Monday, December 7, 2009

Wire Drawing Machinery Types

Single block machines

Bull Block single die.

The wire enters the block via a die and on to the block where it collects.

Overtop block on single vertical shaft with 2 dies -

From 1st die wire enters a block with an 18" race the Wire wraps round the race 3-5 wraps and then exits out via the pulley on the left of the machine from which it enters the 2nd die and on to the upper block race that has a diameter of 24". Note that while the area reduction through the first die can vary from around 25% up to about 35% the area reduction in the 2nd die must be bigger than 25% i.e. exceed the elongation of the block ratio 24" to 18" This means that the area reduction must be 1-18"/24" + a slip of ca. 2%

The wire then wraps around the 2nd block race which is slightly tapered so that the wire can slip upwards on to 4-6 collector pins where the wire accumulates. The wire then exits the upper section (or collector pin section via a spinner arm and over the payoff pulley located over top. The spinner back tension can be adjusted via a disc brake.

Bull Block with riding stripper equipped to operate with either 1, 2 or 3 dies.

This type of machine is popular among producers of rebar and weld-mesh.

Note the inlet roller gate on the first die box that can direct the wire either to the 1st (16") 2nd (22") or 3rd (30") draw-race allowing any wire size from 25mm down to 3.25 mm to be produced in one single operation from wire rod that range in size from 32mm - 5.5mm.

View of large riding stripper of collapsible type.

Before the operation starts the stripper is placed on top of the stripper block and secured (see picture above). During processing wire will collect on the block and the stripper. When full the stripper will be lifted by a crane and the wire stripped off the block. The stripper with the wire is then moved over a tubular carrier and collapsed where by the wire drops down over the carried.

View of Inverted Bullblock or Gravity Block

Inverted drawing machines (or Gravity Blocks) have a special range of applications.These machines are mainly used for coarse wire sizes, which have to be delivered on carriers with higher weights as achievable with a stripper block. Used in place of the conventional vertical type block for drawing or coiling wire that requires a mar free surface such as a plating quality wire.

View of Bullblock mounted on horizontal shaft

The drawing block can also be placed on a horizontal shaft with the wire moving axially along the block from which it falls off the block on to a carrier. These kind of machines are commonly used for cold heading wires with wire inlet diameter sizes of up to 50 mm

Continuous multi die wire drawing machines.

In order to draw wire through a number of sequentially placed drawing blocks an array of different machine types have been developed. As drive motors and controls became more affordable machinery builders were able to develop machinery that were both faster and more productive requiring less and less labor per ton produced. However a lot of machinery are still in operation why it is warranted to describe the more common types.

8-block wire drawing machine of overtop type

The author believes that this was the first or at least one of the first continous wire drawing machine with individual drive motors to each block.

3-block Morgan wire drawing machine

The wire pass on these type of machines differs from other machines in that the wire is pulled through the die wraps round the block that is slightly tapered allowing the wire as it accumulates to climbed and push the wire upwards and as it does the back tension diminishes so that it can be passed over a mushroom like hat and down through the block shaft that has a hollow center. The wire then passes over a pulley located under each block and the out in front of the machine and enters the next die via an inlet guide pulley on to the next block. Originally the machine had a single drive motor for all blocks and the blocks could be disconnected from the common drive shaft via a clutch. Later models had individual drive motors. These type of machines were particularly well accepted by makers of high carbon spring wire and the Morgan company has sold hundreds of these machines over the years.

8-block wire drawing machine of B-B or Double accumulating type

The first B-B Block machine was built in the late 30s by Marchal Richard Barcro. The machine quickly gained wide acceptance since it provided excellent cooling and eliminated the twist between the blocks something particularly appreciated by manufacturers of high carbon wire such as rope wire.

5-block Vaughn loop arm regulated wire drawing machine.

Note that the first block on the machine has 2 drawing races allowing the inlet block to pass 2 consequtive drawing dies before entering block 2. The wire exits the first block via a stationary pulley makes a loop round a pulley mounted on a springloaded arm and then enters the next die via a pulley placed on the soap box goes through the die and on to the 2nd block. The positioning of the loop arm on block 1 regulates the speed on the second block and the positioning of the loop arm on block secondblock regulates the speed on the following (3rd) block etc. The main feature with the loop arm machine was that it allowed the wire to pass from block to block in a straight line without the twist in the earlier overtop machines. A feature shared with the B-B machine shown but with the added advantage of less maintenance. When the Vaughn machine company originally introduced the machine it was powered by a DC motor generator set that fed a common armature voltage to all the individual drive motors and the positioning of the loop arm regulated the motor field voltages. Thousand of these machines were built until 1976 when the company went out of business. We show this machine simply because 25 years later there are still many machines in operation.

