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buscht
11-25-2003, 06:53 PM
I have read about some people trying to cut wood on a scroll saw using the X-Y axis motion of a CNC router.

They clamped the wood to the head (instead of a router motor).

Unfortunatelly, all I have ever read is that they did it. No where can I find out how accurate the finished parts came out or any problems.

I am anticipating accuracy problems with blade drift. If you cut by hand, you have to feed the part in slightly askew because the blades tend to cut to the side a bit.

For the CNC application, they did say that they used a spiral bit, which cuts in all directions.

I would like to purchase a low cost CNC router or MAXNC machine to place in front of my scroll saw to cut some 1" to 1-1/2" wood.

Sort of a wire EDM machine for wood.

Can anybody offer any real life experiences?

Thanks

DDM
11-25-2003, 11:26 PM
Unless you have a special blade for the scroll saw you would need an X and Y and then some kind of rotating table so that you wouldn't be trying to bind the saw blade. It would be tricky but probably a fun project. Code would probably be a pain in the @$$.

chuckknigh
11-26-2003, 12:12 AM
Um, a spiral scroll saw blade would make the rotary aspect unnecessary. I use this type of arrangement all the time, to hand cut complex shapes on my own scroll saw...manually, though. :-)

You can get 'em at any of the normal places, and even at Sears!

-- Chuck Knight

Bloy2004
11-26-2003, 12:19 AM
This is very interesting.....how long can those spiral blades be?
I want to set up a machine that cuts decorative tops in 4X4 posts and pickets for fencing. Around here many want cedar fences and gate systems and I've been using a band saw to manually cut stacks of five pickets. And the posts?........'have been cutting the tops off(ever try to swing a seven foot post and get an accurate cut?), band sawing the top to specs, and then gluing it back on matching the grain and putting in a Vgrove at the joint. Tedious I must say......

Bloy2004
11-26-2003, 01:13 AM
Hmmmm..... a stationary table for the work, an x and y axis to move the continuous spiral blade like a band saw. I guess the sacrificial table would need replacing often. Or maybe the table and rotating blade remain stationary and the x and y axis controls the work piece. A table might not be necessary at all...just a clamp and track system for the piece. It would have to be long to support seven foot posts. ....just thinking....
Are there machines like this for ideas to create a home model?

chuckknigh
11-26-2003, 01:50 AM
I suppose in theory they could be any length. But, you did say *scroll saw* which in my workshop, has about a 5" blade. If memory serves, the clearance between the table and the arm is about 2.5" or so.

With a system that clamps from the sides, it shouldn't be too hard to simply move your wood in a relatively small working envelope, without interference.

Now, fair warning, I've never cut anything thicker than 1" (5/4) with one of those blades...I would think that unless you turned the tension WAAAY up, it would deflect during the cut.

You might go pick up a package of those blades, and play with them on your own scroll saw. Amazing things, really. But, I would try them first, to see if they'll work for you.

http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00927065000
http://www.tufftooth.com/spiral.html

There, that gives you 2 URLs to look at, and gives you a part number, for when the seasonal help at Sears tells you that there's no such thing as a spiral saw blade. :-)

-- Chuck Knight

buscht
11-26-2003, 10:28 AM
I think that I have seen a bandsaw blade that cuts on all sides somewhere. Its like a piece of rope with bits of grit glued on.

For cutting fence post tops, I have seen a non CNC device at the woodworking show in Atlanta. I did not get any contact information because it wasn't of interest to me, but here is how it worked.

Your fence posts are stacked and clamped together. A 14" band saw is mounted on an articulating swivel arm. This arm along with the band saw is balanced so you can move it around with a feather touch. They had grap handles on the arm so you did not have to hold the saw.

Basically, the idea was that you could move the saw contraption around easier than moving large blocks of wood.

I think that they used a 1/4" blade in the saw.

There was also a CNC band saw, but that cost about $80,000. An X-Y device moved the part through the blade. There was some kind of device that twisted the blade right at the cut to keep the blade parallel with the cut line.

You couldn't do circles with this but long parts with sweeping curves were possible.

Back to my original post.

You do get scroll saw blade deflection, you have to have the right size blade thickness with proper tension to minimize this. Also, the cutting speed has to be correct to minimize side thrust on the blade. Thicker or harder wood increases this problem.

Most scroll saws only have a 3/4" stroke so if you are cutting 1-1/2" thick part, the saw kerf doesn't get cleaned out properly which also creates problems.

If I can work out the accuracy issues, I plan on getting an Eclipse scroll saw which has a 1-1/2" stroke.

Last night I tried a low tech experiment. My thoughts were that the CNC motion would do no more than guide the part through the blade exactly the same every time. My issue is what will the wood do under various conditions (thickness, grain, species,etc)

I clamped straight edges to the saw table, and cut parts using these as a guide. The results were encouraging. 5 parts were very consistent with only one being off about .010" in one dimension.

I will cut some more to see if this was operator error.

Bloy2004
11-26-2003, 10:31 AM
Thanks! that info about the blade guide control and "contraption" movement makes a home machine seem plausible.

seansear
11-26-2003, 11:37 AM
I am not sure about turning your scroll saw into a CNC but I use my CNC for scroll work all the time. Typically I find a site with patterns in PDF or DXF format and do the usual modifications to generate g-code. Cutting 1-2" material you will not be able to use a small diameter bit as they do not have that cutting depth. I have found .0625 bits with a cutting depth of .5
I have scanned patterns from Wildwood etc but it takes longer to do all the conversions. Once done however you can cut out all day long. I just finished a clock from one of the online pattern retailers. It makes light work out of cutting out a 75 piece clock. I am going to try a wood gear clock next.

ljoe1969
11-26-2003, 12:19 PM
WHERE DID YOU FIND THAT SIZE BIT?

HomeCNC
11-26-2003, 01:34 PM
I have found .0625 bits with a cutting depth of .5

Thats like cutting with a wet noodle :) I would be affraid to go much deeper than .020 at 2 IPM in wood. What depth and rate did you cut with that bit?

seansear
11-26-2003, 02:49 PM
Here is the link for the bits I was talking about. I have ran the .0625 bits at 30 to 50 ipm through 1/4 solid walnut, with no problem. I uses the .313 depth cut bit for the 1/4" wood currently. These bits are designed for a cnc router. I have no stake in the sale of these bit but I will recommend them for anyone who wants to do detail work.



|Thats like cutting with a wet noodle I would be affraid to go much deeper than .020 at 2 IPM in wood. What depth and rate did you cut with that bit?|


You must go through a lot of bits at this slow speed, unless you are decreasing your spindle speed. The bit goes no where to do any cutting.

http://www.precisecut.com