Advantage & Disadvantage of various types of Coating Heads for Paper & Board

1. Metering Bar ( Rod Coater without Backing Roll )

1.1 Advantage : Simple Device

1.2 Disadvantage :

1 Solid content limitation, Viscosity limitation,

2 Only for low speed operation

3 Difficult control of coating weight

2. Metering Bar Rod Coater with Backing Roll

2.1 Advantage :

1 Good coverage,

2 No scratches & no strikes,

3 High working speed &

4 High solid content possible

2.2 Disadvantage :

1 Low coating weight flexibility,

2 Pattering due to film splitting

3 Lower smoothnes

3. Air-knife

3.1 Advantage :

1 Unsurpassed coverage

2 No mechanical wear

3 High coating weight at low speed possible

3.2 Disadvantage :

1 Low coating solid contents ,

2 Low viscosity,

3 Speed limitation & 4) Low gloss & smoothness

4. Blade ( Stiff or Bent )

4.1 Advantage of both Blade :

1 High coating weight flexibility,

2 High smoothness & gloss,

3 High solid contents possible &

4 High working speed

4.1.1 Advantage of Stiff Blade :

1 Flying splice-no problem,

2 Longer blade life time &

3 Low coating weight possible

4.1.2 Advantage of Bent Blade :

1 Better smoothness, Better gloss,

2 Good runnability,

3 Less tendency to whiskers,

4 Better fiber covering,

5 Less fiber picking,

6 High coating weight &

7 Less danger of mottling

4.2 Disadvantage of both Blade :

1 Low coverage effect ( Opacity )

2 Scratches, Strikes if rheology is not appropriate &

3 Blade wear

4.3 Summary of both Blade

Item	Unit Stiff	Blade-Bent	Blad
Blade Thickness	mm	0.3~0.6 0.	4~0.6
Blade Bevel	°	20~45	Without
Free Extension	mm	14~16	14~16
Blade bending	mm	0 Blade-0 Position	3~6
Coating Angle	°	25~45	20~28
Application gsm	Gsm	6~15	10~25
Solid Contents	%	Ut to 72	Ut to 72
Viscosity	mPas	400~2,000	400~2,000
Coater Speed	Mpm	Up to 1, 500	Up to 1, 500

5. DF ( Curtain ) Coater

5.1 Advantage :

1 Good runnability,

2 No wearing parts,

3 Less sheet brakes and Simple &

4 safe operation

5.2 Disadvantage :

1 It is suitable at high speed,

2 mostly it is applied at the low gsm &

3 Smoothness is not good against Blade Coate

6. Comma Coater

The shape is same to Comma, it is largely used for Glue ( Adhesive ) coating.

7. Roll Coater

There are 2 rolls, 5 Rolls, Gate Rolls & other type of roll coater 8. Film Press : It is mainly used for starch coating instead of the conventional Size Press, Pigment coating with low solid contents at Film Press is applying.