In the most common setup, the fabric is sealed between a die from the desired shape and a flat stationary steel plate engrossed in a brass or aluminum liner. The shaped electrode, too, is often manufactured from a brass strip one or two inches high, as thick as being the seal wanted and fastened to a plate placed on the press ram. The type and dimensions of press, shaped electrode minimizing platen will, needless to say, rely on the necessary application.
To some extent these factors are independent of a single another, for instance, a greater current or more pressure will not necessarily lessen the sealing time. The type and thickness of material and also the total are of your Container Tracker determine these factors.
As you may start up the strength, the material gets hotter and its temperature rises, naturally, since the temperature rises, heat is conducted off throughout the dies and also the air until a stat of heat balance is reached. At this moment, the quantity of heat generated inside the plastic material remains constant. This temperature, indicating a kind of equilibrium condition between your heat generated and also the heat loss for the seal should be higher than the melting reason for the plastic.
It will be the time required (measures in seconds or fractions of the) to arrive at this melting point defined as the “heating time”.
The warmth loss is naturally greater with thinner material and much less with thicker material. Indeed, very thin materials (less than .004″) lose heat so rapidly that it becomes very difficult to seal them. From this we can notice that, overall, thicker materials require more heating some time and less power than thinner materials. Furthermore, it had been found out that certain poor heat conductors which do not melt of deteriorate easily under the impact of high frequency can be used buffers. Bakelite, Mylar, silicone glass and Teflon, for example, are excellent in increasing the seal.
The typical heating period ranges from a to four seconds. To minimize failures, we suggest that this timer determining the heating cycle should be set slightly higher than the minimum time found required for an excellent seal.
The electrodes give you the heating current to melt the material and the pressure to fuse it. Generally, the less pressure the poorer the seal. Conversely, a greater pressure will often develop a better seal. However, a lot of pressure can lead to undue thinning out of the plastic material and also in an objectionable extrusion down the sides in the seal. Arcing may be caused as a result of two electrodes moving closer to each other thus damaging the plastic, the buffer and / or perhaps the die.
To acquire high-pressure nevertheless steer clear of the above disadvantages, s “stop” about the press restrains the moving die in their motion. This is set to prevent the dies from closing completely when there is no material between them. This prevents the die from cutting completely throughout the material and concurrently provides a seal of predetermined thickness. Every time a tear-seal sort of die is utilized, the stops are certainly not set around the press, since a thinning in the tear seal area is wanted.
To insure a uniform seal, the appropriate pressure needs to be obtained at all points in the seal. To insure this, they grind the dies perfectly flat and held parallel to one another from the press. They need to also rigidly construct the dies in order to avoid warping under pressure.
Power needed for an effective seal is directly proportional towards the portion of the seal. Moreover, thicker materials require less power than thinner materials because thinner materials lose heat towards the dies more rapidly. Our sealability calculator shows the most area of the seal obtainable with each unit. However, be aware that these figures are calculated for concentrated areas. The sealable area will be less for long thin seals and then for certain materials that are challenging to seal.
When starting a new sealing job, the 1st test ought to be with minimum power, moderate time as well as medium pressure. In case the seal is weak, you ought to increase power gradually. For greatest freedom from burning or arcing, the power should be kept as low as possible, consistent with good sealing.
The dies needs to be held parallel to make even pressure whatsoever sections. When there is a lot of extrusion or if perhaps the seal is way too thin, the press sealing “stop” needs to be used. To put the stop, place half the complete thickness of material being sealed about the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the total thickness of material from the press and make up a seal. Check the result and minimize or raise the “stop” as required.
In the event the seal is weak at certain spots, the dies are not level. The leveling screws ought to be checked and adjusted. If these adjustments continue to be unsatisfactory, the die might have to be surface ground.
After making many seals, the dies then heat up substantially along with the time and power may require readjustment after several hours of operation. To get rid of readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Use of heated platens is desirable when conducting tear seals applications.
If you do not make the various adjustments correctly, arcing through the material may occur. Arcing can also occur if the material to get sealed has different thickness at various elements of the seal or in which the die overlaps the edge from the material. In these cases, there might be arcing within the air gaps between the material as well as the die. Improving the power can occasionally remedy this.
Arcing could also occur because of dirt or foreign matter in the material or dies. To avert this, care should be taken to keep the material and the machine clean.
Sharp corners and edges on dies could also cause arcing. The die edges should always be rounded and smooth. When arcing occurs, the dies has to be carefully cleaned and smoothed with fine emery cloth. Never make an effort to seal material which has previously been arced.
Because they are now making sealing electrodes larger plus more complex, it is crucial that no damage as a result of arcing occurs about the die. Although dies are repairable, the loss of production time sea1 repairs can be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The function of this product is always to sense the opportunity of an arc then shut down the R.F. power before a damaging arc can occur. Before full production runs are produced, usually a sensing control (which is often set for various applications and sealing areas) is preset. The Fleet Management fails to prevent arcing but senses the arc, then shuts from the power that prevents problems for the die.
Being an option, an Arc Suppressor Tester can be included with the system, which tests the arc suppressor before each cycle to insure proper operation.
Typically rf heating is improved with a thin layer of insulating material called a Buffer. You attach this to a single or both dies to insulate the information being sealed in the die. This will many things: it lowers the temperature loss from the materials for the dies; it compensates for small irregularities within the die surface and could help to make an excellent seal even if your die is just not perfectly flat; it decreases the tendency to arc when a lot of time or pressure is commonly used. Overall, this makes a better seal with less arcing. Buffer materials should have a great heat resistance and high voltage breakdown. Of the many materials used (Bakelite, paper, glassine, Teflon, glass Mylar, silicone, fiberglass, etc.). Bakelite (grade xx about .010 to .030 inches thick) can be utilized successfully in most cases. A strip of cellulose or acetate tape adhered to the shaped die can be used with highly effective results.