Academic Edi o : Raul D. S.
G. Campilho
Recei ed: 24 Janua y 2025
Re ised: 25 Feb ua y 2025
Accep ed: 27 Feb ua y 2025
Published: 1 Ma ch 2025
Ci a ion: Ga cia-Llamas, E.; Rami ez,
G.; Fuen es, M.; Vidales, E.; Pujan e, J.
Explo ing Pos -Machining
Al e na i es Unde D y Condi ions o
Thin-Walled Addi i e Manu ac u ing
Componen s Aided by In a ed
The mog aphy. P ocesses 2025,13, 717.
h ps://doi.o g/10.3390/
p 13030717
Copy igh : © 2025 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license
(h ps://c ea i ecommons.o g/
licenses/by/4.0/).
A icle
Explo ing Pos -Machining Al e na i es Unde D y Condi ions
o Thin-Walled Addi i e Manu ac u ing Componen s Aided
by In a ed The mog aphy
Edua d Ga cia-Llamas 1,* , Giselle Rami ez 2,* , Miguel Fuen es 3, Edua d Vidales 1and Jaume Pujan e 1
1Eu eca , Cen e Tecnològic de Ca alunya, Uni o Me allic and Ce amic Ma e ials, Plaça de la Ciència, 2,
08243 Man esa, Spain; edua d. idales@eu eca .o g (E.V.); [email p o ec ed]g (J.P.)
2CIEFMA, Cen e o Resea ch in S uc u al In eg i y, Reliabili y and Mic omechanics o Ma e ials,
Depa men o Ma e ials Science and Enginee ing, Uni e si a Poli ècnica de Ca alunya, Campus Diagonal
Besòs-EEBE, 08019 Ba celona, Spain
3GSC, G upo Se illa Con ol o Se illa Con ol G oup, C/Manganeso, 2–P.I. Calonge–Se illa,
41007 Se illa, Spain; [email p o ec ed]
*Co espondence: edua d.ga cia@eu eca .o g (E.G.-L.); giselle. ami [email p o ec ed] (G.R.);
Tel.: +34-938-777-373 (E.G.-L.); +34-934-137-400 (ex . 23382) (G.R.)
Abs ac : Addi i e manu ac u ing (AM) echniques ha e ans o med he p oduc ion o
pa s and componen s wi h in ica e geome ies and cus omized designs, d i ing inno-
a ion in sus ainable manu ac u ing p ac ices. The addi i e manu ac u ing echnology
used in his wo k was selec i e lase mel ing (SLM), a p ocess ha uses lase ene gy o
sin e powde ed me als in o solid s uc u es. Among he a ious ma e ials u ilized in
AM, Ti6Al4V i anium alloys a e o pa icula in e es due o hei a o able mechanical
p ope ies, co osion esis ance, biocompa ibili y, and po en ial o educing ma e ial was e.
Howe e , he machining o addi i ely manu ac u ed i anium pa s p esen s challenges
due o he ma e ial’s low conduc i i y, elas ic modulus, and chemical a ini y wi h cu ing
ools, which impac ool wea and su ace inish quali y. Milling, a commonly employed
p ocess o inishing i anium pa s, o en in ol es signi ican ene gy use and ool wea ,
highligh ing he need o op imized and eco-conscious machining s a egies. This s udy
aims o es ablish co ela ions among ou key aspec s: (1) su ace inish o machined
Ti6Al4V AM pa s, (2) cu ing ool damage, (3) d y milling pa ame e s including di e en
cu ing ools, and (4) a ia ion o empe a u e a he con ac su ace o AM pa s and ools
using in a ed he mog aphy. By examining pa ame e s such as eed pe oo h (Fz), axial
dep h o cu (Ap), spindle ajec o ies ( ochoidal, helicoidal, and linea ), and cu ing ool
diame e s, his wo k iden i ies condi ions ha enhance p ocess e iciency while educing
en i onmen al impac . In a ed he mog aphy p o ides insigh s in o empe a u e a ia-
ions du ing milling, co ela ing hese changes o su ace oughness and c i ical machining
pa ame e s, hus con ibu ing o he de elopmen o sus ainable and high-pe o mance
manu ac u ing p ac ices.
Keywo ds: sus ainable machining; addi i e manu ac u ing; Ti6Al4V alloy; selec i e lase
mel ing (SLM); in a ed he mog aphy
1. In oduc ion
Ti-6Al-4V alloy and i s a ia ions a e ex ensi ely u ilized in indus ial applica ions,
including ae ospace, biomedical, and ene gy sec o s, due o hei excep ional pe o mance
cha ac e is ics. These a ibu es include excellen co osion esis ance, a high s eng h-
o-weigh a io, supe io s eng h e en ion a ele a ed empe a u es, and ou s anding
P ocesses 2025,13, 717 h ps://doi.o g/10.3390/p 13030717
P ocesses 2025,13, 717 2 o 18
biological compa ibili y [
1
]. Addi ionally, i s high po en ial o ma e ial e iciency and
was e educ ion makes Ti-6Al-4V an a ac i e ma e ial in indus ies s i ing o mee
sus ainabili y goals. As a esul , he demand o Ti-6Al-4V has signi ican ly inc eased in
sec o s like ae ospace, whe e weigh sa ings and e iciency a e pa amoun [2].
Addi i e manu ac u ing (AM) has eme ged as a ans o ma i e echnology in hese
sec o s, pa icula ly due o i s abili y o ab ica e hin-walled and complex-shaped compo-
nen s wi h nea -ne -shape ea u es. This capabili y signi ican ly educes ma e ial was e,
making AM a iable solu ion o manu ac u ing high-pe o mance ma e ials such as i a-
nium alloys while minimizing en i onmen al impac and p oduc ion cos s [
3
,
4
]. Howe e ,
AM componen s o en p esen poo su ace quali y, which is a c i ical conce n o pa s
subjec ed o complex loading condi ions, including con ac a igue and sliding wea . In
such cases, pos -machining ope a ions a e essen ial bu become pa icula ly challenging
when p ocessing hin-walled su aces [5].
