5 Axis indexed vs 5 Axis continuous

[jwolin]

I have never worked with a 5 axis machine, but am contemplating converting my 3 axis machine to 5. In researching the CAM packages available for 5 axis machines I keep running accross the terms 5 axis continous and 5 axis indexed. I have an intuitve idea of what this might mean, but need some help in clarifying. What specific advantages would continuous have over indexed? Could someone describe a part where this advantage would be obvious? Why isnt all software 5 axis continuous?

[CNCtoday]

With 5-axis continuos you can pretty much do everything with the part and 5-axis index can't do these kind of contour.



No way you can put radius on the edge of the part 5-axis index.

[puzzleman20]

In simplest terms, 5-axis index will aim your B and C axis then remain stationary while you cut a specific location. When you change cutting location, the B and C axis will re-orientate then remain stationary again for that cutting location. It is actually 3-axis cutting using 5 axis' to aim the bit.
In continous 5-axis, the B and C axis' will continously move while cutting to keep the tip of the cutting bit perpendicular to your part. Continous 5-axis takes more skill to program.

[jwolin]

thanks puzzleman, that description really helps. My remaining question has do to with the limitations of 5 axis indexed. Could you describe a part that could not be done with an indexed CAM package. It seems to me that the advantage of countinous over indexed is a speed advantage. If I understand correctly, in theory, repositioning of the B and C axis, then milling, then reposition of B and C axis, then milling, etc... would produce the same net effect as continous motion. It would just be slower. Am i understanding this correctly? Thanks again for the very helpful answers.

[puzzleman20]

Yes, the speed advantage is correct, but with that speed comes more moving parts (wear and tear) and a need for good part crash detection in your software and code editing skills. Off hand I can't think of a type of part that could not be cut with an indexed 5-axis machine. I don't think the loss in speed is really anything to worry about. We have 3 continous 5-axis machines at work and we almost exclusively use them as 5-axis index. We usually run at least two machines continously for an eight hour shift.

[turmite]

Originally Posted by puzzleman20 Yes, the speed advantage is correct, but with that speed comes more moving parts (wear and tear) and a need for good part crash detection in your software and code editing skills. Off hand I can't think of a type of part that could not be cut with an indexed 5-axis machine. I don't think the loss in speed is really anything to worry about. We have 3 continous 5-axis machines at work and we almost exclusively use them as 5-axis index. We usually run at least two machines continously for an eight hour shift.

puzzleman you mention good part crash detection. Can you give me an idea how this works? Do you have to model your part, the 5 axis head, etc, to be able to know that detection is going to be accurate?

Mike

[diarmaid]

Originally Posted by jwolin Could you describe a part that could not be done with an indexed CAM package. If I understand correctly, in theory, repositioning of the B and C axis, then milling, then reposition of B and C axis, then milling, etc... would produce the same net effect as continous motion. It would just be slower. Am i understanding this correctly?.

As is often the case I have zero experience of this. However an uneducated guess would be a sphere type surface. The continuous could mill all around the sphere smoothing it down and maintaining a nice rounded surface, but I think maybe the index wouldnt be able to do this, possibly the closest the indexed could get would be a rough sphere which would need to be ground or maybe just sanded smooth at the end.

As I said a completely uneducated guess.

[JerryFlyGuy]

In reality, I don't think there is anything that can't be machined w/ a index that can be done w/ CM [Continuous motion]. Except, when more than the tool tip is used for a cut. If you look at that giff on the second post of this thread you'll see where using CM kills indexing. That part could be done w/ indexing but the nightmare of programing it would The other thing about indexing is [usually at least... I've not found one that doesn't] you need to create plane's and manually tell the CAM how to orientate the head or part to then enable 3 axis movement. A CM CAM will usually do alot of this for you. If you tell it you want to machine perpendicular to the surface.. it will move the tool for you and simplify some of the code generation.

My understand.. and from what little use of Tutorial's that I've tried. It's worth noting that I have zero experiance using any code for 5 axis.. Yet

Jerry [I to need a CM 5 axis.. but haven't decided which one I'm gonna buy.. it has to fit in w/ SW and I would prefer a Gold Partner.. that limit's my choices alot! ]

[Dan B]

Although continuous 5-axis has it's advantages, it also has some disadvantages not yet mentioned. With positional you index the machine and cut in the X, Y and Z axis. In doing so, you are using the feedrates available to these linear travels. When doing continuous cutting, you are now dealing with the limitations in either a rotatable head or trunnion table. On slower machines, you will pay a price in speed. We have a new Hermle that rotates so fast is makes your heart skip a beat, so it's not that much of a limitation. However, our older Hermle does run substantially slower if doing continuous.

One big advantage of continuous, if you have higher end software like WorkNC or HyperMill, is the ability to convert a 3-axis path into a 5-axis, to reduce cutter lengths. For example, if you need a 100mm tool length in 3-axis, you can shorten it up to, say, 30mm, and the program will calculate the rotations to prevent the holder from hitting.

Hope this helps,

Dan

[Capgama]

Hi there
check out this link
http://www.sescoi.com/us/worknc/func...deo_mach.html#
I have been using this software for around 15 years and it work great for all types of machining + 5 axis machining.
There is only 1 type of 5 axis cnc and thats 5 axis cnc.
When you say 5 axis continuous, your right because all 5 axis can possible moving all at the same time at the same feed.
now 5 axis indexing is really called 3+2 axis, where as you can not move the +2 axis when cutting, the +2 axis is only for positioning the head and or table.
you can get a lot more work done with 5 axis cnc vers 3+2 because of the programming time.
There are some really good 5 axis programming software out there,the programing is almost almost automatic these days.
plan on paying around $15000 to $25000 per seat for these type of 5 axis programming software.
here are 3 top players in cam development
worknc
tebis
powermill

If you buy anything less make sure it has welding rod in the box (you will need it) 8->
and also a machine repair guy. no joke 8->

btw these cam programs have built in error checking so there no need for a 3rd part software cost. ch ching

[big_mak]

Don't forget Catia and NX

[Dan B]

I spent a lot of time at IMTS looking at the NX Cam Express demo's. I thought this was a very capable package, especially if you are using SolidEdge or NX for your modelling. The 5X programming appeared to be extemely easy.

Dan