[ToMMY2ooo]

Quick question, how would a 5th axis work? I know about a 4th axis, rotary so you can do 360 machining, but is a 5th or 6th axis like rotary on a rotary axis?

Cheers,
Tom,

[Turn Man]

usually, i'd say 90% of the time the 5th axis is on the z on a vertical axis machine, it can rotate +/- 60 deg. a 6th axis has a five axis machine with a multiple rotary head on the table. they would be considered a,b, and c axis.

[ToMMY2ooo]

ok so lets see if I understand....

5th axis would be the movement of the vertical head, so the spindle in relation to the x axis would move +-60o.

6th axis, rotary head on another rotary head?

Im thinking of starting a website to help other users out as I have had a hard time learning all this, Im a web developer by trade and I think cnczone is good but I think that a central resource would be nice to have for the beginner.

Cheers,
Tom

[3t3d]

Quick question, how would a 5th axis work? I know about a 4th axis, rotary so you can do 360 machining, but is a 5th or 6th axis like rotary on a rotary axis?

Cheers,
Tom,

Usually a 5 axis machine has a rotary for the A and the B axis.
The A axis coincides with the X axis, and the B axis coincides with the
Y axis. This is referring to a vertical machine.
Some machines are a trunnion type. The A Axis is a trunion or rotary along
the X axis, and a second rotary table, the B axis is mounted on the trunion.
This allows all five sides of a part to be accessed, and features, or
holes drilled in at any angle.
Some machines are similar, with an A axis Trunion, and the head swivels
in the B axis. This will have simular but slightly different capabilities.

Some gantry type machines have a knuckle that can swivel in the
A and B axis. In other words, the head swivels in two axis.

Swiss type lathes can have 11 axes or more. What do they do?
well, there can be multiple independent toolholders all operating at
once, to speed proction of a complex part. The tool holders can
be referred to as X1,Z1 X2,Z2 X3,Z3 etc.
The C axis of a lathe referrs to the ability to stop and position the
spindle in a specific position, so that live tools can preform milling
operations.

Some lathes have a subspindle. The two spindles can synchronize,
and the part is transferred to the second spindle, to be worked on
the backside.

Some lathes have many spindles, with multiple toolholders and axes
per spindle.

On a lathe, the Y axis refers to the ability to move a toolholder up
and down, in relation to how you normally look at a manual lathe.
Since the toolholder may be behind the part, or above it, it is not really
up and down... But you get the idea.
A lathe might also be able to rotate the toolholder, I'm not sure if
that would be an A, or B axis. This can allow milling, or drilling into
the end or side of a part, at an angle. Think of making complex chessmen
in the lathe.
Some machines can synchronise the live tooling, so that hex and square
features can be machines while the spindle is spinning.

Hope this gives some ideas.
Pete

[ynneb]

Im thinking of starting a website to help other users out as I have had a hard time learning all this, Im a web developer by trade and I think cnczone is good but I think that a central resource would be nice to have for the beginner.

Whats not central about here?

If you want you can always make html pages in the FAQ section here.

If you need a hand to know how to make any of those sorts of posts then you can PM me. You can even make PDFs and have them on here. If you prefere we can arrange for an inline frame for your pages too.

Edit: We can even set up a beginners section if you are willing to do the work by writing up all the information. We have 5000 members here, I would imagine that your work would get more hits here than been independant.

[Graham S]

http://www.rainnea.com/cnc_5axis.htm

that is one way, click the desktop mill link for another.

essentially 5-axis allows you to mill perpedicularly on 5 sides of a cube, 4-axis only 4.

Graham

[RotarySMP]

The CNC toolkit site has a very good set of illustrations of the different 5 axis machine configurations here:
http://www.rainnea.com/cnc_support.htm

This was one incredibly clevr peice of work, to take a feature in a software tool designed for creating monsters in video games (3D Max's ablity to extrude lines perpendicular along a spline laid upon a surface), then write a plug in to use this feature to create 4 and five axis tool paths.

With this little free plug in to the free version on 3D-MAX ( called GMAX) plus a bunch of time, you are getting functionality which is only normally available in mega buck CAM packages. Not easy to learn, but in the hoby world there is really no alternative.

[Johnuk]

Tommy,

Manufacturers and notes about CNC machines usually mix A, B and C axes together quite a lot.

Essentially, there are a few distinct groups of machines that use more than four axes.

The first is a tilting head machine. Here, the machine is arranged as it would be on a normal VMC. The A axis on these machines nods the head back and forth and the B axis rolls it from side to side. VMC's that have both axes on the head like this usually don't even have 180 degrees of pivot on the axes. So, for example, the head couldn't roll from vertical to fully horizontal, or right round to the front of the work piece. This is due to the mechanism not being particularly rigid.

Another kind of VMC like this is an off the bar machining centre. Here, there isn't a work table, but a collet style clamping mechanism, under CNC control, pointing along what you'd say is the X axis. A bar of raw stock is automatically fed through the collet, clamped and can then be rotated, just like it would be if it was fixed to a normal vertical rotary table. This axis is usually called the C axis of the machine. These machines almost always have heads that pivot on their B axis - side to side. Since the work piece can be rotated infinitely within the C axis, there is no need for the head to have an A axis. As the head's pivot is more rigid, they usually pivot right up to 90 degrees or more off their vertical starting point - meaning that they can form something almost exactly like a lathe.

Standard VMCs with only a B axis pivot to roll their head from side to side do exist, but they don't seem to have much demand without a C axis horizontal rotary table on the work table it's self.

