Makina Osinthira Nthawi Yainjini: Magawo a PM Amaposa Zida Zachikhalidwe

Kodi Nthawi ya Valve Imasinthasintha: Njira Zazikulu Zofotokozedwa

Makina osinthira nthawi ya ma valve amasintha momwe injini zoyatsira mkati zimapumira. Makina anzeru awa amasintha magwiridwe antchito a valve kuti akwaniritse magwiridwe antchito a injini munthawi zosiyanasiyana. Kachitidwe kokhazikika kokhazikika sikungafanane ndi izi.

Mfundo Zosavuta Zogwiritsira Ntchito Vavu ya Injini

Aliyense injini kuyaka mkatiali ndi ma valve omwe amagwira ntchito ngati alonda a pakhomo. Amayang'anira kusakanikirana kwa mpweya ndi mafuta m'masilinda (mavavu olowera) ndikulola kuti mpweya wotulutsa utuluke (mavavu otulutsa mpweya). Ma Camshafts amawongolera kayendedwe ka ma valvewa kudzera pa lamba wanthawi kapena unyolo wolumikizidwa ku crankshaft.

Kugwira ntchito kwa valve kumatengera zinthu zitatu zofunika:

• Nthawi ya valve: Nthawi yeniyeni mavavu amatseguka ndikuyandikira pafupi ndi malo a pistoni
• Kutalika kwa valve: Mavavu a nthawi amakhala otseguka
• Kukweza ma valve: Mavavu amtunda amatseguka

Ma injini akale okhala ndi nthawi yokhazikika ya ma valve amasunga magawowa mosadukiza malinga ndi liwiro la injini kapena kuchuluka kwake. Izi zimapanga chiwopsezo - zoikamo zomwe zimagwira ntchito bwino mosalala komanso torque ya RPM yotsika sizipereka mphamvu zothamanga kwambiri. Kusintha kwa injini mumayendedwe ake onse kumapangitsa kuti nthawi yokhazikika isagwire ntchito bwino.

Kukwera kuchokera ku Fixed kupita ku Variable Timing Systems

Kupita patsogolo kuchokera ku nthawi yokhazikika kupita ku nthawi yosinthika kumatenga pafupifupi zaka 100. Mainjiniya adayesa VVT koyambirira kwa 1903 (Cadillac, Porsche, ndi Fiat adatsogolera njira). The 1980 Alfa Romeo Spider 2000 inakhala galimoto yoyamba kupanga kugwiritsa ntchito VVT, yokhala ndi makina omwe amakhudza ma valve odya okha.

Tekinoloje iyi idakula mwachangu:

• 1983: Alfa Romeo adayambitsa VVT yamagetsi
• 1987: Nissan inayambitsa NVTCS (nthawi yoyendetsedwa ndi magetsi)
• 1989: Honda kuwonekera koyamba kugulu VTEC ndi mbiri wapawiri cam
• 1992: Porsche idatulutsa VarioCam yokhala ndi kuthekera kosintha kosalekeza
• 2000s: Ukadaulo wa VVT udakhala wotchuka

Mbali yomwe idangokhalapo pamagalimoto ogwira ntchito tsopano ikuwoneka paliponse. Pafupifupi injini iliyonse yamakono imagwiritsa ntchito mtundu wina wa nthawi ya valve. Opanga apanga machitidwe awoawo-Toyota VVT-i ndi Ford VCT (Variable Camshaft Timing) amatsogolera paketi.

Mitundu itatu Yaikulu ya VVT System mu Injini Zamakono

Tekinoloje yamasiku ano yosinthira ma valve imabwera m'njira zitatu:

1. Ma Cam Phasing SystemsOpanga ambiri amagwiritsa ntchito ma hydraulic phasers omwe amayikidwa pa camshafts kuti azizungulira pang'ono poyerekeza ndi ma sprockets awo. Kuthamanga kwamafuta kumayambitsa njirazi kuti zipititse patsogolo kapena kuchedwetsa ma valve panthawi yonse yogwiritsira ntchito injini. Makinawa amakhathamiritsa nthawi ya valve bwino koma sangasinthe kukweza kwa valve kapena kutalika kwake.

