Machining question

[bigseb]

Here's one for my fellow CNC'ers: What roughing strategy do you use? Specifically do you use trochoidial roughing and what do think think are the pros and cons of trochoidial roughing over traditional roughing?

 

[Lew_Merrick]

Hi Sebastian -- Ity has been more than 20 years since I have performed roughing operations that do not fall into the trivial category. Back then my favored approach was to "drill out" material using as large a carbide drill as would "fit" in the "opening" (such that I could get at least 3 holes in any direction) drilling them out on 1.125 X Drill Size on 45° patterns -- and then cleaning up the "points" using a "corncob roughing mill." It actually worked quite well in 17-5PH/H600 material. does this help at all?

 

[bigseb]

Hi Sebastian -- Ity has been more than 20 years since I have performed roughing operations that do not fall into the trivial category. Back then my favored approach was to "drill out" material using as large a carbide drill as would "fit" in the "opening" (such that I could get at least 3 holes in any direction) drilling them out on 1.125 X Drill Size on 45° patterns -- and then cleaning up the "points" using a "corncob roughing mill." It actually worked quite well in 17-5PH/H600 material. does this help at all?

Not really, but appreciate the reply.

 

[Alexander]

Here's one for my fellow CNC'ers: What roughing strategy do you use? Specifically do you use trochoidial roughing and what do think think are the pros and cons of trochoidial roughing over traditional roughing?

Hi Seb,
I use Estlecam for my CNC router which has Trichoidial settings and works great on aluminium roughing. Have a look at this:

 

[bigseb]

Thats interesting, especially the bit about lower cutting forces. I had always believed that due to the larger stepdown the radial forces on the spindle bearings would be far higher than with traditional milling.

I have used trochoidial milling for the first time today. While it is much faster than traditional (2 hours vs 7 hours) I can't help but think that the setup isn't right for this strategy. The machines have HSK40 spindles so the tool's taper is only about 25mm long while the tool overhang is about 120mm. Not great for stability in my opinion. Factor in the high radial forces and ceramic bearings and it seems like a breakdown waiting to happen. On the other hand the cutting times are massively shorter. And colleagues that have been here longer are using it without any hassles, for now.

 

[Alexander]

My router is not particularly stiff so when cutting aluminium with typical method my maximum DOC is 0.5mm but with Trochoidial I can use a 5mm DOC.
I guess it's due to the cutter contact length being less than half of linear milling and the radial toolpath reducing forces.

 

[dwc]

For my mini brass parts in watchmaking things may look different, but I use trochoidal as much as possible to be faster and see a big difference in tool life.

 

[RCH_Projects]

Well - I am actually using a cheap mini-mill designed for engraving to coax out a prototype from crystal clear acrylic, 3-6mm thick.

I keep everything low and slow - like emptying a bathtub with a straw (it is disgusting, but works).

But I start with leveling a cutting board. Trochoidal cutting with shallow but large (sweeps) with a 3mm tool lets me finish a good quality board in one night - without wearing anything out - yet.