4ª part of SEAM THEORY
13º.- ANALYSIS OF THE SEAMS
It is necessary to implement a system of analysis, based on the periodic data obtained in the monitoring of the work of a seamer. If the seamer is perfectly adjusted, any significant change in the quality of the seam is quite likely due to the bodies or ends rather than the machine itself.
Currently very different types of seamers are used, from a simple seaming head to those with 16 heads or more. It is essential that the seaming process be stable, in all heads, requiring a rigorous control of the process of each head.
By establishing a trend analysis, based on the daily representation of the results of the seam, it can be established, for each type of seamer, the necessary frequency of the adjustment actions by objectives. Well-designed and constructed seamers may need adjustment by objectives every three months, while others must do it weekly.
In the case of seamers for irregular containers, the process of adjustment of objectives in general is not so precise, due to the limitations within the design of this type of machines. However, the same principles can be applied.
In general terms, to properly follow the evolution of seams in a seamer, the following principles can be applied:
1.- A sample must be collected at regular intervals, normally one from each seaming station, marking its origin.
2.- Each package is subjected to the measurements and approvals indicated above, noting the results obtained.
3.- The results of the measurements must be compared with the data marked in the specifications. For this, the average of all the measures must be determined, taking into account the maximum and minimum, comparing this average value obtained with the specifications, as well as its range of variation.
4.- The results obtained should be compared with those obtained from other previous samples, in order to check the condition of the machine and to correct its mismatches without having to stop it.
5.- If it appears that the seam is out of control, it is convenient to check 5 containers per station to ensure that the values previously obtained are true
6.- It is also important to carry out an evaluation of 5 containers per station, when starting to work after a long stop, after a change of format, or even when changing tools in the machine.
If the comparison of the measurements shows us that the machine is going out of adjustment, or the seams that are obtained are gradually separated from the specifications, this may be due to one of the following causes:
a.- Some change in the characteristics of the bodies or ends with which the equipment is fed.
b.- Dirt in the machine.
c.- Excessive wear of any part of the seamer.
e.- Any interference or jamming of machine mechanisms.
It should be emphasized that the statistical control of seams, ensures greater efficiency, and gives us a clear indication of when to act on the regulation and adjustment of the seamer.
In a seaming of multiple seaming heads, the task of making frequent monitoring of several containers per head, is a long and laborious task, but it deserves to be penalized, even if this machine has been equipped with new technology tools, which They are expensive; it is a contradiction to make this expense so as not to have the machine at all times well adjusted through this frequent monitoring.
14º.- PROTOCOLS OF MAINTENANCE OF THE SEAMER
The main task of maintenance, with enough difference on the others, is a correct lubrication. The most vulnerable areas of the seamer are the parts that move at a higher speed, such as the spindles of the chucks, compression plates, seaming rolland the bottom feeding system.
The axis of the chuck and that of the compression plate are particularly susceptible to seizing, not only for the lack of lubrication, but also for contamination with the product, in the case of seamers in canning factories.
After each fabrication, sufficient time must be spent cleaning those vulnerable areas, where the product spillage may have caused mechanical damage, or a generation of heat localized by friction. Once the pressure washing process is finished, it is important to make a greasing to ensure the exit of the trapped water, and in particular of the cleaning liquids, to ensure that they do not contaminate the sensitive areas, such as the bearings of the seaming rolls. It is inefficient to develop an adjustment for objectives if it is an obsolete machine, with corroded vulnerable areas. This can frequently occur in seamers that have only seasonal production.
Seam builders perform engineering efforts to reduce the frequency and proper maintenance of the greasing task. However, oil recirculation systems and self-lubricating installations of the routines only exist in modern equipment. Many of the old seamers, which still work perfectly, need the necessary care and attention to stay in good condition, and be able to produce good quality seams.
15º.- TECHNICAL IMPROVEMENTS OF THE SEAM AND EVOLUTION OF THE SAME (MINI SEAMS)
The arrival on the market of high-speed sealing machines, the reduction of the thickness in the tinplate as well as the increase of its hardness, the introduction of the reduced double tinplate, the generalization of use of “two-piece” type container, and the increase of the The use of seam components from other materials, such as TFS or aluminum, has led to the updating of the seam concept.
