What does offset mean? Offset

Operating principle

Seal

In traditional offset printing, the ink hits the paper by passing through at least two rollers - one called the plate roller and the other called the blanket roller. The form is most often a metal plate coated with a photosensitive layer. Then the image is applied to the form. After exposure and development, the exposed parts of the form begin to attract water and repel any oily substance, in particular paint. Such parts are called hydrophilic and (less commonly) oliophobic. The remaining (unexposed) parts of the forms begin, on the contrary, to repel water and attract paint. They, in turn, are called hydrophobic or oliophilic. Thus, the paint gets only and exclusively onto the hydrophobic parts of the form, forming letters and images. With each rotation, the roller with the printing plate is washed with water using a system of dampening rollers, then paint is applied to its hydrophobic parts through a system of ink rollers. The image is transferred from the roller with the printing plate to the offset roller, and from there to the paper. The offset roller results in less plate wear and greater paint evenness.

Transferring an image to a printing form

There are several technologies for transferring an image to a printing form. Among them are computer-to-plate or phototypesetting technology.

Printing Color Images

MAN Roland press

Using the technology described above, it is possible to obtain an image of only one color - the color of the ink used in the ink rollers. There are several ways to print a color image, of which the two most common should be mentioned. This is printing in several passes and printing on a multicolor printing machine. Both of these methods are based on the decomposition of any color into several color components, for example densitometry, colorimetry, and proofing.

Types of offset printing and development

The most modern type of offset printing is considered to be the so-called. digital offset. Using this technology, the image is applied to a printing plate directly installed in the machine. Traditional technology using photoforms is now called photo offset. In addition, a classification is also introduced according to types of materials - sheet and roll (rotary). Rotary offset printing machines do not use individual sheets of paper, but rolls - paper rolled into a huge roller.

Many car owners, even those with serious experience, often do not treat disc offset with due attention and consider it an insignificant parameter. Their logic is simple: the number of bolt holes, their diameter and the distance between them is really important. Any deviation from the factory parameters will make it impossible to install the disc on the wheel hub. While disc offset slightly different from that stated by the manufacturer will not interfere with installation, you just need to apply a little force.

A similar opinion can be heard from specialists at tire centers, who claim that disc offset has virtually no effect on the handling and functioning of the wheel and main suspension components. But is this really so?

Definition and calculation formula

In automotive terminology, disc offset is the distance between the plane of application of the disk to the hub and the vertical plane of symmetry of the wheel. When marking, the disc overhang indicator is designated as ET(measured in millimeters). You can determine the disc offset yourself; there is a simple formula for this:

ET= a-b/2

Here A is an indicator of the distance between the plane of application of the disk to the hub and the internal plane of the disk, and b– its width. Even from a simple analysis of the formula, one can understand that the disc overhang can be both positive and negative (in some cases, zero). In practice, the most common discs are those with a positive offset parameter.

Before making a purchase, pay attention to the marking: ET30 means a positive disc offset of 30 millimeters, and ET-10 means a negative disc offset of 10 millimeters.

It should be noted that the wheel offset is not affected by parameters such as tire diameter and width. This means that, regardless of the type and diameter of the tires used, the permissible wheel offset for a particular model of a certain configuration may be the same.

Disc offset in different configurations of the same model

In practice, the disc offset indicator for cars of the same make, model, and even the same year of manufacture can vary greatly. The only difference in these cars concerns the type of engine used, its power and weight. And this explains everything, because to calculate the permissible disc offset, designers take into account many circumstances that affect the operation of the suspension.

Each engine has its own weight, which affects the direction of the force vector to certain suspension parts. Depending on the force vector, the design parameters that ensure the safety and quality of vehicle controllability when driving at high speed may also change.

Deviations from the norm and possible risks

“Reputable” experts confidently state that the permissible disc offset deviation should not exceed 10–15 millimeters. This disc offset will correspond to the manufacturer's recommendations for a car of a certain make, model and configuration. It is important to remember that a deviation of 10–15 millimeters is the limit value for disk overhang, exceeding which can lead to serious problems. As practice shows, disc ejection with a significant deviation from the factory requirement (20–30 millimeters or more) is a serious risk from a safety point of view. Changing the vector of force to the main suspension components will subject them to loads that the parts are simply not designed for. As a result, the service life of the suspension elements will be significantly reduced, and in the most critical case, they may collapse even while driving.

