Problems with pockets...

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RHince
Posts: 1
Joined: Wed Sep 03, 2008 8:40 pm

Problems with pockets...

Post by RHince »

Hello all, this is my first post on the forum, I wonder if anyone can help me with a bit of advice. I searched for similar discussions but can't find anything specific to this issue.

I'm trying to get the best possible finish and accuracy with pockets. I'm using Cut2D and milling parts out of aluminium, and attempting to get the best finish and accuracy possible. I've determined by experimentation that (from an aesthetic point of view) rastering is better for pocketing.

The problem I'm having though is that if I use the 'profile last' option, the pocket cuts reasonably OK but leaves a few tooling marks here and there which I'm trying to reduce to a minimum. So I tried 'profile first', and when the raster is carried out I end up with a series of vertical ridges around the edge of the pocket - much, much worse. It's almost as if the tool has cut past the edge of the originally cut profile in fact.

In both cases the machining accuracy is also questionable, not something I've had so far with this particular machine, and is puzzling me.

To cut this I am using a 1/8th* [3.175mm, this is how it's described to Cut2D] end mill with about 40% stepover - I appreciate this is quite large by the way - a feed rate of 250mm/min, a rotational speed of around 20,000 rpm, and pass depth of 0.8mm. The machine runs Mach3.

The actual surface of the pocket floor is quite pleasing; it's edges I'm having problems with! Any advice gratefully received!



* Why not metric you ask? Well it's because my laser alignment tool has a 1/4" shank, and I don't need to change collets when using imperial tooling :-)

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RoutnAbout
Vectric Wizard
Posts: 2085
Joined: Mon Sep 19, 2005 11:09 pm
Model of CNC Machine: 24x18 Desktop
Location: North Manchester, Indiana

Post by RoutnAbout »

RHince, Welcome to the forum.
The tool your using... is it an actual endmill or one of those rotozip tools? The reason I ask is because the Rotozip tools are made out of softer steel that industrial tooling, and will flex more.

I'd also try to slow the spindle speed down and change the direction of the last profile cut.
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