8-block wire drawing machine of tuner line type

The first TUNERLINE was built in the late 70s by Ernst Koch and since then KOCH has sold more than 400 machines world-wide, The advantage with this machine is the very small moments in the tuner roll assembly

Several suppliers to day offer sensor roll control machines. Below is a photo of Eurodraws MTS 1200 machine

Wire drawing machines with sensor arm control
and Horizontal axis blocks

GENERAL FEAUTURES

The MTO machine by Euraw draw is a multiple-block machine with horizontal-axis drawing capstans, sensor arm speed synchronization and an additional dancer arm on the finishing block. The high degree of automation and remarkable efficiency of MTO drawing machines, coupled with their sturdy, low-maintenance mechanics, contribute to achieve high quality production at the lowest possible operating cost.

DRAWING BLOCKS
The drawing blocks are made of forged C 50 carbon steel, induction tempered at medium frequency, to obtain a surface hardness of approximately 60 HRC. With this hardness, block wear is about three times less than that evidenced in blocks made of cast iron. Each drawing head is balanced statically and dynamically. Capstans are set in two parallel rows.
MAIN BLOCK FRAME
The following units are mounted on the main block frame: capstan cooling water and ventilation ducts; bush, bearing, junk ring and shaft of drawing capstan; mechanical transmission (see below).
TRANSMISSION
Motor power is transmitted to capstans by V-belts, in some instances assisted by a reduction gear lubricated in an oil bath.
MAIN MOTORS
Each capstan is driven by an AC motor. Motor power is calculated with an ample margin to ensure maximum security even in the most exacting operating conditions. Motors are generally installed horizontally on a slide rail for belt adjustment purposes.
SENSOR ARMS

Capstan speed is synchronized by sensor arms. An induction proximity switch on each sensor arm adjusts the speed of the drawing block according to the position of the sensor itself. Backpull can be adjusted to 10-15% of wire pull by rotating the relative spring mounted on each sensor arm. High working speeds can be achieved and the machine can be stopped in case of emergency without wire breaking.
DIEBOXES
The dieboxes, made of normalized cast iron, are equipped with a lid to avoid dispersal of soap dust in the working area. The dies are cooled directly with running water and are set in an easily removed die cartridge equipped with quick couplings. Dies are adjustable on three planes to ensure correct wire alignment. Motorized rotating dies with soap agitators, etc., are available on request.
SAFETY GUARDS
The machine is totally enclosed by a sliding gate with inspection windows.
WATER COOLING AND VENTILATION
The combined action of water and air cooling makes it possible to keep die wear low even at high working speeds. Capstans are cooled internally by a high-turbulence, "narrow gap" water cooling system, while the entire external pulling surface of the block is air cooled. The flow of air is directed at the motors and capstans through two separate conduits.
ELECTRIC EQUIPMENT
Most suppliers offer a choice of all major brand name electric equipment and the selection is based on local servicibility. Most equipment has a "self-diagnosing" feature that alerts operators to any malfunction, making timely maintenance possible. The electric equipment transforms the alternate current of the mains into direct current for the motors. Each motor has its own static, three-phase, fully controlled, stabilized and protected drive. AC motor powered machines are equipped with vectorial inverters.

Speed is adjusted as follows:

with constant torque: from 0 to max. speed with constant power: max. speed + 50% The stability and synchronism of each motor is controlled by an electronic data processing system which compares the reference signals with the data coming from the A.C. motor taco generators and angle transducers on the sensor arms, and acts on the motors accordingly. The angle transducers are specifically installed to achieve the area reduction range specified in the drafting table. The sensor arms are automatically centered while the machine is running. The dimensions of the electric cabinet comply with container shipping requirements (max. height 2000 mm). Standard machine is colored in blue, yellow and white, with oven-dried epoxy powder The electrics are contained in a modular, dust-proof cabinet equipped with an air/water heat exchanger, access doors at both front and back, and removable side panels.

15-block wire drawing machine with horizontal block shafts

One advantage with this block configuration is easier string up and that the wire pass through the soap boxes are verticle eliminating the risk for tunneling

Common for all types of wire drawing machines is to make sure that the wire has a straight pass from the inlet guide pulley through the wire die on to the block. This is achieved by adjustments on the inlet pulley, the soap box and the die holder. The operator has to watch that there is lubricants in the soap containers and he has to constantly keep watch and regularly check that the wire is round. These aspects will be covered in greater detail in separate chapters. Production speeds have increased as the drive technology improved

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