This is a misconception. The same car often has different wheel configurations, for example, narrow wheels with winter tires with an 18″ diameter will have an offset of +62, summer wheels with a diameter of 20″ with wider tires will have an offset of +52, and for modifying the car with sports styling and arch extensions, wheels with a diameter of 21″ can have an offset of +45. This is further confirmation that the automaker allows the installation of wheels with different offsets. For civilian vehicles, only in extreme cases will it be necessary to adjust the camber and toe of the wheels.

Deviation from the recommended offset value can only significantly affect sports cars designed by manufacturers for track use, since all settings are tied to the parameters of the wheels. In this case, the suspension may need to be reconfigured, but again, this is not relevant for civilian vehicles.

Also, some often argue that random disc flyout affects the degree of wear of the hub bearings, increases the load on the suspension arms and significantly increases the risk of serious problems.

This is again a misconception. The car's suspension suffers from bad roads and large unsprung mass; correction of the offset in this case does not pose any threat to the car. It is better to think about the weight and strength of the discs.

What does departure affect?

The offset allows you to adjust the location of the wheels relative to the arches. Most new cars have factory wheels that are quite recessed inwards, the wheels are literally lost in the arches. By correctly calculating the permissible offset correction, you can “pull” the wheels outward, closer to the edge of the arch, and thereby achieve a finished appearance. When calculating a new offset, it is necessary to take into account the tire size, since by moving the disk, we also move the tire. There must be sufficient clearance between the wheel and the fender liner and other elements located in the immediate vicinity of the wheel.

An excessive change in the offset to a smaller direction (outward) can only have a negative impact on practicality: the risk of damaging the discs when parking along high curbs increases, the car body will become more dirty, and in the car interior it may seem that the noise in motion has increased. In this case, it is recommended to install arch extensions or correct the disc offset.

Spacers and adapters

To change the offset it is not always necessary to purchase new discs; the use of spacers or adapters is allowed.

A spacer is installed between the hub and the disk, which allows you to move the wheels outward, but you must take into account the length of the bolts or nuts (depending on your car). Fasteners should be tightened 6.5 turns. The maximum permissible height of the spacer is 15 mm. Higher spacers are highly not recommended for use, as they will require the use of too long bolts, which may subsequently collapse.

It is best when the disk is provided with matching holes and a platform for the spacer, which allows you to firmly fix the spacer on the disk itself and eliminate the risk of vibrations and beatings in the future.

In cases where it is necessary to increase the overhang by more than 15 mm, adapters are used. The adapter is screwed to the car hub, and the disc is installed on studs pressed into the adapter itself. In this way, overhang correction of up to 60 mm can be obtained. Higher adapters are not recommended due to excessive stress on the structure.

However, if it is possible to order wheels with the “ideal” offset for your car, it is better not to use any additional accessories - this is the most convenient and reliable installation scheme.

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Details

OFFSET is a knife that has the ability to compensate for distortions that occur at break points. Most cutting plotters are equipped with such a knife. But its use has some nuances that a beginner needs to know. This article is a clear and simple instruction on how to use offset, which will help you set up work on your plotter as accurately as possible.

People involved in outdoor advertising with experience know that cutting plotters equipped with a free blade have the ability to compensate for distortions that occur at the bend points of the curve - this is OFFSET. For beginners who do not understand what we are talking about, a brief methodological excursion: cutting vinyl films with a cutting plotter; what is a cutting plotter; What is the difference between a cutting plotter and a drawing plotter? types of cutting plotters.

A classic plotter is a vector peripheral device for a computer, and it is designed to display images that consist of lines. The purpose of a drawing plotter is to accurately move a writing unit with a special drawing instrument (pencil, felt-tip pen or rapidograph) over the medium (often paper). By moving, raising and lowering the tool along the media, you can obtain fairly accurate copies of electronic images/drawings on the computer. Due to the fact that the point of contact between the paper and the drawing tool coincides with the axis of the plotter, copies are extremely accurate. Despite the absolute obviousness of this statement, with a cutting plotter everything is a little different.

The main difference is that the cutting plotter has a cutting unit instead of a writing unit. That is: on a regular plotter, in order to get a mark on the paper (drawing), just a little pressure directly on the drawing tool is enough; on a cutting plotter, the working tool is a small, sharply sharpened knife, but the cutting head and its movement servo unit are designed to withstand much greater pressure forces.