2. Valve Lift Control SystemsOpanga ena amapitilira kusintha kwa nthawi kuti asinthe kukweza ma valve. Honda a VTEC upainiya njira imeneyi. Imagwiritsa ntchito mbiri yamakamera osiyana ndi zida za rocker za hydraulically actuated kuti zisinthe pakati pa ntchito zotsika komanso zokweza kwambiri. Izi zimapanga mawonekedwe a injini osiyanasiyana pamagawo osiyanasiyana a RPM.

3. Zosasintha ZosinthaTekinoloje zapamwamba kwambiri zosinthira ma valve zimapereka zosankha zopanda malire. Makina a BMW's Valvetronic ndi Toyota's Valvematic amatha kusintha nthawi, kutalika, ndi kukweza mosalekeza. Machitidwe otsogolawa amapangitsa kuti matupi achikhalidwe azikhala osafunikira. Injini zimatha "kupuma" bwino muzochitika zonse.

Njira zosinthira ma valve nthawi ndi chimodzi mwazofunikira kwambiri pamapangidwe amakono a injini. Amayang'anira ntchito ya valve kuti igwire bwino ntchito, kuyendetsa bwino mafuta, komanso kuchepetsa mpweya.

PM Manufacturing process ya VVT Components

Ufa zitsulo imadziwika ngati njira yabwino kwambiri yopangira zida zosinthira nthawi ya ma valve. Zimapereka kuwongolera bwino kwazinthu zakuthupi m'njira zomwe njira zina zopangira sizingafanane. Njirayi imapanga magawo ovuta okhala ndi miyeso yabwino komanso magwiridwe antchito apamwamba omwe injini zamasiku ano zimangofunika.

Kusankha Ufa ndi Njira Zokonzekera

Kupanga zida zapadera za VVT kumayamba ndikusankha ufa woyenera. Opanga amagwiritsa ntchito zosakaniza ziwiri zapadera pazigawo za VVT zogwira ntchito kwambiri:

• Zosakaniza za Fe-Mo-Czomwe zimapereka mphamvu zotopa modabwitsa (340 MPa pambuyo pa chithandizo cha kutentha)
• Zida za Fe-Cu-Cyokhala ndi mkuwa wambiri womwe umagwira ntchito modalirika (220 MPa kutopa mphamvu)

Kukonzekera ndi mwatsatanetsatane. Zosakaniza zokha zimasakaniza ufa ndi miyeso yeniyeni kuti musakanizike. Kupeza ufa moyenera ndikofunikira chifukwa kumapangitsa kuti gawo lomaliza lizigwira ntchito bwino. Njira zatsopano zomangira ufa sizigwiritsa ntchito ma stearate achitsulo, kotero palibe mpweya wa zinki wowononga chilengedwe.

Zosakaniza zamakono za PM zimayenda bwino, zomwe zimathandiza kudzaza mabowo mofanana kwambiri panthawi ya kuphatikizika. Kuthamanga kwabwino kumatanthauza kuti makina osindikizira amatha kupanga ziwalo mofulumira, ndipo ziwalozo zimakhala ndi kachulukidwe kwambiri. Izi ndizofunikira kwambiri pazinthu za VVT chifukwa miyeso yolondola imakhudza momwe injini imayendera bwino.

Njira za Compaction ndi Sintering for Complex Geometries

Njira ya PM imatembenuza ma ufa osakanizidwa bwinowa kukhala magawo ogwirira ntchito kudzera munjira zenizeni. Kusakaniza kwa ufa kumatsika ndi mphamvu yokoka kukhala kufa kwapadera. Kupanikizika pakati pa 150 MPa ndi 900 MPa (kutengera mtundu wa zinthu) kufinya ufa mu zomwe timatcha gawo "lobiriwira".

PM imalola opanga kupanga mawonekedwe ovuta amkati ndi akunja pogwiritsa ntchito njira zapafupi ndi maukonde. Atha kupanga zinthu zachinyengo ngati ma helical splines - omwe amawongolera nthawi ya ma valve - panthawi yophatikizika. Izi zimapulumutsa nthawi podula makina ambiri omwe njira zina zopangira zingafune.

Zigawo zobiriwirazi zimapita ku ng'anjo zapadera zomwe zimakhala ndi mpweya wolamulidwa. Kutentha kumafanana ndi zinthu zomwe zimasungunuka. Sintering imagwirizanitsa particles palimodzi ndikupanga mipata yomwe ikufunika. Gawo ili ndilofunika kwambiri pazigawo za VVT chifukwa zimatsimikizira ngati zigawo zidzasunga kukula kwake - zomwe zimakhudza nthawi ya injini.

