HSM or High Speed Machining is becoming more and more popular each day.
Many of us have seen those youtube videos where endmlls remove large amounts of material at high speeds/feeds.

While definitions of HSM may vary between tool manufacturers and even individual shops, the physics behind it remain the same.

In this article i would like to explore flat endmills.

HSM is not about ramping up your speed/feed overrides to 200% and puling out your smartphone to record another youtube-worth video.

What is HSM?

HSM is a complex of programming, machining and tooling techniques aimed at radical increase of productivity.

Programming

The cornerstone of HSM is low radial and high axial engagement of an endmill with the workpiece.

There are many CAD/CAM systems that allow you to create HSM tool-paths. Mastercam's Dynamic milling and SurfCAM's Truemill are some of them.

When radial cutter engagement with the material is smaller than the radius of the tool an interesting thing happens.
Chip load- the distance the tool advances per cutter revolution per tooth- does not equal the actual chip thickness anymore.
Chip thinning mainly happens at radial engagements below 30% of the diameter.

In order to get compensated chipload you need to multiply recommended by manufacturer chipload by the chip thinning factor.

Usual Radial Engagement for HSM toolpaths however is between 5 and 15%.

Axial depth of cut varies depending on geometry, but Read More 

Radial Chip Thinning HSMAdvisor Screenshot

Sevaral weeks ago i saw a post on CNCZone.

A HSMadvisor user Peter Neil used it to calculate cutting conditions for cutting a block of pre-hardened stainless steel.
His machine was Tormach.

Here is an exact copy-paste from that forum post:
_____________________________________________________________________________________

Did a test cut on the Tormach today using feeds & speeds from the latest version of the excellent HSM advisor.
To make it interesting, I did the cut using some 1.2085 pre-hard Stainless Steel as I have plenty of stock of it and have a job in mind for this, and wanted to see how it cut on the Tormach.
The material is like a stainless P20, at 16% Chrome/1% Nickel & 0.5% Sulphur (which makes it slightly free-er machining) and is hardened to around 33-35 Rockwell C, so I used the HSM advisor guidelines for machining P20 rather than Stainless. Cutter was a 10mm 4-flute Carbide TiAlN coated EM.

So...... ticking the HSM/Chip thinning option I got a speed of 5120 and feed of 2214mm/minute( 87 IPM). I used a DOC of 10mm and WOC of 0.5mm/0.020" - and turned off the flood cooling to machine it completely dry. The finish pass on the 1st level was 15mm DOC and 0.5mm WOC and slightly lower speeds/feeds.

Loaded up a 40mm x 63mm block , pressed the start button, and it went from this....





...to this!

Read More 

If you are finishing a pocket with wall corners' radius close to the radius of a cutter. The tool tends to chatter, especially with longer tools and harder materials.

To avoid this you can do one of the following:

• When programming. After roughing the pocket and before finishing. Create a simple drill cycle with finishing tool to remove extra material from the corner. This way when finisher goes to the tight corner, the chatter will virtually disappear.
• Do the same with a drillbit. Before Roughing.