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kunfuzed

Does Mcam do this? (Arc feed adjustment)

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I wrote a Thread about this a couple years ago, and shared some code I started to develop to calculate an "arc correction factor". I even created some code to 'linearize the arc, and output a new feedrate on each line segment (of the converted arc), to "accelerate or decelerate" from/to the cut.

Since then, Mastercam has added "Arc Feedrate Adjustment" functions to the Line/Arc Filter for Contour. This works pretty good, as it tries to adjust "internal arcs" with a slower feedrate, and "external arcs" with a faster feed. All in the name of trying to keep the peripheral cutting speed constant.

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here is one of the best options currently, not available in all toolpaths

 

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18 hours ago, JoshC said:

here is one of the best options currently, not available in all toolpaths

 

How do you calculate the feed for the percentage box? I see in his article it said 50% up for outer & 50% down for inner. 

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Just now, CNCZACK said:

How do you calculate the feed for the percentage box? I see in his article it said 50% up for outer & 50% down for inner. 

In this box you just allow maximum decrease feed.

You can type 99% decrease of your cutting feed, Mastercam will calculate it by formula.

I don't really know which formula they use, it could be same as per Sandvik book or the formula that shows in video HAAS Tip of the day:

 

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On 4/2/2021 at 1:20 PM, CNCZACK said:

How do you calculate the feed for the percentage box? I see in his article it said 50% up for outer & 50% down for inner. 

You just enter the maximum you want it  to decrease or increase, so you dont need to worry about the % if you use the inch value to the right of the % field. 

Like if im running at 10ipm and i don't want it going any slower than 5ipm in corners than my min feed would be 5ipm, the software will use an industry standard formula to adjust the feed while never leaving your min/max feed rate range applied on that page. so you can use whatever % you want but the way i wrap my head around those fields is what is the slowest and fastest i ever want the tool to go, its going to use an formula no matter what, your just setting the slowest and fastest its able to go when making feed rate adjustments. i hope that makes sense

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For those seeing this that work in the multiaxis world, there's an entire options page for surface radius based feedrate adjustment to achieve similar results:

1636789653_SurfaceRadius.thumb.jpg.279b8be41b29c3b3b14f2813424c0ee3.jpg

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On 4/1/2021 at 1:41 PM, Colin Gilchrist said:

I wrote a Thread about this a couple years ago, and shared some code I started to develop to calculate an "arc correction factor". I even created some code to 'linearize the arc, and output a new feedrate on each line segment (of the converted arc), to "accelerate or decelerate" from/to the cut.

Since then, Mastercam has added "Arc Feedrate Adjustment" functions to the Line/Arc Filter for Contour. This works pretty good, as it tries to adjust "internal arcs" with a slower feedrate, and "external arcs" with a faster feed. All in the name of trying to keep the peripheral cutting speed constant.

Thanks Colin!

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Is this something you guys use often?   When I first started programming I was taught that slowing down in corners was an "old school thing" and there really wasn't much need for it, aside from interpolating a hole that is close to the size of your tool, so I've never used it.

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11 hours ago, JB7280 said:

Is this something you guys use often?   When I first started programming I was taught that slowing down in corners was an "old school thing" and there really wasn't much need for it, aside from interpolating a hole that is close to the size of your tool, so I've never used it.

Its very important to  adjust your feed rate when doing thread milling

Factory feeds and speeds are driving the c/l of the tool and that can be 2 or 300% too fast when you are threadmilling

with a tool near the finished size

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42 minutes ago, gcode said:

Its very important to do adjust your feed rate when doing thread milling

Factory feeds and speeds are driving the c/l of the tool and that can be 2 or 300% too fast when you are threadmilling

with a tool near the finished size

Yes, I should have mentioned, I also adjust when I'm threadmilling.  I use the formula on Harvey's website.

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I think this needs to be added to Dynamic Mill at the very least, but ya, it should be included in the milling holemaking cycles as well.

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8 minutes ago, mwearne said:

I think this needs to be added to Dynamic Mill at the very least, but ya, it should be included in the milling holemaking cycles as well.

I BELIEVE the RCTF checkbox takes care of this, but I could be wrong on that, as I don't use it.

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On 5/6/2021 at 1:06 PM, JB7280 said:

I BELIEVE the RCTF checkbox takes care of this, but I could be wrong on that, as I don't use it.

Nah, RCTF does a calculation that increases the feed based on the desired chipload and stepover. It assumes your chipload is at 50%, if you specify a stepover smaller it will increase the resulting feedrate to maintain this chip thickness. What I would like to see is a feedrate that adjusts during the toolpath based on the peripheral of the tool, not centerline.

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