Milling is a widely used pos -machining me hod o p ocessing hin-walled addi i e
manu ac u ing (AM) pa s. Howe e , when componen s a e made om ma e ials clas-
si ied as “di icul - o-cu ”, he cu ing p ocess becomes mo e complex. Ti anium alloys,
such as Ti-6Al-4V, all in o his ca ego y due o hei high chemical eac i i y and poo
he mal conduc i i y [
1
,
6
,
7
]. Addi ionally, hei low modulus o elas ici y esul s in com-
plex and a ypical de o ma ion mechanisms unde ex eme wo king condi ions, including
p onounced he mal so ening a ele a ed empe a u es. This dis inguishes i anium alloys
om con en ional me als like s eel and aluminum.
These challenges no only hinde p oduc i i y bu also lead o ene gy ine iciencies
and g ea e en i onmen al bu dens in adi ional manu ac u ing p ocesses. Mo eo e ,
he machining o i anium gene a es signi ican hea , accele a ing ool wea and educing
ope a ional e iciency. This limi s p oduc ion a es and nega i ely impac s he su ace
quali y o he inished pa s. While hese phenomena ha e been ex ensi ely s udied in he
con ex o milling Ti-6Al-4V blocks (bo h cas and o ged), some o hese limi a ions can be
mi iga ed by inco po a ing a ious lub ican s in o he p ocess [8].
Howe e , he use o lub ican s in oduces i s own se o challenges, such as highe
p oduc ion cos s, he con amina ion o sc ap ma e ial wi h me al chips and cu ing luids,
and ad e se en i onmen al and heal h e ec s. Wo ke s may be exposed o ha m ul ae osols
c ea ed du ing he e apo a ion o lub ican s, aising signi ican heal h conce ns and high-
ligh ing he need o mo e sus ainable app oaches [
9
–
11
]. In esponse, e o s ha e been
made o de elop mo e en i onmen ally iendly lub ican s based on o ganic oils [
9
]. De-
spi e hese ad ancemen s, he mos e ec i e solu ion may lie in minimizing o elimina ing
he use o lub ican s en i ely h ough he adop ion o d y machining echniques.
Beyond lub ica ion, machining AM hin-walled Ti-6Al-4V componen s o he
ae ospace indus y in oduces addi ional challenges, such as ib a ions (cha e ing) and
signi ican displacemen s o bo h he cu e and he wo kpiece. Milling hin-walled s uc-
u es is a dynamically uns able p ocess due o cu ing and clamping o ces ac ing du ing
chip emo al. This phenomenon esul s in wall de lec ions, leading o undesi able ib a-
ions ha u he comp omise machining accu acy and su ace quali y. These issues a e
exace ba ed by he lowe s i ness o AM hin-walled s uc u es compa ed o hei bulk
coun e pa s, making dynamic ins abili y a c i ical ac o o conside [
12
]. Fo his eason,
his s udy p oposes h ee di e en spindle ajec o ies and wo cu ing ool diame e s o
in es iga e he bes op ions o minimizing ib a ions and enhancing su ace quali y.
Finally, i mus be no ed ha hese ac o s do no only a ec he e iciency o he
machining p ocess i sel bu also he pe o mance o he inished p oduc s. Fo ins ance,
he ole o su ace oughness as a limi ing ac o o a igue pe o mance is well known and
epo ed in he li e a u e, e en wi h s udies on he speci ic case o addi i e-manu ac u ed
P ocesses 2025,13, 717 3 o 18
Ti-6Al-4V [
13
]. On he o he hand, he ole o su ace inish is mo e nuanced in medical
applica ions [
14
]; ne e heless, ob aining a well-con olled and epea able su ace quali y
is pa amoun , o ins ance, o ensu e os eoin eg a ion in implan s.
Gi en hese challenges, his s udy aims o explo e di e en cu ing condi ions o
educe hea gene a ion du ing he milling o hin-walled Ti-6Al-4V componen s p oduced
ia selec i e lase mel ing (SLM) [
15
]. The e alua ion will be conduc ed in e ms o ool
wea and su ace quali y o he machined AM componen . To accomplish his, in a ed
he mog aphy is used o co ela e hea gene a ion du ing he milling p ocess wi h empe -
a u e a ia ions and he esul ing su ace oughness. P e ious s udies ha e success ully
applied in a ed he mog aphy in machining esea ch on ma e ials such as s eel, aluminum,
and i anium [16–19]. The key ad an ages o he mog aphic de ices a e hei non-con ac
na u e and apid esponse, allowing measu emen s in a eas whe e chips could damage he
measu emen sys em o in o he wise inaccessible loca ions. Since no he mocouple needs
o be a ached o he ool o sample, in a ed measu emen does no nega i ely impac
indus ial p ocesses, making i a eliable echnique o moni o ing empe a u e in d y
machining ope a ions.
Mo eo e , his s udy examines he co ela ion among ou c i ical aspec s: (1) inishing
su ace quali y o machined Ti-6Al-4V AM pa s, (2) cu ing ool damage, (3) d y milling
pa ame e s—including di e en cu ing ools—and (4) empe a u e a ia ion a he con ac
su ace o he ool and AM pa . The milling pa ame e s in es iga ed include eed pe
oo h (Fz), axial dep h o cu (Ap), h ee spindle ajec o ies ( ochoidal, helicoidal, and
linea ), and wo cu ing ool diame e s. By ocusing on d y machining echniques and
hei en i onmen al implica ions, his wo k con ibu es o he de elopmen o sus ainable
manu ac u ing p ac ices [
8
], and he emo al o he lub ican has a posi i e economic
impac , as seen wi h he mos ecen 90’s e sions [20].
2. Ma e ials and Me hods
2.1. Ma e ials and Specimens
All samples we e ob ained using 3D addi i e manu ac u ing o Ti-6Al-4V powde .
Speci ically, he echnology employed was Selec i e Lase Mel ing (SLM), an ad anced
e sion o he Selec i e Lase Sin e ing (SLS) p ocess. In SLM, a high-powe lase mel s
he me al alloy powde s on he powde bed o o m dense, p ede ined me al objec s. The
SLM pa ame e s used o p oduce he samples included a lase powe o 200 W, a scanning
eloci y o 1500 mm/s, a slice hickness o 30
µ
m, and a ha ch dis ance o 60
µ
m. Finally,
he samples we e hea ea ed by annealing a 850 ◦C o 2 h.
