The development of the first strip thickness gauge worldwide, that could measure the thickness of the strip during the rolling process in cold mills with an accuracy of µm, was the start of our company in 1963.
Vollmer America
January 2007 Newsletter
Detects Waviness and Thickness:
Gauge for Generator Laminations
This measurement device detects the waviness and the cross profile thickness on single lamination sheets as well as the thickness on stacks of such sheets.
The mobile device has an own power unit for compressed air, which is covered by a noise reduction hood. On site, it requires only a standard main power supply.
The lamination sheets are put onto the measurement table single or in stacks of about 1.5″ height. Their position is determined by a set of positioning rails individually designed for each type of sheets. Two digital transducers in the traversable C-frame measure the samples from above and below.
The stacks are measured at a number of single measurement spots which were preselected by the operator. At each spot, the stack is compressed by a defined heavy load. Then the rams of the measurement transducers are released and the measurement tips measure the stack from the top and from the bottom. The transducer data are digitally transferred to the measurement computer where they are added and the stack thickness is displayed on the monitor. In parallel, the computer counts the pulses of a rotary step encoder in order to correlate the thickness data to the corresponding measurement location.
In the next step, the loaded trolley and the ram of the upper transducer are lifted and the trolley is moved to the next measurement spot. After the last spot was measured, the trolley returns to its zero position on the left.
For the measurement of single sheets, the measurement trolley is continuously traversed over the sample, measuring the entire cross profile thickness. In addition, the data of the bottom transducer are evaluated to calculate the waviness of the sheet. Such measurements are automatically terminated 2″ behind the final edge of the sheet, in order not to end it too early in case of cutouts. During the measurement pass, the data curve builds up on the display and the result is stored.
The evaluated measurements are displayed in form of a curve (single sheets only) and as numerical data. The individually designed software offers a large selection of parameters to customize the measurement procedure as well as the data evaluation and visualization. All data and graphs can be printed and stored as requested. The control software offers to store a large number of measurement procedures to meet the requirements resulting from the individual shapes of the lamination sheets for different generator models.
The positioning rails allows to compare the measurements of several samples of the same type and to achieve a good measurement repeatability. The main reason are the cross profile thickness variations of the precursor strip material, which add up the more, the more sheets are piled to a stack. On single sheet measurement, the positioning rails prevent light samples from becoming dislocated by the moving transducer tips.
VBP 2200
This classic type VBP gauge was recently delivered to an aluminium mill for the cross profile thickness measurement of cut samples up to a width of 2200 mm (appr. 86″). The sample is automatically clamped between two hydraulically operated brackets after the protection hood was closed by the operator. Two electronic measurement transducers, installed in a C-shaped measurement frame, are traversed along the sample, measuring the cross profile thickness from the top and from the bottom side.
In this classic type VBP gauge, the sample is inserted flat, lying between two wide, bending resistant brackets. Each bracket has a long slot, through which the transducers can measure the strip sample. Beside the cross profile thickness, this gauge produces very accurate absolute thickness data, especially on medium and thick strip samples.
In comparison, the VBP 04 type offers an advantage on measuring thin strip. Its clamping procedure, (sample inserted vertically, clamped between two rows of separate brackets, starting in the middle and proceeding towards the edges), ensures a fixation without knuckles in the measurement area. This results in an increased profile measurement accuracy. The classic type VBP in comparison, sometimes presses the results of strip shape defects from the wide clamping sections into the narrow measurement slot. There they sum up in form of knuckles. On the other hand, the VBP 04 clamps only one edge of the sample, so that the measured section is not always standing absolutely perpendicular. This doesn’t affect the profile measurement accuracy, but the VBP 04’s absolute thickness measurement data do not always reach the perfect accuracy of the classic type.
VUD 200
This VUD gauge, which was recently delivered to a large roll shop in China, can measure rolls between 2000 and 300 mm (appr. 78″ and 12″) in diameter. The VUD is installed on a bridge stand over the grinders maindrive engine. The two outer measurement arms can be traversed in and out to fit the individual roll diameter. They measure roll form and diameter while the support is traversed along the still standing roll. Alternatively, such a pass can be used to measure the roll alignment by the measurement arm on the grinding wheel side. The same arm is used to measure the roundness on the rotating roll while the support is standing still. The third measurement arm, installed above the center axis of the roll, is used to measure the roll levelling or the cone angle of the roll necks while roll is standing still.
