In the most typical setup, the information is sealed between a die in the desired shape and a flat stationary steel plate engrossed in a brass or aluminum liner. The shaped electrode, too, is often made from a brass strip a couple of inches high, as thick as being the seal wanted and fastened into a plate mounted on the press ram. The type and size of press, shaped electrode and reduce platen will, obviously, rely on the specified application.
To some extent these factors are independent of one another, for instance, a greater current or even more pressure will not necessarily decrease the sealing time. What type and thickness of material and the total are of the Container Tracker determine these factors.
While you start up the energy, the content warms up and its temperature rises, naturally, as the temperature rises, heat is carried out off throughout the dies along with 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 your heat generated along with the heat loss to the seal should be higher than the melting reason for the plastic.
This is the time required (measures within minutes or fractions of the) to achieve this melting point understood to be the “heating time”.
The warmth loss is of course greater with thinner material and fewer with thicker material. Indeed, very thin materials (lower than .004″) lose heat so rapidly which it becomes very difficult to seal them. Out of this we are able to observe that, overall, thicker materials require more heating time and less power than thinner materials. Furthermore, it absolutely was found out that certain poor heat conductors which do not melt of deteriorate easily underneath the impact of high frequency bring buffers. Bakelite, Mylar, silicone glass and Teflon, as an example, are great in boosting the seal.
The typical heating period ranges from one to four seconds. To minimize failures, we recommend that the timer determining the heating cycle must be set slightly on top of the minimum time found needed for a great seal.
The electrodes supply the heating current to melt the material and also the pressure to fuse it. Generally, the low the strain the poorer the seal. Conversely, a higher pressure will usually generate a better seal. However, an excessive amount of pressure can lead to undue thinning out of the plastic material as well as in an objectionable extrusion down the sides of the seal. Arcing can be caused as a result of two electrodes moving closer to one another thus damaging the plastic, the buffer and / or perhaps the die.
To acquire high pressure and yet stay away from the above disadvantages, s “stop” about the press restrains the moving die in its motion. This really is set to prevent the dies from closing completely should there be no material between them. And also this prevents the die from cutting completely through the material and concurrently provides a seal of predetermined thickness. Whenever a tear-seal kind of die is commonly used, the stops are not set in the press, since a thinning of your tear seal area is wanted.
To insure a uniform seal, the appropriate pressure should be obtained at all points of your seal. To insure this, they grind the dies perfectly flat and held parallel to one another in the press. They should also rigidly construct the dies to stop warping under pressure.
Power needed for an excellent seal is directly proportional on the area 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 most area of the seal obtainable with every unit. However, bear in mind that these figures are calculated for concentrated areas. The sealable area will likely be less for long thin seals as well as for certain materials that happen to be challenging to seal.
When starting a new sealing job, the initial test ought to be with minimum power, moderate efforts and medium pressure. In case the seal is weak, you should increase power gradually. For greatest freedom from burning or arcing, the power ought to 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 simply too thin, the press sealing “stop” should be used. To set the stop, place half the total thickness of material being sealed around the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the entire thickness of material from the press and create a seal. Check the result minimizing or enhance the “stop” as required.
If the seal is weak at certain spots, the dies usually are not level. The leveling screws needs to be checked and adjusted. If these adjustments are still unsatisfactory, the die may need to be surface ground.
After making many seals, the dies then heat up substantially and also the efforts and power might 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. Consumption of heated platens is desirable when conducting tear seals applications.
Should you not have the various adjustments correctly, arcing with the material may occur. Arcing might also occur when the material being sealed has different thickness at various parts of the seal or in which the die overlaps the edge of the material. In such cases, there might be arcing within the air gaps between the material and also the die. Improving the power can sometimes remedy this.
Arcing could also occur as a consequence of dirt or foreign matter around the material or dies. To avoid this, care must be come to keep your material and also the machine clean.
Sharp corners and edges on dies may also cause arcing. The die edges should be rounded and smooth. When arcing occurs, the dies should be carefully cleaned and smoothed with fine emery cloth. Never try to seal material which has previously been arced.
Because they are now making sealing electrodes larger plus more complex, it is essential that no damage as a result of arcing occurs around 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 gadget is always to sense the chance of an arc after which shut down the R.F. power before a damaging arc can occur. Before full production runs are made, normally a sensing control (that may be set for various applications and sealing areas) is preset. The Container monitoring fails to prevent arcing but senses the arc, then shuts away from the power that prevents injury to the die.
As being an option, an Arc Suppressor Tester might be added to the unit, 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 called a Buffer. You attach this to a single or both dies to insulate the material to become sealed from the die. This will a number of things: it lowers the heat loss from the materials on the dies; it compensates for small irregularities within the die surface and might help to make an effective seal even if the die is just not perfectly flat; it decreases the tendency to arc when too much effort or pressure is used. Overall, it makes a greater seal with less arcing. Buffer materials should have a very good heat resistance and 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 many instances. A strip of cellulose or acetate tape followed the shaped die works extremely well with successful results.