The chemical composi ion o he Ti-6Al-4V powde o SLM and i s compa ison wi h
bulk ma e ial speci ica ions a e p esen ed in Table 1.
Table 1. Chemical composi ion o he Ti-6Al-4V powde o SLM, compa ed o ASTM B265 Ti6Al4V
g ade alloy [5]; amoun s in [w %].
Ti Al V Fe O C N H Res.
Ti6Al4V powde o SLM
Balance
5.5–6.5 3.5–4.5 ≤0.25 ≤0.13 ≤0.08 ≤0.05 ≤
0.012
≤0.41
ASTM B265 Ti6Al4V alloy Balance
5.5–6.75 3.5–4.5 ≤0.4 ≤0.2 ≤0.08 ≤0.05 ≤
0.015
≤0.40
The d y milling p ocess was pe o med on an SLM componen , as shown in Figu e 1.
The componen consis ed o a pla o m measu ing 70 mm
×
48 mm wi h a hin-wall suppo
o 2.8 mm hickness, a ached o a base measu ing 64 mm
×
64 mm wi h a hickness o
32 mm.
P ocesses 2025,13, 717 4 o 18
P ocesses 2025, 13, x FOR PEER REVIEW 4 o 19
Figu e 1. Schema ic o he SLM componen machined by milling p ocess in his s udy, along i s
dimensions.
2.2. Tes Me hodology
2.2.1. Ini ial Se up T ials
Ini ial es s we e conduc ed wi h he SLM componen igidly ixed in an indus ial
ise. This se up effec i ely p e en ed ib a ions caused by he hin-wall suppo geome-
y. By ensu ing s able clamping, he ocus was placed on analyzing cu ing ool damage
and i s co ela ion wi h empe a u e changes, as well as de e mining he op imal spindle
ajec o y among ochoidal, helical, and linea pa hs.
Once he op imal ajec o y was de e mined, he nex s ep was o pe o m es s on
he componen wi hou he igid ise, obse ing he beha io o he hin-walled suppo
and i s inhe en geome y, as well as i s effec s on empe a u e a ia ions and he su ace
oughness o he inished pa .
All es s we e pe o med using a CNC machining cen e , he i e-axis HAAS UMC-
750. Ini ial ials o de e mine he bes ajec o y ( ochoidal, helical, and linea ) examined
milling pa ame e s such as eed pe oo h (Fz) and axial dep h o cu (Ap). The cu ing
ool used in hese es s was he XDLX 09T308ER-F40 CTC5240, pai ed wi h he holde ool
GA SD090 C 032 Z3, which had a diame e o 32 mm. This con igu a ion was e e ed o
as Se up 1 (see Figu e 2a). Figu e 3 illus a es a schema ic o he h ee diffe en ajec o ies
used in he ini ial ials. The linea ajec o y was pe o med wi h a o al o ou milling
passes o each componen o machine he en i e su ace. Table 2 p esen s he a ia ion in
eed pe oo h (Fz) and axial dep h o cu (Ap) o each sample. The ixed milling pa am-
e e s o all hese es s we e cu ing eloci y (Vc) a 60 m/min, adial cu ing dep h (Ae) a
80%, eed a e (V ) a 229 mm/min, spindle speed (n) a 764 pm, and numbe o effec i e
edges (Zc) a 3. The pa ame e s selec ed o his s udy a e based on a subs an ial amoun
o he li e a u e and e e ences ela ed o i anium machining. A summa y can be ound
in [21], while mo e speci ic e e ences o d y condi ions, simila 3D p in ing echniques,
and he milling p ocess a e p o ided in [22–24]. Taking in o accoun he e e ence da a, as
well as he speci ica ions o ou ools and sys em, he milling pa ame e s and hei a ia-
ions we e de ined.
Figu e 1. Schema ic o he SLM componen machined by milling p ocess in his s udy, along
i s dimensions.
2.2. Tes Me hodology
2.2.1. Ini ial Se up T ials
Ini ial es s we e conduc ed wi h he SLM componen igidly ixed in an indus ial
ise. This se up e ec i ely p e en ed ib a ions caused by he hin-wall suppo geome y.
By ensu ing s able clamping, he ocus was placed on analyzing cu ing ool damage and i s
co ela ion wi h empe a u e changes, as well as de e mining he op imal spindle ajec o y
among ochoidal, helical, and linea pa hs.
Once he op imal ajec o y was de e mined, he nex s ep was o pe o m es s on
he componen wi hou he igid ise, obse ing he beha io o he hin-walled suppo
and i s inhe en geome y, as well as i s e ec s on empe a u e a ia ions and he su ace
oughness o he inished pa .
All es s we e pe o med using a CNC machining cen e , he i e-axis HAAS UMC-
750. Ini ial ials o de e mine he bes ajec o y ( ochoidal, helical, and linea ) examined
milling pa ame e s such as eed pe oo h (Fz) and axial dep h o cu (Ap). The cu ing ool
used in hese es s was he XDLX 09T308ER-F40 CTC5240, pai ed wi h he holde ool GA
SD090 C 032 Z3, which had a diame e o 32 mm. This con igu a ion was e e ed o as
Se up 1 (see Figu e 2a). Figu e 3illus a es a schema ic o he h ee di e en ajec o ies used
in he ini ial ials. The linea ajec o y was pe o med wi h a o al o ou milling passes
o each componen o machine he en i e su ace. Table 2p esen s he a ia ion in eed
pe oo h (Fz) and axial dep h o cu (Ap) o each sample. The ixed milling pa ame e s
o all hese es s we e cu ing eloci y (Vc) a 60 m/min, adial cu ing dep h (Ae) a 80%,
eed a e (V ) a 229 mm/min, spindle speed (n) a 764 pm, and numbe o e ec i e edges
(Zc) a 3. The pa ame e s selec ed o his s udy a e based on a subs an ial amoun o he
li e a u e and e e ences ela ed o i anium machining. A summa y can be ound in [
21
],
while mo e speci ic e e ences o d y condi ions, simila 3D p in ing echniques, and he
milling p ocess a e p o ided in [
22
–
24
]. Taking in o accoun he e e ence da a, as well
as he speci ica ions o ou ools and sys em, he milling pa ame e s and hei a ia ions
we e de ined.