In fact, everything is born of the growing need to reduce the costs of packaging, causing continuous improvements and changes in the manufacturing processes of bodies and ends. A very significant advance in the field of cylindrical cans is the “two-piece” type DWI container, that is, the canister formed by drawing and subsequent stretching and ironing of its walls. Its great diffusion in the field of carbonated beverages and beer, implies the additional requirement that the seams must be hermetically subjected to certain internal pressure, so that it does not reproduce loss of carbon dioxide.
The obvious advantages of this change are the elimination of any type of lateral seam and the need for a single union between the body and the lid. Irregular cans, obtained by shallow drawing, have also benefited from this new manufacturing technology.
Another great advance has been the significant reduction of the thickness of the bottom and body. By using thinner and more resistant materials metal is saved, and also with the introduction of reduced double steel, the properties of the containers can be maintained.
This evolution has required the introduction of the “mini seam” technology, which ensures the maintenance of the seaming process, with the new thinner and harder materials. This seam is also made possible, by the facilities that present it, the sausages or three pieces with electrically welded seam. Obviously, a smaller seam means a greater degree of precision than normal-sized seams. However, if we want to correctly implement the use of very thin and hard materials, it is necessary to change the techniques of using the “mini seam”, to maintain the minimum level of critical sealing parameters. This brings with it, the need to properly train in this new technology, mechanics and people involved in the technique of conventional seam.
Evolution of the seaming
During the last decades, the bodies and bottoms of containers made of coated steel (tinplate, TFS …), have been optimized by the users (for example: improvements in their handling, storage, process conditions …), and packaging manufacturers ( for example: improvements in the manufacturing process, thicknesses, properties …), taking into account the use of thin materials combined with high hardness (for example: the use of reduced double tinplate)
The use of thinner and more rigid thicknesses for the manufacture of ends has directly affected the quality and integrity of the seaming processes. The size or type of seam that was defined and adapted many years ago, for the use of reduced simple tinplate, thicker and softer, is not necessarily adequate to guarantee a good quality of seamd using now a hard and rigid sheet.
As a result, the size or type of seam has not evolved in parallel with the change of specifications of the body of the containers and especially of its bottom. When applying the dimensional criteria of the types of seams in force with these materials, they generate a series of problems, the main one being the presence of an excessive level of wrinkles, which is a detriment to the quality of the seam.
During the seaming process, the metal of the part of the wing of the bottom is “reduced”, and this operation is more pronounced the more peripheral is the point, being maximum at the edge. Thus point “A”, see drawing no. 63, moves from position 1 in its initial state on the cut flat disk, to position 2, when the bottom is already curled. Finally it moves to position 3, once the seam is finished.
Figure nº 63: Evolution of the metal in the wing of a end
In this “reduction” process, there is a “leftover” material caused by the decrease in diameter. The natural tendency of metal is to form wrinkles. While these wrinkles can be minimized or eliminated, applying greater tightening during the seaming process if “soft” tinplate is used; There will be more and more difficulty, regardless of the type of seam routines used, when a thin, hard metal is used. This difficulty will increase significantly in the case of diameters of small containers, affecting the integrity of the seam. Hence, to eliminate the serious problem of excess wrinkles with hard and thin materials it was necessary to rethink the classic criteria of a seam.
The only possible solution is to reduce the amount of metal of the bottom wing to be “reduced”, resizing the seam, depending on the new specifications of the body and bottom of the container. In short, the decrease in thickness and increase in hardness of the material of the body and especially the bottom, forces to redesign the flange of the body and the wing of the bottom, passing to smaller standards. This has led to a new generation of seams designated as “mini seams”
In this way, the range of seam types with smaller sizes is increased. These new types are valid for both thin and hard (DR) and thick and soft (SR) sheets.
