In the most common create, the information is sealed from a die of your desired shape along with a flat stationary steel plate engrossed in a brass or aluminum liner. The shaped electrode, too, is often made of a brass strip a few inches high, as thick because the seal wanted and fastened into a plate attached to the press ram. What type and size of press, shaped electrode and minimize platen will, of course, rely on the specified application.
At some level these factors are independent of just one another, as an example, a bigger current or even more pressure is not going to necessarily reduce the sealing time. What type and thickness of material along with the total are of your unlock electronic seal determine these factors.
As you may switch on the power, the content heats up and its particular temperature rises, naturally, because the temperature rises, heat is carried out off with the dies as well as the air until a stat of warmth balance is reached. At this time, the volume of heat generated in the plastic material remains constant. This temperature, indicating a kind of equilibrium condition involving the heat generated and also the heat loss towards the seal should be higher than the melting point of the plastic.
This is the time required (measures in seconds or fractions on 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 (under .004″) lose heat so rapidly that this becomes very difficult to seal them. With this we can realize that, overall, thicker materials require more heating time and less power than thinner materials. Furthermore, it was actually discovered 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 great in improving the seal.
The normal heating period ranges in one to four seconds. To minimize failures, we propose that this timer determining the heating cycle should be set slightly above the minimum time found needed for a great seal.
The electrodes give you the heating current to melt the content and the pressure to fuse it. Generally, the low the stress the poorer the seal. Conversely, a higher pressure will most likely generate a better seal. However, too much pressure will result in undue thinning out from the plastic material as well as in an objectionable extrusion down the sides of your seal. Arcing may be caused because of the two electrodes moving closer to each other thus damaging the plastic, the buffer and / or perhaps the die.
To get high-pressure and yet stay away from the above disadvantages, s “stop” in the press restrains the moving die in the motion. This really is set to avoid the dies from closing completely when there is no material between them. This too prevents the die from cutting completely throughout the material and as well offers a seal of predetermined thickness. Each time a tear-seal type of die is utilized, the stops will not be set around the press, since a thinning of the tear seal area is wanted.
To insure a uniform seal, the appropriate pressure has to be obtained at all points from the seal. To insure this, they grind the dies perfectly flat and held parallel to one another from the press. They must also rigidly construct the dies to prevent warping under pressure.
Power essential for an excellent seal is directly proportional for the section 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 utmost part of the seal obtainable with each unit. However, keep in mind that 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 challenging to seal.
When setting up a new sealing job, the very first test must be with minimum power, moderate time as well as medium pressure. When the seal is weak, you should increase power gradually. For greatest freedom from burning or arcing, the energy must be kept as low as possible, consistent with good sealing.
The dies must be held parallel to create even pressure at all sections. When there is too much extrusion or maybe if the seal is simply too thin, the press sealing “stop” should be used. To put the stop, place half the entire thickness of material to get sealed around the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the complete thickness of material within the press and make up a seal. Examine 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 should be checked and adjusted. If these adjustments will still be unsatisfactory, the die might have to be surface ground.
After making many seals, the dies then heat up substantially along with the time and power may need readjustment after a few hours of operation. To reduce 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.
Should you not make your various adjustments correctly, arcing through the material may occur. Arcing might also occur when the material being sealed has different thickness at various parts of the seal or in which the die overlaps the advantage from the material. When this happens, there might be arcing in the air gaps involving the material as well as the die. Boosting the power can often remedy this.
Arcing can also occur because of dirt or foreign matter about the material or dies. To avoid this, care must be come to keep your material along with the machine clean.
Sharp corners and edges on dies might 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 attempt to seal material which includes previously been arced.
Considering they are now making sealing electrodes larger and much more complex, it is crucial that no damage as a result of arcing occurs about the die. Although dies are repairable, the losing of production time sea1 repairs may be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The purpose of this piece of equipment would be to sense the potential of an arc after which shut down the R.F. power before a damaging arc can happen. Before full production runs are made, usually a sensing control (which may be looking for various applications and sealing areas) is preset. The Container Tracker does not prevent arcing but senses the arc, then shuts off of the power that prevents harm to the die.
As an option, an Arc Suppressor Tester could be included with the device, 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 1 or both dies to insulate the content to get sealed in the die. This does many things: it lowers the temperature loss in the materials for the dies; it compensates for small irregularities in the die surface and could help make an effective seal even if your die is just not perfectly flat; it decreases the tendency to arc when a long time or pressure can be used. Overall, it can make an improved 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) works extremely well successfully in most cases. A strip of cellulose or acetate tape followed the shaped die works extremely well with very effective results.