P ocesses 2025,13, 717 5 o 18
P ocesses 2025, 13, x FOR PEER REVIEW 5 o 19
Table 2. Summa y o he a ia ion pa ame e s eed pe oo h (Fz) and axial dep h o cu (Ap) and
ajec o y o each es .
Tes Numbe Ap (mm) Fz (mm) T ajec o y
1 0.1 0.1 Linea
2 0.1 0.5 Linea
3 0.25 0.1 Linea
4 0.1 0.1 T ochoidal
5 0.1 0.1 Helical
(a)
(b)
Figu e 2. (a) Image o cu ing ool XDLX 09T308ER-F40 CTC5240 and he ool holde GA SD090 C
032 Z3; (b) Image o cu ing ool T290 LNMT 100405TR IC808 and he ool holde T290 ELN D20-
03-W20-10.
Figu e 3. Scheme o he h ee diffe en ajec o ies used in he es s.
New-edge ools we e used o all es s unde a d y cu ing en i onmen o elimina e
he in luence o ool wea on cu ing empe a u e and su ace oughness. This ensu ed a
eliable co ela ion among he samples machined unde diffe en es condi ions.
2.2.2. Se up Va ia ions
Once he op imal pa ame e s and ajec o y we e iden i ied, a diffe en se o cu ing
ools and holde was used. The second cu ing ool was a T290 LNMT 100405TR IC808
wi h wo cu ing edges and a g ade IC808, offe ing a submic on subs a e wi h excellen
chipping esis ance, combined wi h a “SUMO TEC” PVD coa ing o TiAlN/AlTiN+TiN.
The co esponding holde was he T290 ELN D20-03-W20-10, wi h a diame e o 20 mm.
This con igu a ion was e e ed o as Se up 2 (see Figu e 2b). The es s conduc ed wi h
his cu ing ool and holde u ilized a ochoidal ajec o y. In hese es s, he eed pe oo h
(Fz) and axial dep h o cu (Ap) we e ixed a 0.1 mm. The ixed milling pa ame e s in-
cluded a cu ing eloci y (Vc) o 120 m/min, a adial cu ing dep h (Ae) o 20%, a eed a e
(V ) o 573 mm/min, a spindle speed (n) o 1910 pm, and a numbe o effec i e edges (Zc)
Figu e 2. (a) Image o cu ing ool XDLX 09T308ER-F40 CTC5240 and he ool holde GA SD090
C 032 Z3; (b) Image o cu ing ool T290 LNMT 100405TR IC808 and he ool holde T290 ELN
D20-03-W20-10.
P ocesses 2025, 13, x FOR PEER REVIEW 5 o 19
Table 2. Summa y o he a ia ion pa ame e s eed pe oo h (Fz) and axial dep h o cu (Ap) and
ajec o y o each es .
Tes Numbe Ap (mm) Fz (mm) T ajec o y
1 0.1 0.1 Linea
2 0.1 0.5 Linea
3 0.25 0.1 Linea
4 0.1 0.1 T ochoidal
5 0.1 0.1 Helical
(a)
(b)
Figu e 2. (a) Image o cu ing ool XDLX 09T308ER-F40 CTC5240 and he ool holde GA SD090 C
032 Z3; (b) Image o cu ing ool T290 LNMT 100405TR IC808 and he ool holde T290 ELN D20-
03-W20-10.
Figu e 3. Scheme o he h ee diffe en ajec o ies used in he es s.
New-edge ools we e used o all es s unde a d y cu ing en i onmen o elimina e
he in luence o ool wea on cu ing empe a u e and su ace oughness. This ensu ed a
eliable co ela ion among he samples machined unde diffe en es condi ions.
2.2.2. Se up Va ia ions
Once he op imal pa ame e s and ajec o y we e iden i ied, a diffe en se o cu ing
ools and holde was used. The second cu ing ool was a T290 LNMT 100405TR IC808
wi h wo cu ing edges and a g ade IC808, offe ing a submic on subs a e wi h excellen
chipping esis ance, combined wi h a “SUMO TEC” PVD coa ing o TiAlN/AlTiN+TiN.
The co esponding holde was he T290 ELN D20-03-W20-10, wi h a diame e o 20 mm.
This con igu a ion was e e ed o as Se up 2 (see Figu e 2b). The es s conduc ed wi h
his cu ing ool and holde u ilized a ochoidal ajec o y. In hese es s, he eed pe oo h
(Fz) and axial dep h o cu (Ap) we e ixed a 0.1 mm. The ixed milling pa ame e s in-
cluded a cu ing eloci y (Vc) o 120 m/min, a adial cu ing dep h (Ae) o 20%, a eed a e
(V ) o 573 mm/min, a spindle speed (n) o 1910 pm, and a numbe o effec i e edges (Zc)
Figu e 3. Scheme o he h ee di e en ajec o ies used in he es s.
Table 2. Summa y o he a ia ion pa ame e s eed pe oo h (Fz) and axial dep h o cu (Ap) and
ajec o y o each es .
Tes Numbe Ap (mm) Fz (mm) T ajec o y
1 0.1 0.1 Linea
2 0.1 0.5 Linea
3 0.25 0.1 Linea
4 0.1 0.1 T ochoidal
5 0.1 0.1 Helical
New-edge ools we e used o all es s unde a d y cu ing en i onmen o elimina e
he in luence o ool wea on cu ing empe a u e and su ace oughness. This ensu ed a
eliable co ela ion among he samples machined unde di e en es condi ions.
2.2.2. Se up Va ia ions
Once he op imal pa ame e s and ajec o y we e iden i ied, a di e en se o cu ing
ools and holde was used. The second cu ing ool was a T290 LNMT 100405TR IC808
wi h wo cu ing edges and a g ade IC808, o e ing a submic on subs a e wi h excellen
chipping esis ance, combined wi h a “SUMO TEC” PVD coa ing o TiAlN/AlTiN+TiN.
The co esponding holde was he T290 ELN D20-03-W20-10, wi h a diame e o 20 mm.