How a knife cuts film

There are two options for solving this problem:

1. The first option is “frontal” - make the knife rotate “by force”, that is, turn it every time in the direction of movement of the head. In this case, a high-speed and precise servomechanism for rotating the plotter knife is installed on the head. When the cutting plotter changes the direction of movement of the head, a special microprocessor accurately calculates the degrees of rotation, and then rotates the knife to the required angle. Cutting plotters with this control method are called plotters with a tangential knife.

It is worth noting that on plotters of this type there are no problems with cutting distortion, since the cutting edge of the knife is located exactly on the mathematical axis of the plotter. Thus, the plotter knife at the turning point is forcibly directed in the required direction, where it remains in this position until the next turn. Regarding the cost of tangential plotters, they are definitely more expensive than conventional plotters, ranging from 15-30%.

2. The second option, making the knife rotate in the direction of cutting, is more practical and cheaper. It is enough for the plotter knife to be allowed to rotate freely around its own axis, so it itself will rotate in the direction of movement of the carriage. In this case, the guiding role is played by the cutting edge of the knife, which is located behind the mathematical axis. Once the direction of movement of the carriage is changed, the knife automatically aligns with the cutting edge forward along the path of least resistance. Cutting plotters of this type are the most common, and they are called plotters with a free knife.

Application of offset in plotter cutting of film

Despite the fact that such plotters make up the vast majority of the range of such equipment on the market, they have one annoying problem. During a sharp turn, for example, 90 degrees, the plotter knife cannot instantly move to a new axis in relation to the movement of the carriage. This fact can be explained quite simply: when changing the cutting direction, the plotter knife must “run” a certain distance until friction aligns it exactly with the given cutting direction, because with a sharp change in direction, the knife remains in the previous position for some moment. The rotation of the knife occurs during the movement of the carriage “on the fly”, as a result, in order to get on the desired path, the plotter knife describes a certain curve. This is how distortions arise.

These distortions are small and, by and large, unnoticeable in the final result of the work, but there is one big “BUT”. The point here is that the contact point of the film and the knife in the cutting area is not located exactly on the mathematical axis of the plotter. The cutting point itself is slightly shifted from the axis of the plotter, which makes it slightly difficult to track the deviation of the carriage movement. It is this feature that is the main trouble for quickly and efficiently turning the knife. When turning, the plotter blade slightly bevels the corners, thus distorting the entire work. Of course, with large cutting sizes this problem is barely noticeable, but on small elements, for example, some symbols 1-2 cm in size, these distortions are noticeable to the naked eye. These distortions can render the final work unusable - which is absolutely unacceptable for any enterprise.

What to do in this situation

First of all, you need to make sure that the plotter at turns “jumps” a little further than the turn itself, thus, the slightly lagging cutting area will “reach” the coordinates of the turn. To compensate for the distortions that occur when aligning the knife in the cutting direction, you need to make the carriage move along the required path. With the right values, distortion is fully compensated, resulting in ideal results.

The predistortion itself is called OFFSET, which stands for (counterbalance, compensation, compensation). The amount of distortion introduced into the cutting process depends on several factors. The main one is the distance from the cutting edge to the mathematical axis of the knife. If (the thickness of the processed film is taken to be “infinitesimal”), then the result will be exactly the distance that the cutting plotter must “overshoot” before turning. In determining the value of offseta, this factor, contributing 90% of the value, plays a decisive role. In practice, when the actual offset values ​​are established empirically, knowing the offset value of the knife is extremely important as a starting point during experiments. The characteristic offseta value of knives for the vast majority of plotters is 0.03 mm - 0.05 mm.

What does the value of offseta depend on?

It should also be noted that the offseta value also depends on the thickness of the material being processed, that is, the thinner the film, the greater the offset value should be, respectively, the thicker, the less. However, the influence of this factor in everyday practice is hardly worth taking into account because most of the films used have almost the same thickness. However, if it is necessary to cut thick materials, for example, such as sandblasting templates or textile thermal films, the offseta value must be taken into account, since you can quite easily encounter such a problem as undercutting the material at the bends.