In the drawing no. 64, the evolution of the process of reducing the size of the bottom wing, which has taken place over the last decades, is linked to the use of new materials. This has brought with it, the reduction of the initial cutting diameter of the disk, and consequently a decrease in the consumption of material, and consequently a significant saving.
Figure nº 64: Evolution of the size of the seam
The use of this type of DR material affects not only the seam, it is necessary to redesign the background profile, modifying elements such as the depth and configuration of the tray, and redefining the shape of the expansion rings of the central panel.
The reduction in the thickness of the bottom and the adoption of reduced double material, inevitably requires a smaller radius of the base of the same tray, and increase the depth of said tray to achieve good results in the seam. This change reduces the penetration effort of the chuck in the bottom.
The technique of realization of the “mini seams”, requires a degree of precision superior to the conventional seam, the tools to use must of better quality, and it is always desirable to use parts (chucks and routines at least) covered with chromium carbide or nitride of titanium. Let’s specify the necessary advances in each seaming operation.
The correct formation of the first seaming operation is always the most important factor to achieve a good quality. The technology of the “mini seam” requires extra care at the time of the 1st operation, since the harder and thinner the blade, the more difficult it is to control the presence of wrinkling. Hence, the profile design of this seaming roll is decisive to be successful in this step. During the process of shaping the metal, it is essential that the edge of the bottom loop be positioned in the center of the radius of the flange of the container. See figure nº 65.
Figure nº 65: Correct section of the 1st operation of a “mini seaming”
The new reduced design of the bottom wing is such that it only contains the minimum material sufficient to achieve the adequate length of the bottom hook. Therefore, if the first operation seaming roll does not have a correct profile, or is ruled defectively, and does not place the wing material in its exact position, there will be insufficient overlap at the end of the seam. The alternative of adding more material to the bottom wing, to ensure a better bottom hook would have an adverse effect, because it would generate unacceptable wrinkles from the point of view of tightening the seam.
The ends designed for “mini seams” have an end or edge of the curl, in which the final straight section has been eliminated, having it rounded up to the cutting edge. Figure 66 shows the straight part of the end of the curl in a conventional background and next to it the aspect that a background of this new type should present.
Figure nº 66: Comparison of a 1st operation in conventional seam and a mini seam
On a black background you can see the images of the 1st operations that both types of curls would generate. It is evident that this design gives an additional control of the material during the formation of the bottom hook in the 1st operation of the seam.
When we analyze the aspect of the section of a 1st operation, achieved with this new background design, we can see that a radical improvement has been achieved using this technology. The material is better controlled and it is possible to place it in the optimal position.
Let’s insist once again on the end of the action of the second operation: Compress the assembly obtained in the 1st operation, to a point where the tightness of the seam is guaranteed.
During this operation, the rubber gasket flows to fill any existing vacuum within the seam. The profile of the second operation seaming roll, for this type of new ends, is designed to meet two basic requirements. First and foremost, its silhouette must be designed to achieve the correct tightness, which allows covering the critical parameters of the seam. Second, the shape of the profile should try to combine the lowest possible pressure of the seam with the necessary tightness of the same.
The new generation of seams, allows to solve the problems generated in the conventional seams, with the increase of hardness and decrease of thickness of the materials, and suppose an advance in the technology of the seaming.
Valuation of the “mini seaming”
The task of carrying out a “mini-seam” requires a degree of precision superior to that of a conventional seam, “so we have to introduce in the typical evaluation process of a classic seam, a series of special actions that we detail below.
Once the 1st seaming operation has been carried out by the seamer, it must be evaluated both dimensionally and optically. With the help of a hook-meter or micrometer for seams, the thickness of the 1st operation is measured and recorded.
In addition, the resulting countersink depth must be measured once this operation has been carried out. Therefore, with the gauge already indicated in the heading “SEAM EVALUATION – Measurement of the depth of the tray”, the depth of the tray will be measured just at the end of the radius thereof. Due to the small size and configuration of the seam and the reduction in the size of the bottom wing, it is of great importance to achieve a correct depth of countersink in the 1st operation.
