In the most common put in place, the information is sealed between a die from the desired shape as well as a flat stationary steel plate engrossed in a brass or aluminum liner. The shaped electrode, too, is generally manufactured from a brass strip a few inches high, as thick as the seal wanted and fastened into a plate attached to the press ram. What type and dimensions of press, shaped electrode and lower platen will, naturally, depend upon the desired application.
To some extent these factors are independent of merely one another, for instance, a greater current or higher pressure fails to necessarily lessen the sealing time. What type and thickness of material and the total are from the electronic seal device determine these factors.
As you turn on the energy, the material heats up and its temperature rises, naturally, because the temperature rises, heat is carried out off from the dies and also the air until a stat of heat balance is reached. At this stage, the level of heat generated within the plastic material remains constant. This temperature, indicating a sort of equilibrium condition involving the heat generated as well as the heat loss towards the seal should be on top of the melting point of the plastic.
This is the time required (measures within minutes or fractions of the) to achieve this melting point considered the “heating time”.
The heat loss is of course greater with thinner material and fewer with thicker material. Indeed, very thin materials (under .004″) lose heat so rapidly it becomes very difficult to seal them. Using this we can easily see that, overall, thicker materials require more heating time as well as less power than thinner materials. Furthermore, it was actually discovered that certain poor heat conductors that do not melt of deteriorate easily beneath the impact of high frequency can be used as buffers. Bakelite, Mylar, silicone glass and Teflon, as an example, are fantastic in increasing the seal.
The standard heating period ranges from a single to four seconds. To lessen failures, we suggest how the timer determining the heating cycle needs to be set slightly on top of the minimum time found needed for a good seal.
The electrodes supply the heating current to melt the fabric and also the pressure to fuse it. Generally, the reduced pressure the poorer the seal. Conversely, a greater pressure will most likely develop a better seal. However, a lot of pressure will lead to undue thinning from the plastic material and then in an objectionable extrusion down the sides of your seal. Arcing could be caused because of the two electrodes moving closer to each other thus damaging the plastic, the buffer and / or possibly the die.
To acquire high-pressure nevertheless avoid the above disadvantages, s “stop” around the press restrains the moving die in its motion. This can be set to avoid the dies from closing completely if you find no material between them. This also prevents the die from cutting completely throughout the material and simultaneously gives a seal of predetermined thickness. Whenever a tear-seal sort of die is used, the stops will not be set around the press, since a thinning in the tear seal area is wanted.
To insure a uniform seal, the right pressure must be obtained whatsoever points of the seal. To insure this, they grind the dies perfectly flat and held parallel to one another in the press. They must also rigidly construct the dies to avoid warping under pressure.
Power necessary for a great seal is directly proportional for the section of the seal. Moreover, thicker materials require less power than thinner materials because thinner materials lose heat to the dies more rapidly. Our sealability calculator shows the maximum section of the seal obtainable with each unit. However, bear in mind that these figures are calculated for concentrated areas. The sealable area will be less for very long thin seals and for certain materials which are tough to seal.
When setting up a new sealing job, the 1st test must be with minimum power, moderate time as well as medium pressure. In case the seal is weak, you must increase power gradually. For greatest freedom from burning or arcing, the energy ought to be kept as little as possible, consistent with good sealing.
The dies should be held parallel to create even pressure by any means sections. When there is excessive extrusion or if the seal is simply too thin, the press sealing “stop” needs to be used. To create the stop, place half the whole thickness of material to be sealed about the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the full thickness of material in the press making a seal. Look into the result and minimize or enhance the “stop” as required.
In case the seal is weak at certain spots, the dies are certainly not level. The leveling screws ought to be checked and adjusted. If these adjustments remain unsatisfactory, the die may need to be surface ground.
After making many seals, the dies then warm up substantially and also the some time and 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. Usage of heated platens is desirable when doing tear seals applications.
If you do not make your various adjustments correctly, arcing through the material may occur. Arcing might also occur when the material to be sealed has different thickness at various areas of the seal or where die overlaps the edge from the material. When this happens, there might be arcing within the air gaps between your material along with the die. Improving the power can occasionally remedy this.
Arcing might also occur as a result of dirt or foreign matter about the material or dies. To avert this, care should be delivered to keep the material along with the machine clean.
Sharp corners and edges on dies can 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 make an effort to seal material which includes 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 in the die. Although dies are repairable, losing production time sea1 repairs may be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The purpose of this device is to sense the potential of an arc after which switch off the R.F. power before a damaging arc can take place. Before full production runs are manufactured, usually a sensing control (which may be set for various applications and sealing areas) is preset. The Container Tracker is not going to prevent arcing but senses the arc, then shuts off the power that prevents damage to the die.
For an option, an Arc Suppressor Tester could be included in the machine, which tests the arc suppressor before each cycle to insure proper operation.
Typically rf heating is improved by a thin layer of insulating material known as a Buffer. You attach this to one or both dies to insulate the content to be sealed through the die. This does several things: it lowers the heat loss through the materials for the dies; it compensates for small irregularities inside the die surface and may help make an excellent seal even if the die is just not perfectly flat; it decreases the tendency to arc when a long time or pressure is utilized. Overall, it can make a much better seal with less arcing. Buffer materials should have a very good 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) may be used successfully in many instances. A strip of cellulose or acetate tape followed the shaped die can be used with highly effective results.