For measurement, the two outer arms are first traversed motor driven to their outer limit and then lowered pneumatically. From this position they are traversed inwards until they touch the roll surface. The third measurement arm, above the roll axis, is lifted and lowered by a motor. All three measurement arms are lowered only for measurement, they remain in their upper positions during the loading of the grinder as well as during the grinding process.
The VUD is controlled by a Vollmer PC, running the roll measurement software VWM. The VUD is controlled manually by means of a touchscreen, only some control signals are exchanged between the grinder and the gauge. Some functions within the VUD are running semiautomatically in form of follow-up-sequences. If a command is not accepted, e.g. because not all conditions are fulfilled, a clear text error message is displayed on the monitor. However, by switching into the service mode, an experienced operator is enabled to control the VUD machine regardless of the electronic interlocks which protect the gauge in the standard operation mode.
VPM/07
This system was designed for a customer who wants to measure the flatness of thick strip and sheets on the outgoing side of a leveler. The data are evaluated for the calculation of control signals for the leveller.
The automatic flatness control was derived from the shape control systems with shapemeter rolls, which Vollmer has already installed on a large number of levellers. However, a roll could not be used in this case. First, the thick material is too strong and its springback effects would disturb the shape measurement, second there is no strip tension which is always required for measurement by a shapemeter roll.
So the VPM/07 measures the topographic flatness of sheets by a row of separate measurement wheels, each wheel forming a measurement zone.
The sheets pass over the measurement device, and all wheels are pushed against the sheet’s underside with the same defined load. Each wheel runs on top of an own column, so that it can independently follow the vertical movements caused by the strip waves in its measurement zone.
A digital sensor inside each column measures the up and down movements of the wheel. The data of all sensors are evaluated by the flatness control computer. The measured topography of the strip is then utilized for the calculation of control signals so that the correction elements of the leveller can optimize the strip flatness.
The columns are pneumatically pushed up from the down position into the measurement position, the stroke is 100 mm (appr. 4″). If – on narrow strip – the outer wheels would run free, they stay down automatically to prevent them from becoming damaged by the strip edge.
Since the lateral strip position is not exactly defined in this first application of the VPM/07, a camera based optical strip edge detector was added.
The camera frame is mounted on a slidebase which is traversed by a motor, controlled by the PLC. In the standard operation mode, it moves forward and stops automatically once it has detected the strip edge.
Since edge detection is performed only on one side, the flatness computer puts out the strip width to the camera controller. To find the strip edge, the camera C-frame moves forward and stops at a position when the strip edge is in the middle of the camera range. The flatness computer adds the camera measurement data to the drive distance. This leads to a calculation of the positions of both strip edges. Those measurement wheels not fully covered by the strip are then held down.
Since the camera has a limited measurement range, the automatic edge detection (if activated) traverses the camera frame forth and back to follow the laterally moving strip edge. The computer pulls down every wheel which is not covered by strip any more, and the measurement data of the rulers in the affected columns are eliminated from the current flatness measurement.
In this individual application, the flatness measurement device is used to measure cold strip of stainless steel. The thickness ranges from 1,5 to 8mm (approx. .05″ to .32″) and the width from 800 to 2100 mm (approx. 31″ to 83″). The strip speed is 20 to 50 m/min (approx. 22 to 55 yards/minute).
Portable Light-Gauge Inspection Device
This small, mobile thickness measurement device has been a successful part of the Vollmer product range already for a number of years and is still sold frequently. A solid aluminum case protects the thickness gauge and, when opened, it provides a suitable workbench.
The case comes with a punching device which is used to cut small samples from the test material. By means of the delivered tweezers the sample is inserted between the feeler tips in the C-shaped measurement frame.
The standard version of the VMK is designed to measure samples of cold strip up to 1mm (approx. .04″) thick. This corresponds to the measurement stroke of the LVDT transducer.
