Rubber Mixing Mills

Process of Rubber Mixing in Mills :
In mill mixing, the elastomer is first added to the nip (Gap between two rolls), open to about 6mm, at the top of the rolls. A band of elastomer then passes through the nip & is formed around the front roll. Depending on the elastomer used, varying degrees of difficulty may be encountered in forming the band initially. However after a few passes, a band will form & can be fed back into the nip continuously. The elastomer is then cut back & forth twice to assure proper blending & to allow the elastomer in the bank to go through the nip. All dry ingredients, except the fillers & the cure system, are then added to the nip. The compound is then cut back & forth twice to assure good dispersion of these dry ingredients throughout the batch.

The next step is to open the mill slightly & add the fillers slowly to the batch. In order to prevent excessive loading of fillers at the centre of the roll several times during this operation & thrown back in to the bank. When most of the fillers have been mixed into the compound, the liquid plasticizers & the rest of the fillers are added filler is visible, the batch is cut back & forth twice more to assure good distribution of fillers ''PIG'' roll the batch & feed the ''Pigs'' back into the nip at right- angles as a past of the cross-blending process.

The next step is to open the mill more & add vulcanizing agents to the batch. When the vulcanizing agents are well distributed, the entire batch is cut back & forth at least five times to assure thorough cross-blending, before being sheeted off the mill.

Type of Rubber Mixing Mills manufactured by Santec :

Conventional Bull Gear Types
Unidrive Type
Laboratory Type Mixing Mill with Heating Arrangement

Construction Details :-
To know more details on SANTEC Rubber Mixing Mills, please contact SANTEC.

Comparison Chart:
Comparison chart for Mixing Mill, Dispersion Kneader and Banburry :

	Mixing Mill	Dispersion Kneader	Banburry
Initial Cost	Low	High	Very Expensive
Mixing Quality	Good	Better	Best
Degree of Dispersion	Good	Better	Best
Construction	Open Type	Enclosed Type	Fully Enclosed
Safety	Risky	Completely Safe	Completely Safe
Operator's Experience	3 to 4 Years Experienced Operator	Semi Skilled Operator	Fully Skilled Operator
Mixing Time	15 - 50 minutes	7 - 15 minutes	3 - 5 minutes
Dispersion Effect	Good for High Viscosity Material, but not for Low	Good for both High & Low Viscosity Material	Good for High Viscosity Material, but not for some low viscosity materials
Production Output	Small	Very Good Production	Highly Productive
Heat Conductivity	Good for low temperature mixing, but high temperature mixing is impossible	Good for both high & low temperature mixing	Good for high temperature mixing, but low temperature mixing is impossible
Batch Capacity	Can be increased	Constant	Constant
Colour Charge	Easy	Easy	Difficult

Lab Mixing Mills (6"x12")

"SANTEC" Laboratory Mill is an essential equipment in the rubber & plastic processing industry.It plays an important role in quality control of the product.

Salient Features

Many years production experience results in a compact. Streamlined machine body which Facilities Installation and sale maintenance work.
Built – in driving units less, space requirement 6- pole Electric motor using circular type reducer gives lowest noise level.
Rolls are hard-chromium plated ground and polished, surface hardness 60 HRC or above (hardness depth approx 1.5 mm)roughness height of 0.5 µm.
Roll bearings are in the from of double – row Taper Sell-Aligning Roller bearings. Roll precision allows sheeting thickness to 0.12 mm (thinner on request ).
The bearings are lubricated with a auto-lubricating system.
Specially produced Roll Mill prevents the two rolls from touching each other during operation.
An emergency safety device by a knee pedal to facilitate automatic stopping the machine and to enable the rolls to be reversed about 1/4 of the circumferences.
Materials guide plate produced of Teflon, heat and acid-resistant, no staining and will do harm to the rolls as comparing with convectional bronze guide bras.
Maximum working temperature upto 240 Degree Celsius. (electric heating system higher on request). Most precise temperature control thanks to specialized heating systems. For electric heating. Most precise automatic temperature controller and specially designed temperature sensors are used with accurate indication of working temperature to also allow tolerance of ± 2 degree celsius.
Surface temperature deviations are ± 2 degree celsius.

Machine Designation
Laboratory 2- Roll Mill capable to carry cut the following tests:-

Pigment amalgamation test (plasticizing. mixing masticating)
Hardness test
Stabilizing test
Physical and /or Chemical test
Various specific formulations and formulate preparation
Small output production operations

Construction Details
Rolls: The rolls are cored type and are made from alloy steel material hardened from 500 to 550 BHN duly ground & hardchrome plated. The thickness of the hardchrome will be 0.1 mm to 0.15 mm on the working surface of the roll.

a. Roll Dia : 6" x 12"

Roll Heating	The temperature will be achieved by electrical cartridge Heaters having power capacity of 2.5 KW fitted at the Centre of the roll.
Maximum Working Temperature	The maximum working temperature will be 50 to 200 Degree C on the working surface of the roll. The temperature stability on the roll, reffering to values reached during normal operating, will be + 1.5% on center part of the roll (100 mm about). Independent temperature control for each roll maintained by two nos. P.I.D. temperature control units with PT 100 thermal probes sensor located on the shell of each roll.
Stands & Caps	2 Set of stands made from C.I. castings accurately Machined. Stands are bolted and dowelled to mill base On assembly.
Mill Base Frame	Base frame is made from carbon steel alignment of mill And drive motor, suitable for vibromount pads. The base Frame of the machine is made by carbon steel, properly Polished and coated by two components epoxy paint.
Roll Speeds :
Roll speed of front roll slow	21.4 RPM
Roll speed of back roll	30 RPM
Friction Ratio	1:1.4
Roll Gap Adjustment	With worm reduction gear box hand wheel operated, will Be fitted to threaded spindle with phosphorous bronze. Bush and dial indicator of scale 0.01 mm will be provided. To adjust the fine thickness of the P. V.C. compound. Between Two Roll is adjustable 0.2 mm to 8 mm.
Drive Motor	5 HP, 1000 RPM A.C. Motor TEFC , 415/380 V, 50 Hz, 3 Ph., ABB/ Siemens make.
Transmission	Worm reducer Gear Box input coupled to motor shaft and Output coupled to rear and front roll by chain sprocked. Independent ally to each roll. The chain sprocket will be Made from forged (EN-9) steel with hob generated teeth.
Safety Features	Additional knee operated switch fitted on front side with Reversible rotation.
Electrical Control Equipment	Electric equipment enclosed in dust proof box mounted. On the machine and complete with protection and control. For proper and safety operating of the machine. The electric panel will be assembled with all the reputed components and push button with indication lamps Will be of Teknie make and the P.I.D temperature Controller will be of Radix or imported make.
Standard Accessories :
	a. Guards : 2 Set
	b. Mill Pan : 1 No. made from stainless steel
	c. Stock guides made from phosphorous bronze material : 1 Set
	d. Limit Switch : 1 No.
	e. Scrapper arrangement on rear and front roll.
Display	Speed of Rolls, Temperature of two rolls.

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