It's a Tech Challenge

Leo Voisine

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East Freeetown, Massachusetts
Went to an Arts and Crafts Festival today.

YES - I steal ideas. If you don't want yours ideas stolen - don't put them out in public.

Anyway - I saw some really nice picture frames and I am liking to be making picture frames.

This one I want to do larger than my machine is capable of. Also - it would not be good to make it from one huge piece - the grain direction would be wrong.

My machine is 24 x 24 - the frame is 24 x 36.

The challenge is --- HOW do I set up to cut the segments? How do I cut the recess in the back side - it will not fit on my machine after it is assembled.

How do I get the PERFECT miter cuts. - NO - the CNC is NOT going to do that. Not yet anyway.

How do I fixture the parts - so that individual parts can be make.

Just thinking too - maybe I will tile it.

Anyway - what do you all think?


In Process Tech Challange.jpgOval Frame-1.jpgOval Frame-2.jpg
 
It's already drawn up as 3 boards that could be cut and assembled in rough mode. When the glue has set up, cut off most of the excess on the bandsaw, then stage it on your CNC. Do that two times and you've got a complete frame.
 
Bill,

Been thinking something similar to that.

The issue is - the finished frame is bigger than my CNC machine - which is where I plan to make the profile.

I am trying another approach - tiling. To do that I scaled the frame down 1/2 inch so I could fit it in one direction. In the other direction I can "feed" it through the machine and cut it in two tiled sections. I have never done that - but maybe its time to learn a new technique.

I love the frame - now I need to find something to put in it.

Dave? Do you have a duck of something that you painted that may look great in this frame - We can talk.
 
I'm have a brain fart with this one.

I am on to round two.

I saved the first file and created a second file thinking - tiling.

Where I am right now is not precisely CNC - it's more woodworking related-

Hang on a minute - I'll grab a screen shot. .................................................. ......

screen-2.jpg

What I am thinking right now is - just cut the six boards - glue them together - mount on machine - cut the form. I am thinking - tile the pattern.

I will also do the back side undercut - I just like the way it works. I will also engrave something cool, just because. I will go as far as masking painting and all the stuff I do with engraving.

Soooo - here is what I am up against.

1) You can see the orange lines representing the board. The piece is inside the board. The ends are at "some" angle inside the board. Those are the "miter" cuts - they need to be "perfect". What is the best way to do that? (I am thinking to do the board separately on the CNC and not on the conventional stuff. Trying to figure out the angles to get it on the miter saw seems like a nightmare at best. I don't like the CNC cut ends - but maybe a cleanup on the sander or miter saw will take care of it.

2) How am I going to orient this on the CNC machine - there will be no place to register the X-Y zero position. I am going to need an alignment fixture - for both sides.

3) Cut which side first - probably the back side first.

4) Clamping it down - this is a small problem.

Any ideas?
 
So how deep is the recess on the back side, is it something you could use a rabbet bit for with a guide bearing afterwards?

Just curious, what software do you use for Tiling?

As far as getting indexes correct, could you use some indexing dowels on the back that are consistent for each piece, say if you tiled the drawing and did a quart of the oval x4 and then join them afterwards?
 
Darren - yes the doweling for orientation is going to be critical.

I use Vectric Aspire - bur V-Carve Pro also has the tiling feature.

On the cut pieces to get the ROUGH oval shape so that I have really nice super tight miters is what is puzzling me mostly right now.

Yes I can cut the recess in the back with a bearing guide router bit - but I like what I get from CNC much better. Besides - I really want to JAZZ up the back side.
 
...The issue is - the finished frame is bigger than my CNC machine - which is where I plan to make the profile. ...

To clarify a bit: The top and upper left quadrant of your frame is identical to the bottom and lower right quadrant. Each could be assembled prior to placing them one at a time on your CNC. When the CNC is done, you have only two joints to glue up to complete it.
 
Bill - yep - they are.

In fact - just as rough pieces - all 4 pieces are identical. That is before the form is cut.

Both of the side pieces are identical.

What I am thinking of doing is to cut the miters on the boards - then assemble the boards into a ROUGH oval.

The question is - how do I cut the miter cuts - so that they are perfect after assembly.

I can get the angles, but they are not in exact one degree increments. I don't think I can get the Miter Saw set to the exact stuff.

I don't want any gaps in the miter cuts after assembly.

I also don't want to waste a lot of wood.

Miter cuts are a real challenge - even on a 4 sided frame. Seems easy - but it's not.

I think - I am going to try some experimenting on sample pieces first.

I might try getting it on the CNC
 
When I have joints to cut on a curved piece, I sometimes "cheat" a little. I print out my design drawing in a 1 to 1 ratio to give me a "life-size" pattern and place it on the wood using repositionable spray adhesive so it aligns properly with the grain. Next, I align the cut line square to the blade on my miter saw and cut at the joint line. I reinforce the resulting butt joint with a spline or biscuit.
 
Bill, yeah that's gettin closer to where I am.

I was thinking about a template.

The miter cuts though. That's where I am stressed over this project.

The splines are the easy part.

In making an oval frame - are there any rules - guides - tips? Is there a right way or wrong way?

Every time I try to do a miter cut - there is a tiny gap somewhere.

That tiny gap to me - nearly trashes my efforts.

When I have a tiny gap - I feel like I have failed.

NOW - I want to make an OVAL - with six miters - at weird angles.

THAT is where my apprehension is.
 
The miter saw can be set dead nuts with an adjustable drafting triangle (less than $20, but indispensable). Use Bill's suggestion to build a positioning jig for the miter saw. Easy peasy.
 
Couple of options

Well --- after playing around with this in between other stuff I have come up with a couple of possible scenerios.

FIRST - look at the layout. I know it's a lot of lines but if you study it enough, you will see what I am looking at.

The light green is the actual oval frame.

The Dark Blue - is the shape of the "rough" piece - IF - I cut it on the CNC.

The Orange is the board I will cut out of the Walnut. The first test pieces will be scrap pine.

The two angles at 119.8 and 130.2 will be actual at 120 and 130. I thing there is a little due to the way I positioned the orange board. I KNOW I laid out the out on the model at 20 degrees from horizontal. The orange board not at any particular angle - it is placed there by eye.

So - the 2 options are.


1) - I can grab the orange and dark blue and make is horizontal with the "X" axis and cut it on the CNC.

2) I can layout the numbers on a board - screw 4 boards together - set the Miter Saw accurately with my protractor, as Carol suggested, - and cut the four pieces together.

The sides will done the same way - in whatever process I go with.

I might do both just to see which works better.



Angle Layout.jpg
 
Here's What I'm Thinking for the CNC operation

What I did was to take the segments and copy to a layer. That way I have not made any mistakes in redrawing.

I then oriented so the segments were parallel to the "X" axis.

Then I adjusted the material size so the segments "just" fit into the material.

I used a 3/8 end mill to cut around the material. There is 1/4 per side on the radiuses and the miters are cut to size (hopefully).

I calculated the toolpaths and saved the toolpaths.

Now - I just need to gather up some scrap pine, and give it a go.

I have plenty of scrap pine that I tore out of the house from my remodeling project.

Long Board just board.jpgLong Board Rough Dimensioned.jpg

This one is for the sides - I need 2 of these.
Stock size is 20.5 x 5.5

Short Board just board.jpgShort Board Rough Dimensioned.jpg

These are the short segments, that make up the top and bottom segments - I need 4 of these.
The stock size is 13.0 x 5.0

After I cut then up - I am thing I need some sort of fixture to assemble the pieces so I can get everything lined up.


Any Ideas on the assembly part?
 
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