In the most frequent setup, the information is sealed between a die from the desired shape along with a flat stationary steel plate engrossed in a brass or aluminum liner. The shaped electrode, too, is usually made from a brass strip a couple of inches high, as thick as being the seal wanted and fastened to a plate installed on the press ram. The type and size of press, shaped electrode and minimize platen will, of course, depend upon the necessary application.
At some level these factors are independent of just one another, for example, a larger current or even more pressure does not necessarily minimize the sealing time. What type and thickness of material and the total are from the unlock electronic seal determine these factors.
When you activate the power, the material gets hotter and its temperature rises, naturally, since the temperature rises, heat is carried out off throughout the dies and also the air until a stat of heat balance is reached. At this point, the volume of heat generated inside the plastic material remains constant. This temperature, indicating a kind of equilibrium condition in between the heat generated as well as the heat loss to the seal needs to be over the melting point of the plastic.
It will be the time required (measures in seconds or fractions with this) to arrive at this melting point understood to be the “heating time”.
The warmth loss is of course greater with thinner material and much less with thicker material. Indeed, very thin materials (below .004″) lose heat so rapidly that it becomes very difficult to seal them. Out of this we can notice that, overall, thicker materials require more heating time as well as less power than thinner materials. Furthermore, it had been found out that certain poor heat conductors that do not melt of deteriorate easily under the impact of high frequency can be used buffers. Bakelite, Mylar, silicone glass and Teflon, for instance, are fantastic in improving the seal.
The standard heating period ranges from a to four seconds. To minimize failures, we suggest how the timer determining the heating cycle needs to be set slightly over the minimum time found essential for a good seal.
The electrodes give you the heating current to melt the material along with the pressure to fuse it. Generally, the low pressure the poorer the seal. Conversely, a greater pressure will usually generate a better seal. However, a lot of pressure can lead to undue thinning out of your plastic material and then in an objectionable extrusion over the sides from the seal. Arcing may be caused due to the two electrodes moving closer to one another thus damaging the plastic, the buffer and / or perhaps the die.
To have high pressure nevertheless stay away from the above disadvantages, s “stop” on the press restrains the moving die in their motion. This can be set to prevent the dies from closing completely if you have no material between them. This too prevents the die from cutting completely through the material and simultaneously gives a seal of predetermined thickness. When a tear-seal type of die can be used, the stops will not be set in the press, since a thinning in the tear seal area is wanted.
To insure a uniform seal, the correct pressure should 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 have to also rigidly construct the dies to prevent warping under pressure.
Power essential for a great seal is directly proportional for the portion 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 portion 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 too long thin seals as well as for certain materials which can be difficult to seal.
When establishing a new sealing job, the first test needs to be with minimum power, moderate some time and medium pressure. When the seal is weak, you need to increase power gradually. For greatest freedom from burning or arcing, the power should be kept as low as possible, consistent with good sealing.
The dies should be held parallel to create even pressure at all sections. When there is excessive extrusion or maybe the seal is too thin, the press sealing “stop” needs to be used. Setting the stop, place half the complete thickness of material to be sealed around 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 boost the “stop” as required.
If the seal is weak at certain spots, the dies usually are not level. The leveling screws ought to be checked and adjusted. If these adjustments remain unsatisfactory, the die may need to be surface ground.
After making many seals, the dies then warm-up substantially and the some time and power might need readjustment after several hours of operation. To remove readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Consumption of heated platens is desirable when performing tear seals applications.
If you do not create the various adjustments correctly, arcing with the material may occur. Arcing might also occur if 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 can be arcing from the air gaps involving the material as well as the die. Increasing the power can occasionally remedy this.
Arcing may also occur because of dirt or foreign matter about the material or dies. To prevent this, care has to be delivered to keep the material along with the machine clean.
Sharp corners and edges on dies may also cause arcing. The die edges should always be rounded and smooth. When arcing occurs, the dies should be carefully cleaned and smoothed with fine emery cloth. Never make an effort to seal material that has previously been arced.
As they are now making sealing electrodes larger and a lot more complex, it is crucial that no damage due to arcing occurs around the die. Although dies are repairable, the decline of production time sea1 repairs could be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The function of this device is to sense the potential of an arc and then switch off the R.F. power before a damaging arc can happen. Before full production runs are created, commonly a sensing control (which may be looking for various applications and sealing areas) is preset. The Fleet Management does not prevent arcing but senses the arc, then shuts off of the power that prevents injury to the die.
As being an option, an Arc Suppressor Tester can be put into the machine, which tests the arc suppressor before each cycle to insure proper operation.
Typically rf heating is improved by a thin layer of insulating material known as a Buffer. You attach this to just one or both dies to insulate the fabric being sealed in the die. This does a number of things: it lowers the heat loss from your materials for the dies; it compensates for small irregularities in the die surface and might help make a good seal even if your die is not perfectly flat; it decreases the tendency to arc when a lot of time or pressure is utilized. Overall, it can make a greater 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 used successfully in most cases. A strip of cellulose or acetate tape adhered to the shaped die can be utilized with very effective results.