In real life, as a rule, most manufacturers deal with a permanent (one) plotter with standard films and standard knives. Therefore, a high-quality offset value set once resolves all significant potential problems of a cutting plotter with a free knife. In modern plotters, the manufacturer sets the average offseta value, which is the most suitable for most cases. But a deeper knowledge of the problem will significantly help the music maker to manage this or that current situation, as well as successfully find the easiest and most effective way out of difficult situations, for example, with non-standard orders.

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Offset- one of the types of counter transactions, which in its essence is very similar to counter purchases, barter or compensation transactions. The main difference between offset is its focus on certain types of goods (for example, military products). When registering an offset, the parties put forward counterclaims regarding the investment of a share of capital in the economy of the importing party.

Offset- one of the forms of transactions that involves the customer party putting forward counterclaims against the product supplier.

Offset- the process of closing a previously open position to sell or buy an instrument by creating an equivalent position, but in the opposite direction.

Offset: essence, goals, forms

Offset transactions are part of back-to-back trade transactions and represent a countertrade option. In its essence, an offset is a variant of a gentleman’s agreement concluded orally. This is an informal agreement that is not documented in any way. The basis of the relationship is mutual trust. The main feature of offset-type transactions is that within their limits it is possible to formalize not only an informal type of transaction for the exchange of services (goods), but also provide the importing party under the contract with the opportunity to invest funds for further receipt of benefits and services from the exporting party. As a result, offset operations have all the signs of industrial cooperation between the parties.

Purpose of offset- compensation for the costs of purchasing expensive equipment. In slang terms, offset is often called “rollback.”

The main forms of an “offset” transaction include:

1. Trading. In this case, a certain product is carried out by the exporting country to another state.

2. Investment. This implies an investment of capital in one of the industries by a party selling a certain type of product. In this case, it is not necessary that the investment object be related in characteristics to the product itself.

.4. Educational. This type of offset transaction involves the training of specialists servicing the purchased equipment.

Offset: distinctive features, types

The main difference between offset and transactions involving the exchange of goods between the parties to the contract is the formalization of several (usually two) signed contracts with a group of mutual requirements that bind the parties to certain obligations. The essence of the latter is to carry out a counter-purchase within a certain time period.

Another feature of offset is the lack of legal force for the obligations of the exporting party regarding the counterpurchase of goods. And this despite the fact that the exporter gives his consent to the purchase of a certain batch of goods from the importing party to compensate for the contract price. The only thing is that the volume of such a transaction is not legally established.

When concluding an offset operation, the parties can agree on an offset price, which may be greater than the total price of the concluded export contract. Such deals are very popular for companies operating in developed countries. As a rule, they have a close connection with purchases of equipment for nuclear power plants, purchases of military equipment, and so on. Such operations are most actively used in India and Malaysia. For example, the transfer of military goods to Malaysia is carried out on the basis of a counter purchase of palm oil.

Offset feature- inclusion in the operation of certain supplies that are directly related to the exported products. The counter-delivery price is usually offset by the exporting party in the form of a proportional reduction of the full price of the international sales agreement.

Compensatory commercial transactions within the boundaries of countertrade relations imply the process of counter-delivery of the object of the transaction within a certain period of time. Delivery is made on the basis of a more complex purchase and sale contract, a specified contract or annexed advance and counter purchase agreements.

In terms of calculations, offset is distinguished by a coordinated mechanism of financial settlement transactions, determined by counter and real financial (including commodity) flows between the parties to the agreement. produced in various forms:

Through the use of a clearing mechanism, where the arbitration function is assumed by;

Through transfers of hard currency (cash).

Based on the specifics of the supply of goods and settlements between them, several types of transactions can be distinguished :

Short term;
- on counter purchases;
- for advance purchases.

In turn, short-term operations can be divided into several forms - with full or partial compensation, as well as with a 3-party compensation option. The last type is a cross between commodity exchange and compensation transactions.

Transactions involving full compensation are based on an equivalent purchase of products by the exporter for an amount equal to or greater than the exporting party's delivery price. The development process of such operations has a number of main stages:

Valuation of goods to be exchanged (in financial form);

Mutual supplies of goods in the volume determined by the parties and within the agreed time frame;

Carrying out a mutual offset operation, which is often carried out through special proceeds from the sale of supplied compensation products of the importing party against the funds that form for the object of the transaction supplied by the exporter.

In operations with partial compensation, only a certain portion of the goods supplied by the exporter is covered.

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