[rovingmind]

Has anybody used a 4-th axis head mount like this and did it work very well?

I've been looking at all of the 3axis units but will need to undercut more and don't want a lathe style rotation.

This is what i've been thinking about. The small hole at the top of the large gear is for a zero locator (ir transmitter/reciever pair) actual hole would be very small. Use an idler gear to connect the stepper to the motor. At zero a simple solenoid could lock the gear in place using the top gear spacing.

The back plate keeps it from rotating all the way around (switches for stop points added of course).
I could get a decent angle without having to use a complex wiring setup for the z axis and router power. It wouldn't rotate around itself and twist the cables to pieces. Of course the angle would depend on the router mount and table size.

I could make a stiff enough gang beam making a sandwich of mdf, foam, and fiberglass with a pipe and bushing insert. I'm going back and forth between thoughts of using a smaller spindle and smoothing out a piece of copper plumbing pipe for the bushing or, trying my hand pouring a babbit bearing.


I was shown Mach3 and its configurability would work for this head.

The large mounting plate and spindle would be an aluminum disc with an adaptor to either 2 or 3 inch steel plumbing pipe.

The z-axis would use a spindle extension with a floating brace to get an extra couple inches of travel to make the angle usable.

Right now its just an idea, if anybody has a better one let me know please.

[rovingmind]

The carraige mount for the y-axis would be the top and bottom of the long beam, I didn't show it. All sizes in this are at the moment just for showing the idea.

[Coogrrr]

I want to see more and where this device connects to the router.

My thought was to have one end of my table with this hanging from it free whelling. The stepper that has the other end holding the product and rotating would be clamped to the bed of the table at whatever lenght I wanted so on my 5' table i could do a 8in piece or a 48" piece lathe like.

That way I get the full Y and Z ability...

I will make a drawing real quick of my idea and you have to look at my table real quick so it makes sense.

http://www.cnczone.com/forums/showthread.php?t=29877

Wanted to add the concept here it is...

[rovingmind]

I was thinking about this basic style of y-axis. I'm thinking drill rod for the long pieces and mounting them with jgro's end blocks. It would be easy enough to attach (weld) an adjustable center mount for flex.

I would use plate for the sides and make an aluminum box for the cross pieces. A boxed square opening could be easily put in the cross pieces then the tubes filled with expanding foam. Gusset plates would go on the outside to strengthen the gantry.

I don't know and would appreciate comments on whether it would be better to use a moving table or moving gantry for strength. I know the moving table takes up more room. A 4 foot span would use just over 8' with the moving table, and just over 6' with a stationary.

[rovingmind]

I was thinking about using this style of mount for the z-axis to keep the distance from the router to the support bearing shallow. Its not shown but the hole would be completely through the slide, using nuts at the upper and lower end.

I mentioned earlier possiby using a spindle extension but that is beyond my means. Careful router choice would work along with a little bit of parts blocking to raise off the table.

Has anybody used something like this? Is it worth pursuing? Ideas? Comments?

[rovingmind]

Ok i added threads to the drive rods although its still not dimensionaly accurate.

Any ideas yet? Has anybody tried this on a homebuilt before?

After looking at nema 34 steppers I'm thinking they would be the smallest stepper used practially, for this size of machine.

It also became readily apparent that the z-axis would have to run this way to get any depth. a basic "Doh" on my part initially.

Bracket is simple porter-cable clamp design for now.

[paulC]

Interesting idea, but before you put too much effort into it you need to think carefully about how you are going to use it. The code generation for this would be extreemly complex. I don't think the out of the box code generation solutions would work for this. I'm not saying it can't be done. It would just be a shame if you put all the effort into building it and never be able to use it.
Paul

[rovingmind]

Interesting idea, but before you put too much effort into it you need to think carefully about how you are going to use it. The code generation for this would be extreemly complex. I don't think the out of the box code generation solutions would work for this. I'm not saying it can't be done. It would just be a shame if you put all the effort into building it and never be able to use it.
Paul

Do you know of any software that could control a machine head like this? I've seen the full 4 axis, router/lathe designs but the table size would put it out of my reach for the size of item i'm looking at, and for the space available. I don't need a full rotation for the fourth axis, just enough to get an undercut.

Can you point me towards any other ideas? (besides the a-axis lathe style)

[paulC]

I'm not sure, but I think with an axis like this, the centre of rotation is set to the tip of the bit which makes it much simpler to control. I dont think you could do this with a gantry machine as the gantry would collide with the work piece. I think with gantrys the common solution is the one Coogrr sketched. The math for your idea would be quite complex and you would proberbly have to write the software yourself.
Please dont think I'm trying to pour cold water on your idea. I just want to make sure you know what you are getting into.
Paul

[rovingmind]

I'm not sure, but I think with an axis like this, the centre of rotation is set to the tip of the bit which makes it much simpler to control. I dont think you could do this with a gantry machine as the gantry would collide with the work piece. I think with gantrys the common solution is the one Coogrr sketched. The math for your idea would be quite complex and you would proberbly have to write the software yourself.
Please dont think I'm trying to pour cold water on your idea. I just want to make sure you know what you are getting into.
Paul

Looking over mach3 it mentioned up to 6 axis of configurable control.
Bobcad mentions the ability to use 4th axis indexing for cam toolpath generation. Of course without the machine to test with i cant really test them out fully with the idea.

A gantry width of 4 feet on a workpiece 18" wide should get enough space at the side to keep the top of the mast clear on tool retraction if something went wrong. Thats also why the head sits forward of the mast sides. It should be able to slide all the way to the side stops even with the head tilted.