In seamers that use chucks and “unguided” seaming routines, it is necessary to resort to adjusting the height of the profile of the seaming roll in relation to the lip of the chuck using gauges of thickness, as we have indicated previously. For this type of seams it is very good to use sets of routines and guided chucks.
Once these two dimensions are noted, the seam obtained in the first operation is divided into two opposite points, far from the area of the lateral seam of the body and said cuts are observed in the seam projector. In addition to fulfilling the specified measures, the confirmation that a good geometrical formation of the seam has been achieved in its first operation, is an important aspect to achieve a good final seam
Figure No. 67 shows three types of a 1st operation of a “mini seam” that correspond to the following results:
Figure nº 67: Different types of 1st operation in a mini seam
Ideal: It is very important that the edge of the curl of the bottom is seen to be in a position coinciding with the center of the radius of the body flange.
Loose : If the seam is too loose, an inadequate bottom hook will be generated.
Tight: If the 1st operation is too tight, a distortion will be generated between the bottom hook and the body hook.
As in the case of the 1st operation, it is necessary to value the seam obtained dimensionally and visually. All the dimensions are recorded in a process control sheet, from which the critical parameters are calculated.
It is essential that the quality assurance gauges used are capable of measuring “mini seams”, allowing precision readings. This is particularly relevant for gauges that measure the depth of the tray and the thickness of the seam.
Every aspect of the finished seam is important, but the critical parameters that must be achieved are essential. The recommended sequence of measures is:
It is important that the probe of the gauge measuring the depth of the tray, rest on the area where the radius of the tray ends. In figure No. 68 it is seen where said probe should make contact.
Figure nº 68: Measurement of the countersink in a mini seam
Unlike conventional backgrounds, there is a large dimensional difference between the depth of the tray and the length of the seam. In drawing 65 it can be seen that the bucket in the mini seam is much larger than the seam, different from what occurs in a conventional seam. In many respects this means that fitting a seamer is easier, particularly in those that use seaming rolland guided chucks, where adjustments to correct the relationship between these two elements of the seam is very difficult.
In seamers where there is a vertical adjustment in height of the routines, special care must be taken to ensure that the seaming roll is never in contact with the sharp edge of the lip of the chuck. The sophisticated coatings that are provided with most of the seaming tools in this technology are destroyed in an instant, if there is a contract even if it is light.
The bottom bucket depth is measured at two opposite points after the contents of the container have been emptied, if the seam evaluation is performed in a canning factory, as it may result in a false reading if measured in a container that is subjected to an internal vacuum, particularly in the bottoms of low metal thickness, which is normal case in the mini seam.
Measured in two points, the length of the seam reflects primarily when the torque of the second operation wheel is tight. In addition, a careful monitoring of the length of the seam is a good indicator of the state of wear of the first operation seaming roll.
If the second operation roller is set too loose, the length of the finished seam will be short, for example below 2.40 mm. If this seaming roll is too tight the length of the seam can exceed 2.70 mm. Excessive seaming lengths can also be an indication that the 1st operation seaming roll is worn.
The thickness or thickness of the seam is linked to the free space in it, as we saw in the concept “Determination of the free space” in the section 5ª EVALUATION OF THE SEAM. In the case of the “mini seam” that we are dealing with, the difference is that the constant is reduced by 0.19 mm. maximum to 0.13, due to the lower thickness of metal and small dimensions of the seam. The expression would want:
Actual seaming thickness = (2 Gc + 3 Gf) + 0.13
The thickness of the body in two-piece type (DWI) containers is difficult to measure, due to the proximity of the transition from the thick to the thin zone in the area immediately below the body flange. Therefore, the packaging supplier should be asked to provide this information. However, the thickness of the bottom must be measured accurately with the appropriate thickness gauge.
The thickness of the seam must be measured at two points, at the 10 o’clock and 14 o’clock positions, where the 12 correspond to the position of the side seam on the three-piece containers, and at two opposite points on two-piece containers.
The process of preparing the seams, sectioning, scrapping, etc., for the mini seam is analogous to that already mentioned for a conventional seam.
