In the most typical create, the material is sealed between a die from the desired shape along with a flat stationary steel plate covered with a brass or aluminum liner. The shaped electrode, too, is generally manufactured from a brass strip one or two inches high, as thick because the seal wanted and fastened to your plate placed on the press ram. What type and measurements of press, shaped electrode and lower platen will, of course, rely on the necessary application.
To some degree these factors are independent of a single another, as an example, a larger current or more pressure will not necessarily reduce the sealing time. What type and thickness of material and the total are in the electronic seal device determine these factors.
While you switch on the strength, the information gets hotter and its temperature rises, naturally, because the temperature rises, heat is carried out off with the dies along with the air until a stat of heat balance is reached. At this stage, the amount 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 towards the seal needs to be higher than the melting reason for the plastic.
It will be the time required (measures in seconds or fractions with this) to arrive at this melting point defined as the “heating time”.
The high temperature loss is of course greater with thinner material and less with thicker material. Indeed, very thin materials (below .004″) lose heat so rapidly it becomes tough 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 within the impact of high frequency can be used buffers. Bakelite, Mylar, silicone glass and Teflon, by way of example, are fantastic in boosting the seal.
The standard heating period ranges from a single to four seconds. To minimize failures, we recommend that the timer determining the heating cycle ought to be set slightly above the minimum time found needed for a good seal.
The electrodes provide the heating current to melt the fabric along with the pressure to fuse it. Generally, the low the pressure the poorer the seal. Conversely, an increased pressure will often develop a better seal. However, an excessive amount of pressure will lead to undue thinning out of the plastic material as well as in an objectionable extrusion down 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 even the die.
To have high pressure however prevent the above disadvantages, s “stop” about the press restrains the moving die in their motion. This is set to prevent the dies from closing completely if you find no material between the two. This too prevents the die from cutting completely from the material and concurrently provides a seal of predetermined thickness. When a tear-seal kind of die is commonly used, the stops usually are not set on the press, since a thinning of the tear seal area is wanted.
To insure a uniform seal, the correct pressure needs to be obtained by any means points in the seal. To insure this, they grind the dies perfectly flat and held parallel to each other inside the press. They need to also rigidly construct the dies to prevent warping under pressure.
Power required for an excellent seal is directly proportional for the area of the seal. Moreover, thicker materials require less power than thinner materials because thinner materials lose heat on the dies more rapidly. Our sealability calculator shows the utmost section of the seal obtainable with every unit. However, bear in mind that these figures are calculated for concentrated areas. The sealable area will probably be less for too long thin seals and also for certain materials which are hard to seal.
When starting a new sealing job, the first test needs to be with minimum power, moderate efforts and medium pressure. In the event the seal is weak, you ought to increase power gradually. For greatest freedom from burning or arcing, the ability needs to be kept only possible, consistent with good sealing.
The dies has to be held parallel to generate even pressure whatsoever sections. If there is an excessive amount of extrusion or if the seal is simply too thin, the press sealing “stop” must be used. To create the stop, place half the entire thickness of material to get sealed in the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the full thickness of material in the press and make a seal. Look at the result and minimize or raise the “stop” as required.
In the event 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 remain unsatisfactory, the die may have to be surface ground.
After making many seals, the dies then warm-up substantially as well as the efforts and power may require readjustment after a few hours of operation. To eliminate readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Consumption of heated platens is desirable when you are performing tear seals applications.
Should you not create the various adjustments correctly, arcing through the material may occur. Arcing may also occur once the material to become sealed has different thickness at various aspects of the seal or in which the die overlaps the advantage of the material. When this happens, there can be arcing within the air gaps between the material as well as the die. Boosting the power can occasionally remedy this.
Arcing could also occur due to dirt or foreign matter in the material or dies. To avert this, care must be delivered to maintain the material and also the machine clean.
Sharp corners and edges on dies might also cause arcing. The die edges should invariably be rounded and smooth. When arcing occurs, the dies has to be carefully cleaned and smoothed with fine emery cloth. Never try and seal material which includes previously been arced.
Since they are now making sealing electrodes larger plus more complex, it is essential that no damage because of arcing occurs about 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 piece of equipment would be to sense the opportunity of an arc after which shut off the R.F. power before a damaging arc can occur. Before full production runs are manufactured, usually a sensing control (which can be set for various applications and sealing areas) is preset. The Container monitoring fails to prevent arcing but senses the arc, then shuts off of the power that prevents problems for the die.
As being an option, an Arc Suppressor Tester may be put into the unit, which tests the arc suppressor before each cycle to insure proper operation.
Typically rf heating is improved by a thin layer of insulating material called a Buffer. You attach this to one or both dies to insulate the content being sealed through the die. This may numerous things: it lowers the high temperature loss from your materials for the dies; it compensates for small irregularities within the die surface and may help to make a good seal whether or not the die is not perfectly flat; it decreases the tendency to arc when too much time or pressure is utilized. Overall, it makes a greater seal with less arcing. Buffer materials should have a very good heat resistance and high voltage breakdown. Of 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 typically. A strip of cellulose or acetate tape followed the shaped die can be utilized with highly effective results.