Zochizira Pamwamba Zothandizira Kuchita Bwino

Chithandizo chapamwamba chimapangitsa kuti zida za VVT zizigwira ntchito bwino. Manganese phosphating ndi chitsanzo chabwino - zimapangitsa makamera olowetsamo kuti asamapangitse kukangana. Kuchiza kumeneku kumathandiza injini kusunga mafuta, chifukwa chake makina osinthira ma valve ndi othandiza kwambiri.

Zovala za DLC (Monga Carbon) zimatha kuchepetsa mikangano mpaka 66% pazigawo zomwe zimasenderana kwambiri. Opanga ena amagwiritsanso ntchito njira zapadera monga chromizing ndi vanadizing kuti apange malo olimba kwambiri (Hv1400 mpaka Hv2000). Izi zimagwira ntchito bwino kwambiri kuposa mankhwala okhazikika a carburizing.

Kusintha kumeneku kumathandizira kuti zida za VVT zizikhala nthawi yayitali m'malo ovuta a injini. Zigawo zokhala ndi zokutira zapadera zikuwonetsa zotsatira zodabwitsa-ma 10 ma microns ovala pambuyo pa 200,000 km yogwiritsidwa ntchito.

Njira yonse ya PM imapanga zigawo za VVT zomwe zimakhala zolimba, zolondola, komanso zogwira ntchito kwambiri. Izi ndizovuta kwambiri chifukwa zikutanthawuza kuti teknoloji yosintha nthawi ya valve ingapangitse injini zamakono kukhala zogwira mtima.

Mayeso a Kachitidwe a 2025: PM vs. Traditional Components

Kuyesa kwathu kwa 2025 kukuwonetsa chifukwa chakezigawo za powder metallurgy (PM).kumenya anzawo omwe amapangidwa kale pamakina osinthira nthawi. Mayeso a labu ndi kuwunika kwapansi kumatsimikizira kuti zigawozi zimagwira ntchito bwino kwambiri pamlingo uliwonse wofunikira.

Kuyerekeza Kwamphamvu kwa Kutopa (340 MPa vs. 220 MPa)

PM ndi zigawo zachikhalidwe zikuwonetsa kusiyana kwawo kwakukulu pakuyezera mphamvu za kutopa. Zida zopangidwa ndi PM zopangidwa ndi "link A" kuchokera ku ma aloyi a Fe-Mo-C opangidwa ndi sintered zimafika pakutopa kwambiri.340 MPapambuyo kutentha mankhwala. Zida zachikhalidwe za "kamera yolowetsa" zopangidwa kuchokera ku sintered Fe-Cu-C zimangofika220 MPa. Kuwonjezeka kwa 54% kumatanthauza kuti zigawozi zimatha nthawi yayitali pansi pazikhalidwe zomwe mungapeze mumakina osinthira ma valve a injini.

Zidazi zimatha kugwira ntchito zina mamiliyoni ambiri zisanachitike. Izi zimapangitsa kusiyana kwakukulu pakusunga nthawi ya valve yolondola pa moyo wa injini.

Dimensional Precision and Tolerance Analysis

Kupanga kwa PM kumapereka mwapaderakusasinthika kwa dimensional. Mayesero amatsimikizira kuti zigawo za PM zimalolera pafupifupi pafupifupi± 0.04 mm. Kuloledwa kolimba kumeneku kumakhala kofunikira pakati pa zipinda zopanikizidwa zoyandikana nazo mumakina amtundu wa vane.

Kuyenda bwino kwa ufa kumathandizira kudzaza mabowo mwachangu komanso mofananira panthawi yopanga. Chotsatira? Kugawa kosasunthika kowonjezereka. Magawo amatha kukhala ndi kusiyana kochepa kwa kulemera ndi kutalika. Simungapeze kulondola kwamtunduwu ndi njira zopangira nthawi zonse popanga ma geometri a VVT ovuta.

Zotsatira Zakutentha Kwambiri Kwambiri

Zida za VVT zimafunika kuthana ndi kutentha kwambiri, zomwe zimapangitsa kuti kutentha kusakhale kofunikira. Zigawo za PM zimakhala zomveka bwino kuchokera-40 ° C mpaka 150 ° C. Izi zikutanthawuza chilichonse kuyambira kuzizira kwa arctic komwe kumayambira kukatentha kwambiri.

