What is 2.5D?

[cadman]

Originally Posted by cncwhiz I run "pro nc" and do threadmills all the time? I have not run into anything with 2.5 in pro that it will not do using "X, Y and Z"? I also program "4 axis" machines with one axis being an indexing axis? Cncwhiz

Not exactly sure what you are saying, but 2.5, 3, 4, 5 axis refers to machine controller configuration, not cad or cam system ablility. A mill capable of only 2.5 axis motion cannot interpolate more than 2 axis at a time, generally X & Y. If you can do a programmed feed in all three axis simultaneously then you have a 3 axis machine.

[DareBee]

Like Cadman says - DON'T confuse 2.5D programming with 2.5 Axis MCS.
A 2.5 axis machine WILL NOT rigid tap or thread mill.
A 2.5 axis CAM program will do these things, no problem.

Zrrigid
You can check out VisualMill and SprutCam as good CAM software (I have used VM for awhile).
Integrated CAM for SW is WAYYYY more money ie.EdgeCAM

[under-dog]

Please correct me if I am wronge.
From my undrstanding:

***2.5 is based on a flat drawing such as a DXF but unlike 2d which only controls X and Y movement there is control for Z movement as well. This alllows for varied depth with regards to pockets and islands and such in one NC file. Where as 2D requires manual positioning of the Z position.
2D and 2.5 are generally a plotted path or collection of paths made up of of segments(curves and lines).

***3D is based on a three dimensional surface or solid part file and not just a flat drawing. 3D is created with a rastering effect where the machine moves simultaniousley in multiply axis and actually traces/ mimicks the cutting tool along the surfaces dictated by the file.Basically to the left or right with a whole series of ups and downs along the way.

Not entirely farmiliar but 5 and 6 axis but I believe theymay have the ability to somewhat use a hybred of both methods. Sort of complex.Up down left right and all around in unison.


I think the confusion that is coming in is that it is not about how dimensional of an object that can be created that defines it but the process in which the nc file is created and the way the machine produces the part.

One used 2D images to created somewhat 3D(appropriately named 2.5D) objects by using flat linear paths to define the tool paths that on a path to path basis can be cut to certain depths.

The other uses complex digital 3D surface structures and basically makes a file that replicates that 3D surface areas

Both methods can create 3 dimensional objects or entirely flat objects. Staying within both processes limitations it is entirely possible to mill the same exact parts with each method. The process to create each part will be entirely diferent but the ruslt ssimilar I think undercuts and the ability to be able to mill entilerely 360 degrees around an object is irrelivent to whether it is 2.5 or 3D. It is more about the process and not the finished part. A 3 dimensional opject can still have draft and no undecuts form a certaing direction of pull. It makes it no less three dimensional.

With that said certain parts are better suited to one process or the other. Whether for efficiency or capability reasons.

[DareBee]

I agree

With only a couple of small nitpicks.
All CAD has clearly defined points in space - therefore all CAD models are defined by vectors as opposed to rasters.

I don't believe there is such a thing as 6 axis machining but 4 and 5 axis is common.

Another point to note. You do NOT need a 3D model or surface to do 3 axis machining.
If I give my machine the simple coordinates of G1X1.Y1.Z1. it will move the machine in all 3 axis simultaneously and truly be doing 3 axis machining. Generally it is very difficult to program true 3 axis machining without a CAD model and 3 axis CAM software.
Also most programs output by true 3D CAM software will be made up of 95% 2 axis moves as this is the most efficient and accurate method to move the machine tool servos.

[under-dog]

Originally Posted by DareBee I agree With only a couple of small nitpicks. All CAD has clearly defined points in space - therefore all CAD models are defined by vectors as opposed to rasters. I don't believe there is such a thing as 6 axis machining but 4 and 5 axis is common. Another point to note. You do NOT need a 3D model or surface to do 3 axis machining. If I give my machine the simple coordinates of G1X1.Y1.Z1. it will move the machine in all 3 axis simultaneously and truly be doing 3 axis machining. Generally it is very difficult to program true 3 axis machining without a CAD model and 3 axis CAM software. Also most programs output by true 3D CAM software will be made up of 95% 2 axis moves as this is the most efficient and accurate method to move the machine tool servos.

Entirely true. The cut strategy differs though. The 3D surfacing while defined by vector points behaves and cuts in a raster pattern. Multiple rows of specific points(Z height) where as the 2.5D is a plotted tool path sets to a certain Z height and then proceeds to cut the path then resets itself to another hieght and proceeds to cut the next path and so on. It is much like the difference between a ink jet printer and a plotter but working into Z axis dimensions as well.


