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Everything related to numerical metal cutting theory

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Numbers Behind High Speed Machining (HSM)

May 28, 2013, 8:01 am by Eldar Gerfanov

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 toolpaths. 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.

Radial Engagement vs chip thinning factor
100%             

1.0

50% 1.0
30% 1.091
25% 1.212

 

20% 1.641
15% 2.1
10% 4.375
5% 6.882

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 Engagement_Angle-Chip Thinning.PNG HSMAdvisor Screenshot 0.750in 4FL Carbide TiAlN coated Solid HP End Mill.JPG

Plunging and Ramping Recomendations and Techniques

February 12, 2013, 2:03 pm by Eldar Gerfanov

Quite often in order to start cutting in x-y direction you need to first plunge into the material.

Here is a compliled list of recommendations for different kinds of plunging that works in most if not all cases.

Plunge with center cutting endmill:

  • Regular Chipload/Number of flutes , half the cutting speed. (for 3 flute endmill divide normal chipload by 3)

Ramp:

  • Ramp Radius (For Helical ramping): .90-.95 of cutter radius
  • Ramp Angle: Indexed/non center cutting endmills: 1-2.5 degree; Center cutting endmills- Up to 45 deg

Ramp chipload ajustment for 4 flute Center cutting endmills:

  • 0-2.5deg=100% of normal feedrate
  • 2.5-5deg=75% of normal feedrate
  • 5-15deg=50% of normal feedrate
  • 15-30deg=25% of normal feedrate
  • 30-45deg=5% of normal feedrate

Dont forget to reduce cutting speed for ramping above 5deg by half!


Calculating Tool Engagement Angle, Radial Depth of Cut

August 18, 2012, 12:14 pm by Eldar Gerfanov

Here i will show you how to calculate Tool Engagement Angle using tool diameter and Width Of Cut (radial deopth of cut)

Lets first draw a pretty image that shows us everything we need.

Where:

  • r: Radius of the cutter = Diamater /2
  • a: TEA - Enagagement angle we are trying to find here
  • WOC: Width of cut or RADIAL Depth of Cut
  • r2: The difference between r and WOC, r=r2+WOC

 

Below we develop 2 formulas that allow us to find TEA and WOC

Read More 


General Speeds and Feeds Formulas

December 24, 2010, 3:10 pm by Eldar Gerfanov

Here are basic formulas to get you going. Learn formulas to find put Spindle Speed and Feed rate for your application.

RPM= 12 x SFM or   RPM= 4 x SFM
 
3.14 x Diameter Diameter

FR=RPM x T x CL

Read More 


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