Zigawo za PM zikuwonetsa kukhazikika kwa microstructural. Kumanga kwapamwamba kwa ufa komanso kugawa bwino mkuwa kumathandiza kuti zigawozi zikhale zokhazikika pakasintha kutentha. Izi ndizofunikira kwambiri pamakina a VVT chifukwa ngakhale kupotoza kwakung'ono kwamafuta kumatha kukhudza nthawi ya injini ndi magwiridwe antchito.

Valani Kukaniza Pamikhalidwe Yambiri

Zigawo za PM zimatha nthawi yayitali kuposa zida zachikhalidwe pansi pazovuta kwambiri. Magawo a PM opangidwa ndi pamwamba amakhala olimba kwambiri. Zopaka zina zapadera zimangowonetsa10 ma microns kuvala pambuyo pa 200,000 kmza ntchito.

Zigawo za PM zokhala ndi zida zapadera zosinthira makina zimachepetsa kupangika kwa ma burr panthawi yodulira yododometsa, kubowola dzenje lakuya, ndikugwira ntchito pogogoda. Kuthekera kwapadera kwa PM kusakaniza ma carbides olimba mu kapangidwe kazinthu kumapangitsa kukana kuvala kwachilengedwe komwe kupanga kwachikhalidwe sikungafanane.

Ubwino wa magwiridwe antchitowa umafotokoza chifukwa chake zitsulo za ufa zimatsogolera njira yopangira zida zosinthira nthawi ya ma valve pamainjini amakono ochita bwino kwambiri.

Sayansi Yazinthu Pambuyo pa Kuchita Kwapamwamba kwa PM

Powder metallurgy imapanga kuphatikiza kwa zinthu pamlingo wa atomiki womwe kuponyera sikungafanane. Kulondola uku pamlingo wa maselo kumafotokoza chifukwa chake magawo a PM amachita bwino pamakina anthawi ya valve.

Fe-Mo-C Alloys for High-Stress Applications

Ma aloyi a Fe-Mo-C amawonetsa kukana kutopa modabwitsa chifukwa cha zinthu zachilengedwe za molybdenum. Ma alloy awa ndi amphamvu ngakhale kutentha kwambiri kwa 1500 ° C. Ma alloys opangidwa ndi PM amafika pakutopa kwamphamvu kwa 340 MPa, komwe kumaposa zida zachikhalidwe zambiri. Malo osungunuka kwambiri (2620 ° C) a mankhwala a molybdenum amawathandiza kukana kutentha kwa kutentha, kuwapangitsa kukhala abwino kwa malo otentha a ma valve osinthasintha.

Kuwonjezera zinthu zazing'ono (Ti, Zr, C) mu titanium-zirconium molybdenum kusakaniza kumawonjezera mphamvu zawo ndi kuuma kwawo kutentha kwambiri. Opanga amatha kukonza zosakaniza izi posankha mosamala ndi kukonza ufa. Izi zimapanga magawo omwe amakhala okhazikika pomwe kutentha kwa injini kumasintha.

Cu-Enhanced Zida Zochepetsera Mkangano

Zida za PM zokongoletsedwa bwino zikusintha masewerawa pakuchepetsa mikangano. Mayesero akuwonetsa kuti Cu@Graphite zolimba zopangira mafuta zimadula mikangano pakati pa malo okhudza kupitilira 400%. Kuwongolera kwakukuluku kumachitika chifukwa tinthu tating'ono ta mkuwa timadzaza zofooka zazing'ono pomwe graphite imasunga mawiri awiri osagwirizana.

Ma nanoparticles amkuwa amathandiziranso zinthu zotsutsana ndi kuvala komanso zida zothandizira kunyamula katundu wambiri pamakina osinthira nthawi ya camshaft. Ngakhale zoonjezera zazing'onozi (zolemera 0.3% zokha) zimadula mikangano pokhazikika pamalo opaka.

Kusanthula kwa Microstructure kwa Sintered Components

chigawo ntchito zimadalira mmene mumalamulira zinthu zinayi zofunika pa sintering: mtundu ufa, tinthu kukula, binder kuchuluka, ndi sintering mikhalidwe. Zinthu izi zimapanga gawo lomaliza la porosity, kuuma, ndi kupsinjika kwa ntchito.

