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Forum topic by badcrayon posted 02-03-2018 08:44 PM 1555 views 0 times favorited 6 replies Add to Favorites Watch
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badcrayon

38 posts in 1936 days


02-03-2018 08:44 PM

Topic tags/keywords: new cnc

I have finally saved enough to buy my first CNC (budget 2k + or – 500). I am a little confused by the description of 2.5D and 3D machines . Most of my work involves making wooden jewelry so my pieces are small so a large machine is not necessary. The units I have been looking at are the Shapeoko,Xcarve, or the Piranha but I want to be doing 3D carving . I’m looking for someone that is carving with one of these machines not making 2D parts to ask questions to. My background is in 3D animation so the software and modeling I’m not concerned with just the machines ability’s. Plus is my budget realistic and should I be looking at any other machines?

-- Bad Crayon Studio


6 replies so far

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John Smith

1308 posts in 278 days


#1 posted 02-03-2018 10:20 PM

#1 – would be to contact any of the CNC companies you are sincerely interested in
to see if they have product videos and sales brochures to send you (for free).
the cheap introductory price may only include the machine and not the software
that has to go with it – then the support tools and carving bits.
when you get it all bundled together – it could go way, way past your budget.

can you possibly attend any trade shows in your area that would
advertise such machines ? Sign Shows in particular always have
a vast selection of CNC carving systems for different applications.
this is not “just another tool” that you are looking for.
it is an investment that will help your hobby be financially rewarding.
$2 – 5k is a realistic price for a decent machine with the software that you need.

-- some people are like a Slinky - - - pretty much good for nothing. But still make you smile when you push them down a flight of stairs.

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Lazyman

2384 posts in 1503 days


#2 posted 02-03-2018 11:04 PM

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.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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CaptainSkully

1601 posts in 3674 days


#3 posted 02-05-2018 04:54 PM

My suggestion is that you join the X-Carve forum and post your question and an image you’d like make and get some feedback from members there. Or you could post a pic here since there are several X-Carvers here too. There is a difference between 2.5D and 3D but it may not apply to your designs. Are you going to be making molds out of a plug that you carve?

The good news is that the money you’ve set aside for this project should be quite sufficient for a small, accurate machine that will fit your needs. Good luck with your journey and keep us posted.

-- You can't control the wind, but you can trim your sails

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bbasiaga

1240 posts in 2110 days


#4 posted 02-05-2018 06:20 PM

2.5 axis can set a cut depth, then move in X and Y directions to make a shape. Like carving a letter. The cut , or Z height remains the same for the whole move.

A 3 axis can move Z, cut depth, Continuously as it moves in X and Y.

Both types can achieve many of the same designs. There are features that ponly a 3axis can do. You’ll need to search around to see some examples. The only direct example I can think of now was when I machined a gear out of plastic that had a done shaped center hub. On the go fishing passes, the machine moved in X Y and Z to trace the exact curve of the shape and leave a nice surface. It did this by going left to right, and top to bottom (picture the gear sitting in the table being cut) to make the dome.

A 2.5 axis machine would only have been able to make a pass at the top of the dome, then step out and do the next layer slightly lower, etc, until it reached the bottom layer. The result would have been like stacking disks to get the shape, as opposed to really carving out the shape. Follow?

Both methods can work. With the right tool selection and stepovers on your passes it can even look dry similar. But the cost in the end is time and/or quality.

There are other cuts that a 3axis can make as well. Like an included sloped groove. This would be hard to do it impossible with the layered approach. Look around online for better examples. I hope this helped some.

Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

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ArtMann

1041 posts in 931 days


#5 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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oldnovice

7115 posts in 3483 days


#6 posted 02-06-2018 08:25 AM

ArtMann is correct about 2.5D and 3D.
Even ramping into a cut will typically involve more than just one axes.

-- "I never met a board I didn't like!"

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