Trochoidal milling is a machining technology that uses spiral movements to create pockets with a width (Lc) greater than the cutter diameter (d). Trochoidal milling allows a strong increase in cutting speed (Vt) and feed rate (Vf), high working depths (ap) and low radial use values (ae). Other points of strengths are: - Increased tool life
- Reduction in cutting forces - Reduction in heat generated - Use of the same tool for slots of different widths - Reduction in working time In order to make the best use of this technique it is necessary to consider the following basic rules: - Maximum cutter diameter: d ≤ 70% of the slot width (Lc)
- Increment of pass: w ≤ 10% d - Maximum radial cut: ae ≤ 20% d
It is important to know that the feed rate at the tool centre (Vf) is different to the feed rate at the periphery (Vfm). If the feed rate is programmed with respect to the tool centre, it can be calculated using the following formulae:
D vf d
x V fm
D vf = L c - d
V f =
V fm = n x f z x z
FORMULE - FORMULAS
d • π • n 1000
z = n° denti - n° flutes d = diametro frese - End mill’s diameter
V C =
Vc = velocità di taglio m/min - cutting speed m/min Vf = avanzamento mm/min (F) - feed mm/min (F) n = numero giri/min (S) - RPM (S) fz = avanzamento per dente - feed x tooth fn = avanzamento al giro - feed mm x rotation
d
V c • 1000 d • π
n =
Vf = fz • n • z fn = fz • z
a e = profondità radiale di passata - radial depth of cut a p = profondità assiale di passata - axial depth of cut Q = volume di truciolatura cm 3 /min - material removal rate cm 3 /min
ae
a p • a e • v f 1000
Vf n
Q =
fn =
d = diametro fresa - End mills diameter d e = Diametro effettivo di taglio (mm) - Effective diameter of cutting (mm) V e = Velocità di taglio effettiva (m/min) - Effective cutting speed (m/min) a p = profondità assiale di passata - axial depth of cut n = n° giri del mandrino (giri/min) - RPM (S)
d e = 2 a p (d - a p )
d
n • π • d e 1000 V e • 1000 d • π
V e =
a p
n =
d e
325
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