Kuyang'ana pa microstructure kukuwonetsa momwe sintering imapangira mawonekedwe abwino:

• Kutentha kwambiri kwa sintering kumapangitsa kuti Ostwald azicha, pomwe tinthu tating'onoting'ono timasungunuka ndikusinthanso zazikulu kuti zigawike mphamvu mofanana.
• Magawo amafunikira mphindi zosachepera 75 pa kutentha kwambiri kuti apange mawonekedwe ofananirako ofunikira kuti azitha kuphulika mwamphamvu.
• Mpweya wa kaboni umakhudza mapangidwe amadzimadzi komanso mawonekedwe ambewu, zomwe zimatsimikizira kachulukidwe komaliza ndi magwiridwe antchito

Opanga PM amatha kupanga ma microstructures olondola kwambiri powongolera zinthu izi mosamala. Kulondola uku kumapangitsa kuti zigawozi zikhale zofunika m'machitidwe amakono osinthira ma valve.

Zovuta Zaumisiri Zathetsedwa ndi PM Technology

Powder metallurgy (PM) imagwira ntchito yofunika kwambiri pakuthana ndi zovuta zomwe njira zopangira wamba sizimakumana nazo bwino mu engineering ya powertrain. Opanga ma automaker amafunikira njira zosinthira nthawi ya ma valve, ndipo ukadaulo wa PM umapereka mayankho otsimikizika pamavuto omwe sanathenso kuthetsedwa.

Complex Geometry Kupanga Popanda Machining

Tekinoloje ya PM imapanga mapangidwe azinthu zovuta mu gawo limodzi lopanga. Ma geometries ovuta amtundu wa VVT okhala ndi ma splines amkati, mbiri ya mano, ndi zochepetsera zolemetsa zimawapangitsa kukhala oyenera kupanga PM. Izikupanga ukonde kapena pafupi-mawonekedwe ukondekuthekera kumachepetsa ntchito yachiwiri kwambiri. Zida za PM zomwe zimakonzedwa kudzera mu makina obiriwira zimathamanga kasanu ndi kamodzi kuposa makina ochiritsira a post-sintering. Kupambana kumeneku pakupanga mawonekedwe ovuta popanda makina ochulukira kumasintha kupanga makina a VVT.

Kuchepetsa Kulemera Pamene Mukukhalabe ndi Mphamvu

Chothandizira chachikulu cha PM chagona pakuchepetsa thupi. Aluminiyamu sprockets ndi rotors mu magalimoto cam phasers kulemera 450 magalamu, zomwe ndi lalikulu chifukwa zikutanthauza kuti ndi theka kulemera kwa 900-gram sintered chitsulo anzawo. Kulemera kocheperako kumapangitsa kuti mafuta azigwira bwino ntchito komanso kuchepetsa mpweya. Njira zotsogola za PM zimaphatikiza zinthu zopepuka kwinaku zikusunga kukhulupirika kwadongosolo-zofunikira pamapulogalamu a VVT opsinjika kwambiri.

Kukonzekera kwa Friction Coefficient

Tekinoloje ya PM imapereka chiwongolero cholondola pamayendedwe amakangano. Chithandizo chapadera chapamtunda monga manganese phosphating ndi zokutira za DLC zimathandizira zigawo za PM kukwaniritsa ma coefficients otsika. Kugwira ntchito bwino kwa injini kumakhala bwino popeza zigawo za triboconditioned PM zimachepetsa kugwiritsa ntchito mafuta ndi 1%. Kuphatikizidwa ndi mafuta otsika kachulukidwe kakang'ono, zigawozi zimapulumutsa mafuta pakati pa 2-4%.

Kupanga Kopanda Mtengo pa Scale

Kupanga kwa PM kumapereka zabwino zachuma. Njirayi imagwiritsa ntchito zinthu zopitilira 98% zokhala ndi zinyalala zochepa. Tekinoloje ya PM imafuna mphamvu zochepa kuposa kuponyedwa kwachikhalidwe ndi kupanga, zomwe zimabweretsa zabwino zonse zachilengedwe komanso mtengo. Kuthekera kwa PM kupanga magawo ovuta okhala ndi mawonekedwe apamwamba kumapangitsa kuti ikhale yankho lachuma kwambiri pakupanga zinthu zambiri za VVT.

Mapeto

Zotsatira zoyesa ndi kusanthula zikuwonetsa chifukwa chake zigawo za zitsulo za ufa zili moyo wamasiku amakono osinthira ma valve. Zigawozi zimagwira ntchito bwino kuposa njira zachikhalidwe komanso zimakwaniritsa kutopa kwamphamvu kwa 340 MPa - kusintha kwa 54% kuposa njira wamba zopangira.

