Spoilboard support surface?

[kvaughn]

I've got a BT48 PRSAlpha Buddy with an 8' powerstick. I haven't found a spoilboard support surface that I'm pleased with so far. I've tried 3/4" MDF, 1" MDF with some material removed for weight considerations, and I've also tried laminating together two layers of 1/2" ply. In all cases, I've had issues with my board bowing. Resurfacing doesn't help as much as I'd like, as the board bows up off of the support wheels below it, and flexes as the cutter presses into it.

Honeycomb aluminum seems like it would work really well, but I've never worked with the stuff. How difficult would it be to mount it to the powerstick? Has anyone tried using that material?

[dana_swift]

Hello Kate-

I have quit using MDF for spoilboards. Plywood will work, but you have to get good plywood. Its hard to find sometimes. The cheap imported stuff wrinkles like a potato chip.

One option is use something other than wood, HDPE plastic, 1/4" aluminum plate, etc. Those get heavy if you have to put the table on and off by yourself. An advantage is they are not subject to moisture.

HDPE is really easy to machine with the bot, and Aluminum works nice too. But its pricy!

I have looked at optical breadboards for base boards on my powersticks, but not spent the money (yet). They are drilled and tapped on a 1x1 grid at 1/4x20 which is just what I want. Clearly a product of someone elses CNC machine!

My old BT-32 has the 1/2" aluminum table base which is a nice solid foundation for the upper layers.

Hope that helps-

D

[gene]

What is your humidity levels ? do you think that may be causing the mdf to bow?

[CNYDWW]

Hi Kate,

Here's a post i made about a bed support for the buddy. It's just in the idea stages but might help you out and give u some ideas.

Regards
Randy

http://talkshopbot.com/forum/showthread.php?t=12889

[Acmeaviator]

I'm interested to hear about the solutions you try - my bot is in an un-airconditioned shop right now and I'm worried the moisture will soon push everything out of whack. I think HDPE will be great for my short stick but I'm worried about the weight on my larger table.

[Antti]

I am using 8 ft power stick and had the same issue with my support table. I tried plywood, MDF etc. and was not quite satisfied. Then I tried a laminated structure where upper and lower outer surfaces are 1/8" coated glasfiber and inside there is 1" foam (weight issue) on areas where I don't need "strength" or have to attach anything. Edges and areas where I do have to attach screw etc. or areas that need to resest pressure (power stick assembly bolts etc.) there is 1" plywood between the fiberglas surfaces.
This sheet has been streight enough and stable surface for spoilboard support. These kind of sheets are used to build truck cargo cabinets.


Regards,
Antti

[ArtFun]

I have a Buddy also and have been considering a power stick. I'm also wondering how to set up the spoil board.

One option I am considering is end grain balsa wood. It is used in marine applications. Costs about $5 per square foot. Thinking about fiberglass coat and plywood similiar to the other post. They say the end grain balsa wood is 3 times stronger than PVC foam.

Would like to know if anyone else has tried this option.

[Charlie Iliff]

I installed a 4 x 8 table on a 10 foot power stick with the ShopBot outfeed supports. I used 5/8 MDO with a 3/8 MDF spoilboard epoxy glued to it. The results have not been satisfactory. With changing temperature and humidity, I have had bows and corners raised or drooped.
In response to an inquiry, ShopBot support indicated a target top weight for my standard Buddy should be about 250 lb. I'm considering a 5 x 10 1/4 ply eggcrate with 4 x 8 3/4 MDF spoilboard which can be done within the weight, with about 2.75 total thickness. Has anyone tried an eggcrate or box to try to get it to stay flat?

[Ajcoholic]

WHen I received Buddy (48 Alpha with the 6' power stick) I made a spoil board from 1" MDF. AFter a few days, after it was surfaced, it started to curl upwards.

About a month ago, I made a new table. Base is 3/4" MDF with another layer of 3/4 MDF glued to it.

I also made up a set of rollers, and mounted them to each side to press down on the MDF to keep it tight down on the three table steel rollers.

SO far, it has worked perfectly. No sign of curling, and the table has remained flat.

AJC

[Charlie Iliff]

WHen I received Buddy (48 Alpha with the 6' power stick) I made a spoil board from 1" MDF. AFter a few days, after it was surfaced, it started to curl upwards.

About a month ago, I made a new table. Base is 3/4" MDF with another layer of 3/4 MDF glued to it.

I also made up a set of rollers, and mounted them to each side to press down on the MDF to keep it tight down on the three table steel rollers.

SO far, it has worked perfectly. No sign of curling, and the table has remained flat.

AJC

Thanks Andrew: I saw the photos of your setup. As I noted above, I have had both upward curl and downward, mostly at the corners, which don't get to the rollers except at full X travel. It is variable from day to day. My shop is essentially open to the outside, so sees wide swings in temperature and humidity. It appears that the MDF reacts to temperature, particularly, quite differently than the MDO underneath.
My original equipment table was MDF, which also had some corner droop, but I was only cutting a 2 x 4 area, so it wasn't a problem.
If I keep acquiring projects that need the big table and outfeeds, I'll have to do a new one, and am leaning toward either eggcrate or two pieces of MDO sandwiching some foam.

Charlie

[Ajcoholic]

There is one other product that I might try some day... I use this in my cabinets for thick tops, or floating shelves, or other uses where you want a stiff but reasonably light material.

It is two layers of 1/4" MDF separated by a honeycomb paper. Similar to what is found inside of a door.

The material comes in various thicknesses. I have some 1 1/2 and 2" in my shop.

This is the product..

http://www.richelieu.com/en/standard-panels-1047162-c

Would be neat to try it, but I dont have reason to right now, and it isnt cheap at about $100/ 4x8 sheet

AJC

[Michaelodunk]

Look into making a torsion box. They are very strong and light.
A cheap hollow core door is a torsion box thin ply with a corrugated cardboard interior.