Raster climb angle

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Janettx
Posts: 14
Joined: Sun Apr 02, 2017 9:46 am

Raster climb angle

Post by Janettx »

When using the the pocket tool path and choosing raster-climb instead of off set, what would the raster angle be on a straight trim bit? And what is pocket allowance?
TIA,
Janet

sharkcutup
Posts: 408
Joined: Tue Mar 08, 2016 5:23 pm

Re: Raster climb angle

Post by sharkcutup »

When using the the pocket tool path and choosing raster-climb instead of off set, what would the raster angle be on a straight trim bit? And what is pocket allowance?
That would depend on a number of factors such as depth of pocket, raster with or against the wood grain (assuming you are carving wood), pocket bottom smoothness, whether it is a pocket just for clearance to another carving feature or an actual featured pocket as in a text on text sign, and if you are trying to avoid tear out within a pockets perimeter, etc...

Too many unknown details to provide a sufficient answer to your first question! Sorry!

Pocket Allowance
It is used to leave material on the perimeter of a pocket for a cleanup pass. It is often handy to ensure a clean surface perimeter after roughing out the pocket.

Have a NICE DAY!!! :)

Be SAFE around those AWESOME machines!!! ;)

Sharkcutup
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Rando
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Re: Raster climb angle

Post by Rando »

Janettx wrote:When using the the pocket tool path and choosing raster-climb instead of off set, what would the raster angle be on a straight trim bit? And what is pocket allowance?
TIA,
Janet
The simplest way to describe the raster angle isn't about the bit, it's about the raster. A raster is a set of closely-spaced, parallel lines of carving. If you only use one pass, very often there will be "scalloping" in the carving, as rasters are often done with ballnose endmills to achieve nice smooth surfaces. To get rid of that scalloping, people typically add a second raster toolpath, where the new parallel lines are at an angle from the first set. Most people use two of them, offset by 90-degrees. I suppose if you have infinite time, three passes (60-degree offsets) might produce a slightly smoother surface, but sanding will get you there quicker in most cases, unless it's the fine detail you're trying to preserve.

Okay, so now you know that the angle **IS**....now, how you choose it. Let's say you're carving on a piece of wood where the grain of the wood is sitting roughly parallel to the t-slots in the bed of the CNC. Depending on the wood, the bit, the cut depth and a small set of other parameters, you might find that cutting one set parallel to the grain produces more strings, and so you might want to do the first pass at 45-degrees, and then the second pass at 135 (45 + 90). No matter how the "best" cut is made, that first pass will get your angle, and then the next one(s) will get that start angle PLUS the offset between them.

Hope that makes sense.

And, Sharkcutup's description of the Pocket Allowance is correct. I'm not sure in Vectric whether that value affects both the sides AND the bottom, or just the sides....yeah, I think in Vectric it's just the sides. I mostly use BobCAD, where you can separately set the margin/allowance for the bottom and sides. Either way, it's what you leave on for that final, smoooooth-as-silk finishing pass.

Regards,

Thom
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