Multi-axis "turning"....

[Doug Rasmussen]

Multi-axis is one of my interests. There are some issues with it though, like blending between the turning axes. So I thought maybe doing it on the CNC could solve that.

First off was to come up with a design. A tallish vessel like a weed pot would be a good start. Design a profile of one side, then modify that for the opposite profile using a graphics program. Then convert it to a surface model for viewing from any angle. IMO, having the multiple profiles adds to the interest (but, what do I know about design?).





The surface model in CAD is sliced at horizontal intervals which become the cutter path. Each horizontal slice has a circular cross section. Off setting the circles from the vertical central axis creates the effect of multi-axis.

The cutting is done with the part standing vertically with a thin wood shaper cutter revolving around the part. The cutter spirals down the part leaving surface that almost doesn't need sanding.


And the completed "turning". For technical reasons the part is not quite as tall and thin as the surface model



How many here are involved with CNC machines? They seem to be slow to catch on with woodturners.

 

[hockenbery]

That is a cool design. With the lathe it is easy to do something similar to what you have shown.

What the CNC could do is shift the center on each pass as you move up or down the piece.

A half oval tool handle is a common example where the center is shifted and one side or the round tool handle is turned away with a larger radius.

By changing centers and/or axis we can turn things that appear less round.
I do some some simple multi center turnings to make 2 or 3 sided napkin rings, the 3 sided ball stand, or for off center platers. I do some multi axis turnings in my suspended spherical forms or when turning balls

We don't have a good common language yet.

Most people refer to muti axis as a turning that is rotated in direction more or less about the center of the turning. When I turn a ball a I start with endgrain toward the lathe centers, rotate the piece so the side grain is toward the centers, then rotate it so the face grain is toward the centers.

With muti-center or off-center turning the work moved to different centers with grain orientation kept close to same with respect to lathe axis.

Below is a multi-axis piece I turned on one axis and hollowed on another axis after rotating it 90 degrees.
The ball, outline of the tail, and the edge of the front leg are turned on one axis. The ball is held in a vacuum chuck to hollow it.

 

[Bill Boehme]

Here is a little candlestick article that talks about Mark Sfirri and his approach to multi-axis turning.

One thing I learned from doing it the wrong way on non-parallel multi-axis turning is that you can only change axes on inside corners

 

[john lucas]

I simply would rather be in the shop actually holding tools than playing on the computer. That and there isn't any way in the world I can afford CNC and don't have the computer skills to even attempt to set one up.

 

[John Torchick]

Funny, my first attempts at turning came out multi-axis. Didn't plan on it being that way. I just chalked it up to inexperience.

 

[hockenbery]

@Doug Rasmussen
It occurs to me that you should be able to cut a spiral surface with a CNC machine.
The lathe is good at cutting circles and arcs.
The CNC can do surfaces that are not circles or arcs.
Parabolic curves, hyperbolic curves, spirals.....

You might hang out with the ornamental turners...
Here is box we have by Gorst Duplessis, who is no longer with us.
An ornamental lathe can do some cool stuff.
.

 

[Doug Rasmussen]

Thanks for all the replies..

John Lucas, I understand what you're saying about the CNC learning curve. My response to that is it's getting much easier. Software like the Vectric programs included with some of the low end CNC's is very much in the hand holding category. As to affordability, I expect you and many others here have a great deal more invested in your lathes and related support tooling, etc than you'd pay to get into a very capable CNC setup.

hockenberry, Thanks for posting Gorst's piece. I look at that thinking it's about 95% design with about 5% execution for me on the CNC. The piece has a hand done look to the base with cutting marks left visible and the top lip with a sort of random scallop. Same with the lid. The finial is a nice contrast in perfection. All of that is possible with advanced programming techniques where the cutting paths are calculated mathematically in real time. Add in a random multiplier to cutter positioning, step over or depth of cut to achieve the "hand made" look. The common misconception I hear all the time is "who wants fifty identical pieces off the CNC machine?". With the state of technology parts like in my posting can be changed from tall and skinny to short and squat or any combination with a simple change of a couple parameters. Fifty similar pieces all different with one program. Anything is possible with CNC.

Whatever is made, it's still the design that's most important IMO. For me the CNC is just the tool. I happen to like doing wood "turning", but ever since my first try at turning in high school shop I've never cared much for hand turning.

I was sorry to hear of Gorst's passing. Through the ornamental turning subgroup I met him and we had several long conversations.

 

[Bruce Schoenleber]

Why not just a 3D printer then?

 

[Doug Rasmussen]

Bruce, sure, why not, if it could have exactly the look, feel and characteristics of real wood?

As I said about Gorst's piece, for me, it's all in the design. Does it really matter how it's made? That piece is especially interesting because I knew the artist, but from my conversations with Gorst he didn't have problems with my displayed ornamental turnings done with CNC. That's not to say other ornamental turners didn't have problems with CNC because they did.

Like it or not CNC is coming. So far, on the low end of the market (Rockler and Woodcraft types) the CNC machines are mostly oriented to sign making, engraving, relief carving and such rather than turning. The machines don't lend themselves to work on lathe sized chunks of wood because of low clearance under the spindles. Most of the low end guys are now starting to offer a 4th axis option which allows rotary (lathe type) work to be done.

 

[Bill Boehme]

The piece has a hand done look to the base with cutting marks left visible and the top lip with a sort of random scallop. Same with the lid. The finial is a nice contrast in perfection...

