In the most typical setup, the content is sealed between a die in the desired shape along with a flat stationary steel plate covered with a brass or aluminum liner. The shaped electrode, too, is often made from a brass strip one or two inches high, as thick as being the seal wanted and fastened into a plate mounted on the press ram. The type and dimensions of press, shaped electrode minimizing platen will, needless to say, depend upon the specified application.
To some extent these factors are independent of just one another, for example, a more substantial current or maybe more pressure will not necessarily decrease the sealing time. What type and thickness of material and the total are of your electronic seal device determine these factors.
As you may switch on the ability, the fabric heats up along with its temperature rises, naturally, as the temperature rises, heat is conducted off from the dies along with the air until a stat of warmth balance is reached. At this stage, the volume of heat generated in the plastic material remains constant. This temperature, indicating a kind of equilibrium condition in between the heat generated and the heat loss on the seal should be above the melting reason for the plastic.
This is the time required (measures in seconds or fractions on this) to reach this melting point understood to be the “heating time”.
The temperature loss is naturally greater with thinner material and less with thicker material. Indeed, very thin materials (lower than .004″) lose heat so rapidly that it becomes very difficult to seal them. From this we are able to observe that, overall, thicker materials require more heating time and less power than thinner materials. Furthermore, it was actually learned that certain poor heat conductors which do not melt of deteriorate easily underneath the impact of high frequency can be used buffers. Bakelite, Mylar, silicone glass and Teflon, for instance, are excellent in enhancing the seal.
The usual heating period ranges from one to four seconds. To reduce failures, we suggest how the timer determining the heating cycle ought to be set slightly over the minimum time found essential for an effective seal.
The electrodes supply the heating current to melt the fabric and the pressure to fuse it. Generally, the lower pressure the poorer the seal. Conversely, a greater pressure will most likely create a better seal. However, a lot of pressure can result in undue thinning from the plastic material and in an objectionable extrusion across the sides from the seal. Arcing may be caused because of the two electrodes moving closer to one another thus damaging the plastic, the buffer and / or even the die.
To get high pressure however stay away from the above disadvantages, s “stop” around the press restrains the moving die within its motion. This is set to stop the dies from closing completely if you have no material between them. And also this prevents the die from cutting completely throughout the material and simultaneously gives a seal of predetermined thickness. Whenever a tear-seal kind of die can be used, the stops will not be set about the press, since a thinning of the tear seal area is wanted.
To insure a uniform seal, the correct pressure should be obtained by any means points in 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 stop warping under pressure.
Power required for an effective seal is directly proportional to the portion of the seal. Moreover, thicker materials require less power than thinner materials because thinner materials lose heat towards the dies more rapidly. Our sealability calculator shows the most portion of the seal obtainable with every unit. However, keep in mind these figures are calculated for concentrated areas. The sealable area will probably be less for very long thin seals and for certain materials which are difficult to seal.
When setting up a new sealing job, the 1st test needs to be with minimum power, moderate time as well as medium pressure. If the seal is weak, you should increase power gradually. For greatest freedom from burning or arcing, the energy should be kept as low as possible, consistent with good sealing.
The dies needs to be held parallel to generate even pressure by any means sections. If you have too much extrusion or if the seal is just too thin, the press sealing “stop” must be used. To create the stop, place half the entire thickness of material to be sealed around the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the complete thickness of material from the press and make a seal. Look into the result and reduce or raise the “stop” as required.
In case the seal is weak at certain spots, the dies will not be level. The leveling screws ought to be checked and adjusted. If these adjustments are still unsatisfactory, the die may have to be surface ground.
After making many seals, the dies then heat up substantially and also the time as well as power may need readjustment after a few hours of operation. To get rid of readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Utilization of heated platens is desirable when conducting tear seals applications.
If you do not make the various adjustments correctly, arcing throughout the material may occur. Arcing might also occur once the material to be sealed has different thickness at various aspects of the seal or where the die overlaps the advantage from the material. In these cases, there could be arcing in the air gaps between the material along with the die. Improving the power will often remedy this.
Arcing may also occur due to dirt or foreign matter about the material or dies. To prevent this, care should be taken up retain the material and the machine clean.
Sharp corners and edges on dies might 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 and seal material that has previously been arced.
As they are now making sealing electrodes larger and more complex, it is essential that no damage on account of arcing occurs in the die. Although dies are repairable, the losing of production time sea1 repairs can be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The purpose of this piece of equipment is always to sense the opportunity of an arc and then switch off the R.F. power before a damaging arc can occur. Before full production runs are created, normally a sensing control (which is often set for various applications and sealing areas) is preset. The Container Tracker will not prevent arcing but senses the arc, then shuts off the power that prevents problems for the die.
For an option, an Arc Suppressor Tester could be included with the system, 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 referred to as a Buffer. You attach this to one or both dies to insulate the fabric to get sealed from the die. This does numerous things: it lowers the temperature loss from the materials towards the dies; it compensates for small irregularities from the die surface and may help make an excellent seal whether or not the die is just not perfectly flat; it decreases the tendency to arc when too much effort or pressure is used. Overall, this makes a better seal with less arcing. Buffer materials should have a 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 utilized successfully typically. A strip of cellulose or acetate tape adhered to the shaped die may be used with very successful results.