Babban dalilan da mafita ga launi mara kyau na kayayyakin allura da aka sanya su kamar haka:
(1) Rashin yaduwar launi mai launi, wanda yawanci yakan haifar da alamu don bayyana kusa da ƙofar.
(2) kwanciyar hankali na zafin robobi ko launuka ba shi da kyau. Don daidaita launin sassan, dole ne a daidaita yanayin samarwa, musamman kayan zafin jiki, ƙarar abu da zagayen samarwa.
(3) Don robobi masu kara kuzari, yi ƙoƙarin sanya yanayin sanyaya na kowane ɓangare na ɓangaren. Ga sassa tare da manyan banbancin kaurin bango, ana iya amfani da launuka don rufe bambancin launi. Don sassa tare da kaurin bango iri ɗaya, yakamata a gyara kayan zafin jiki da kuma zafin muddin. .
(4) Siffar ɓangaren, ƙofar ƙofa, da matsayin suna da tasiri a kan cika filastik, yana haifar da wasu ɓangarorin ɓangaren don haifar da ɓarna na chromatic, wanda dole ne a sake shi idan ya cancanta.
Dalilai na launi da lahanin sheki na kayan kwalliyar allura:
A karkashin yanayi na yau da kullun, mai sheki na farfajiyar allurar da aka ƙera shi yafi ƙaddara ta nau'in filastik, mai launi da ƙarewar dutsen ƙirar. Amma galibi saboda wasu dalilai, launin saman da lahanin shekin samfurin, launi mai duhu da sauran lahani.
Dalilin irin wannan da mafita:
(1) moldarshen ƙarancin ƙira, tsatsa a saman ramin, da ƙarancin ƙarancin ƙirar.
(2) Gating system of the mold is m, sanyi sanyi sulug da kyau ya kamata a fadada, da mai gudu, goge babban mai gudu, mai gudu da kuma ƙofar kamata a fadada.
(3) Kayan zafin jiki da yanayin zafin jiki sun yi ƙaran, kuma ana iya amfani da dumama na ƙofar idan ya cancanta.
(4) Matsayin sarrafawa yayi ƙasa ƙwarai, gudun ma yayi jinkiri sosai, lokacin allura bai isa ba, kuma matsin lamba baya isa, wanda hakan ke haifar da ƙarancin tsari da duhu.
(5) Robobi dole ne su zama cikakkun filastik, amma don hana lalacewar kayan, zama mai karko lokacin dumi, da wadataccen sanyaya, musamman masu kaurin katanga.
(6) Hana abu mai sanyi daga shiga sashin, yi amfani da maɓallin kulle kai ko ƙananan zafin jiki na hanci idan ya cancanta.
(7) Ana amfani da kayan sake sakewa da yawa, robobi ko launuka basu da inganci, tururin ruwa ko wasu ƙazamta sun haɗu, kuma man shafawa da ake amfani da su basu da inganci.
(8) carfin matsewa ya isa.
