Confusion About Axis' (or "what the heck is a 5th axis?)

[jemelby]

I understand perfectly what the x, y and z axis' are. What I don't entirely understand is what the 4ths and 5th are. I gather that an indexer provideds the 4th axis thru rotation of stock (like a lathe), and I surmise that the 5th axis involves tilting the cutter head.

To further regale you with what I think I know, I'll go out on a limb and guess that the SB does not come out of the box with a 4th or 5th axis, but that it can achieve the 4th axis with the addition of an indexer.

So then, I guess my real question is: Does the cutter head on the SB tilt at all? Or is all the variation in the Z axis achieved by slicing and cutter head shape?

To futher illustrate my question, Let's say I were to "carve" a three inch tall cone with a 45° slope(with the point up) from a solid material. I could use a straight bit make a bunch of ever widening concentric circles as I lower the cut head(figure A), or I could use a 45° V bit and make a few less concentric circle(figure B). Either way, I'm going to be doing some post-proccess clean-up to get rid of the ridges. Is there a system that allows the cutter head with a straight bit to tilt 45° and do a spiral cut path down the side to achieve the cone (figure C)?


8470

BTW: If it's not obvious, I don't yet own a shopbot. I am REALLY trying to get a handle on how it works befor I purchase one. My next challenge will be to develop an appreciation for the various software packages.

[gerald_d]

A SB works like A or B above - it is very far from working like C.

To cut A or B, the cutter must be able to:
1. move from left to right
2. move towards you and away from you
3. move up and down
A total of 3 directions of motion, hence 3-axis, standard ShopBot stuff.

To cut C, the cutter must be able to:
1. move from left to right
2. tilt from left to right
3. move towards you and away from you
4. tilt towards you and away from you
5. move up and down
A total of 5 directions of motion, hence 5-axis, something that ShopBot has experimented with, see this (http://www.shopbottools.com/images/Jamboree02pics/5axisani.gif), but it is not in production.

The indexer is a variation on 3-axis only. Typically the indexer lies for example parallel to the y-axis - then the simple way of operation is:
1. move cutter along y-axis
2. move cutter up and down (z-axis)
3. rotate the workpiece
And the x-motors are locked in position. However, if one does move the x-axis as well, then one effectively "tilts" the cutter in one plane only.

A recent thread (http://www.talkshopbot.com/forum/messages/312/5229.html) on this topic.

[daniel]

I think you got it pretty much figured out.
And with the shopbot you will machine like picture "A" or "B" in your illustration. You would need a 5th axsis to tilt the cutter in order to machine Like picture "C".

[jemelby]

Consider Illustration D. Is this the concept of the indexer and the 4th axis? The blue arrow indicates rotation.


8471

[gerald_d]

D is the concept of the indexer. But you shouldn't make the assumption this scenario is automatically "4-axis". As you have drawn it, the red tool has no need to move toward/away from you - it only needs to go left/right and up/down. So you need 3 servo/stepper motors as follows:
1. rotate the workpiece
2. move tool left/right
3. move tool up/down
Only 3-axis

The number of axes is the number of motors that are being controlled. (the double motors on the x-axis of a standard SB count as one because they are "in parallel")

Some of the indexer guys actually unplug the cable to their standard x-motors and then plug it into the rotator motor of the indexer. Still only 3-axis.

Some of us have controllers that can drive 4-axis, but then we use no. 4 to drive a second z-slide (a second parallel plunging router). This machine would still be called a 3-axis machine. As with the parallel x-motors, any other parallel motor/slide/pivot does not count as an additional axis for the description of the machine.

Our controller has 5 output channels and they can all be controlled independently for a true 5-axis machine, but already 2 of them are paralleled for the x-axis, while the 5th is not connected to anything yet. Our machine would be called a 3-axis machine.

If we connect the 5th output to the rotation motor of the indexer, and we wrote a control program that simultaneously controlled rotation, up/down, left/right and toward/away then that would be a true 4-axis setup. But, as you may realise, that becomes a complicated control program, and 5-axis programs become even worse.

