In the most frequent create, the information is sealed from a die of the desired shape and a flat stationary steel plate covered with a brass or aluminum liner. The shaped electrode, too, is normally created from a brass strip one or two inches high, as thick as the seal wanted and fastened into a plate installed on the press ram. The type and dimensions of press, shaped electrode and lower platen will, naturally, rely on the required application.
At some level these factors are independent of just one another, for instance, a more substantial current or more pressure is not going to necessarily lessen the sealing time. The type and thickness of material and the total are from the electronic seal device determine these factors.
When you start up the power, the fabric warms up and its particular temperature rises, naturally, because the temperature rises, heat is carried out off with the dies and the air until a stat of heat balance is reached. At this stage, the amount of heat generated within the plastic material remains constant. This temperature, indicating a kind of equilibrium condition between the heat generated and also the heat loss to the seal needs to be above the melting point of the plastic.
It will be the time required (measures in seconds or fractions with this) to reach this melting point defined as the “heating time”.
The temperature loss is of course greater with thinner material and less with thicker material. Indeed, very thin materials (under .004″) lose heat so rapidly that it becomes hard to seal them. From this we are able to notice that, overall, thicker materials require more heating time as well as less power than thinner materials. Furthermore, it had been learned that certain poor heat conductors that do not melt of deteriorate easily beneath the impact of high frequency bring buffers. Bakelite, Mylar, silicone glass and Teflon, as an example, are fantastic in boosting the seal.
The normal heating period ranges from one to four seconds. To lower failures, we recommend the timer determining the heating cycle needs to be set slightly higher than the minimum time found required for a good seal.
The electrodes give you the heating current to melt the material and the pressure to fuse it. Generally, the reduced pressure the poorer the seal. Conversely, a better pressure will normally produce a better seal. However, too much pressure can result in undue thinning out of the plastic material as well as in an objectionable extrusion along the sides of your seal. Arcing could 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 avoid the above disadvantages, s “stop” in the press restrains the moving die within its motion. This is certainly set in order to avoid the dies from closing completely when there is no material between them. This too prevents the die from cutting completely throughout the material and concurrently gives a seal of predetermined thickness. When a tear-seal sort of die can be used, the stops are certainly not set about the press, since a thinning in the tear seal area is wanted.
To insure a uniform seal, the appropriate pressure needs to be obtained whatsoever points of your 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 in order to avoid warping under pressure.
Power required for an effective seal is directly proportional to 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 utmost section 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 too long thin seals and also for certain materials that are difficult to seal.
When starting a new sealing job, the initial test ought to be with minimum power, moderate time as well as medium pressure. In the event the seal is weak, you should increase power gradually. For greatest freedom from burning or arcing, the ability ought to be kept only possible, consistent with good sealing.
The dies needs to be held parallel to produce even pressure at all sections. If you find excessive extrusion or maybe the seal is just too thin, the press sealing “stop” should be used. To put the stop, place half the entire thickness of material to become sealed around the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the total thickness of material in the press and make a seal. Check the result and reduce or enhance the “stop” as required.
If the seal is weak at certain spots, the dies usually are not level. The leveling screws must be checked and adjusted. If these adjustments continue to be unsatisfactory, the die may have to be surface ground.
After making many seals, the dies then warm-up substantially along with the time as well as power may require readjustment after a few hours of operation. To reduce readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Utilization of heated platens is desirable when you are performing tear seals applications.
Should you not make your various adjustments correctly, arcing throughout the material may occur. Arcing might also occur when the material to become sealed has different thickness at various parts of the seal or in which the die overlaps the edge from the material. In these instances, there may be arcing within the air gaps in between the material and also the die. Enhancing the power can occasionally remedy this.
Arcing could also occur due to dirt or foreign matter in the material or dies. To avoid this, care needs to be delivered to retain the material and also 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 attempt to seal material which includes previously been arced.
Since they are now making sealing electrodes larger and more complex, it is vital that no damage due to arcing occurs about the die. Although dies are repairable, the decline of production time sea1 repairs could be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The purpose of this device would be to sense the potential of an arc after which turn off the R.F. power before a damaging arc may appear. Before full production runs are produced, often a sensing control (which may be looking for various applications and sealing areas) is preset. The Fleet Management does not prevent arcing but senses the arc, then shuts away from the power that prevents injury to the die.
Being an option, an Arc Suppressor Tester may be put into the device, 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 1 or both dies to insulate the information being sealed from the die. This does several things: it lowers the high temperature loss from the materials on the dies; it compensates for small irregularities inside the die surface and might help make an excellent seal even if the die will not be perfectly flat; it decreases the tendency to arc when a long time or pressure is used. Overall, it makes a much 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) works extremely well successfully generally. A strip of cellulose or acetate tape followed the shaped die may be used with very successful results.