Critical parameters in the mini seam
Undoubtedly, it is the most difficult assessment of the acceptability of the seam, due to the subjectivity of the task of carrying out a visual evaluation of the state of the bottom hook, to establish whether the seam is sufficiently ironed or not.
This is made even more difficult in the “mini seam”, simply because the smallness of the bottom hook, masks and hinders the easy identification of wrinkles without ironing.
One of the main objectives of the development of “mini seam”, was to ensure that the deformed metal of the bottom during the operation of the seam, remained under control, therefore minimizing the risk of resistant wrinkles formed in the 1st operation of the seam, which could be ironed during the 2nd operation.
However, thin double reduced quality (DR) material for bottoms, requires a high seaming pressure to maintain the integrity thereof and equal or even improve the performance of conventional bottom seams.
In addition to the visual inspection of the bottom hook, we recommend following the instructions below to ensure that the correct decision is made when judging the tightness of the seam.
Indicators of seaming tightness:
1º.- A direct calculation of the space occupied by the rubber seal inside the seam, gives a good confirmation of the degree of pressure in the seam. This area is called “free space” and for its calculation we refer to what was said earlier on this point in conventional seams.
When the calculation is made for a two-piece type container, for the reasons given above, the manufacturer of the can must be asked for the thickness of the body metal in this area (including the varnish) to perform said calculation.
2º.- To make sure that a too tight seam is not responsible for an artificially high result of the free space value, two more factors should be considered:
First and foremost, it is to check if there is evidence of a “muelleo” of the seam, observing a section of it in the projector. In Figure 69 the compassion between a correct seam and another with “muelleo” is presented.
Figure nº 69: Comparison of seams
Secondly, if the measure of the length of the seam is larger than what is specified for a mini seam. For example, when it is greater than 2.70 mm.
If the answer was affirmative to both questions, care must be taken in defining the correct judgment of the conditions of seam, since erroneous information is facilitated to make a readjustment of the seamer, because if the pressure were increased to reduce the space free, the result will be worse if the seam was already tight enough.
The evaluation of the degree of pressure or tightness of the mini seam, follows the same percentage criterion in relation to the height of the bottom hook, than that applied for a conventional seam. The same must be said about peaks, wrinkles, creases, etc.
Overlap or overlap:
It is necessary to follow the same criteria as for a conventional seam, with a difference that the minimum absolute value falls, as a reference it can be taken at a minimum of 0.9 mm.
Penetration of the body hook:
The criteria established for a conventional seam are followed
The criteria established for a conventional seam are followed.
Influence of the eyelash
The dimensional specification of the flange of the body of the container, will have a greater contribution to the good execution of the seam than in a conventional container.
The value of this tab is reduced little for a mini seam, and can even seam containers with conventional ends or mini seam with the same type of tab. However, it is inevitable that due to the smaller size of the wing in the latter case, there is less space between the edge of the flange of the body and the edge of the curl of the bottom wing. This forces the dimensions of the flange to be more under control, reducing its tolerance field.
If the eyelash was excessive, there would be an interference between it and the curl, generating tabs folded down during the seaming operation, which results in false seams. In FIG. 70, the relative positions of the bottom flange and body flange are compared in the case of a conventional container and another with a mini seam.
Figure nº 70: Relationship between curl / tab in conventional seam and mini seam
Changes in the production line
The introduction of ends manufactured with DR material, requires changes in the conditions of manipulation of the same in the line of production of boats or filling. These changes affect both the management and the feeding of these ends.
The thinness of the bottom makes it very vulnerable and can be damaged at different points prior to the seaming operation. The damage will inevitably occur in the form of dents or notches in the curl of the bottom wing, experience shows that it will result in failures in the double seaming, if said bottom is not removed from the sealer’s turret of endraiser before the seaming. Typical defects are: drop in the seam, spikes, or residual wrinkles in the bottom hook.
Damages produced in the forklift, as a result of rolls of bottoms stacked on the pallet, traveling in contact with the mast or nails of the truck, have been presented as the most common cause of the problem. To prevent these failures, the forklift trucks should be modified, with a spacer on the nails to avoid the contact of the pallet of ends with the mast of the same. See figure nº 71.
