In the most frequent put in place, the material 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 made from a brass strip a couple of inches high, as thick because the seal wanted and fastened to your plate mounted on the press ram. What type and dimensions of press, shaped electrode minimizing platen will, of course, depend upon the desired application.
To some degree these factors are independent of merely one another, for instance, a greater current or higher pressure fails to necessarily reduce the sealing time. The type and thickness of material as well as the total are from the Container Tracker determine these factors.
While you turn on the power, the fabric heats up along with its temperature rises, naturally, since the temperature rises, heat is carried out off through the dies along with the air until a stat of heat balance is reached. At this stage, the quantity of heat generated throughout the plastic material remains constant. This temperature, indicating a kind of equilibrium condition between the heat generated as well as the heat loss towards the seal should be higher than the melting point of the plastic.
It is the time required (measures in seconds or fractions of the) to reach this melting point defined as the “heating time”.
The high temperature loss is naturally greater with thinner material and much less with thicker material. Indeed, very thin materials (under .004″) lose heat so rapidly which it becomes hard to seal them. Using this we could see that, overall, thicker materials require more heating efforts and less power than thinner materials. Furthermore, it was actually found out that certain poor heat conductors which do not melt of deteriorate easily within the impact of high frequency bring buffers. Bakelite, Mylar, silicone glass and Teflon, as an example, are fantastic in enhancing the seal.
The standard heating period ranges from one to four seconds. To minimize failures, we advise that this timer determining the heating cycle should be set slightly higher than the minimum time found required for a good seal.
The electrodes provide you with the heating current to melt the material and the pressure to fuse it. Generally, the lower the pressure the poorer the seal. Conversely, a greater pressure will most likely create a better seal. However, an excessive amount of pressure can lead to undue thinning out of your plastic material as well as in an objectionable extrusion across the sides in the seal. Arcing might be caused due to the two electrodes moving closer to each other thus damaging the plastic, the buffer and / or possibly the die.
To acquire high-pressure nevertheless prevent the above disadvantages, s “stop” in the press restrains the moving die within its motion. This is set to avoid the dies from closing completely should there be no material between them. This also prevents the die from cutting completely throughout the material and simultaneously gives a seal of predetermined thickness. Every time a tear-seal kind of die is used, the stops will not be set about the press, since a thinning in the tear seal area is wanted.
To insure a uniform seal, the correct pressure has to be obtained at all points of the seal. To insure this, they grind the dies perfectly flat and held parallel to each other inside the press. They should also rigidly construct the dies to avoid warping under pressure.
Power essential for a good 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 highest portion 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 too long thin seals as well as for certain materials which are hard to seal.
When establishing a new sealing job, the initial test should be with minimum power, moderate some time and medium pressure. If the seal is weak, you need to increase power gradually. For greatest freedom from burning or arcing, the ability must be kept only possible, consistent with good sealing.
The dies has to be held parallel to create even pressure at all sections. If you find excessive extrusion or maybe the seal is simply too thin, the press sealing “stop” must be used. To create the stop, place half the whole thickness of material to get sealed in the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the total thickness of material from the press and create a seal. Check the result minimizing or increase 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 are still unsatisfactory, the die may need to be surface ground.
After making many seals, the dies then heat up substantially as well as the time and power might require 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. Usage of heated platens is desirable when you are performing tear seals applications.
If you do not have the various adjustments correctly, arcing from the material may occur. Arcing can also occur when the material to be sealed has different thickness at various elements of the seal or where the die overlaps the advantage from the material. In these instances, there can be arcing in the air gaps involving the material and also the die. Enhancing the power can occasionally remedy this.
Arcing may also occur as a result of dirt or foreign matter in the material or dies. To avert this, care needs to be come to keep your material and 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 to seal material that has previously been arced.
Since they are now making sealing electrodes larger and more complex, it is important that no damage as a result of arcing occurs on the die. Although dies are repairable, the decline of production time sea1 repairs may be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The purpose of this device would be to sense the possibility of an arc then shut off the R.F. power before a damaging arc can happen. Before full production runs are made, usually a sensing control (that may be set for various applications and sealing areas) is preset. The Container Tracker will not prevent arcing but senses the arc, then shuts from the power that prevents damage to the die.
Being an option, an Arc Suppressor Tester could be included in the system, which tests the arc suppressor before each cycle to insure proper operation.
Typically rf heating is improved with a thin layer of insulating material called a Buffer. You attach this to 1 or both dies to insulate the material to be sealed through the die. This does several things: it lowers the temperature loss in the materials towards the dies; it compensates for small irregularities within the die surface and might help to make a great seal even if your die is not perfectly flat; it decreases the tendency to arc when too much effort or pressure is utilized. Overall, it will make a greater seal with less arcing. Buffer materials should have a great 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 most cases. A strip of cellulose or acetate tape adhered to the shaped die may be used with very effective results.