In the most common setup, the material is sealed from a die of your desired shape along with a flat stationary steel plate covered with a brass or aluminum liner. The shaped electrode, too, is usually manufactured from a brass strip one or two inches high, as thick as the seal wanted and fastened to your plate attached to the press ram. The type and scale of press, shaped electrode and lower platen will, naturally, depend upon the required application.
To some extent these factors are independent of a single another, by way of example, a greater current or even more pressure will not necessarily reduce the sealing time. The type and thickness of material and also the total are from the Container Tracker determine these factors.
When you activate the ability, the material gets hot and its particular temperature rises, naturally, as being the temperature rises, heat is conducted off through the dies along with the air until a stat of warmth balance is reached. At this time, the amount of heat generated in the plastic material remains constant. This temperature, indicating a sort of equilibrium condition involving the heat generated and the heat loss to the seal must be higher than the melting point of the plastic.
It is the time required (measures within minutes or fractions of the) to reach this melting point considered the “heating time”.
The warmth loss is naturally greater with thinner material and much less with thicker material. Indeed, very thin materials (less than .004″) lose heat so rapidly which it becomes very difficult to seal them. With this we can easily see that, overall, thicker materials require more heating efforts and less power than thinner materials. Furthermore, it was actually found that certain poor heat conductors that do not melt of deteriorate easily under the impact of high frequency can be used as buffers. Bakelite, Mylar, silicone glass and Teflon, for example, are great in improving the seal.
The standard heating period ranges from a single to four seconds. To lessen failures, we advise that this timer determining the heating cycle needs to be set slightly over the minimum time found necessary for an effective seal.
The electrodes supply the heating current to melt the fabric and the pressure to fuse it. Generally, the reduced the pressure the poorer the seal. Conversely, a higher pressure will usually produce a better seal. However, an excessive amount of pressure will result in undue thinning out of the plastic material and also in an objectionable extrusion across the sides of your seal. Arcing could be caused due to the two electrodes moving closer to one another thus damaging the plastic, the buffer and / or it could be the die.
To get high pressure but 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 if you have no material between the two. And also this prevents the die from cutting completely from the material and simultaneously gives a seal of predetermined thickness. When 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 proper 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 in order to avoid warping under pressure.
Power required for an effective seal is directly proportional for the section 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 maximum part of the seal obtainable with every unit. However, keep in mind that these figures are calculated for concentrated areas. The sealable area is going to be less for long thin seals as well as for certain materials that are challenging to seal.
When setting up a new sealing job, the initial test should be with minimum power, moderate time and medium pressure. If the seal is weak, you must increase power gradually. For greatest freedom from burning or arcing, the power needs to be kept only possible, consistent with good sealing.
The dies should be held parallel to produce even pressure by any means sections. When there is a lot of extrusion or if perhaps the seal is simply too thin, the press sealing “stop” ought to be used. Setting the stop, place half the entire thickness of material to be sealed on the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the entire thickness of material in the press and create a seal. Check the result and lower or boost the “stop” as required.
When the seal is weak at certain spots, the dies are certainly 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 efforts and power might require readjustment after several hours of operation. To eliminate readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Use of heated platens is desirable when conducting tear seals applications.
Unless you create the various adjustments correctly, arcing throughout the material may occur. Arcing may also occur as soon as the material to become sealed has different thickness at various elements of the seal or in which the die overlaps the advantage of the material. In such cases, there could be arcing inside the air gaps in between the material and the die. Improving the power can often remedy this.
Arcing can also occur as a consequence of dirt or foreign matter around the material or dies. To avert this, care must be taken to keep the material as well as the machine clean.
Sharp corners and edges on dies can also cause arcing. The die edges ought to always 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 which has previously been arced.
Because they are now making sealing electrodes larger and much more complex, it is vital that no damage due to arcing occurs around the die. Although dies are repairable, losing production time sea1 repairs could be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The function of this gadget would be to sense the possibility of an arc and then turn off the R.F. power before a damaging arc can take place. Before full production runs are produced, normally a sensing control (which may be set for various applications and sealing areas) is preset. The Fleet Management will not prevent arcing but senses the arc, then shuts off of the power that prevents injury to the die.
As an option, an Arc Suppressor Tester could be included in the unit, which tests the arc suppressor before each cycle to insure proper operation.
Typically rf heating is improved from a thin layer of insulating material referred to as a Buffer. You attach this to 1 or both dies to insulate the fabric to get sealed through the die. This may many things: it lowers the temperature loss from the materials towards the dies; it compensates for small irregularities inside the die surface and might help make a great seal even if your die is not really perfectly flat; it decreases the tendency to arc when a lot of time or pressure is commonly used. Overall, it can make a better seal with less arcing. Buffer materials should have a 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) can be utilized successfully in most cases. A strip of cellulose or acetate tape adhered to the shaped die can be utilized with successful results.