Flat bed source?

[fred ungewitter]

I've not been able to figure out how to pull for cleaning my honeycomb bed from the Redsail 500x700 clone. There's four philips head screws on the aluminum perimeter, but pop rivets front and rear. The locking rings on the lift screws might be removable, but getting the bed over the top and off would not be practical. The brackets are welded to the bed, so removing it there is out.

To combat this problem, I figured a nice pin bed would be the right direction. Somewhere in the deep recesses of my alleged mind, I found MIC-6 cast aluminum to be a solution for a flat surface. The frame is 730 mm x 600 mm (28.74" x 23.6"). I figure for my project, I'll be using 6 mm/0.25" sheet.

Pretty darn expensive on the 'net so far. US$216.26 from the lowest price source I could find: https://store.buymetal.com/aluminum/she ... -0.25.html

With a sheet that size, shipping is going to be a chunk too, although I might be able to get it sent to a business friend.

I plan to drill a grid of holes, tap them and thread in a bunch of cut rod pieces with pointed ends. I figure I can also tram the entire bed once the pins are in place, by threading each row end to the nozzle and using lock nuts. The intermediate pins can be trammed by a straight edge over the ends, making it easier by removing the sheet after the initial setting up.

Does anyone have a lower cost source for cast aluminum sheet?

Other options are entertained and encouraged.

fred

[Jeffrey Aley]

I'd use steel instead of aluminum because it's magnetic.
https://www.amazon.com/Unpolished-Finis ... 73&sr=8-38


Then, instead of holes, just buy some cheap neodymium magnets and get some pins to use. I use deck screws, but you could use punk spikes or whatever.
https://www.amazon.com/gp/product/B073T ... UTF8&psc=1


There's no real need for the pins on the pin bed to be regularly spaced. In fact, I find it's helpful to be able to move the pins around for some jobs.

[fred ungewitter]

One of the reasons I selected MIC-6 aluminum is that it's certified to be flat. Can one be equally assured with steel? I like the magnetic idea, as I use magnets on the steel honeycomb with good results. The punk spikes are another good thought, saving hours of chucking threaded rod in the lathe, but can one get adjustable height spikes? Perhaps a bolt that threads into the spike would provide for height adjustment.

I see amazon has a huge selection of spikes, with threaded mountings. Seems like a good idea.

[Jeffrey Aley]

One of the reasons I selected MIC-6 aluminum is that it's certified to be flat. Can one be equally assured with steel? \

I don't know how flat the steel would be. I assume (!) that thicker steel (e.g. 1/8" or 3mm) is more likely to be flat than sheet metal.

[Doug Fisher]

When I unscrewed those four screws, my honeycomb table lifted off. The steel bar bed/frame remained below. One word of caution, the four screws strip the threads in the holes in the bed frame very easily .

You might look up the thread I started regarding acquiring a sheet of steel to put on top of my honeycomb bed. I called the Metal Supermarket mentioned in that thread. One of my questions to them was regarding flatness. The lady said she could not guarantee the thinner sheets would be perfectly flat because the thinner thicknesses were cut via a shear versus laser or water jet.

I was worried about total weight with the thicker pieces. In the end, I went and picked up a 1/16" sheet of sheet welding steel (no galvanizing or coating!) at Lowes. I was able to sift through their rack of sheets and find one that would lay flat on BOTH sides using the store floor as a test. Most sheets were not acceptable but I did find one (check all the bins because people put things back in the wrong place). These must have been cut via shear yet the edges didn't have a bend to them. There was a slight curve in the piece but I was able to easily straighten that by hand.

They don't make a sheet that fits my bed size but I was able to find a fairly large piece that gave me enough working area. It lays flat and works well. I bought it to use when cutting things I don't want to get dirty due to vaporizing flashback from the gunk in the honeycomb (particularly paper and card stock). It works well if you have your power settings dialed-in so you have just enough power to cut but definitely not excessive amounts of power. The metal is easy to clean between each item cut. Windex works fine (no need for acetone, 409 or similar).

I did not use aluminum because I thought I read somewhere that some aluminum is much more reflective of a CO2 glass tube's laser beam compared to steel and thus could do damage to your lens over time.

[fred ungewitter]

I've realized that the majority of the answer is in the punk spikes. I can replace the machine screws in the spikes with longer versions that thread into magnets with countersunk holes. These will stick well to the existing metal bed, yet raise the work piece above the flash-back zone. I was resistant to this approach at first, because most of my plywood is slightly curved, despite being laser grade and having magnets atop the plywood pulling it flat to the bed has worked well.

I realize also that I can take bolts through a pair of magnets, one for the bed, one for the top of a standoff and match it atop the work piece to accomplish the same result with just enough elevation to remove the flash-back.

I may yet take a shot at Doug Fisher's reference to the four screws. I can understand how the screws can strip the soft aluminum frame, but your words of caution are well received. No power screw driver for this portion of the project!

I rarely cut anything larger than 300 x 600 mm and could create more than one steel plate with magnet studs to cover my bases.

Thanks to all for the suggestions.

[Gene Uselman]

I have a selection of different sizes/lengths of steel bars handy on top of my laser for flattening recalcitrant sheets on blade, honeycomb and pin beds.
It will not work in every case but works well when it does work.

[Willy Ivy]

Square bar stock works well for this also. I use 3/4" x 3/4" x 12".