Reply by ArtMann

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Posted on I’m looking to buy a small format CNC

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1483 posts in 1699 days

#1 posted 02-06-2018 04:26 AM

I’m sorry but you are mistaken about the meaning of 2.5-D and 3-D. Either mode requires that the bit be moving in the X, Y, and Z directions simultaneously. 2.5-D is one of those things that is difficult to explain until you see it and then it is perfectly obvious. It makes use of a V shaped bit to vary the width of cut and the depth of cut at the same time. It is used to produce 3-D like text and graphics without requiring a 3-D model. True 3-D is usually cut with a ball nose bit and the shape is created by a series of many, many straight line passes while varying the depth of cut. After each pass, the bit is advanced a tiny bit. The lines are so close together that they create a smooth surface. Watching videos of these techniques will provide a better explanation than anything I can say. There are thousands of these on Youtube.

I am just in the process of researching CNC myself but my understanding of the difference between 2.5D and 3D is that 2.5 can control any 2 axis at once and 3D can control 3 axis at once. I think that both the machine and the software that creates the tool paths both have to be able to handle that. Both can achieve a 3D relief carving so I am not sure under what circumstances or types of cuts a 3D machine would be better.

Your best bet may be to find one of the stores that can demo the machines you are interested in. Describe what you want to do and see if they can show you an example. My Rockler store has a demo every now and then and they have examples of their results on display.

- Lazyman

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