The piece by Gorst duPlessis looks like it was turned on his Holtzapffel Rose Engine and Ornamental Turning lathe. The pattern isn't random, although it could be mistaken for that by a casual observer. Just my personal taste, I have more appreciation for something created on an ornamental lathe than I do for a piece created via a set of software instructions to an automated machine. But, things are always changing ... a century ago painters were concerned that photography would lead to the demise of their art.

 

[hockenbery]

How a piece is made matters most to the maker. Collectors occasionally want to know the story of how a piece came to be. Some shows have restrictions too

A bowl made with a chainsaw, bandsaw, lathe, or CNC one may not be able to tell if it is round.

I have heard people try to explain natural edge bowls to their significant other as having been formed with a hydraulic press.

 

[Bill Boehme]

How a piece is made matters most to the maker. Collectors occasionally want to know the story of how a piece came to be.

I would say that depends on whether the intended market is craft shows, high end galleries, or something in between. If we're talking about the well known professional artists then the collector is buying the name of the artist and the message expressed through the work as much or probably even more than the artwork itself. At the other end of the spectrum, if we're talking about something that I made, a potential buyer might ask how much did I pay for the wood as a negotiating starting point. 😀 (mostly I turn free wood). 🙄

 

[Emiliano Achaval]

Guilio Marcolongo is coming to Maui next week. He's staying with me! And he's bringing a Vermec off center chuck. Looking forward to my first off center experience...

 

[john lucas]

It does matter how it's made if your selling in Craft shows. Many have an agreement that all things must be hand made. However we had a good discussion about letting photography in but they decided that it was OK because they were hand developing the prints. However I know that has now changed since they are allowing digital photography in. So I suppose if you can get a photo in that is done by typing on a keyboard then why not CNC. I certainly hope the consumer is more knowledgeable because I would hate to be competing with a "turner" who makes things on CNC and can turn out 100"s of things exactly the same (once you design it of course) when all of my work would be hand turned.

 

[Bill Boehme]

The craft shows around here that I am familiar with (mostly the Christmas shows) don't allow things that aren't unique and individually hand crafted by the seller.

 

[Owen Lowe]

I have more appreciation for something created on an ornamental lathe than I do for a piece created via a set of software instructions to an automated machine. But, things are always changing ... a century ago painters were concerned that photography would lead to the demise of their art.

It struck me that a CNC “lathe” is not far removed from an ornamental lathe. Both use specific instructions input by an operator with none of that hand-eye coordination stuff involved in the outcome. Up to now, I held ornamental lathe operators on a higher pedestal than CNC programers; I think my outlook on one of those is going to have to be adjusted. (more thought is required)

 

[Doug Rasmussen]

john lucas, you make some good points. I don't mean to dispute them, just commenting.

How far does/should the hand made rule go? Should hand turners be allowed to use laser guided hollowing systems? Factory processed, stabilized woods, high tech finishes? I know owners of two local, 50+ employee, businesses making high end stringed musical instruments who are highly automated with multiple CNC machines (one has six CNC's). Their products are sold worldwide for their quality which they couldn't provide without CNC. One changed their logo from "hand crafted" to "hand crafted quality".

Galleries, it seems sometimes there's an economic reality to survival. Seattle recently lost a 30 some year old co-op gallery specializing in wood art of locals that at one time had two locations. The gallery was very selective of who they represented. Apparently, they could no longer make in affluent Seattle. In contrast, yesterday I stopped in to the Wood Merchant gallery in La Conner (north of Seattle). "no imports, your purchase supports American Craftsmen", etc. A nice gallery, a never miss stop when I'm in town. A guess, maybe 50% of their 3,000 sq ft space is custom one-offs. The remainder consists of high quality, obviously factory made goods. The item that struck me yesterday was the 50 or so displayed hinge lidded boxes about 4" x 6" all with different CNC lasered marquetry work on the lids, $59. That represented economic reality, affordable and quite a bargain considering the quality.

CNC does not necessarily mean all pieces are identical. I meant to mention in my previous posting that with clever programming you can introduce a randomness in minor design details. And, the selection of wood makes no two pieces identical anyway.

 

[Mike Johnson]

You know the old time wood turners were saying the same thing about electric motors on lathes.
Just not the same as being hand turned on a treadle lathe. 🙂

 

[Doug Rasmussen]

A couple pictures of more experimenting with multi axis. As much visualization as is possible in the computer before cutting it's still a surprise how the part actually comes out.

 

[john lucas]

I see a place for CNC it's just not for me. What CNC can't do is change it's mind midstream to make the grain or other figures in the wood stand out. I often start a piece with a shape in mind but then as I turn and see what's happening to the figure in the wood I change what I'm doing to better enhance that or use that figure.
On one hand I don't care how a piece is made. It's all about the final product as far as a viewer is concerned. As far as the maker is concerned it's about creating the piece whether it's done by hand or by CNC. Each person has to make his or her own decision. I talked to a guy today who's woodworking hobby is all about building and setting up the shop. He does make some stuff but he has more fun looking for new or old machines and fixing them up. So to each his own.

 

[Doug Rasmussen]

"What CNC can't do is change it's mind midstream to make the grain or other figures in the wood stand out. I often start a piece with a shape in mind but then as I turn and see what's happening to the figure in the wood I change what I'm doing to better enhance that or use that figure. "

john, It seems to me the same issues apply whether hand turning or CNC'ing. A CNC is not like a speeding freight train, it can be stopped at any time to evaluate your work to that point. I do it all the time.

The part to the far right in my latest picture posting started out to be larger. After a bit of cutting I noticed the wood was cracked near the top. Stopped the machine, I sawed the top cracked portion off.. Rescaled overall size (a couple keystrokes) to fit remaining wood and restarted.