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Ramp Vs Spiral Vs Plung Lead-in Technique

Boswell

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#1
I would like to hear opinions on the use of RAMP, SPIRAL and PLUNG as lead-in to interior pockets. I have almost exclusively used the Spiral technique mostly due to small pockets with limited space but recently I have been working on parts with large interior pockets and started wondering what advantage (if any) using a Ramp technique would have. Plung does not seem very practical unless there is no choice because it is so hard to clear the chips from the cutter. Plung might make more sense if I had a high velocity flood coolant delivered through the tool but I only use a Fog Buster type.

Thanks for your thoughts on this?
 

T Bredehoft

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#2
I used a spiral ramp, leaving stock on the side of the "bore,", then changed the cutter diameter for a final pass. I'd written sub-routines for these where I just filled in depth of finish cut diameter and tool no.
 

TomS

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#3
I u
I would like to hear opinions on the use of RAMP, SPIRAL and PLUNG as lead-in to interior pockets. I have almost exclusively used the Spiral technique mostly due to small pockets with limited space but recently I have been working on parts with large interior pockets and started wondering what advantage (if any) using a Ramp technique would have. Plung does not seem very practical unless there is no choice because it is so hard to clear the chips from the cutter. Plung might make more sense if I had a high velocity flood coolant delivered through the tool but I only use a Fog Buster type.

Thanks for your thoughts on this?
I have used ramping only because my CAM program (D2NC) won't do it any other way. It works OK but there have been instances where I would have liked to have a choice. Just bought CamBam and still learning what it can do. It has spiral, tangent and plunge pocketing and profile capability. I really like the tangent option. It allows you to set a lead out radius rather than having to manually tweak the code to run the cutter off the end of the part. I avoid plunging if at all possible for the reasons you gave and also because it's hard on the cutter.

Tom S.
 

Boswell

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#4
thanks. I should say that I have been using BobCad for a while now and overall have been very happy with it as a CAM system. Not so much as a CAD system though and still use Autocad for drawing. For profiling, where I can approach the work from the side, BobCad also allows me a number of options.
 

JimDawson

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#5
I avoid plunging if at all possible for the reasons you gave and also because it's hard on the cutter.
When I have to plunge in a pocket, I normally drill a hole where the plunge will occur. Normally the first operation is to drill all the holes in the work, so this doesn't require an extra operation. Generate the tool path first, then add a circle at the cut start point(s), put it in the drill operation, and regenerate the tool paths. Where possible, set up a plunge off of the part, cutting air is really easy on the tool.;)

I also have CamBam and have found it to be very flexible and easy to torture it into doing things my way. Been using it for about 4 years. Slowly transitioning to Fusion360, but it's painful for me. No problem using the CAM functionality, but I'm having a hard time getting my head around 3D modeling.:confused:
 

RJSakowski

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#6
The problem that I see with plunging is that the end mill is least efficient at cutting at its center because of the the zero cutting radius. Either ramping or spiraling in eliminates the problem. Spiraling is simply ramping in a circle. They are essentially equivalent in their effect. Which one I use depends on the part. I would use a ramp for cutting a slot and spiral for circular pockets.

One advantage of a spiral is you are not cutting full depth sidewalls simultaneously as you ramp in.

In cases where I cannot use either a ramp or spiral entry, I will pre-drill a pilot hole to eliminate the cutting at zero cutting radius.
 

Boswell

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#7
When machining an internal pocket that is large enough that both a Spiral and a Ramp approach will fit the space is there any advantage to one over the other? Is one faster or easier on the tool?

RJ, good point about a spiral entry will never result in a full depth full slot cut where at the end of a ramp this will be true.
 

tmarks11

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#8
Ramp or Spiral will make your endmill last longer.

As RJ said, when plunging you are engaging the material near the center of the endmill with it turning at sub-optimum speeds, leading to excessive wear.

I would say spiral is better for tool life than a ramp, simply because it generally would result in better chip clearance, which could result in less re-cutting of chips. Maybe your flood coolant solves that, maybe not.
 

Metal

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#9
when you are ramping you are also cutting with more of the tool so you can go a little faster.
fusion 360 also has a "profile ramp" which cuts roughly the shape of the final pocket's shape as part of the ramp which I use since it is less finicky about setting the ramp diameter correctly.
 

Boswell

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#10
When I was using CAMBAM it also would ramp on the profile shape external or internal I used this more than Sprial. But when I switched to BobCad the RAMP entry just seems to go in a straight line although there might be more config options I have not figured out yet.
 
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