In the most prevalent set up, the fabric is sealed between a die in the desired shape and a flat stationary steel plate covered with a brass or aluminum liner. The shaped electrode, too, is normally manufactured from a brass strip one or two inches high, as thick as the seal wanted and fastened to your plate installed on the press ram. The type and dimensions of press, shaped electrode minimizing platen will, naturally, rely on the desired application.
To some degree these factors are independent of one another, by way of example, a larger current or higher pressure fails to necessarily minimize the sealing time. The type and thickness of material and also the total are from the unlock electronic seal determine these factors.
When you start up the power, the information gets hotter along with its temperature rises, naturally, since the temperature rises, heat is carried out off throughout the dies and the air until a stat of heat balance is reached. At this point, the quantity of heat generated throughout the plastic material remains constant. This temperature, indicating a kind of equilibrium condition in between the heat generated and the heat loss for the seal has to be above the melting point of the plastic.
It is the time required (measures in seconds or fractions of this) to reach this melting point understood to be the “heating time”.
The high temperature loss is naturally greater with thinner material and less with thicker material. Indeed, very thin materials (under .004″) lose heat so rapidly which it becomes hard to seal them. Out of this we can easily observe that, overall, thicker materials require more heating efforts and less power than thinner materials. Furthermore, it was discovered that certain poor heat conductors that do not melt of deteriorate easily under the impact of high frequency can be used buffers. Bakelite, Mylar, silicone glass and Teflon, as an example, are excellent in increasing the seal.
The typical heating period ranges from a to four seconds. To minimize failures, we propose the timer determining the heating cycle should be set slightly higher than the minimum time found required for a great seal.
The electrodes give you the heating current to melt the information as well as the pressure to fuse it. Generally, the reduced pressure the poorer the seal. Conversely, an increased pressure will normally produce a better seal. However, too much pressure can result in undue thinning out from the plastic material and also in an objectionable extrusion over the sides from the seal. Arcing may be caused due to two electrodes moving closer to one another thus damaging the plastic, the buffer and / or perhaps the die.
To acquire high pressure nevertheless avoid the above disadvantages, s “stop” in 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 simultaneously provides a seal of predetermined thickness. When a tear-seal sort of die is utilized, the stops are certainly not set around the press, since a thinning of the tear seal area is wanted.
To insure a uniform seal, the right pressure has to be obtained by any means points from the seal. To insure this, they grind the dies perfectly flat and held parallel to each other within the press. They have to also rigidly construct the dies to stop warping under pressure.
Power required for a great seal is directly proportional on 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 highest portion of the seal obtainable with each unit. However, keep in mind these figures are calculated for concentrated areas. The sealable area will likely be less for very long thin seals as well as for certain materials which can be tough to seal.
When starting a new sealing job, the 1st test should be with minimum power, moderate efforts and medium pressure. In the event the seal is weak, you need to increase power gradually. For greatest freedom from burning or arcing, the ability should be kept as little as possible, consistent with good sealing.
The dies should be held parallel to generate even pressure in any way sections. When there is too much extrusion or maybe if the seal is too thin, the press sealing “stop” needs to be used. To set the stop, place half the complete thickness of material to become sealed in the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the full thickness of material inside the press and create a seal. Look at the result and minimize or raise the “stop” as required.
If the seal is weak at certain spots, the dies are certainly not level. The leveling screws needs to 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 along with the time and power might require readjustment after several hours of operation. To remove readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Usage of heated platens is desirable when conducting tear seals applications.
Should you not make your various adjustments correctly, arcing with the material may occur. Arcing could also occur when the material to become sealed has different thickness at various elements of the seal or where die overlaps the advantage of the material. In these cases, there might be arcing within the air gaps in between the material along with the die. Boosting the power can sometimes remedy this.
Arcing can also occur as a consequence of dirt or foreign matter about the material or dies. To prevent this, care has to be taken to keep the material and also the machine clean.
Sharp corners and edges on dies could also cause arcing. The die edges ought to always be rounded and smooth. When arcing occurs, the dies needs to be carefully cleaned and smoothed with fine emery cloth. Never try to seal material which includes previously been arced.
As they are now making sealing electrodes larger plus more complex, it is vital that no damage because of arcing occurs around the die. Although dies are repairable, the losing of production time sea1 repairs might be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The purpose of this product would be to sense the opportunity of an arc and after that shut off the R.F. power before a damaging arc can happen. Before full production runs are made, normally a sensing control (which can be set for various applications and sealing areas) is preset. The Fuel sensor does not prevent arcing but senses the arc, then shuts off the power that prevents problems for the die.
As being an option, an Arc Suppressor Tester might be added to 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 referred to as a Buffer. You attach this to one or both dies to insulate the fabric to get sealed in the die. This will a number of things: it lowers the warmth loss through the materials on the dies; it compensates for small irregularities within the die surface and could help make an excellent seal even if your die is not really perfectly flat; it decreases the tendency to arc when too much effort or pressure is utilized. Overall, it 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 used successfully in most cases. A strip of cellulose or acetate tape adhered to the shaped die can be utilized with very successful results.