Figure nº 71: Positioning of spacer on forklift trucks
When incorporating these spacers, it must be verified with the truck manufacturer that the displacement of the center of gravity of the load does not affect the stability of the machine.
In addition, operators should be properly trained, making them understand the vulnerability of the new ends, in the same sense will be required to implement revisions in the “Operating Instructions” of the plant.
It must be borne in mind that conventional ends are more insensitive to these failures due to their greater thickness, which means that these damages occur in lesser amounts, and even when they occur, they become less defects on the seam. The ends for the mini seam do not give such capacity, due to the reduced thickness of the material.
Recapitulating and practical levels, we must say that the use of these mini seams allows the use of harder and thinner metals in ends, which means a double saving of raw material:
a.- Thickness savings with equal surface, to maintain its mechanical properties.
b- Savings due to the redesign of the seam, which is reflected in a decrease in area.
On the contrary, to implement a new seam of this type in a certain format, it is necessary to take into account that it is necessary to introduce a series of changes that represent an important cost. The modifications to be established are:
- Reconstruction of the coil cutting tool in primary scroll, depending on the new reduced cut of the redesigned bottom. The same must be done with the secondary scroll tooling for obtaining strips.
- Renewal of tooling in presses for the manufacture of the bottom. This affects both the die, as well as the crimper tooling and a readjustment of the crimper according to the new outer diameter of the bottom.
- The seamers of the container and filler manufacturers will require new exchange parts for the supply of ends, as well as seam tools. That is, all the parts of change that affect the ends need to be replaced or modified (chucks, routines, ejectors …), including the feeder that is usually an expensive element.
However, although the initial investment is important, when it comes to high production formats, the return period of the investment is short.
16º.-PROGRESSES IN THE SEAMERS TOOL
In recent decades, equipment manufacturers have focused their improvements on the manufacture of seamers, in various areas that we could specify in the following segments:
– Advancement of technology through the introduction of new materials.
– Improvement of productivity reducing downtime.
– Improvements in the integrity of seams.
– Reduction of operating costs.
Comentaremos solamente el pri We will comment only the first of them. New materials in the technology of the seaming:
These materials find their main application in equipment where mini-seam technology is used, since it demands great precision and quality in the tooling.
In the conventional tooling of the seamers, the life of the seaming rollnormally exceeds the life of the chuck by a certain margin. The new advances in materials have had in order to produce parts of tooling (chucks, seaming rolls, bearings) of analogous duration.
In this sense, among other new contributions deserve to be highlighted the following:
A.- Titanium nitride: It is a coating that is provided to the tools (chucks and seaming rolls) and that significantly improves the finishing surface thereof, reduces the damage to the protective varnish of the bottoms and substantially increases the life of the tooling . A work on this matter has already been published on this website and can be accessed by going to the page:
In figure no. 72, a chuck coated with this material appears.
Figure nº 72: Chuck coated with titanium nitride
B. – Ceramic bearings for seaming seaming roll: The increase of life of the seaming rolls, with the use of the titanium nitride coating, has had an impact on the use of the bearings used in them. Using a well-lubricated conventional quality bearing, it can reach a magnitude of 25 million seams. With the use of nitrided seaming rollcan reach a duration that exceeds 40 million seams per seaming roll. The hourly costs of qualified personnel make it not economical to replace the bearings in these partially used wheels. To achieve a life in the bearing comparable to the seaming roll on which it is mounted, an opposite angular contact was developed, characterized by being made of ceramic balls and a composite material that forms the cage. The inner and outer tracks of the bearing are made of stainless steel.
With this type of bearings has achieved a significant reduction in the lubrication required. Bearing in mind that many seamers need enough minutes of daily stop, working 24 hours / day, the improvement of productivity by reduction of the time of lubrication is evident.
C.- Other materials : For the chucks of seam there are certain options of materials that tend to extend the life of the same in addition to the already stated coating with titanium nitride, without going into detail of the same as its use today by Today is a minority, we can point out:
– Use of a coating based on chromium carbide.