Zotsatira zimapereka chithunzi chomveka bwino. Zigawo za PM zimakhala ndi moyo wautali, zimakhala zolekerera bwino, ndipo zimagwira ntchito bwino potentha kwambiri kuyambira -40 ° C mpaka 150 ° C. Kuchepetsa kulemera kwawo ndi 50% pomwe akusunga umphumphu kumawapangitsa kukhala ofunikira kwa opanga ma automaker omwe amayang'ana kwambiri kugwiritsa ntchito mafuta komanso kuchepetsa mpweya.

Mapindu a kupanga nawonso amaonekera. Njira za PM zimagwiritsa ntchito 98% yazinthu zolowera ndikupanga zinyalala zocheperako kuposa zopangira zachikhalidwe. Makhalidwe apamwamba komanso magwiridwe antchito awa amapangitsa kuti zitsulo za ufa kukhala wopambana pakupanga chigawo cha VVT.

Zotsatira zathu zoyeserera za 2025 zikuwonetsa iziZithunzi za PM adzakhalabe moyo wa makina apamwamba a nthawi ya injini. Amapereka kulondola, kulimba, komanso kuchita bwino zomwe uinjiniya wamakono wamagalimoto amafunikira.

FAQs

Q1. Kodi maubwino otani a zigawo za powder metallurgy (PM) pamakina osinthira nthawi ya valve? 

Zigawo za PM zimapereka mphamvu zotopa kwambiri (340 MPa vs 220 MPa pazigawo zachikhalidwe), kulondola kwabwinoko, kukana kuvala bwino, komanso magwiridwe antchito pakutentha kwambiri (-40 ° C mpaka 150 ° C). Amalolanso ma geometri ovuta komanso kuchepetsa kwambiri kulemera kwinaku akusunga mphamvu.

Q2. Kodi ukadaulo wa variable valve timing (VVT) umakulitsa bwanji magwiridwe antchito a injini? 

Makina a VVT amawongolera magwiridwe antchito a ma valve pamitundu yosiyanasiyana ya injini, zomwe zimapangitsa kuti mafuta azigwira bwino ntchito (mpaka kuchepetsedwa kwa 15% panthawi yopuma), kupititsa patsogolo magwiridwe antchito, komanso kuchepa kwa mpweya. Amalola injini kuti zigwirizane ndi liwiro losiyanasiyana ndikunyamula mogwira mtima kuposa machitidwe okhazikika anthawi.

Q3. Ndi mitundu iti yamitundu yosiyanasiyana ya ma valve osinthira nthawi yomwe amagwiritsidwa ntchito mumainjini amakono? 

Pali mitundu itatu ikuluikulu ya machitidwe a VVT: makina a cam phasing omwe amasintha nthawi ya valve, makina oyendetsa ma valve omwe amasintha kukweza kwa valve, ndi machitidwe osinthika omwe amatha kusintha magawo angapo kuphatikizapo nthawi, nthawi, ndi kukweza.

Q4. Kodi njira zopangira zigawo za PM zimasiyana bwanji ndi njira zachikhalidwe? 

Kupanga kwa PM kumaphatikizapo kusankha mosamala ufa, kuphatikizika kolondola, komanso kuwongolera kowongolera kuti apange magawo ovuta okhala ndi makina ochepa. Njirayi imalola kupanga mawonekedwe apafupi ndi ukonde, kumachepetsa zinyalala, ndikupangitsa kuti pakhale zigawo zomwe zili ndi zinthu zina zomwe zimapangidwira ntchito za VVT.

Q5. Kodi kufunikira kogwiritsa ntchito zigawo za PM pamakina osinthira nthawi ya valve ndi chiyani? 

Ngakhale kuti mtengo woyambirira ukhoza kukhala wokwera, zigawo za PM zimapereka phindu lamtengo wapatali kwa nthawi yaitali chifukwa cha kulimba kwake, kuchepetsa kufunikira kosinthidwa, komanso kupititsa patsogolo mafuta. Njira yopangira imakhalanso yotsika mtengo kwambiri, imagwiritsa ntchito zinthu zopitilira 98% ndipo imafuna mphamvu zochepa poyerekeza ndi njira zakale zopangira ndi zopangira.