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Author Topic: 2.5 vs 3 axis whats the difference  (Read 7914 times)

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johndolecki

• 71
2.5 vs 3 axis whats the difference
« on: November 03, 2014, 05:11:53 PM »
As i dive deeper into the cnc pool im confused by 2.5 vs 3 axis.

can mach 3 do 3 axis

thanks john

Hood

• 25,838
• Carnoustie, Scotland
Re: 2.5 vs 3 axis whats the difference
« Reply #1 on: November 03, 2014, 05:22:02 PM »
2.5D is where the X and Y can be commanded together in synchronisation but the Z can only be raised and lowered on its own.
3D is X Y and Z can all be synchronised
Mach can synchronise 6 axis.
Hood

ger21

• 6,292
Re: 2.5 vs 3 axis whats the difference
« Reply #2 on: November 03, 2014, 05:24:01 PM »
Yes, Mach3 can do up to 6 axis coordinated motion.

2.5D (or 2D) is when the Z axis first moves to cutting depth, then cutting occurs in the XY plane, with just the X and Y axis moving.

With 3D, all 3 axis move simultaneously.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
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mc

• 380
Re: 2.5 vs 3 axis whats the difference
« Reply #3 on: November 03, 2014, 06:31:08 PM »
My understanding of it is a 3-axis machine can only machine in 2.5D, as you can only ever machine the outline or to depth without repositioning the workpiece.

For true 3D machining, you require 5-axis or more, depending on what you're doing, so you can machine the workpiece from all directions.

Hood

• 25,838
• Carnoustie, Scotland
Re: 2.5 vs 3 axis whats the difference
« Reply #4 on: November 04, 2014, 04:57:20 PM »
A 3 axis machine can machine in 3D, plenty of videos on YouTube showing people carving female forms etc.

Hood

mc

• 380
Re: 2.5 vs 3 axis whats the difference
« Reply #5 on: November 04, 2014, 05:38:46 PM »
To me that's still 2.5D machining though.

Having just done a quick google for 2.5D machining, the first wikipedia link explains it pretty well - http://en.wikipedia.org/wiki/2.5D_(machining) and also mentions the difference between 2.5D machining and a 2.5D machine, which is what most likely causes the misunderstandings.

ger21

• 6,292
Re: 2.5 vs 3 axis whats the difference
« Reply #6 on: November 04, 2014, 06:20:54 PM »
At least you and the guy who wrote the Wikipedia article are on the same page.

In 20 years of CNC use, I've never hear 2.5D machining explained that way.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

JohnHaine

• 357
2.5 vs 3 axis whats the difference
« Reply #7 on: November 05, 2014, 03:55:03 PM »
I think the point he's making is that if you clamp something to the table and move the table in only xyz, you can't undercut the shape, which is kind of obvious really.  Clearly you could use a ball nose cutter and make a shape which is everywhere convex or concave wrt to x and y, but it couldn't be concave wrt to z if you see what I mean.  You could imagine a tool which is a bit like a tee slot cutter, but even them there would be limitations on undercut.  On the other hand if you could rotate the work around the x and y axes then undercut is obviously possible.

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rcaffin

• 1,035
Re: 2.5 vs 3 axis whats the difference
« Reply #8 on: November 07, 2014, 03:41:13 AM »
Quote
My understanding of it is a 3-axis machine can only machine in 2.5D
You can use what ever terminology you want: it's a free world.
But if you want other CNC users here to understand you, then you need to conform to the commonly accepted jargon. See what Hood wrote.

Quote
For true 3D machining, you require 5-axis or more, depending on what you're doing, so you can machine the workpiece from all directions.
I understand what you are saying, but that is not the generally accepted terminology.  See above.

Cheers
Roger