– Realization of a chuck formed by a combined metal / deposited metal material. It is a semi-stainless steel body and a “stoody” lip.
– Chuck composed of a sintered metal / ceramic material, combining the properties of both materials.
In short, it is about looking for combinations of materials that improve the resistance and fatigue of the chuck lip, also progressing in its hardness.
17º.-SUMMARY OF DEFECTS IN THE SEAM
There is much that can be written about the seam, its possible quality problems, the causes that originate it and the way to solve it, but when a difficulty arises, it is not comfortable to search through as much literature as finding a way to solve it.
One way to shorten this task is to use summary tables where, knowing the defect, indicate the possible cause, and in this way act in the indicated sense. Or also the opposite, known a possible error or initial imperfection, which effects can generate us in the seaming.
For this reason we have prepared the following tables focused for this purpose.
A.- ORIGIN AND EFFECT
If we observe that some of the initial components of the seam, such as: loose ends, bodies or empty containers, tools or settings of the seamer, present a previous anomaly and we want to know what it can mean about the seam, the following table deals with Summarize in a concise way the different options.
B.- FAULTS AND THEIR CAUSES
The most normal situation is the opposite, that is to say that we find ourselves analyzing a seam with a certain defect and try to find out its possible origin. The following table responds to this idea.
As a recapitulation to this work, it can be said that in order to obtain an optimum quality of seam, and a high efficiency in seaming operations, it is essential to observe the following points:
a.- Quality of the seaming:
For a seam to meet its purpose of resistance and tightness must have the following characteristics:
1.- The hooks of the body and the bottom must be straight, parallel and of the same length.
2.- The lower edge of the seam must be attached to the body of the container and not show signs of rolling.
3.- The top of the seam should not have edges, sharp angles or signs of rolling.
4.- The top of the seam should be slightly flat.
5.- The external curvature of the seam must be uniform and typical of the profile of the second operation seaming roll.
6.- The depth of the tray should be slightly or moderately higher than the height of the seam.
7.- The compound must cover any gap or free space.
8.- The seam must be uniform along the entire perimeter.
9.- The compactness must be greater than 75% in round containers and 60% in form containers.
10.- The degree of tightness must be at least 75% in round containers and 60% in form containers.
11.-The overlap or overlap must be greater than 45% and in general greater than 1 mm.
12.- The penetration of the body hook must be at least 70%.
b.- High efficiency in seam equipment.
In order for the seamers to work properly and maintain a quality uniformity in the seam, the following must be taken into account:
1.- Carry out an effective preventive maintenance of the seamer.
2.- Clean and oil the seamer in the manner recommended in the manual of the machine.
3.- Handle the equipment strictly following the specifications given by the manufacturer.
4.- Use the machine according to the characteristics of the ends and containers to be seamd, taking into account the ideal type of seam to be implemented.
5.- Verify that the seamer is producing an adequate seaming quality.
6.- Note all the operations and adjustments made, as well as the results obtained, in order to determine which are the most suitable actions that we must carry out when similar problems arise again.
19º.-SEAMING TERMS EQUIVALENCES: ENGLISH – SPANISH
The most frequent sources of information on seams are usually written in English, and sometimes difficulties are encountered in finding the most appropriate word in their translation into Spanish. That’s why we consider it useful, in this work on seams, to include a list of the most usual fears in English, with its equivalent in Spanish.
– Foodcan “Euroseam” Double Seam Manual by Pete Moran
– “Seamer Tooling” – IX Seminar on seaming technology.
– “The sealing of the cans” by Pete Moran.
– “Seaming Manual” – Carnaud packaging.
– “Double Seam Manual” – CMB Engineering
– “Recommended Industry Specifications for Opon Top Processed Food Cans” – MPMA (Metal Packaging Manufacturers Association)
– “Seams and Defects of Metallic Packaging for Food Products” Carlos Paños – Soivre
– “Canning of fish and meat” by RJ Footitt and AS Lewis