How many fluorescent lamp is enough in a room? Steps of simple calculations to determine.

Sometimes your room is too dark? How can we calculate the number of lighting needed in a room? Too little lighting will bring discomfort to our eyes. Therefore, it is important for us to know the minimum lighting required in a room. By seeking a lighting engineer, it is the best way to solve the problem. However, it may be too expensive for many of us.

In fact, for a simple space area, we can calculate the number by ourselves using some basic calculation techniques. Here will show the steps on how to do it with an example:

A lighting design for a small drawing office, 6m², with a 3m ceiling height. Luminaires are to be used whose photometric data are given in Tables. The Luminaires are general diffusing distribution. Triphosphor fluorescent lamps will be used. The lamp will be bulk replaced at 12,000 hours. The office room reflectances are 0.7 ceiling, 0.3wall and 0.2 floor. The lighting is cleaned every year. 

With the information given above,

Step 1: Determine the mounting height

Mounting height(H)= (ceiling height- desk height) 3- 0.8 = 2.2m

Step 2: Determine the room index, K.

K= L x W/ (L+W) x H

K= 6 x 6/ (6+6) x 2.2

K= 1.4

Step 3: Obtain the Utilisation Factor, UF

UF = 0.49

Step 4: Determine Maintenance Factor, MF

MF = LLMF x LSF x LMF x RSMF

MF= 0.84 x 0.75 x 0.88 x 0.9

MF= 0.5

Step 5: Determine the required illumination level

E = 600lux

Step 6: Solve for the total number of luminaires needed

Assume that we use 3 x36W lamp luminaires. Thus, from Table, the initial lumen for a 36W tri-phosphor fluorescent lamp is 3350 Lumen (ø)

N= E x Area/ n x ø x UF x MF

N= 600 x (6x6)/ 3 x 3350 x 0.49 x 0.5

N= 10.2 = 11 luminaires needed

Therefore, a minimum of 11 luminaires is needed for small drawing room, 4 columns and 3 rows will be a good choice (total of 12 luminaires). 

Many of the data can be obtained from the manufacturer. Therefore, the value given in this example might not be accurate. Please use manufacturer's data to ensure the accuracy.

*Tables are obtained from Temasek Polytechnic.

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Problems and solutions for plastic injection molding

Plastic products are mostly produced by injection molding machine. With the injection molding method, there are often defects occurred in plastic products, such as jetting, flow marks, short shot and many more. Therefore, it is important for us to know the defects as to ensure a high quality product.

Most commonly, defects happen when there are errors in materials used for the product, mold itself or the machine setting.

Some of the common defects and solutions are:

Defects name	Descriptions	Possible solutions
Bubble	It is referred to the phenomenon where bubble or blister occur within the plastic product.	- Increasing the back pressure - Dry the material properly - Decrease the material temperature - Reduce the injection speed
Drag marks	It is referred to the phenomenon where scratches occur when it is ejected from the mold.	- Maintenance of the mold itself
Flash	It is referred to the phenomenon where excess plastic overflow and penetrate out of the mold gap.	- Reduce the injection speed - Reduce the injection pressure - Reduce the material temperature - Increase the clamping pressure
Flow marks	It is referred to the phenomenon where wave pattern is formed around the gate.	- Increase the mold temperature - Raise the gate and runner.
Jetting	It is referred to the phenomenon where a snake line of material formed on the surface of the molded product.	- Reduce the injection speed - Increase the mold temperature
Short shot	It is referred to the phenomenon where the plastic does not reach certain portions of the mold.	- Increase the injection speed - Increase the pressure - Increase ventilation lines
Silver streaks	- It is referred to the phenomenon where circular marks appear at the molding surface.	- Proper drying of material before use - Increase back pressure
Sink mark	It is referred to the phenomenon where indentation occurs on the surface of the plastic product.	- Increase injection speed - Increase back pressure - Reduce material temperature
Warping	It is referred to the phenomenon where deformation caused by difference in the degree of shrinkage.	- Increase injection pressure - Increase barrel temperature
Weld Line	It is referred to the phenomenon where the two different flow fronts meet and formed a narrow V-shaped line.	- Increase injection speed - Increase mold temperature - Increase material temperature

The following information is provided for reference only, without guarantee of any kind. It is encouraged to verify all information with experienced plastic experts, as there are always specific conditions that cannot be anticipated.

Please feel free to contact YHK design for more plastic advices or new product development.