Waste board flex


(Mark Bellon) #21

Should likely avoid dividing lengths/areas in perfect halves, as each will likely result in equal frequencies which are additive. Probably better to go 60-40?

That gotcha is if the 60/40 leaves a nice distance with a good frequency itself!

The best is divide by thirds or fifths. That said, half - when the stiffness is really good (plywood) - is, as I said, very likely to be enough. The frequencies of vibration from CNC tend to not be so hard to dampen.

It’s also remember that when I’m talking about this, that the desk material is screwed down to the cross pieces and around the periphery.

mark


(Dan Nelson) #22

Hey Jude,

I have a question about the self leveling concrete and maybe I can pick your brain a little? In addition to my XXL I also own a small bench top 7x16 mini lathe. I have it propped up on a very substantial wooden bench (4x4" legs, 1" thick plywood top, 2x4" framing) similar to the bench my XXL is on. I’m having no issues with the lathe or accuracy really, but your mention of the leveling concrete got me to thinking (painful just thinking about me thinking too much, haha!!). If I’m understanding you correctly you poured the concrete on TOP of your bench? Not a concrete pad on the garage floor? My lathe is not strapped to the bench itself, it sits on rubber feet. I’ve read where people have strapped them down only to find out that the tiniest warp on the bench actually produced some twist to their tiny lathes. But if I could somehow make the bench top entirely flat it then should be possible? Maybe this should be moved to my musings thread?

Thanks,

Dan


(Jude Marleau) #23

Well Dan, over thinking is my main nemisis also. The floor of my enclosure is where I poured the self leveling cement, to provide a solid and level surface inside the enclosure to place the shapeoko onto. Amusingly the floor of my workshop is plywood. I’ve over thought your issue of strapping down the corners of the cnc to the concrete floor of the enclosure and have not because it will be difficult to remove it for maintenance or repair and imo way overkill. I have a small lathe on a similar bench as yours and simply wedged under the lowest foot to level the bed. I did screw the feet down but I don’t think thinking about the possibility of 5/4 board (shelf) warping will result in enough warping to conteract the thoughts of the thinking about the possible reinforcing required to counteract the warping I thought I was thinking about (musible painless thoughts only).


(Dan Nelson) #24

My thoughts exactly, for now, haha!!!

Thanks,

Dan


(Rob K.) #25

Really appreciate the forum and so much help from the more knowledgeable.

XXL is in the box and i’m reading a ton and trying to learn as quick as i can.

On-topic… Would 3/4 plywood be more rigid and avoid flex? A single piece instead of two halves? Eventually i’m looking at insets for clamps, or possibly adding a top HDPE/Starboard and t rails maybe?


(Jude Marleau) #26

Next time I need to redo my waste board, I’m going to replace the mdf base board with a 1 1/2" thick spline jointed ipe(sp?) bread board recessed on the edge for the angle iron rails and holes to recieve the pemm nuts, I’ll surface that for a 1/8 hard board waste board that will be roughly level with the top of the bread board base. Ipe is so dense that it sinks, it’s heavier that water, it’ll make a super boat but it better be real big. That will give me a solid base and absolutely no flex. I have to resharpen the planer blades after that. Has anyone tried working from bottom of material and cutting down to zero to cut thru the material without cutting into the waste board. Sounds good in theory, something Dan can muse about over his coffee in the Motorcycle Display Area / Workshop. What ya think Dan ?


(William Adams) #27

Yes, plywood should be more rigid than the MDF, but not sure if it’s sufficiently rigid enough to offset the sag over the span. My inclination would be to use the MDF on top of the plywood as a spoilboard, or to set it aside for re-use as a template after using transfer punches to machine a single piece MDF spoilboard.

Stiffening elements such as @grumpa describes will help.

Yes, measuring the material and cutting only it and not the wasteboard is something folks try pretty regularly — if your machine is dialed in, you’re not losing Z-steps, and your stock is in plane w/ your X- and Y-axes it works quite well (best to either tram the wasteboard, or if the stock is small enough, machine a fixture w/ a pocket to hold the stock).


(Dan Nelson) #28

Ipe is some crazy heavy/hard wood. Friend of mine sent me some offcuts a few years ago and I honestly had a hard time working with it(I was hand making pistol grips at the time). I ended up giving it to another friend, who in return gave me one single ball point pen he turned on his wood lathe. Yes, big box of walnut, maple and Ipe offcuts traded for a single pen, a very nice pen, haha!!! I would suspect if you can get a big piece like an XXL waste board Ipe would make a very solid bed.

I’ve tried to cut through many projects without cutting the waste board. Current setup is an 18x24" HDPE cutting board that I threaded and trammed flat. What I usually do is set my Z zero on the cutting board, with a thin piece of paper between the tool and the board. Then I jog up by the material thickness and reset Z zero. The results haven’t been too bad, but works best with small parts where I’ve used 2-sided tape for work holding. I’m currently planning a totally different waste board setup, but this idea should transfer over pretty well think.

I honestly haven’t had time to get back to my bed flatness musings. I’ve been working on the new house and preparing for “The Move” which is slated for this coming Friday. Add to that some sort of ugly cold/sinus infection this past week or so and all I’ve managed to do is go to work and sleep for the most part. I hope to get back to this very soon!!!

Dan

Oh yea, I finally got a shed installed last week to house those pesky “garage” things that tend to muck up my workshop space!


(Jim Amos) #29

My recommendation for an immediately more rigid machine is to leave the leveling feet in the box… Not only is it more rigid, but it removes the intrinsic sag… Went from .015: edge to center sag to .005 edge to edge. Here’s the thread where I broached these questions originally:


(Jude Marleau) #30

I think you set zero to the top of the waste board (trammed) and cut from a start point above zero likt the thickness of the material. Estlcam has that feature for cutting holes in the bottom of pockets (start at bottom of pocket that was cut to14mm cut 5.05 mm deeper to cut it out of 3/4" material.Or rather start at 19.05mm and cut 19.05 to cut out a part. Only trying to figure it out, so musing about it. I also redid my waste board because I forgot to screw it to the base board and it rose and warped. On the end of the new one on the outside of the rail screwed onto the edge of the waste board I screwed a small blockof oak surfaced 0.06mm below the waste board surface, I taped a piece of aluminum tape (0.06mm thick) onto the block and now I have a tool height measuring with the probe fixture that is exactly the same as the waste board and shouldn’t be in the way of material cutting… Another Estlcam feature, measure first tool and after a tool change measure 2nd tool and any height differences are handled in the program, uses the probe with alum. tape and aligator clip. Nice shed, maybe you could paint a “garage door” on the side of it, than you’d have a “garage” along with your Motorcycle / / Wood Pen Display Area/ Work shop, or even “shadow” silloettes…(sp?), time for more coffee, congrats on the new digs Dan. Jude


(John Gowrie) #31

so you keep your Shapeoko on the floor? ( thread necro ) lol


(Chris) #32

I was looking in my garage today and noticed a pair of 48" x 7" x 1/4" sheets of steel hiding in one corner. I’m thinking about using those on the front and back of the XXL replacing the original MDF. Maybe add a 4" x 1/4" one for the center.

This will leave space where I can run two T tracks about 1/3 of the way from the front for a 4th axis mounted directly to the original steel mounting brackets. I can then place 3/4" waste board on top of that with a cut out section for when I want to use the 100mm 4th axis.

The 4th axis is kinda large so I want to mount it as low as possible. I have it, the T track, a TinyG and a 24V power supply tucked away ready to be installed.

I’m not worried about weight just keeping it all squared by adding all that steel.