Method to Save Spoil Board?

[gerryv]

I don't want to hijack Sean's great thread so starting this one. On reading some of the questions and comments on his thread made me wonder.

Has anyone wishing to cut right through the their material without damaging their spoil board tried laying down a layer of thickish, porous paper like that black weed control material or filter paper between the spoil board and the pieces being cut?

[coryatjohn]

I tried using a 1/4" piece of MDF as a removable spoil board but my vacuum system just wouldn't hold though it.

It just seems that the spoil board as it is, works good enough for me.

[jTr]

Someone suggested a few months ago to use 1/8 or 1/4" MDF, as he was getting it for as little as $5 a sheet and used it as you are describing.
Sounded great, so I tried the 1/4", even though it runs closer to $20 a sheet in my market. Skinned both sides by surfacing, but still could not get a good bleed of air.
Unless you have access to Ultralight MDF in those thicknesses, I don't think you'll have much luck. At one point in time, some of the MDF in some markets would bleed vacuum quite well, but recent manufacturing changes have converted regular MDF into more of a vacuum plug. :rolleyes:

I have occasionally seen 1/8" Particle board come through as cover sheets in plywood shipments. May be worth a try if you can get some - since it is pressed so coarse, it may work.


jeff

[gerryv]

I probably didn't express that very well, I'm not suggesting replacing the spoil board :-)

The other thread speaks of not damaging the spoil board so my thought is whether a highly porous layer of filter paper or woven weed control type material for example, perhaps only 1/32" to 1/16" thick could be temporarily laid between the spoil board and the material being cut. It would then act as a one-time use "spoiled" component if, as discussed in the other thread, the goal is to keep the actual spoil board surface completely smooth for ongoing drag knife use. Basically dual-purpose.

In this way, it would allow the cutting bit to cut fully through the workpiece yet not damage the spoil board. It would not be glued down.

[jerry_stanek]

I would be afraid of the cloth getting snagged and pulling up the piece you are cutting

[billp]

You would also lose a lot of your holding power if you were using vacuum and had a porous material between the material to be cut and the spoil board.....

[gerryv]

That's a good point Jerry, I can see how strong woven fibres could do this, less likely for a paper type material as it would have less strength than the material being cut?

Also a good point Bill. I'd wondered about that. But then I thought, where would it leak - only along the edges and if they are only maybe 1/32" deep, how much loss could there be compared to say, a typical spoilboard with leaky spots as well. Maybe a tiny bead of "goop" around the edge would take care of that?

Sure wish I had a vac table on my Buddy so I could try it - nothing ventured nothing gained...

[waynelocke]

I use a 3/4" mdf spoil board, skimmed on both sides and can hold 3/4" plwood with one Fein. It seems that 1/8" or 1/4" mdf would make a better, more porous spoil board but apparently not. I don't remember why but Brady or someone posted an explanation some time back and recommended replacing the spoil board when it is 3/8" thick. Works for me.

Wayne

[gerryv]

Hi Wayne, thanks for the feedback but it's not actually about a spoil board - it's really about having a very thin, disposable gasket between the spoil board and the material being cut in order to save the face of the vac. table spoil board from grooving.

[jerry_stanek]

They call it a spoil board for a reason and that is to save your plenum from being cut up. I don't care much what my spoil board looks like as long as it is flat

[Bob Eustace]

Gerald there is a guy south of you that used to regularly post that swears by 1/8 dense cardboard. Have been meaning to try this for yonks. Of course Andrew uses the disposable MDF method so that obviously works. Since I have Andrews roller idea on the Buddy I can get away with the onion skin without breaking through method then using the 3/16 Amana trim cutter. Very, very, pleased with this method.

[gerryv]

Thanks Bob, it's hard to even suggest a potentially helpful change to a paradigm sometimes eh :-)

[davidp]

Hi All,

I am with Wayne, 18mm MDF skinned both sides and throw it away when it gets to around 6 mm thick. I always cut into the spoilboard 0.5 mm and depending upon the work on the table I level the spoilboard by removing .25 mm when needed. Last week we used up three spoilboards. It is a cost of the job, just like bits, electricity, and depreciation and certainly cheaper than a part moving while being cut and having to be recut.

Work out the economics. One sheet of 18 mm MDF $24.75, 60 to 100 sheets cut per spoilboard equals at worst $0.41 cents per sheet cut. To recut one part : re-toolpath, say 5 minutes @ $1.75 per minute, re cut the part 1 minute @ $2.10, you are already up to almost $11, and you haven't included extra material and all the other associated time and costs of loading and unloading the table etc.

I understand that for most, running the ShopBot is not about making money and your time is your time, but it is still false economy. You would be better spent using the extra time with your family.

My 2 cents worth.

David

[cowboy1296]

I cant even remember what this material is called but you use it to make your custom gaskets. It comes in sheets of about 5"x5" and I bought it at Ace Hardware. Its about .05 thick. I cut it up in smaller pieces and position them under the work piece. Of course this wont work for a vacuum but it works fine for a clamping system I use a 15 dollar caliper to measure the thickness of my work piece so on occasion I still cut into the sacrifice board but only a little.

[Jerome]

I tried the 1/8 inch mdf over my trupan spoilboard and find it works very well. I cut mine into 2' x 4' pieces. That allows me to replace only the sections that need replacing and I can sand both sides on a wide belt sander before using it. I am using 2 Fein vacs so I have plenty of vacumn.

Jerome

[dlcw]

I use 1/8" MDF surfaced both sides as a sacrificial board when cutting large numbers of sheets of material. This has a couple advantages:

1. NO loss of vacuum since the sacrificial board is so thin
2. I can cut about 4 to 6 sheets per side of the 1/8" MDF so it goes a long way
3. When the main material has been cut, I built an "outfeed" table for my bot that I simply push the sacrificial board and the main material on to for parts processing. I then load up another 1/8" sheet and the main material and it's being cut while I'm separating that previous sheet.

Adds an additional 2 to 3 sheets an hour using this method. Plus I don't have to resurface my spoilboard. I make enough 1/8" sacrificial boards up for the job using the 4 to 6 sheets per side rule and things hum along very nicely. Of course, the 1/8" MDF and time to surface it are included in the price of the overall project.

[gerryv]

Really appreciate everyones input on this. I'd not seen discussions about "thin" often replaced, sacrificial boards before but I'm not surprised that the insight is coming from some serious pro's. Thanks much, I suspect others will benefit from this knowledge.