Waste board flex

CNC Machines Shapeoko
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Proper prior planning prevents (alliterative rude word for urine)-poor performance.

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Yes, the higher outside lip of surfacing is a pain — at one point I was actually trying to work up a way to make a jig to cut tempered Masonite panels to use as insets into that area — my new plan is to try to take advantage of it — just always do a surfacing pass on whatever fixture I’m using, and ensure that it perfectly fits the stock along two edges square to the machine.

One concern with your image is you’re not getting the best mechanical advantage on the clamping — the clamped part should always be lower so that it is held acutely and the other end of the clamp should be higher — yes, this makes keeping the clamps from interfering with the works more difficult, but it makes the work less likely to raise difficulty.

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I only draw in sketchup make 2017. SVG files are lousy, always broken and scattered into Carbide Create, but it’s what I’m used to. 30 years ago I was an AutoCad expert but I will NOT work in a cloud enviroment so Sketchup works fine for me. That SimpleCad of the other member looks amazing for carving pictures and I’ll look into that soon, but still within sketchup.
Oh, the Shapeoko 3 model is from Edward Ford on the wiki, It is exact down to the screw threads, wonderful but very intense drawing wise.

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Hi Will, Why the language warning ?? I try t keep all my texts family friendly. But thanks for the clamping tip, haven’t thought of that cuz of the possible interference with the rail assembly. Trial and error will prevail, maybe I’ll make some styrofoam clamps to test with first.

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The language warning was in reference to myself — I edited out a word in my post out of an abundance of caution for delicate sensibilities.

Shouldn’t’ve used a quote block there, and have removed it

Your post was fine.

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I have a standard-size SO3 but that isn’t going to stop me from making some observations.

I arrived at this point at about the same time as I noticed this thread. I’ve replaced the stock spoil board (the previous owner had chewed it up pretty good) and then I wanted to add a second 1/2" board on top of that, so I can clear the front and rear brackets of the SO3 (so I can use longer pieces).

I wanted to make sure my board was fairly flat relative to the Z so I made a DI holder that goes where my dust boot would normally mount.

When I purchased my SO3 (used), I noted that there were no feet on the bottom of the unit. Having the unit sit on my workbench, I didn’t want the waste/spoil board screws that were protruding from scratching-up my bench top.

So I visited my local Ace hardware store and purchased some vinyl bumpers. They’re 3/4" square and 1/2" high. I placed nine of them on the bottom of the SO3. I had figured these bumpers would be made from hard enough vinyl/rubber that they would not compress.

Checking w/ the DI, I think I can compress them by about .004 or .005" by applying pressure to the spoil board with my thumb. It is also possible my bench itself is moving that much. Could be a combination of the two, as well.

In testing various areas of the spoil board, I’m about +/- .003 or .004" across almost all of it, save for the front left corner which I think is about -.009.

My intent all along was to shim under the feet of the SO3, or under the corners of my top spoil board, to get everything to +/- .003" or better.

Before proceeding, though, I think I will replace the bumpers with some discs I’ll cut from plywood, so I can remove the compression of the bumper from the equation.

The thing is, if you guys are setting your entire machines on top of foam rubber padding, it doesn’t surprise me you can get quite a bit of movement.in your spoil boards. I assume with those larger units you’re using foam to deaden sound coming from the larger panel, sort of acting like a drum head?

If that is the case, the solution may be to use some panel damping stuff normally used in cars and speakers to reduce noise, while also using some sort of solid/hard feet that can accommodate shimming. So the SO3 ultimately sits on hard feet.

Or I may have completely misread the problem in which case, never mind.

FWIW, the DI shows quite a bit of action ( a few thousandths is easy to achieve) when pushing the Z-carriage to and fro. And I can push the rails and get .001 or .002". My point being, if I’m going to start quoting machining jobs for NASA (kidding), I’m going to need to fix any variability I can actually fix.

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To suppress the dirchilet (sp) effect (drum) I followed Mark Bellum’s advice and mounted an uprite 4x4 under the center of my enclosure base to prevent vibration. The foam duct wrap I used to act as cheap dynamat was nil to minimal effect, but the homemade MLV (alum flashing w/ rubber tape on each surface) removed 20 decibles on it’s own. MLV is very expensive and I had that stuff laying around. Couch cushion foam does nothing but acoustic ceiling panels added roughly 5 more decibels of reduction. A solid door is much quieter than one with a window. All these items are credited to Mark Bellum and remember not to [quote=“mbellon, post:5, topic:5016”]
SCHNAPPEN DER SPRINGENWERK, BLOWENFUSEN UND POPPENCORKEN MIT SPITZENSPARKEN
[/quote]

I will yield to Mark.

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To suppress the dirchilet (sp) effect (drum) I followed Mark Bellon’s advice and mounted an uprite 4x4 under the center of my enclosure base to prevent vibration.

The fundamental resonances in a Dirichlet problem are the full and half tone. Placing a support half way - in the middle - prevents a huge number of resonances. If the skin material is stiff (furniture grade plywood is an excellent choice), this is often sufficient. The best results come from TWO cross pieces - split the drum head in thirds - or fifths.

My CNC table, design to handle a huge amount of weight and vibration, is split in fifths (5 segments) for near perfect suppression; the deck material is screwed to the frame and the cross pieces. Admittedly, this is extreme and has to deal with conditions FAR more than any Nomad or SO3 will have to deal with.

Couch cushion foam does nothing but acoustic ceiling panels added roughly 5 more decibels of reduction.

This is EXACTLY why I suggest acoustic ceiling tiles for people on a budget! Acoustic ceiling tiles are CHEAP and they work! Using MLV or more exotic materials offer 10 dBA and up… 30 dBA is possible. A bit of care is necessary to make it work out.

We can talk about wall design for noise suppression separately. Inside the enclosure, we need LAYERS. Closest to the machine is light, more open material to diffract high frequencies and prevent resonances. Next comes heavier materials, typically MLV. Next, if one can swing it, should be an air space filled with open sound suppression insulation (it must not be under compression (loosely fitting). Finally comes the walls. MASS is your friend (MDF, pressure treated plywood, furniture grade plywood, steel!).

There are some AMAZING materials available out there… but they cost. Creativity can go pretty far; the rest is the tough part of Physics.

A solid door is much quieter than one with a window

Sure is! Yes, It’s possible to design a window that can suppress sound fairly well… but nowhere as well as a solid wall. A single pane of polycarbonate or tempered glass is largely sound transparent.

With todays costs so low, leaving out the window and installing a high definition camera is well with reach of many.

The foam duct wrap I used

Ductwork can be a significant emitter of sound. In large shops special care is taken to acoustically insulate (or at at least isolate) ductwork.

mark

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I didn’t mean to miss quote Mark here, He advised me about the center beam under the floor (base) and I added the vertical 4x4 on my own thoughts, so I do have a center cross member and a vertical 4x4 to reduce vibration. I get carried away trying to respect and credit others as I see their intelligent observations. He also advised me NOT to use the couch foam but I did because I did. The homemade MLV , when I installed it in the vacuum cleaner enclosure did reduce 20 decibels as per my decibel meter (actual meter not phone app).reading before MLV 101 and reading after MLV 81 decibels. Their are many members here on this forum whom are due their proper credit even for their humor. Thanks Mark for all your advice.

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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?

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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

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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

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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).

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My thoughts exactly, for now, haha!!!

Thanks,

Dan

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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?

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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 ?

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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).

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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!

IMG_1248.JPG3024×4032 2.45 MB

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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:

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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

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