3D Plaque Warping During Machining

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3D Plaque Warping During Machining

Postby johnelle » Fri Nov 10, 2017 1:39 pm

Still fairly new to Vcarve and have only done one 3d project (other than the tutorial). Working on a 3d plaque for Xmas and have ruined many nice pieces of woods and a few bits. The plaque is just some objects from the pay-library on a flat 3/4" board. A large part of the board gets cut away and the problem that I am having consistently is that as the board gets thinner it begins to bow upwards so that by the time the finish pass is done it is punching through the upper and lower edges because they've warped upwards almost .25" I am using the painters tape/super glue hold down method with three strips (top/bottom/middle) which usually would hold things very solid but the board warping seems to be overpowering the superglue.

I tried to attach a photo but the upload function never works for me.

My only thought is to leave a pocket-border around the perimeter about 1/2 inch which might prevent some of the warping and would give me room for some clamps. Also thinking of using some 1" rough sawn pine to give me more depth so I can have a minimum of .4 base underneath.

Comments/suggestions from you experienced folks please!
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Re: 3D Plaque Warping During Machining

Postby ElevationCreations » Fri Nov 10, 2017 2:38 pm

With as much movement as you are referencing, it is likely internal stresses in the wood being released causing movement as it is cut or extremely high moisture content. If you clamp the wood down the wood will still move after you remove the clamps.

Try a different piece of wood from a different board or from a different supplier if necessary, try quarter sawn wood, or MDF.
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Re: 3D Plaque Warping During Machining

Postby johnelle » Fri Nov 10, 2017 4:04 pm

Well so far I've tried:

Poplar from a high end lumberyard
Solid Oak from Home Depot
Clear Pine from a local saw mill
Knotty Pine from Depot

They all behave more or less the same way. Poplar warped the worst. The Oak is like iron and just burned up my bits (but it didn't warp as much)
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Re: 3D Plaque Warping During Machining

Postby Adrian » Fri Nov 10, 2017 4:28 pm

If you use forum search for warping you'll find lots of posts about it. It's a common problem. Make sure the moisture content of the wood is as low as possible but if you're taking a lot of material away from one side of a board you're always going to get some sort of movement. That's why a lot of people use glue ups of smaller pieces rather than one wide board.

If you're getting burning when machine oak you're running your bits at too high an rpm or moving the bit too slowly. Feed rates that work in pine/poplar will be way too fast for oak.
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Re: 3D Plaque Warping During Machining

Postby johnelle » Fri Nov 10, 2017 6:24 pm

Anybody know how to do a 3D inside a square pocket (i.e. a "frame" around the edge of the material)? I still would like to try that to maybe reduce the warping.

I tried drawing an inner rectangle 1/2" in from the edge of the material, highlighting the rectangle and the 3D models, and then doing a roughing path. It just ignores rectangle. Two rectangles with one on the edge(?)
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Re: 3D Plaque Warping During Machining

Postby Rcnewcomb » Fri Nov 10, 2017 6:31 pm

Also thinking of using some 1" rough sawn pine to give me more depth so I can have a minimum of .4 base underneath.

Any time you remove more than 50% of the material the wood will move. Thicker is better. I found that I had good stability if I left 75% of the material thickness.
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Re: 3D Plaque Warping During Machining

Postby Leo » Fri Nov 10, 2017 8:26 pm

What you are experiencing is absolutely, normal, natural and expected. Particularly if you are using wood products from the BIG box stores. What you get in those stores is construction grade wood. Though it may be clear of knots it is still not TOP quality wood. It is GOOD wood.

The issue is drying the wood. Furniture quality wood is not sold at the big box stores and is dried to a lower level than construction grade wood. Generally construction grade wood is about 12-15% moisture where furniture grade wood is about 7%

What does that means to you? When you cut away the surface and expose the inside the core starts to dry out faster. With the uneven drying the wood will distort. You are seeing that distortion.

If you use thicker wood - 3" or 4" thick and don't cut as deep - that will help

If you cut a shallow pocket on the backside and a shallow relief on the front to even out the material removal - that will also help

Rough sawn pine is generally going to be green, depending on how and where you buy it. The condition will be worst.
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Re: 3D Plaque Warping During Machining

Postby Metalbender » Sat Nov 11, 2017 4:35 am

I know this sounds crazy, but if your lumber will fit in the wife's oven...set it for 225 degrees and "kiln dry" it for about 4 to six hours.
I make some outdoor signs and I remove half of the thickness over 80% of the surface area and I only get about a 1/16" bow over 12"

BUT...I use big box 2x6s split them down the middle and cut to 26". Kiln dry them overnight and make a glued up panel out of the 2-1/2" pieces.
I've been looking for a cheap used pizza oven! Trying to save my marriage! :D

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Re: 3D Plaque Warping During Machining

Postby highpockets » Sat Nov 11, 2017 4:44 am

Metalbender wrote:I know this sounds crazy, but if your lumber will fit in the wife's oven...set it for 225 degrees and "kiln dry" it for about 4 to six hours.
I make some outdoor signs and I remove half of the thickness over 80% of the surface area and I only get about a 1/16" bow over 12"

BUT...I use big box 2x6s split them down the middle and cut to 26". Kiln dry them overnight and make a glued up panel out of the 2-1/2" pieces.
I've been looking for a cheap used pizza oven! Trying to save my marriage! :D

Greg
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Hadn't thought about that, I bought a used electric oven from a Habitat for Humanity outlet for $50 for my power coating projects. I'll give it a try and the SO can't say a word about it :lol: :lol: :lol: :lol:
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Re: 3D Plaque Warping During Machining

Postby Metalbender » Sun Nov 12, 2017 4:36 pm

..."SO"...?
I've heard of SWMBO...She Who Must Be Obeyed! :mrgreen:
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Re: 3D Plaque Warping During Machining

Postby redwood » Thu Nov 16, 2017 11:27 pm

I do a fair amount of wood signs. I buy air dried 2x12 redwood at a Big Box store. Additionally, I let it set, stickered, in my shop for a couple of months. When I'm ready to use it, I cut it to length and then run it through a thickness planer, alternating sides, until it is perfectly flat. I don't think I've ever had a issue with warping after that process.
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