Am I generating heat or light?

[jemelby]

There was a little heat there, but enough light so that I now understand more than I used to. And isn't that the objective?

Taking a bit of a detour from this thread... When I set out to get information about CNC routers, I narrowed it to the Shopbot and the Shop Sabre. I sent a simutanious email inquiry to 3 folks at shop sabre and 2 folks at shopbot. Same text/questions in both. The killer question was "what does the other (competition's)machine do better?" While no one bit on that particular question, Shopbot DID get a viable response back in less than an hour, while sabre's response took 23 hours.

I really like the almost-un-healthy fanatisism that folks throw behind the SB. This forum is almost like being at an Amway® convention.

As long as folks are humoring me, I'll keep asking. Thanks to all.

p.s. Still looking for a demo with-in an hour of Nashville.

[normand]

http://www.reichenbacher.de/site.asp?breite=1024 another kind of 5 axis http://www.reichenbacher.de/site.asp?breite=1024 would this considered a 5 axis? these carving machine are usualy operated by hand no cam program.If the movement could be recorded like probing

[normand]

first link product pegasus
second link product carving machine

[mikejohn]

I made, and use a copy carver.
Cost me about $100.
I use a Bosch 500 router, another $100
On mine you can copy 'y' 24ins, z 6ins and x 48ins.
Make your own, x can be as long as you like, y up to 4 or 5 feet, I would guess.
z easily 12 ins, but the depth of plunge would be limited by the length of bit for small 'holes'.
Go from large to small ball end bit, and you can carve pretty fine.
Accuracy depends on how well you make the copy carver, and how well you use it.
A lot more tiring than a ShopBot though
.
Indexer would also work (I've done it), and a possible 4th (or is it 5th ) axis.
You need a real pattern to copy, of course.


8472

The head in the background has been sanded.
This picture is known as 'The Godfather' picture!
....Mike

[gerald_d]

How do you get the horse to stand still?

[mikejohn]

We tell it stories about Springbok rugby matches, and they fall sound asleep

....Mike

[gerald_d]

[bill.young]

I've played around with 5 axis motion a little using a camera instead of a router. There's a draft of an upcoming Bill's Corner article with some pictures and video clips at http://www.seasidesmallcraft.com/mycorner/sbhack/5axis.htm The 5-axis stuff is crude but might give some ideas of the possibilities.

PLEASE do me a favor and don't all try to look at the videos in the next couple of hours...it's a small ISP and I'm afraid they'll be overwhelmed. If you're just mildly interested in 5-axis stuff, please wait a day or so before looking at the videos.

Bill

[beacon14]

Here is the other end of the spectrum in CNC machining.

This is for when you really are making rocket parts.

http://www.scaled.com/services/cms_mill.html

[billp]

David,
I'd LOVE to see what THEY use for hold downs......
Maybe double sided tape that's an inch thick? Or at that scale I guess gravity would work pretty well too...

[gerald_d]

An ice-rink floor would make a nice hold down....

[stickman]

Guys,

Can you imagine the lettering I could cut with that CNC machine. Can we say Times Square, New York City.

Bill,

I like the little camera item you created. Its a start of something very capable with the ShopBot.

[jsfrost]

Things have changed in Mojave! When I passed through enroute to the Naval Air Station at China Lake Ca in the early 60's there were a few houses, a bus stop, beer, food, and hundreds of miles of sand. An ice rink would melt there. At 11PM in summer 110F is cool.

[john_amonson]

Mike and Gerald....you two start my day off with a laugh. Thanks!

[bill.young]

The new Bill's Corner article with the 5-axis info is up on the ShopBot web site at http://www.shopbottools.com/billscorner.htm

[jthelen]

Free floating multi axis mill. The future or just cool? (4th one down)
http://www.cuttingedgecnc.com/movies.htm

[jemelby]

"Free" floating multi axis mill....

I'll bet it's not free!

hehe

[paco]

Awesome!? Did you look the movie??