使用哪個Size噴槍噴汽車? 0.2, 0.3 or bigger?

我最初都想當然地以為噴咀size是關鍵, 後來才知道不是.

這去讀讀 : http://www.badgerairbrush.com/pdf/airbrush101printfinal.pdf

"....Nozzle sizes -

There are varying airbrush nozzle sizes for spraying a range of materials. Although they have **some effect** on the line an airbrush produces,
重點原來是:
****nozzle sizes (Fine(0.33mm), Medium, Heavy or 1, 3, and 5) apply more to the material that should be sprayed through the airbrush than the fineness of line an airbrush will produce.****

The line fineness is ultimately determined by multiple factors :–
1. nozzle size
2. the needle’s linear air flow angle
3. pigment/base ratio of paint, pigment size, operating pressure, etc.

補充 : Badger fine nozzle 的直徑是 0.33mm, needle's linear air flow angle 是 6.5 degree
它的 ultra fine nozzle 直徑才是 0.21mm, 而 needle's linear air flow angle 是 6.0 degree

上述那叫 needle's linear air flow angle 噴針角度, 憑肉眼已能看出分別, 不信就去看看郡仕0.3mm噴針及0.5mm噴針尖端形狀的分別是頗大的!!
再有一最佳例證, 是郡仕0.5mm 扇槍 (LWA Trigger Type PS290) 的針咀, 根本是"掘"的! 即是那 linear air flow angle 極大!


NOTE: You must to have the right nozzle/needle size with the right spray medium for optimum airbrush performance.

我現正在噴緊架1比24的F1車模, 因某種需要, 採用0.2mm噴筆.

你自己因應你的需要吧.

其實真係因人手勢而定，但亦都無標準
以小弟為例，一直都係sparmax  0.2走天涯，筆只得一支

但我手法都算古怪，油好傑高bar數，為求噴既範圍唔需太大，因為我手勢用0.3噴好易流眼淚……
以小弟砌緊既車為例，層光油我只噴在三層，可想而知幾重手，橙皮多抛光耐

不過習慣了，慢慢抛總好過流眼淚，俾啲時間效果都一樣

總括黎講用幾粗都要試，工具一樣手勢都唔可能一樣，加油

以前會認為噴筆範圍大過車殼，越大越好

但現在用0.2，會覺得油粒子越細越好，感覺較容易handle

Thanks for the input c-hings

你講緊個角度應該係出油nozzle部份的角度，而唔係針尖，大nozzle的針一般前部都會改變角度，以避免針尖太長而突出個cap，容易撞曲同漬油。另外，近nozzle位的出氣部份，其設計亦會影響噴油面積同霧化效果，如果出氣位壓力加得越急，噴出來的氣會散得越快越大，假如大家壓力一樣，而出氣孔面積不同，空氣流過的速度會不同孔越細，流速越快。好多時國產台產的筆就是這個部份設計得不好。亦是這個原因，同口徑的GSI筆可以比田宮噴得闊一點，而田在幼線效果夠好，就是大家設計上的不同取向。

噴車或噴大件野，都係要買支0.5，因為噴得快同效果平均。

或者再補充少少吧

你所講的 ".......假如大家壓力一樣，而出氣孔面積不同，空氣流過的速度會不同孔越細，流速越快........"

上述的是文氏管原理 Venturi  Effect   http://en.wikipedia.org/wiki/Venturi_effect

文氏管原理對加快氣體流速作用至大. 汽車的化油器就是採用文氏管原理.

那是對霧化效果的影響, 對噴塗範圍無關. 至於氣壓大小則與出油量成正比, 不是範圍面積.

霧化 Atomization 的成因是 :

Atomization refers to the process of breaking up bulk liquids into droplets. Common home atomizers you may be familiar with include shower heads, perfume sprays, garden hoses, and deodorant or hair sprays.
A classic example of atomization occurring naturally involves pouring liquid from a pitcher. As you are pouring and gradually lift the pitcher higher, the stream of liquid elongates and breaks into droplets at some point. This breakup of a liquid stream is a simplistic example of atomization.

霧化可分為 5 類:-
• Pressure atomization
• Air atomization
• Centrifugal atomization
• Electrostatic atomization
• Ultrasonic atomization

至於噴筆的霧化是屬於 Air (Airspray) Atomization 類別. 其原理是:-
In airspray atomization, fluid emerging from a nozzle at low speed is surrounded by a high speed stream of air. Friction between the liquid and air accelerates and disrupts the fluid stream and causes atomization.
The energy source for air atomization is air pressure. 氣壓是源頭, 它驅動的是空氣的流速. 流速才是霧化成因的主角.
Recall that it is the ***relative difference in velocity between fluid and air that causes atomization.***

至於 "....同口徑的GSI筆可以比田宮噴得闊一點，而田在幼線效果夠好......"

那是因為雙星Super Fine 0.2mm 噴針的 linear air flow angle 較郡仕0.2mm 噴針的角度細所致.

我也是擁有上述兩支噴筆 ----- 雙星 Super Fine 0.2mm 及 GSI FWA 0.2mm PS270, 你說得對, 同是0.2mm 口徑, 雙星能夠噴出比郡仕幼的線, 相對地, 郡仕能噴出比雙星廣闊的範圍.

你正好證明左噴塗範圍不關噴咀/針口徑的事.

或者再說說, 噴真車 (即是1:1啦 ) 用幾大口徑的噴槍?
以替日本 JGTC Tom's 車隊的 Toyota SC 噴油的廠家為例, 它用的是德國 Sata 噴槍, 口徑有1.0mm 和1.3mm 兩種, 視乎噴乜野油而定. 的確是mm, 不是cm.

不過話說回頭, 用0.5mm 噴筆噴大面積, 這說法可不是錯, 只要明白 : 你用的是噴針角度而不是口徑. 不過現實卻正正是廠商生產一支噴筆絕大部份只配一款噴針設計!!!

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寫稿佬, 你夠資格出書了, 唔好講,你下次做比我睇

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