At the moment its a research project for me. I'm planning on building joes kit after i get a small metal lathe first.

[rovingmind]

Like this
Although upon rotating it through its motions, the bottom corners of the z-axis slide would have to be rounded off and usable table space becomes rather small for the y axis.

the straight up and down z-axis will not work to get the motion of freedom needed and tilting the table wouldn't work.

Aaargh!!!

[rovingmind]

For me this design is dead.
If anybody does build something like this I would like to see it.
The size of the table to do something like this makes it a no-go for me.
The Table clearance is a non-issue and a moving table, fixed gantry gives the support for the higher gantry head but 4x8 panel cutter size is needed to make the extra angle useful for anything.

[Coogrrr]

For me this design is dead.
If anybody does build something like this I would like to see it.
The size of the table to do something like this makes it a no-go for me.
The Table clearance is a non-issue and a moving table, fixed gantry gives the support for the higher gantry head but 4x8 panel cutter size is needed to make the extra angle useful for anything.

well there is another thought when we talk about 6th axis or more than 3 anyway what about a second Z axis hanging beneath the first Z hanging from the Y upside down that is that can do the work on the back side?

Thoughts?

[rovingmind]

When i think of that I picture the part being on a rotating axis anyway for clearance, like a conventional A-axis, unless the 4th axis was mounted sideways to begin with which kinda takes away from the whole, cnc auto cut anyway when you have to recode, and rotate the head mount manualy. It would work though.

What I was looking at was taking about a 45deg plunge cut for example, cutting the underside of a petal on a rosette. Old hand carvers achieved amazing detail on carousel horses because they weren't restricted to 2.5d. A standard 3 axis 2.5d machine can make a good rosette but being able to undercut the littles bit gets closer to accurate reproductions.

What the machine would be for is cutting life size carousel horses (legs not attached while maching obviously) work piece about 2' square by 4' long possibly done in halves at 1' x 2' x 4'.
Do-it yourself glue and paint kits.

[rovingmind]

When i think of that I picture the part being on a rotating axis anyway for clearance, like a conventional A-axis, unless the 4th axis was mounted sideways to begin with which kinda takes away from the whole, cnc auto cut anyway when you have to recode, and rotate the head mount manualy. It would work though.

What I was looking at was taking about a 45deg plunge cut for example, cutting the underside of a petal on a rosette. Old hand carvers achieved amazing detail on carousel horses because they weren't restricted to 2.5d. A standard 3 axis 2.5d machine can make a good rosette but being able to undercut the littles bit gets closer to accurate reproductions.

What the machine would be for is cutting life size carousel horses (legs not attached while maching obviously) work piece about 2' square by 4' long possibly done in halves at 1' x 2' x 4'.
Do-it yourself glue and paint kits.

[Coogrrr]

When i think of that I picture the part being on a rotating axis anyway for clearance, like a conventional A-axis, unless the 4th axis was mounted sideways to begin with which kinda takes away from the whole, cnc auto cut anyway when you have to recode, and rotate the head mount manualy. It would work though.

What I was looking at was taking about a 45deg plunge cut for example, cutting the underside of a petal on a rosette. Old hand carvers achieved amazing detail on carousel horses because they weren't restricted to 2.5d. A standard 3 axis 2.5d machine can make a good rosette but being able to undercut the littles bit gets closer to accurate reproductions.

What the machine would be for is cutting life size carousel horses (legs not attached while maching obviously) work piece about 2' square by 4' long possibly done in halves at 1' x 2' x 4'.
Do-it yourself glue and paint kits.

Well this is the solution for joo then!!!!!
http://www.vectric.com/WebSite/Vectr.../c3d_index.htm

scroll to bottom and watch the movie thingy play!

P.S. I am actually getting the whole suite plus mach3 I think with that I can make just bout anything.

Coog

[rovingmind]

YES!!!!!! That is really awesome. Thank you for the link.

[Pete Stenabaugh]

Hey guys, you really need to decide upon the type of 4th axis machining you want to do. If you are going to do continuous rotary machining that is one thing, but if you only need to do various sides, then one thing I can suggest is to take serious look at Vectric's new Cut3D software at www.vectric.com. This software sells for $250 if you are a current vectric customer.

This will allow you to machine on 1, 2, 3 or 4 sides of a project, although you will need to have some sort of rotary or indexible material support.

I have made up a solidworks, quickie model and drawing for a manual indexer, employing a wood working 4 jaw 6" chuck. You would likely need a pair of them. The chucks are available in Canada for about $60 ea at Busy Bee. I dont have the drawings available on this computer but I could post them in a day or so, or email them directly to anyone interested if you send me your personal email to [email protected].

If you need or want to do continuous rotary machining, then the simple way is to make an adapter to attach a stepper motor to a regular machinine shop rotary table. You can attach your material to that in various ways. You will of course need something to support the other end if it is very long.

Pete Stenabaugh,
Calgary

[Coogrrr]

I am drawing up a device to be made with a chuck a stepper and a ball screw to dial in the length.

If there is interest I might be compeled to do them sooner

[rovingmind]

Hi Pete
The initial idea was to see if i could get a 4th axis without the space a rotary axis would take up. The answer has become no. Ideally i would (pipe dream) like to have both the rotary a-axis AND some form of this head.
I don't want to manually index the part or the cutting head.

As both you and Coogr posted, that vectrix software comes Really Close and would work for an intermediate level of detail. I say intermediate because it wouldnt be feasible to do a part in 1/4" slices to get the undercutting on something 18" thick. The time factor would be to great. Its definately on my watch list though when i get a cnc router.