tuning up your cutter? One will make life better for you and the other will not....... trust me I know :whistling


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## Leo G (May 12, 2005)

Sounds like both can make life easier>


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