This con igu a ion was e e ed o as Se up 2 (see Figu e 2b). The es s conduc ed wi h his
cu ing ool and holde u ilized a ochoidal ajec o y. In hese es s, he eed pe oo h (Fz)
and axial dep h o cu (Ap) we e ixed a 0.1 mm. The ixed milling pa ame e s included
a cu ing eloci y (Vc) o 120 m/min, a adial cu ing dep h (Ae) o 20%, a eed a e (V )
o 573 mm/min, a spindle speed (n) o 1910 pm, and a numbe o e ec i e edges (Zc) o
3. Wi h he new se o ools and holde s, he objec i e was o e alua e how damage o he
cu ing ool impac s he su ace inish and empe a u e a ia ions.
P ocesses 2025,13, 717 6 o 18
2.2.3. Su ace Roughness De e mina ion
The su ace quali y o he machined componen s was assessed using Ra and RSM
alues, bo h o which ep esen su ace oughness bu a e calcula ed di e en ly. Ra, o
Roughness A e age, is de e mined as he a i hme ic a e age o a su ace’s measu ed
mic oscopic peaks and alleys. RSM is he a i hme ic mean alue o he wid hs o he
p o ile elemen s o he oughness p o ile. The oughness images we e acqui ed using
an in ini e ocus mic oscopy (Alicona In ini e Focus SL, Alicona Imaging GmbH, G az,
Aus ia) and da a analysis was pe o med wi h Moun ainsMap 5.1 so wa e, adhe ing o
ISO 4287 and ISO 25178 s anda ds [
25
,
26
]. The analysis in ol ed he e alua ion o he
absolu e o dina e Z(x) wi hin he sampling leng h. Figu e 4illus a es an example o a
componen su ace a ea measu ed by he op ical p o ilome e , including he 3D image
ob ained and he g aph showing he a ia ion o he oughness.
P ocesses 2025, 13, x FOR PEER REVIEW 6 o 19
o 3. Wi h he new se o ools and holde s, he objec i e was o e alua e how damage o
he cu ing ool impac s he su ace inish and empe a u e a ia ions.
2.2.3. Su ace Roughness De e mina ion
The su ace quali y o he machined componen s was assessed using Ra and RSM
alues, bo h o which ep esen su ace oughness bu a e calcula ed diffe en ly. Ra, o
Roughness A e age, is de e mined as he a i hme ic a e age o a su ace’s measu ed mi-
c oscopic peaks and alleys. RSM is he a i hme ic mean alue o he wid hs o he p o ile
elemen s o he oughness p o ile. The oughness images we e acqui ed using an in ini e
ocus mic oscopy (Alicona In ini e Focus SL, Alicona Imaging GmbH, G az, Aus ia) and
da a analysis was pe o med wi h Moun ainsMap 5.1 so wa e, adhe ing o ISO 4287 and
ISO 25178 s anda ds [25,26]. The analysis in ol ed he e alua ion o he absolu e o dina e
Z(x) wi hin he sampling leng h. Figu e 4 illus a es an example o a componen su ace
a ea measu ed by he op ical p o ilome e , including he 3D image ob ained and he g aph
showing he a ia ion o he oughness.
Wo n and adhe ed ma e ial a he cu ing edge o ools we e analyzed using he same
mic oscopy echnique, and hey we e exp essed in e ms o olume adhe ed in mm3. The
so wa e o he in ini e ocus mic oscope allows us o o e lap he ini ial and inal opo-
g aphic images o sub ac he adhe ed o emo ed ma e ial du ing he es ing.
Figu e 4. F om le o igh , he igu e shows he machined componen wi h he analyzed su ace
highligh ed by a black ec angle, ollowed by he ex ac ed 3D image and he g aph illus a ing he
su ace oughness a ia ion.
2.2.4. Tempe a u e Measu emen by Means o The mal Imaging
The mal imaging was used o measu e wo kpiece empe a u e unde he diffe en
machining ials. This allowed co ela ing he diffe en cu ing con igu a ions wi h he
esul ing wo kpiece hea ing gene a ed.
Figu e 5a shows he expe imen al se up wi h he i e-axis CNC machining cen e ,
he HAAS UMC-750. On one side, he da a acquisi ion compu e can be seen, while inside
he HAAS UMC-750, he SLM componen and he black squa e indica ing he loca ion o
he in a ed came a o cap u ing in a ed images a e isible. The window glass o he
i e-axis CNC machining cen e was emo ed o ensu e clea IR imaging wi hou any
in e e ence. The FLIR SC645 high- esolu ion LWIR science-g ade in a ed came a (Figu e
Figu e 4. F om le o igh , he igu e shows he machined componen wi h he analyzed su ace
highligh ed by a black ec angle, ollowed by he ex ac ed 3D image and he g aph illus a ing he
su ace oughness a ia ion.
Wo n and adhe ed ma e ial a he cu ing edge o ools we e analyzed using he same
mic oscopy echnique, and hey we e exp essed in e ms o olume adhe ed in mm3.
The so wa e o he in ini e ocus mic oscope allows us o o e lap he ini ial and inal
opog aphic images o sub ac he adhe ed o emo ed ma e ial du ing he es ing.
2.2.4. Tempe a u e Measu emen by Means o The mal Imaging
The mal imaging was used o measu e wo kpiece empe a u e unde he di e en
machining ials. This allowed co ela ing he di e en cu ing con igu a ions wi h he
esul ing wo kpiece hea ing gene a ed.
Figu e 5a shows he expe imen al se up wi h he i e-axis CNC machining cen e , he
HAAS UMC-750. On one side, he da a acquisi ion compu e can be seen, while inside he
HAAS UMC-750, he SLM componen and he black squa e indica ing he loca ion o he
in a ed came a o cap u ing in a ed images a e isible. The window glass o he i e-axis
CNC machining cen e was emo ed o ensu e clea IR imaging wi hou any in e e ence.