I agree you dont need a 3D model for 3 axis machining. 2.5D is just that a flat two dimensional drawing which creates guidelines for paths that can be set to specific and varying heights.
Interpolated or true 3 axis as you mentioned, yes is a whole other animal. But the question is over 2.5 vs 3D and not interpolated simultanius axis movement

[ger21]

With 2.5D all cutting moves are in the X-Y plane, but they can be at any depth or multiple depths. With 3D cutting moves can be in 3D space and are not restricted to any specific plane.

[ObrienDave]

Having been a CNC programmer for the past 25 years, I have to say some of the explanations are wrong.

2-1/2 D machines CAN do helical interpolation if the control supports it.
Simply because the rise or fall of the helix is LINEAR.

2-1/2 D machines CAN do 3 axis LINEAR interpolation. G1

The difference lies in CIRCULAR interpolation. G2 or G3.
2-1/2 D machines can ONLY do circular interpolations when the arc is parallel to an axis plane.

G17 x-y plane perpendicular to Z axis using I and J or R to define the arc.
G18 x-z plane perpendicular to Y axis using I and K or R to define the arc.
G19 y-z plane perpendicular to X axis using J and K or R to define the arc.

2-1/2 D machines CAN NOT do simultaneous 3 axis circular interpolation.
You would have to define not only the arc center or radius but also something to define the PLANE of the arc.

To clarify something for DareBee,

You can have as many axis as you need to control MULTIPLE slide machines.

Let's look at a MULTIPLE slide lathe with LIVE tooling for example.
Since I don't program lathes, please don't flame me if I don't get the explanation 100% correct.
Ok, here goes...

Axis 1 The chuck rotational ORIENTATION. C axis.
Axis 2 The table slide POSITION. Z axis.
Axis 3 The cross slide POSITION. Y axis?
Axis 4 The tool holder rotational ORIENTATION.
Axis 5 The tailstock POSITION.
Axis 6 The tailstock LIVE tool rotational ORIENTATION.
Axis 7 The secondary slide POSITION along the spindle.
Axis 8 The secondary slide cross POSITION. Like diameter.
Axis 9 The secondary slide live tool ROTATIONAL orientation.

ad nauseam...

The point is, you are thinking of axis like, height, width, and depth.
They are NOT.
They are CONTROL axis.

Thanks for reading my rant.

[DareBee]

I learn something new everyday.
I like it that way.
I am also wrong at least once a day.
Don't care for that much but I freely admit it and learn from it.

Cheers

[HIRAH]

Having been a CNC programmer for the past 25 years, I have to say some of the explanations are wrong. 2-1/2 D machines CAN do helical interpolation if the control supports it. Simply because the rise or fall of the helix is LINEAR. 2-1/2 D machines CAN do 3 axis LINEAR interpolation. G1 The difference lies in CIRCULAR interpolation. G2 or G3. 2-1/2 D machines can ONLY do circular interpolations when the arc is parallel to an axis plane. G17 x-y plane perpendicular to Z axis using I and J or R to define the arc. G18 x-z plane perpendicular to Y axis using I and K or R to define the arc. G19 y-z plane perpendicular to X axis using J and K or R to define the arc. 2-1/2 D machines CAN NOT do simultaneous 3 axis circular interpolation. You would have to define not only the arc center or radius but also something to define the PLANE of the arc.

that's what i was going to say.
i think a lot of people get confused and think you can't do a helical move in 3 axis. you can, but on a 2.5 axis , you can only specify the arc in 2 planes. also,a 2.5 axis machine will also only move 3 axis at once. so no x,y,z and a at the same time. try to zero return 4 axis at once. if one axis waits, there you go.

[zrrigid]

Thank you guys for all you replies.Here is what I really want some input on.I have solid works that I am learning. When I bought the machine I have I got a Mastercam X program with it. I want to be able to do 3D solid modeling and then be able to mill that shape. I hear some people complain about the Mastercam and because I am learning all this new I am trying to decide what is going to be the easiest and cost friendly thing to do.Right now I just program at the machine or use my offline program to convert .dxf files.Basically a 2D guy trying to go 3D.

Ian

[DareBee]

The most cost friendly is using the software you already own. UNLESS you are paying the yearly maintenance on both of those which is probably around $4k/year.

Then you could look at something new to remove that cost.

You are going to get many, many, many, many, many comments on who likes what and what works best for them.
You are going to have to decide for yourself what you need.
If you are just designing single parts to machine CAM with an integrated CAD modeler MAY be the solution for you.
If you are paying license on SW and will not give it up (I won't :-) then why would you spend extra money on CAM with modelling capabilities?
Not enough info provided as to what you are machining, what you want to machine in the future, type of machine, type of projects modelled, hobby use, R&D use, production use,etc, etc