Aluminum waste board for XXL


(Mike Price) #1

Sorry if this has been spoke about before, I couldn’t find anything on it. Would 3/8 6061 be OK to replace the 3/4 MDF? Would it hold up with a sea of holes every 2.5" and not sag? Iv seen talk about doing it out of aluminum but not the type and thickness.


(William Adams) #2

The stock SO3 table is 1/2" thick and I believe all the others have followed suit.

Unfortunately http://www.enclos.com/assets/docs/Insight01-Chapter09-Light-Gage_Metal_Panel_Deflections.pdf tops out at 1/4"

Bit of discussion here: https://www.eng-tips.com/viewthread.cfm?qid=156988


(Mike Price) #3

So do you think at 1/2” 6061 would be ok?


#4

For a simply supported plate, meaning roughly that the edges are free to move a little such that the support does not put the plate in tension like a drumhead and does not try to force the edge to stay straight and flat:

The deflection (out of plane) is proportional to 1/t^3, so doubling the thickness reduces deflection by a factor of 8 for a given life load. (ie: not counting self loading… the self-load deflection is a constant that the live load is added to)

If the deflection due to loading is 1.00mm for 6.3mm thick material (1/4"), then it will be 0.13mm for a 12.7mm thick plate (all other dimensions and loads being the same).

The self loading:

The weight of the plate will be double when the thickness is doubles. If the deflection at the center of the 6.3mm plate due to its own weight is 1.00mm, then the self loading deflection of the 12.7mm plate will be 0.25mm.

Tripling the thickness (from 6.3mm to 19mm) would reduce live load deflection by a factor of 27, and self load by a factor of 9.

Adding any further support (ribs, support posts, and so on) can improve this a lot more, but, if done wrong, can make things worse. For example, a central rib could cause the plate to be twisted if a load is placed to one side (causing the other side to lift). It turns out that doing this well can be difficult.


(William Adams) #5

Thanks.

That’s been one of my concerns for working up a gridded array of T-track and angle extrusion and spacers — seems simple enough, but every time I start to look into how far an unsupported span will deflect it seems hard to be certain of being better than the MDF in all ways/directions.

I keep pricing out T slot plates on eBay, but that’s a real budget-buster to me.


(Mike Price) #6

My bottom is 3/4. Did they just start using 1/2”? That would give me an extra 1/4 inch. On second thought. Material would hit the metal edge If I needed to overhang


(William Adams) #7

The aluminum threaded table for the Shapeoko 3 ( https://shop.carbide3d.com/collections/tools/products/shapeoko-threaded-table ) is 1/2" (actually 13mm, just measured mine to be sure) thick.


(mikep) #8

Really wish there was a middle ground between MDF and $400-800 t-slot tables.


(William Adams) #9

Agreed.

Even Starboard or HDPE can be pricey at these sizes and thicknesses.

My idea was just to source aluminum T-track which has holes for mounting hardware from front–back, attaching it to angle bracket at the front and back, and at the front, adding aluminum spacers to create room between the angle and track to load hardware — when I priced it out it was looking like less than $200 for an XL.


(Patrick Andersen) #10

Had you thought to look at this? It works for me on my XL.


(William Adams) #11

Unfortunately, this doesn’t quite fit an XXL:

If you were willing to cut off a bit might work for an XL though, but at that point, might as well just make something.


(William Adams) #12

4-pack set of 1" thick HDPE which could be cut to fit in 3 sections:

$114.95 for 4

Or eplastics has 24" x 48" sheets in 0.5"–1" thickness for from $63.38–126.79

Or, buy a custom cut one (22 7/8" x 42" x 0.75") for $167.24 from https://www.cuttingboards.net/3-4-black-poly-cutting-board/


(Dan Nelson) #13

At one point I was considering using ‘tis:

https://us.misumi-ec.com/vona2/detail/110302261820/?CategorySpec=00000042724%3A%3Ab unitType%3A%3A1&Inch=0&curSearch={"field"%3A"%40search"%2C"seriesCode"%3A"110302261820"%2C"innerCode"%3A""%2C"sort"%3A1%2C"specSortFlag"%3A0%2C"allSpecFlag"%3A0%2C"page"%3A1%2C"pageSize"%3A"60"%2C"jp000191143"%3A"mig00000000356686"%2C"00000332837"%3A"1000"%2C"fixedInfo"%3A"MDM000013035691103022618201464180471|5"}&Tab=wysiwyg_area_0

250mm wide 1000mm long around $55. Not exact measurements, but roughly $220 for an XXL bed.

Dan


(William Adams) #14

Yeah, that was popular for the SO2 — underscores the size difference, since while two short lengths would do for an SO2 bed (I think a couple of people got them for just shipping during the “reddit150” offer), you need quite a bit more for even an SO3.

Thing is you’d also need to pay for shipping, and you’d need a structure to bolt it to — at least for it you could connect from underneath or the front.

@patonclover’s bed is pretty much that — I’m just not wild about the orientation.


(Patrick Andersen) #15

@WillAdams, reversing the orientation to North/South on an XXL would be dead simple.


(Mike Price) #16

Since its readily available to me. I’m going to use 3/8 6061 and see how it goes. Going to double it up on the steel slats to get my 3/4 height back for the overhang.