In the most frequent setup, the fabric is sealed from a die of the desired shape and a flat stationary steel plate covered with a brass or aluminum liner. The shaped electrode, too, is normally made from a brass strip a few inches high, as thick as the seal wanted and fastened to your plate mounted on the press ram. What type and scale of press, shaped electrode minimizing platen will, obviously, depend upon the specified application.
To some extent these factors are independent of just one another, for instance, a greater current or more pressure will not necessarily decrease the sealing time. The type and thickness of material along with the total are from the electronic seal device determine these factors.
As you may start up the strength, the material heats up as well as its temperature rises, naturally, because the temperature rises, heat is conducted off throughout the dies along with the air until a stat of warmth balance is reached. At this stage, the level of heat generated within the plastic material remains constant. This temperature, indicating a kind of equilibrium condition in between the heat generated along with the heat loss towards the seal must be above the melting point of the plastic.
This is the time required (measures within minutes or fractions with this) to achieve this melting point defined as the “heating time”.
The high temperature loss is of course greater with thinner material and less with thicker material. Indeed, very thin materials (below .004″) lose heat so rapidly that this becomes hard to seal them. Using this we could realize that, overall, thicker materials require more heating time as well as less power than thinner materials. Furthermore, it had been found that certain poor heat conductors which do not melt of deteriorate easily under 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 in one to four seconds. To minimize failures, we recommend that this timer determining the heating cycle needs to be set slightly over the minimum time found needed for an effective seal.
The electrodes supply the heating current to melt the fabric and the pressure to fuse it. Generally, the low the stress the poorer the seal. Conversely, a better pressure will most likely produce a better seal. However, a lot of pressure will lead to undue thinning out of your plastic material as well as in an objectionable extrusion over the sides from the seal. Arcing can be caused due to two electrodes moving closer to each other thus damaging the plastic, the buffer and / or it could be the die.
To have high-pressure nevertheless prevent the above disadvantages, s “stop” around the press restrains the moving die within its motion. This is set to stop the dies from closing completely if you have no material between the two. This also prevents the die from cutting completely with the material and concurrently provides a seal of predetermined thickness. Every time a tear-seal sort of die is used, the stops usually are not set about the press, since a thinning of your tear seal area is wanted.
To insure a uniform seal, the correct pressure should be obtained whatsoever points from the seal. To insure this, they grind the dies perfectly flat and held parallel to one another from the press. They have to also rigidly construct the dies to stop warping under pressure.
Power needed 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 for the dies more rapidly. Our sealability calculator shows the maximum part of the seal obtainable with each 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 are challenging to seal.
When generating a new sealing job, the first test needs to be with minimum power, moderate time as well as medium pressure. In case the seal is weak, you ought to increase power gradually. For greatest freedom from burning or arcing, the power must be kept as little as possible, consistent with good sealing.
The dies should be held parallel to produce even pressure by any means sections. If you find too much extrusion or maybe the seal is just too thin, the press sealing “stop” must be used. To create the stop, place half the entire thickness of material to become sealed on the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the full thickness of material within the press and create a seal. Check the result and minimize or enhance the “stop” as required.
In case the seal is weak at certain spots, the dies will not be 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 warm up substantially and also the some time and power may require readjustment after several hours of operation. To get rid of readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Consumption of heated platens is desirable when you are performing tear seals applications.
Should you not make the various adjustments correctly, arcing with the material may occur. Arcing might also occur when the material to be sealed has different thickness at various parts of the seal or the location where the die overlaps the advantage in the material. In such cases, there may be arcing from the air gaps in between the material along with the die. Boosting the power can sometimes remedy this.
Arcing might also occur as a consequence of dirt or foreign matter about the material or dies. To avert this, care needs to be come to retain the material as well as the machine clean.
Sharp corners and edges on dies can 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 which includes 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 in the die. Although dies are repairable, the decline of production time sea1 repairs might 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 and then turn off the R.F. power before a damaging arc can occur. Before full production runs are manufactured, usually a sensing control (which can be looking for various applications and sealing areas) is preset. The Container monitoring is not going to prevent arcing but senses the arc, then shuts away from the power that prevents injury to the die.
As being an option, an Arc Suppressor Tester might be added to 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 termed as a Buffer. You attach this to one or both dies to insulate the information to be sealed in the die. This may several things: it lowers the high temperature loss through the materials on the dies; it compensates for small irregularities inside the die surface and could help make an excellent seal even if your die is just not perfectly flat; it decreases the tendency to arc when a long time or pressure is used. Overall, it makes an improved seal with less arcing. Buffer materials should have a good heat resistance and high 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) works extremely well successfully in most cases. A strip of cellulose or acetate tape adhered to the shaped die may be used with very successful results.