For thicker samples, the VMK can be ordered with an adjustable transducer. The punching device is made for samples up to 1mm.
The measurement feelers are one electronic transducer (optionally adjustable in a micrometer thread) and a stationary feeler pin at the opposite side of the measurement frame. The transducer signal is passed to the VMF measurement amplifier which displays the measurement result in analogue form as well as a digitally.
With Digital Long Stroke Transducers
For some suitable applications, the thickness gauges VBM 1076 and 1065 Module can be delivered with digital long stroke transducers.
The digital transducers (type DG) provide a large measurement stroke (bottom transducer up to 5mm, appr. .2″, upper transducer up to 10mm, appr. .4″), so that they can measure strip up to 7mm (appr. .27″) thick, without requiring mechanical adjustment of the upper transducer.
This means, such gauges have no gear drive, no stepper motor and no motor control. Instead of the VMF amplifier, a PC indicates the measurement data, and optionally the data can be visualized and evaluated by the software VGraph or VRecoS.
In suitable applications, this makes the gauge operation easier and the gauge servicing as well.
VBKÂ 1596/11
The VBK 1596 is a double track thickness gauge for thin strip which runs flat and relatively slow in a strip processing machine or in an inspection line. The strip is measured continuously while it passes the 130mm deep measurement mouth.
Two C-shaped measurement frames each carry an electronic transducer, measuring from above, and a firm measurement feeler pin, measuring the strip from below. Due to strip thickness changes, the transducer measurement tips are pushed in or come closer towards the firm feeler pins.
The gauge height is adjusted to the passline by its spring suspended vertical guide. Two horizontal rollers guide the strip through the gauge. The frame, which carries those rollers can be rotated to a position where the roller axes are not rectangular to the strip edge. This causes the gauge to pull itself against the rear strip edge, thus ensuring that the transducers will always measure in the selected tracks. This goal is supported by a spring, which pulls the set of Cframes towards the strip while the gauge is blocked in the slidebase by a pneumatic brake.
The C-frames can be set across the strip independent of the lateral guide rollers. This enables the gauge to measure any track up to 130mm (appr. 5,1″) off the rear strip edge.
The slidebase allows to pull the gauge forth into the measurement position and to push it back into the resting position at the rear.
The transducer rams are pneumatically lifted when the gauge is not at the rear limit or when the brake is not activated. This prevents them from hitting the strip edge while the gauge is pulled into the measurement position.
Automatic Kanban System
“No, it’s not a vending machine for softdrinks” explained Wolf Achilles when I asked him about the new blue cabinets in the machinery department, “its an automatic vending machine for carbide tips”.
This paragraph is an explanation only for the nonmetalists among us: Carbide tips are small, hardened metal plates with one or more sharp edges. In many different shapes they are used as cutting and chipping tool tips for turning lathes and milling machines. The cutting edges of the tips wear off relatively fast, and therefore they have to be replaced quite often, so that every workpiece gets a nice and smooth surface and comes out with accurate dimensions.
The machine tools in our machinery department require hundreds of different shapes of carbide tips. And since we have the big CNC machines, the consumption of tool tips has considerably increased. So did the size of our tool tip stock. But holding large amounts of goods in stock is binding capital, which can be used more effective when being invested elsewhere in our company.
The new vending machine contains all kinds of carbide tips which are used in our machinery department. All members of staff have a chip-card and a PIN to access the system. The monitor displays a table with the available cutting tips including the properties and a picture of each tip. When the tool kind is entered, the machine automatically puts out the right number of cutting tips, and not before this moment our company has to pay for them.
The vending machine has an on-line connection to the supplier of the carbide tips. As soon as the number of remaining tips falls below a preset limit, a fill-up supply is actuated.
This principle of production management is called ”Kanban”, the Japanese word for “file card”. The main idea is, that the consuming station exercises control about the output performance of the source. Kanban is said to enable a company to react more flexible on variable demands without having to hold in stock large amounts of precursor material. Kanban’s automatic regulation circuits (checking of the amount in stock and fill-up supply) relief everybody from ineffective and time consuming sidework, so one can concentrate on the work he is specialized in.
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