Corner rounding toolpath

[memeryR2HAC]

I’m looking to round an exterior edge on an 6061 aluminum part with a 1/4” radius.

The cutting data for the HAAS tool I will probably get doesn’t explicitly say it but seems to be for cutting the radius with a single pass.

https://www.haascnc.com/content/dam/haascnc/ecommerce-assets/linedrawings/milling/corner-rounding-en...

I was looking at the cutting data for corner rounding tools at Harvery Tool and they are giving cutting data for zero stepover with multiple step downs or zero step down with multiple step overs interchangeably.  That would be easy enough to accomplish with a contour tool path.

They also have a chart giving the calculations to both step down and step over with each pass.  To accomplish this I think I would have to create a separate operation for each pass and manually enter an offset.  Am I right about that?

[memeryR2HAC]

https://harveyperformance.widen.net/content/cuysefsxro/pdf/SF_21000.pdf?u=d9orjt

[memeryR2HAC]

I misread, I think the table is giving a breakdown of the engagement each pass when taking passes that either step down or step over.

[memeryR2HAC]

Okay, so with the HAAS cutting data, as I understand it.  I set the tool up like this and get a single pass tool path at 7 ipm that takes 51 seconds.

[memeryR2HAC]

Keeping the rpms the same because the tool is cobalt but using the Harvey data as a guide to guess at a two pass toolpath I set the stepdown to corner radius *.7 and increased the ipt to .0024 increasing the feed to 11 ipm I get a two pass two path that takes a minute and 5 seconds.

Right now I’ve got it setup to use the single pass strategy on one end and the 2 pass strategy on the other for comparison but I’d love to get feedback from anyone with experience with corner rounding.  Do my setups seem reasonable?

Also I’ve changed my horizontal lead in to zero degrees.  I’m thinking I should do the same for vertical to give myself some margin for error in chucking the stock up in the vise.

[programming2C78B · Accepted solution]

You can cut the rad in one go, start with 500sfm and .0015 fpt 

[memeryR2HAC]

thank you,

so 500 sfm would be at an effective diameter of .625 (tip diameter + radius)—> 3056 rpms?

The default calculation for surface speed in fusion is using tip diameter which would give the surface speed at the slowest part of the cutter

[programming2C78B]

Yes at the widest point. This is just a starting point and can easily be doubled. 

[memeryR2HAC]

Well, I think you answered my question.   I adjusted the cutting speed as suggested on the single pass tool path and the multi-pass tool path on the other and will cut them both for comparisons sake.  I almost wonder if I could cut this on a benchtop router but I don’t have a benchtop router so we don’t have to worry about me getting too experimental.

I’ve got the HAAS tool ordered.  When cut this I’ll video and post results.

[memeryR2HAC]

I have another part that has 3/8” radius edges.  Assuming things go well with the HASS tool on the 1/4” radius corners they have the 3/8” version of the same tool which would be a top contender but I also see a lot of 3&3/4” - 4&1/4” shell mill type cutters for 3/8 corner rounding.  I’m assuming as the radius gets bigger the shell mill cutter becomes the better option.  Any experience with this/input on if and at what point to make the switchover?

[programming2C78B]

Ive never heard of a shell mill used for corner treatment. Stick with a 4fl endmill style tool.