There is a kind of machining head that has a 45 degree split down it. By indexing the head around the split, it can go from vertical to horizontal machining - like an A axis. Instead of nodding back and forth, these swivel from vertical to horizontal. But these, again, have a limited amount of demand, as they're still only allow limited machining. Combined with a horizontal rotary table however, to give them a C axis, they can become much more useful. The swivelling is tricky to imagine. It's lacks usefulness as it moves from vertical to horizontal as it is moving through two axes, in a fixed pattern, so it is tilting on it's side and pivoting from vertical to horizontal at the same time.

Another kind of VMC uses a trunnion table. A rotary table arrangement holds the work table at either end. Mounted horizontally on the work table is another rotary table. The rotary mechanisms holding the work table it's self form the A axis, tilting the table back and forth along the Y axis, and usually pivot less than 180 degrees - if they pivoted the table 180 degrees in one direction from starting as level, the machine would be milling into the back of the work table. The rotary table on the work table is just a normal table that forms the C axis and can rotate 360.

The final unique arrangement is a gantry mill. It works just like a normal gantry mill but the head of the machine is fitted to a rotary table like arrangement to form a C axis, letting it pivot 360 around, like a drill head. Sometimes this is only indexable, but usually not. The spindle of the machine can then pivot on an A axis about 180 degrees.

This final type of machine is sometimes called a portal mill, as an arch, fixed or stationary, is also called a portal.

If the gantry part of the machine can't move on a Y axis, it's often called a bridge mill, because then the gantry part looks a bit like a bridge; it doesn't move.

Because portal mills have work tables that are stationary, they are excellent for machining very heavy work pieces. Also, as the head can pivot to such a degree, they are the weapon of choice for machining complex curves and bends for aeronautics.

Despite their pivotings, portal mills are inherently rigid. Since only the most necessary parts of the machine have to move, and not the work piece, more of the machine's weight can be put into making the machine's moving sections stronger.

I am aware of portal and bridge type mills being DIY'ed now. Although they have the potential to be very rigid, they are also fairly complex, and one of the other arrangements would be much simpler if it'll suit what you need. Commercially, portal mills are only made by a limited number of companies and will usually cost you around a quarter of a million dollars or more.

These things are much easier to understand if you just think that whenever you read about a C axis, it will be a continuous axis - a lathe's spindle is usually called a C axis. A rotary table would be a C axis. The A axis pivots the head over the Y. The B axis, where ever else you need one, but mainly across the X.

You can kind of wonder why bother with all the extra axes. It's to try and eliminate interplotation error. If you want to cut a 2D curve on a three axis machine, you have to move two axes as the same time. If you have an axis that pivots through the axis of the curve, you can have the entire cut controlled by one axis. This eliminates the demand on the machine's controller to try to combine two axe's movement into one curve. It also makes five, or even six, sided machining possible in one operation, as well as improving the surface finish.

Regardless, a lot of machine shops still opt to do as much of their work on three axis machines. As these are cheaper and simpler, the same money will buy a very high speed machine. Such shops usually have the three axis high speed machine do as much of the roughing out work as possible and then transfer the work for finishing on a multiaxis machine. One company here in England is competing with those in the East for work costing by using such a technique.

Most of the newest machines also use very high pressure coolant systems that run at 1000psi or so to blow the swarf off the cutting surfaces as they work.

I'm sorry if this seems a bit disordered or hard to understand. It's early and I wanted to try to cover as much as possible, but not go on for too long. If there are any mistakes in there, I'm sorry.

There are a lot more options for how to arrange axes, the ones I've mentioned are just the ones that are used commercially. All of them require a certain degree of skill to implement correctly.

One of the newest commercial arrangements are turn mills - mills with directly driven rotary tables, capable of simultaneously performing precision milling and turning operations on a single set up. You can watch a really cool video clip of one at work here - http://www.monarchmt.com/Turnmill_HB_384k.wmv (Right click and save it first for smoother playback)

I've spent a great deal of time looking at multiaxis machines. If you'd like any help compiling an FAQ, I'd be more than happy to help. Please email me if you'd like to put something together on it.

Best wishes,
John

[email protected]

[ESjaavik]

@JohnUK: That seemed quite well ordered to me.
Now with a few sketches, that would be an excellent tutorial on multiaxes. But there are some drawing wizards around here, so that could happen.

[imserv]

Tommy,

Manufacturers and notes about CNC machines usually mix A, B and C axes together quite a lot.

These things are much easier to understand if you just think that whenever you read about a C axis, it will be a continuous axis - a lathe's spindle is usually called a C axis. A rotary table would be a C axis. The A axis pivots the head over the Y. The B axis, where ever else you need one, but mainly across the X.

The C axis does not stand for continuous.

Rotary axis designations are standardized as follows

Axis letter....Rotates about/center of rotation is parallel to

A.................X
B.................Y
C.................Z

When a rotary table can be setup parallel to any of the 3 axes, usually the controller will be hard wired to support one only. Some controllers even compromise this standard by using the W axis for the rotary 4th.

Fred Smith - IMService
http://www.cadcamcadcam.com

[Johnuk]

The C axis does not stand for continuous.

Rotary axis designations are standardized as follows

Axis letter....Rotates about/center of rotation is parallel to

A.................X
B.................Y
C.................Z

When a rotary table can be setup parallel to any of the 3 axes, usually the controller will be hard wired to support one only. Some controllers even compromise this standard by using the W axis for the rotary 4th.

Fred Smith - IMService
http://www.cadcamcadcam.com

I'm sorry, Fred is correct... I did say it was early!