In the most frequent create, the information is sealed from a die from the desired shape as well as a flat stationary steel plate covered with a brass or aluminum liner. The shaped electrode, too, is generally created from a brass strip a couple of inches high, as thick as the seal wanted and fastened to a plate installed on the press ram. What type and scale of press, shaped electrode and reduce platen will, naturally, depend upon the required application.
To some extent these factors are independent of just one another, by way of example, a larger current or maybe more pressure is not going to necessarily reduce the sealing time. What type and thickness of material as well as the total are of the unlock electronic seal determine these factors.
When you start up the energy, the material warms up as well as its temperature rises, naturally, since the temperature rises, heat is conducted off from the dies and the air until a stat of heat balance is reached. At this point, the amount of heat generated within the plastic material remains constant. This temperature, indicating a kind of equilibrium condition between your heat generated along with the heat loss to the seal needs to be above the melting point of the plastic.
This is basically the time required (measures within minutes or fractions of this) to reach this melting point considered the “heating time”.
The heat loss is naturally greater with thinner material and much less with thicker material. Indeed, very thin materials (under .004″) lose heat so rapidly it becomes hard to seal them. From this we can 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 that do not melt of deteriorate easily beneath the impact of high frequency bring buffers. Bakelite, Mylar, silicone glass and Teflon, for instance, are great in increasing the seal.
The standard heating period ranges from one to four seconds. To lower failures, we recommend the timer determining the heating cycle needs to be set slightly over the minimum time found required for an excellent seal.
The electrodes supply the heating current to melt the information along with the pressure to fuse it. Generally, the less the strain the poorer the seal. Conversely, a higher pressure will usually create a better seal. However, a lot of pressure will result in undue thinning out from the plastic material and also in an objectionable extrusion across the sides from the seal. Arcing could be caused because of the two electrodes moving closer to one another thus damaging the plastic, the buffer and / or possibly the die.
To have high pressure however stay away from the above disadvantages, s “stop” in the press restrains the moving die within its motion. This is certainly set to prevent the dies from closing completely when there is no material between the two. This prevents the die from cutting completely from the material and at the same time offers a seal of predetermined thickness. Whenever a tear-seal sort of die can be used, the stops usually are not set on the press, since a thinning of your tear seal area is wanted.
To insure a uniform seal, the appropriate pressure has to be obtained by any means points of the seal. To insure this, they grind the dies perfectly flat and held parallel to one another within the press. They have to also rigidly construct the dies to prevent warping under pressure.
Power necessary for a good seal is directly proportional towards the part 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 maximum part of the seal obtainable with every unit. However, bear in mind that these figures are calculated for concentrated areas. The sealable area will be less for too long thin seals and for certain materials that happen to be difficult to seal.
When generating a new sealing job, the 1st test should be with minimum power, moderate some time and medium pressure. In case the seal is weak, you must increase power gradually. For greatest freedom from burning or arcing, the energy must be kept as little as possible, consistent with good sealing.
The dies should be held parallel to generate even pressure in any way sections. If you have excessive extrusion or maybe if the seal is way too thin, the press sealing “stop” ought to be used. To create the stop, place half the total thickness of material being sealed about the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the entire thickness of material in the press and make a seal. Check the result and lower or increase the “stop” as required.
In case the seal is weak at certain spots, the dies are not level. The leveling screws should 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 warm up substantially as well as the some time and power might need readjustment after several 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.
If you do not have the various adjustments correctly, arcing with the material may occur. Arcing might 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 in the material. In these cases, there may be arcing from the air gaps between the material and also the die. Increasing the power can occasionally remedy this.
Arcing may 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 as well as the machine clean.
Sharp corners and edges on dies can also cause arcing. The die edges should always be rounded and smooth. When arcing occurs, the dies has to be carefully cleaned and smoothed with fine emery cloth. Never make an effort to seal material that has previously been arced.
Because they are now making sealing electrodes larger plus more complex, it is vital that no damage as a result of arcing occurs around the die. Although dies are repairable, losing production time sea1 repairs can be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The function of this piece of equipment is always to sense the chance of an arc after which switch off the R.F. power before a damaging arc can take place. Before full production runs are made, commonly a sensing control (which is often set for various applications and sealing areas) is preset. The Fuel sensor does not prevent arcing but senses the arc, then shuts from the power that prevents problems for the die.
Being an option, an Arc Suppressor Tester may be put into the system, 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 a single or both dies to insulate the content being sealed through the die. This may many things: it lowers the temperature loss through the materials to the dies; it compensates for small irregularities from the die surface and might help to make an excellent seal even when the die is not perfectly flat; it decreases the tendency to arc when a long time or pressure can be used. Overall, it will make a greater seal with less arcing. Buffer materials should have a very good heat resistance and high 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 in many instances. A strip of cellulose or acetate tape adhered to the shaped die works extremely well with successful results.