The FLIR SC645 high- esolu ion LWIR science-g ade in a ed came a (Figu e 5b) ea u es
an uncooled mic obolome e de ec o wi h a esolu ion o 640
×
480 pixels, a 17-mic on
pixel size, and a spec al de ec ion ange o 7.5–13
µ
m. The he mal came a ope a es
P ocesses 2025,13, 717 7 o 18
a a ame a e o 25 Hz and wi hin a empe a u e ange o 120
◦
C o 650
◦
C. Figu e 5c
shows an example o an in a ed image ob ained using he FLIR SC645. To de e mine he
emissi i y o he i anium samples du ing milling ials, labo a o y es s we e conduc ed. A
machined i anium sample wi h an a ached he mocouple was hea ed o 650
◦
C. Then, he
he mog aphic came a was used o measu e empe a u e a ia ions and he cooling p ocess,
which we e co ela ed wi h he app op ia e emissi i y alues o ma ch he he mocouple
eadings. The 0.30 emissi i y o he Ti6Al4V was de e mined, and i is consis en wi h
e e ences, which place i in he ange o 0.20 and 0.35 [
19
,
27
]. A he s a o he expe imen s,
he dis ance om he sample o he IR came a, as well as he en i onmen al empe a u e
and humidi y, we e measu ed and assumed o emain cons an h oughou all es s. The
e lec ed empe a u e was de e mined using he e lec ion me hodology speci ied in ASTM
E1862-14.
P ocesses 2025, 13, x FOR PEER REVIEW 7 o 19
5b) ea u es an uncooled mic obolome e de ec o wi h a esolu ion o 640 × 480 pixels, a
17-mic on pixel size, and a spec al de ec ion ange o 7.5–13 µm. The he mal came a
ope a es a a ame a e o 25 Hz and wi hin a empe a u e ange o 120 °C o 650 °C.
Figu e 5c shows an example o an in a ed image ob ained using he FLIR SC645. To de-
e mine he emissi i y o he i anium samples du ing milling ials, labo a o y es s we e
conduc ed. A machined i anium sample wi h an a ached he mocouple was hea ed o
650 °C. Then, he he mog aphic came a was used o measu e empe a u e a ia ions and
he cooling p ocess, which we e co ela ed wi h he app op ia e emissi i y alues o
ma ch he he mocouple eadings. The 0.30 emissi i y o he Ti6Al4V was de e mined,
and i is consis en wi h e e ences, which place i in he ange o 0.20 and 0.35 [19,27]. A
he s a o he expe imen s, he dis ance om he sample o he IR came a, as well as he
en i onmen al empe a u e and humidi y, we e measu ed and assumed o emain con-
s an h oughou all es s. The e lec ed empe a u e was de e mined using he e lec ion
me hodology speci ied in ASTM E1862-14.
Figu e 5. (a) Expe imen al se up wi h he i e-axis CNC machining cen e , he HAAS UMC-750.
Inside, he SLM componen is isible, and he black squa e indica es he loca ion o he in a ed
came a; (b) FLIR SC645 high- esolu ion LWIR in a ed came a; (c) Example o an in a ed image
acqui ed by he in a ed came a. The wo egis e ed empe a u e a eas a e ep esen ed by wo
Figu e 5. (a) Expe imen al se up wi h he i e-axis CNC machining cen e , he HAAS UMC-750.
Inside, he SLM componen is isible, and he black squa e indica es he loca ion o he in a ed
came a; (b) FLIR SC645 high- esolu ion LWIR in a ed came a; (c) Example o an in a ed image
acqui ed by he in a ed came a. The wo egis e ed empe a u e a eas a e ep esen ed by wo
ec angles. The bo om ec angle ocuses on he componen empe a u e, while he op ec angle
ocuses on he ool empe a u e. The ed iangles indica e he maximum empe a u e in each a ea.
P ocesses 2025,13, 717 8 o 18
The in a ed came a measu emen s we e conduc ed in si u wi hou in e e ence om
chips o ool-wo kpiece in e ac ion, as he machined a ea and cu ing ool we e su icien ly
la ge o ensu e accu a e empe a u e egis a ion (see Figu e 5c). In his wo k, in a ed
images we e used o measu e and p esen he maximum empe a u e, as he he mal e ec
plays a c ucial ole in me al machining. Tool li e and su ace quali y la gely depend on he
maximum empe a u e eached in he cu ing egion [16,19].
3. Resul s and Discussion
3.1. Se up 1: E ec o Cu ing Pa ame e s on Su ace Roguhness and Tempe a u e
Su ace inish is a c i ical aspec o machining and milling p ocesses, no only because
i a ec s he inal aes he ic appea ance o he componen and i s unc ionali y, bu also
because i p o ides eliable insigh s in o he condi ion o he cu ing ool. Fu he mo e,
changes in he cu ing ool’s condi ion can lead o signi ican a ia ions in he empe a u e
eached du ing he milling p ocess, bo h on he su ace o he componen and he ool i sel .
The esul s o he expe imen al Se up 1 (cu ing ool XDLX 09T308ER-F40 CTC5240 and
he ool holde GA SD090 C 032 Z3), p e iously desc ibed, a e p esen ed below. In his
se up, he componen was igidly ixed in a ise o analyze how a ia ions in eed pe oo h
(Fz) and axial dep h o cu (Ap) a ec su ace oughness and empe a u e changes. The
mos eliable empe a u e da a was eco ded du ing he second and hi d passes, whe e
he cu ing ool main ained ull con ac wi h he componen . These wo passes we e used
o d aw conclusions and es ablish co ela ions be ween su ace oughness, empe a u e,
and cu ing ool damage.
Figu e 6and Table 3show how he oughness pa ame e s Ra and RSM, as well as he
maximum empe a u e changes du ing he ou milling passes, a e a ec ed by he inc ease
in Fz and Ap. I was obse ed ha inc easing he Fz pa ame e 0.1 and 0.5 mm had no
signi ican e ec on ei he su ace oughness o empe a u e. In con as , inc easing Ap
om 0.1 o 0.25 mm caused a ma ked deg ada ion, pa icula ly in he RSM oughness
pa ame e . The measu ed oughness pa ame e s o Ra we e consis en and compa able wi h
o he e e ences [
24
,
28
], whe e milling was pe o med unde d y condi ions. Mo eo e ,
he maximum empe a u e ob ained wi h he Fp and Az 0.1 alues is simila o he ones
ob ained in [
19
], bu o his e e ence, he machining was he u ning, no he milling, as i
is ocused on wo k.
