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  Home   Product   BPS-SB-Polished Belt
  BPS-SB-Polished Belt
New film casting applications result in increasing demand for polished steel belts
Polished steel belts have been used for many years in the manufacture of photo films in a production method known as film casting.
More recently, the growth in the market for electronic equipment such as LCD displays, digital cameras and mobile phones has led to strong demand for high technology thin plastic films – including polyimide (PI), polycarbonate (PC), polypropylene (PP) and other high technology plastic materials – and film casting is again proving an ideal production process
Film casting often uses a stainless steel belt on which the raw material is solidified as a thin film. The inherent benefits of this method – consistent thickness & flatness and good optica performance – means that it is the preferred process for most new production facilities.
The surface quality of a film is critical to its performance, and polished belts therefore need a high specification surface to meet application requirements. At BPS,we can provide various grades of polished surface to meet different needs.
Selection of correct steel belt material
BPS-polished steel belts are produced by applying a polished finish to BPS-SB-OFFICE
This means that, unless otherwise stated, they retain most of the mechanical properties of the original steel belts (please refer to the catalog of each steel belt for detailed information). 
Table 1. Typical plastic films produced by film casting method
Plastic Material Usage
Cellulose Triacetate (TAC) Polycarbonate (PC)
Poly Vinyl Alcohol (PVA)
LCD film, photo film
LCD film, memory disk material LCD film



Standard thickness (mm)





1.0, 1.2
1.1, 1.6
0.6, 0.8, 1.0, 1.2, 1.6, 2.0
1.1, 1.6
0.8, 1.0, 1.2
0.8, 1.0, 1.2, 1.6, 1.8, 2.0


Table 2. Stainless steel grades used for polished steel belts and standard dimensions
#1. See steel belt catalog (PS-SB-TYPES) for details.
#2. Contact BPS for available stock information  
• Quality controlled from material level to final production
• World-leading polishing technology for maximum quality
• Various polishing grades for different application needs
• Total support including field welding and polishing
However, it is not possible to create a good surface simply by polishing; a high grade surface requires the use of a steel belt with low inclusion levels. Steel belts produced using the ESR (Electro-Slag-Remelting) melting practice are therefore used for high grade polished belts. This is a material in which inclusion level is tightly controlled.
We are also able to produce belts manufactured via the standard AOD (Argon-Oxygen-Decarburization) melting practice. Table 2 lists steel belts available in AOD and ESR materials.
Table 3. Polished steel belt surface specifications  
Inclusions Surface
variation Typical
Major Usage
BPS-PF-0 500µm< :Not allowed
δ500µm :No restriction
(except cross
welding zone)
BPS-PF-1 500µm< :Not allowed
100µmδ δ500µm :Max.20/m2
<100µm   :No restriction
(Rz 0.08µm)
(except cross
welding zone)
High grade sheet
BPS-PF-2 100µm< :Not allowed
50µmδ δ100µm :Max.5/m2
<50µm :No restriction
δ50µm   ESR Thin plastic film
BPS-PF-3 70µm< :Not allowed
40µmδ δ70µm :Max.5/m2
<40µm :No restriction
δ40µm   ESR High grade
thin plastic film
BPS-PF-4 50µm< :Not allowed
δ50µm :No restriction
δ40µm   ESR Special high
grade thin
plastic film
Polishing surface grade
The table above shows the typical surface grades we can currently offer. Other specifications are available including ground and buffed. Please contact your loca Biquick office for details.
There are five different grades of polished belt available, from PF-0, used for regular surface specification like packaging materials, to PF-4, which is used for very high specification needs such as LCD films.
Surface specification is defined by acceptable inclusion size and numbers, and typical surface roughness. These factors are carefully controlled and checked during and after the polishing process.
Offering total support

When using a polished belt, potential downtime will be kept to the minimum if it is checked regularly and any repairs that may be necessary are carried out quickly and effectively.
With our long-term experience in this market, we can provide full training, consultancy and repair/service support, enabling you to maximize the return on your investment, and our global sales and service organization means we can support you anywhere in the world.
This expertise extends to the specific support required by users of polished belts, ensuring field welding and polishing of the highest quality.
We also supply process equipment and can provide consultation, service and advice for a wide range of different process equipment needs.
Reference Data
Steel Belt Material: See Table 2
Mechanical Property of Belt: See each steel belt catalog. Physical Properties of Belt: See each steel belt catalog. Polish Surface Grade: See Table 3.
Belt Dimensions for Polishing: Width: up to 2000 mm (single belt) up to 3000 mm (with longitudinal welding)
Length: approx. 5 m to 80 m (endless) up to approx. 200 m (open)
Thickness: up to 2 mm
Forms of Supply: Endless, Open (field welding)