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§ 17

Chip thinning at small radial depth

Which tooth engagement should I programme at small side engagement?

Answer: When the milling cutter only goes a little into the side of the part (small ae), the chip becomes thinner than tooth feed fz. This is called chip thinning. If the chip is too thin, the cutter rubs instead of cutting and tool life falls. The calculator works out the actual maximum chip thickness hex at your fz and what fz you should programme to get the chip thickness the tool's datasheet recommends. It's everyday with trochoid milling and side milling in CAM.

Formula

hex = fz × √(1 − (1 − 2 × ae ÷ Dc)²), når ae < Dc ÷ 2

Ved ae ≥ Dc ÷ 2 er hex = fz (ingen udtynding)

Nødvendig fz = ønsket hex ÷ √(1 − (1 − 2 × ae ÷ Dc)²)

The formula applies an adjustment angle of 90° (end mill). With smaller κr the chip becomes even thinner

Symbols and units in the formula
SymbolMeaningUnit
dcCutter diameter Dcmm
aeRadial engagement aemm
fzProgrammed tooth feed fzmm/tand
hex_maalDesired max. chip thickness hex (data sheet)mm
=fz that gives desired chip thicknessmm/tand
=Actual max. chip thickness at programmed fzmm
=Thinning factor (fz ÷ hex)×
=Radial engagement in % of Dc%

Validity and source

Source
Sandvik Coromant fræseformler: hex = fz · √(1 − (1 − 2·ae/Dc)²) ved ae < Dc/2

Does not apply when

  • If you raise fz, Vf rises and so does the load on the machine. Check cutting power and the tool's maximum fz. The manufacturer's recommended hex for the cut is in the datasheet.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

  • Cutter diameter Dc12 mm
  • Radial engagement ae1.20 mm
  • Programmed tooth feed fz0.05 mm/tand
  • Desired max. chip thickness hex (data sheet)0.05 mm

Giver

  • fz that gives desired chip thickness0.083 mm/tand
  • Actual max. chip thickness at programmed fz0.0300 mm
  • Thinning factor (fz ÷ hex)1.67 ×
  • Radial engagement in % of Dc10 %

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Sådan bruger du den

Ved sidefræsning, slutsnit og trokoidefræsning går fræseren kun lidt ind i siden af emnet. Så bliver spånen tyndere end fz, og skæret gnider i stedet for at skære. Beregneren regner den fz, du skal programmere for at få den spåntykkelse, databladet anbefaler.

Step by step

  1. Indtast fræserens diameter Dc.
  2. Indtast det radiale indgreb ae fra CAM-strategien.
  3. Indtast den fz du har nu og den hex, databladet anbefaler.
  4. Programmér den beregnede fz, og tjek at Vf og effekt er i orden.

Typical errors

  • At glemme effekt og belastning.
  • At bruge ved ae over halv diameter.
  • At glemme κr.

Examples from everyday life

Sidefræsning med 10 % ae

Du sidefræser en kant i stål med en Ø12 mm fræser og ae 1,2 mm (10 %). Databladet anbefaler en spåntykkelse på 0,05 mm.

Cutter diameter Dc
12 mm
Radial engagement ae
1.2 mm
Programmed tooth feed fz
0.05 mm/tand
Desired max. chip thickness hex (data sheet)
0.05 mm

It means: Programmér fz 0.083 mm/tand. Med fz 0,05 er spånen kun 0.03 mm. Udtyndingsfaktoren er 1.67 ×.

Trokoidefræsning

En trokoidebane i CAM bruger en Ø10 mm fræser med ae 0,5 mm. Databladet anbefaler hex 0,04 mm.

Cutter diameter Dc
10 mm
Radial engagement ae
0.5 mm
Programmed tooth feed fz
0.04 mm/tand
Desired max. chip thickness hex (data sheet)
0.04 mm

It means: Programmér fz 0.092 mm/tand. Indgrebet er 5 % af diameteren.

Rule of thumb

Ved ae 10 % skal fz ca. ganges med 1,7.

How to check the answer

Ved ae = Dc ÷ 2 er faktoren 1.