P ocesses 2025, 13, x FOR PEER REVIEW 8 o 19
ec angles. The bo om ec angle ocuses on he componen empe a u e, while he op ec angle
ocuses on he ool empe a u e. The ed iangles indica e he maximum empe a u e in each a ea.
The in a ed came a measu emen s we e conduc ed in si u wi hou in e e ence om
chips o ool-wo kpiece in e ac ion, as he machined a ea and cu ing ool we e suffi-
cien ly la ge o ensu e accu a e empe a u e egis a ion (see Figu e 5c). In his wo k, in-
a ed images we e used o measu e and p esen he maximum empe a u e, as he he -
mal effec plays a c ucial ole in me al machining. Tool li e and su ace quali y la gely
depend on he maximum empe a u e eached in he cu ing egion [16,19].
3. Resul s and Discussion
3.1. Se up 1: Effec o Cu ing Pa ame e s on Su ace Roguhness and Tempe a u e
Su ace inish is a c i ical aspec o machining and milling p ocesses, no only because
i affec s he inal aes he ic appea ance o he componen and i s unc ionali y, bu also
because i p o ides eliable insigh s in o he condi ion o he cu ing ool. Fu he mo e,
changes in he cu ing ool’s condi ion can lead o signi ican a ia ions in he empe a u e
eached du ing he milling p ocess, bo h on he su ace o he componen and he ool
i sel . The esul s o he expe imen al Se up 1 (cu ing ool XDLX 09T308ER-F40 CTC5240
and he ool holde GA SD090 C 032 Z3), p e iously desc ibed, a e p esen ed below. In
his se up, he componen was igidly ixed in a ise o analyze how a ia ions in eed pe
oo h (Fz) and axial dep h o cu (Ap) affec su ace oughness and empe a u e changes.
The mos eliable empe a u e da a was eco ded du ing he second and hi d passes,
whe e he cu ing ool main ained ull con ac wi h he componen . These wo passes we e
used o d aw conclusions and es ablish co ela ions be ween su ace oughness, empe -
a u e, and cu ing ool damage.
Figu e 6 and Table 3 show how he oughness pa ame e s Ra and RSM, as well as he
maximum empe a u e changes du ing he ou milling passes, a e affec ed by he in-
c ease in Fz and Ap. I was obse ed ha inc easing he Fz pa ame e 0.1 and 0.5 mm had
no signi ican effec on ei he su ace oughness o empe a u e. In con as , inc easing Ap
om 0.1 o 0.25 mm caused a ma ked deg ada ion, pa icula ly in he RSM oughness
pa ame e . The measu ed oughness pa ame e s o Ra we e consis en and compa able
wi h o he e e ences [24,28], whe e milling was pe o med unde d y condi ions. Mo e-
o e , he maximum empe a u e ob ained wi h he Fp and Az 0.1 alues is simila o he
ones ob ained in [19], bu o his e e ence, he machining was he u ning, no he mill-
ing, as i is ocused on wo k.
Du ing es numbe 3, in a ed empe a u e eco dings e ealed ha ixing Ap a 0.25
mm led o a sudden ise in empe a u e on bo h he componen and he cu ing ool. This
empe a u e su ge was p ima ily a ibu ed o he accumula ion o i anium swa o
chips, which in u n accele a ed ool wea . As a esul , he ou h milling pass could no
be comple ed, and he es was hal ed a e he hi d pass.
Figu e 6. Va ia ion o Ra and RSM oughness pa ame e s while keeping Ap ixed a 0.1 and inc easing
Fz wi h alues o 0.1 and 0.5 (le cha ), and while keeping Fz ixed a 0.1 and inc easing Ap wi h
alues o 0.1 and 0.25 ( igh cha ).
P ocesses 2025,13, 717 9 o 18
Table 3. Maximum empe a u es eco ded du ing he ou milling passes o he ma e ial and ool
unde a ying eed pe oo h (Fz) and axial dep h o cu (Ap).
Tes
Numbe Ap (mm) Fz (mm) Ra (µm) RSM (µm) Passes Max. Tempe a u e (◦C)
Ma e ial Tool
10.1 0.1 1.34 ±0.04 46 ±1.7
1s 203 93
2nd 552 184
3 d 615 217
4 414 189
20.1 0.5 1.37 ±0.04 46 ±1.7
1s 423 90
2nd 471 159
3 d 567 159
4 462 155
3 0.25 0.1 1.45 ±0.06 60 ±2.5
1s 650 280
2nd <660 325
3 d <660 388
Du ing es numbe 3, in a ed empe a u e eco dings e ealed ha ixing Ap a
0.25 mm led o a sudden ise in empe a u e on bo h he componen and he cu ing ool.
This empe a u e su ge was p ima ily a ibu ed o he accumula ion o i anium swa o
chips, which in u n accele a ed ool wea . As a esul , he ou h milling pass could no be
comple ed, and he es was hal ed a e he hi d pass.
3.1.1. T ajec o y Changes A ec a ion
Nex , he e ec o ajec o y changes on he machining p ocess was speci ically an-
alyzed. Di e en milling ajec o ies, including linea , ochoidal, and helicoidal, we e
e alua ed o de e mine hei impac on su ace oughness, empe a u e, and ool wea .
Figu e 7a illus a es he maximum empe a u es eco ded du ing he milling p ocess
o di e en ajec o ies. These empe a u es signi ican ly in luenced he dis ibu ion o
cu ing o ces and he hea gene a ed du ing machining. Speci ically, lineal and helicoidal
ajec o ies we e ound o p o ide be e cooling and educed ool wea , whe eas ochoidal
ajec o ies led o highe empe a u es and inc eased ool damage unde simila cu ing
condi ions. Consequen ly, he machining p ocess using he ochoidal ajec o y had o be
hal ed o p e en ca as ophic damage o he cu ing ool, holde , and componen .
These inc eased empe a u es appea ed o co ela e wi h highe esul ing wo kpiece
oughness. Figu e 7b p esen s he oughness pa ame e s measu ed on he componen
su ace o he di e en milling ajec o ies, showing a majo inc ease o he ochoidal
pa h. Bo h Ra and RMS inc ease by an app oxima e 50%, a signi ican de e io a ion in
su ace inish.
