In the most typical setup, the content is sealed from 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 made of a brass strip one or two inches high, as thick since the seal wanted and fastened to a plate installed on the press ram. The type and dimensions of press, shaped electrode minimizing platen will, naturally, rely on the required application.
At some level these factors are independent of a single another, for example, a larger current or even more pressure does not necessarily decrease the sealing time. What type and thickness of material and the total are of your electronic seal device determine these factors.
When you start up the ability, the material warms up and its particular temperature rises, naturally, since the temperature rises, heat is carried out off throughout the dies as well as the air until a stat of warmth balance is reached. At this point, the level of heat generated throughout the plastic material remains constant. This temperature, indicating a sort of equilibrium condition between the heat generated and the heat loss towards the seal needs to be above the melting reason for the plastic.
This is basically the time required (measures in seconds or fractions with this) to reach this melting point described as the “heating time”.
The warmth loss is naturally greater with thinner material and much less with thicker material. Indeed, very thin materials (below .004″) lose heat so rapidly it becomes very difficult to seal them. Using this we could notice that, overall, thicker materials require more heating 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 underneath the impact of high frequency can be used buffers. Bakelite, Mylar, silicone glass and Teflon, for instance, are fantastic in enhancing the seal.
The usual heating period ranges from a to four seconds. To minimize failures, we recommend that the timer determining the heating cycle needs to be set slightly over the minimum time found required for a great seal.
The electrodes provide you with the heating current to melt the fabric as well as the pressure to fuse it. Generally, the low the strain the poorer the seal. Conversely, a better pressure will usually develop a better seal. However, too much pressure can lead to undue thinning from the plastic material and then in an objectionable extrusion over 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 have high-pressure nevertheless steer clear of the above disadvantages, s “stop” about the press restrains the moving die in the motion. This is certainly set to avoid the dies from closing completely if you have no material between them. And also this prevents the die from cutting completely with the material and as well offers a seal of predetermined thickness. Each time a tear-seal kind of die is used, the stops are certainly not set on the press, since a thinning of the tear seal area is wanted.
To insure a uniform seal, the correct pressure must be obtained whatsoever points of your seal. To insure this, they grind the dies perfectly flat and held parallel to one another in 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 section of the seal. Moreover, thicker materials require less power than thinner materials because thinner materials lose heat for the dies more rapidly. Our sealability calculator shows the maximum portion of the seal obtainable with every unit. However, keep in mind these figures are calculated for concentrated areas. The sealable area will likely be less for too long thin seals as well as for certain materials that are challenging to seal.
When starting a new sealing job, the 1st test needs to be with minimum power, moderate some time and medium pressure. If the seal is weak, you ought to increase power gradually. For greatest freedom from burning or arcing, the strength should be kept only possible, consistent with good sealing.
The dies should be held parallel to create even pressure at all sections. If you have excessive extrusion or if the seal is way too thin, the press sealing “stop” ought to be used. To put the stop, place half the complete thickness of material to get sealed around the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the full thickness of material from the press and make a seal. Examine the result and minimize or boost the “stop” as required.
In case the seal is weak at certain spots, the dies are certainly not level. The leveling screws must be checked and adjusted. If these adjustments remain unsatisfactory, the die might have to be surface ground.
After making many seals, the dies then warm-up substantially and the time as well as power might need readjustment after a few hours of operation. To remove readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Use of heated platens is desirable when you are performing tear seals applications.
If you do not create the various adjustments correctly, arcing throughout the material may occur. Arcing could also occur as soon as the material being sealed has different thickness at various parts of the seal or where the die overlaps the advantage of your material. In these instances, there could be arcing in the air gaps involving the material and the die. Boosting the power will often remedy this.
Arcing can also occur as a result of dirt or foreign matter in the material or dies. To prevent this, care should be taken up keep the material and also the machine clean.
Sharp corners and edges on dies might also cause arcing. The die edges should always be rounded and smooth. When arcing occurs, the dies should be carefully cleaned and smoothed with fine emery cloth. Never try to seal material that has previously been arced.
As they are now making sealing electrodes larger and much more complex, it is vital that no damage on account of arcing occurs about the die. Although dies are repairable, losing production time sea1 repairs may be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The function of this product would be to sense the opportunity of an arc and then switch off the R.F. power before a damaging arc may appear. Before full production runs are produced, normally a sensing control (that may be set for various applications and sealing areas) is preset. The Fleet Management does not prevent arcing but senses the arc, then shuts from the power that prevents problems for the die.
For an option, an Arc Suppressor Tester might be included with the machine, which tests the arc suppressor before each cycle to insure proper operation.
Typically rf heating is improved by way of a thin layer of insulating material known as a Buffer. You attach this to one or both dies to insulate the information to get sealed from the die. This may many things: it lowers the warmth loss through the materials for the dies; it compensates for small irregularities in the die surface and could help make a great seal even if your die is not really perfectly flat; it decreases the tendency to arc when a long time or pressure is used. Overall, it will make a better seal with less arcing. Buffer materials should have a great heat resistance and voltage breakdown. Of the numerous materials used (Bakelite, paper, glassine, Teflon, glass Mylar, silicone, fiberglass, etc.). Bakelite (grade xx about .010 to .030 inches thick) works extremely well successfully in most cases. A strip of cellulose or acetate tape adhered to the shaped die can be utilized with highly effective results.