Simila obse a ions could be d awn o he deg ada ion o he wo kpiece.The Hea -
A ec ed Zone (HAZ) on he cu ing ool edge co esponding o each ajec o y is illus a ed,
along wi h a cha ep esen ing he HAZ ex en , in Figu e 7c,d. Resul s show a clea inc ease
in he ex en o he HAZ o he machining bi s used in he ochoidal pa h expe imen
(almos 6 mm), wi h he linea pa h keeping he minimal HAZ (1 mm), and spi al pa h an
in e media e alue (2 mm).
As a conclusion, he ochoidal ajec o y can be dismissed as a easible op ion o
achie ing he mos e icien and e ec i e machining p ocess in Se up 1, as i appea s o
esul in he mos hea being eleased and he wo s wo kpiece su ace quali y.
P ocesses 2025,13, 717 16 o 18
ool, eliable esul s we e achie ed. Addi ional and mo e de ailed conclusions d awn om
his wo k include:
•
Changes in eed pe oo h (Fz) and axial dep h o cu (Ap) signi ican ly in luence ool
wea and empe a u e. While a ying Fz and change in diame e o he cu ing ool
did no ha e a majo impac , inc easing Ap led o mo e no iceable ool deg ada ion,
especially in e ms o su ace oughness. In u u e wo ks, op imizing hese pa ame e s
can lead o mo e ene gy-e icien and en i onmen ally iendly machining p ocesses.
•
Among he wo oughness pa ame e s, Ra (a i hme ic a e age oughness) and RSM
( oo mean squa e oughness), he RSM pa ame e p o ed o be mo e sensi i e and
eliable in de ec ing su ace inish di e ences. As a esul , i is conside ed mo e de-
pendable o compa ison wi h in a ed came a empe a u e eadings, o e ing a p ecise
me hod o moni o ing sus ainabili y-d i en imp o emen s in su ace inish quali y.
•
Fo Se up 1, i was shown ha he linea and helicoidal ajec o ies p o ided be -
e cooling and educed ool wea compa ed o ochoidal ajec o ies. T ochoidal
pa hs esul ed in highe empe a u es and mo e se e e ool damage, indica ing ha
op imizing cu ing ajec o ies can lead o mo e ene gy-e icien and sus ainable p o-
duc ion p ocesses.
•
In Se up 2, i was demons a ed ha he me hod o ixing he componen , whe he
wi h a ise o a 3D-p in ed hin-wall suppo , had an e ec on ool pe o mance.
The 3D-p in ed suppo led o inc eased ool wea , po en ially due o ib a ions
du ing he milling p ocess. Howe e , bo h me hods pe o med be e han Se up 1,
emphasizing he ole o ma e ial and sys em s abili y in op imizing ene gy use and
p ocess sus ainabili y.
•
As cu ing ool wea /damage inc eased, in a ed empe a u e eadings showed a
ise in empe a u e, which co ela ed wi h inc eased RSM oughness alue o he
Ti-6Al-4V su ace pa ame e s due o he inc emen o ib a ions o wo sened su ace
inishes. These indings unde sco e he impo ance o minimizing ool wea o enhance
ope a ional e iciency and educe ma e ial was e.
•
The use o in a ed came as has been con i med as an e ec i e ool o moni o ing
ool condi ion and su ace quali y, especially in d y machining condi ions, whe e
adi ional lub ica ion is absen . This echnique aids in de ec ing empe a u e inc eases
ha signal po en ial issues, such as ool wea o su ace oughness deg ada ion, while
p omo ing mo e sus ainable p ac ices by elimina ing he need o chemical lub ican s.
The s abili y o he machining sys em is c ucial in p e en ing ool damage and achie -
ing op imal su ace inishes. Any ins abili y, such as ib a ions, can lead o inc eased wea
and poo componen quali y. Ensu ing sys em s abili y no only imp o es ool li e and pa
quali y bu also suppo s mo e sus ainable, cos -e ec i e manu ac u ing p ac ices.
Fu u e s udies a pilo plan s o indus ial le els will be necessa y o e alua e he
economic easibili y o he d y milling p ocess, conside ing he sa ings om no using
lub ican s, as well as he inc eased wea on he ool and he su ace inish o hin-wall
suppo 3D AM complex s uc u es p esen ed in his wo k.
Au ho Con ibu ions: Concep ualiza ion, G.R., M.F. and E.G.-L.; Me hodology, G.R., E.V. and
E.G.-L.; Valida ion, G.R. and E.G.-L.; Fo mal Analysis, G.R., E.V. and E.G.-L.; In es iga ion, G.R., M.F.
and E.G.-L.; Resou ces, G.R. and M.F.; Da a Cu a ion, G.R., E.V. and E.G.-L.; W i ing—O iginal D a
P epa a ion, E.G.-L.; W i ing—Re iew & Edi ing, G.R., J.P. and E.G.-L.; Visualiza ion, G.R., J.P., M.F.,
E.V. and E.G.-L.; Supe ision, J.P. and G.R.; P ojec Adminis a ion, G.R.; Funding Acquisi ion, G.R.
and J.P. All au ho s ha e ead and ag eed o he published e sion o he manusc ip .
Funding: This esea ch was unded by Minis y o Science and Inno a ion h ough he 2019 CIEN call
as well as by he Ca alan Go e nmen ia he ACCIÓ-Eu eca TRAÇA-IMPULSENS unding g an .
P ocesses 2025,13, 717 17 o 18
Da a A ailabili y S a emen : The o iginal con ibu ions p esen ed in his s udy a e included in he
a icle. Fu he inqui ies can be di ec ed o he co esponding au ho s.
Acknowledgmen s: This wo k was pe o med inside he p ojec LUBRINTEL, which ecei ed
undings om CDTI and suppo ed by he Minis y o Science and Inno a ion h ough he 2019
CIEN call. Mo eo e , his wo k was inancially suppo ed by he Ca alan Go e nmen h ough he
unding g an ACCIÓ-Eu eca TRAÇA-IMPULSENS.
Con lic s o In e es : The au ho s decla e no con lic s o in e es .
Re e ences
1.
Pe e s, M.; Hemp enmache , J.; Kump e , J.; Leyens, C. S uc u e and P ope ies o Ti anium and Ti anium Alloys; Wiley-VCH Ve lag
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