In the most frequent create, the fabric is sealed between a die of the desired shape and a flat stationary steel plate covered with a brass or aluminum liner. The shaped electrode, too, is often created from a brass strip a few inches high, as thick since the seal wanted and fastened to some plate attached to the press ram. What type and size of press, shaped electrode and minimize platen will, obviously, depend upon the required application.
To some degree these factors are independent of merely one another, by way of example, a bigger current or higher pressure will not necessarily minimize the sealing time. The type and thickness of material and also the total are of the unlock electronic seal determine these factors.
As you activate the energy, the content heats up and its particular temperature rises, naturally, since the temperature rises, heat is conducted off through the dies as well as the air until a stat of heat balance is reached. At this point, the amount of heat generated in the plastic material remains constant. This temperature, indicating a kind of equilibrium condition in between the heat generated and also the heat loss to the seal must be on top of the melting point of the plastic.
It will be the time required (measures within minutes or fractions of the) to reach this melting point described as the “heating time”.
The warmth loss is of course greater with thinner material and fewer with thicker material. Indeed, very thin materials (under .004″) lose heat so rapidly that it becomes hard to seal them. From this we can easily observe that, overall, thicker materials require more heating time and less power than thinner materials. Furthermore, it absolutely was found that certain poor heat conductors that do not melt of deteriorate easily within the impact of high frequency bring buffers. Bakelite, Mylar, silicone glass and Teflon, as an example, are perfect in increasing the seal.
The usual heating period ranges from a to four seconds. To lessen failures, we propose that the timer determining the heating cycle ought to be set slightly higher than the minimum time found essential for a good seal.
The electrodes supply the heating current to melt the information and the pressure to fuse it. Generally, the less the stress the poorer the seal. Conversely, a higher pressure will normally develop a better seal. However, too much pressure will lead to undue thinning out of your plastic material and also in an objectionable extrusion along the sides of your seal. Arcing could be caused due to the two electrodes moving closer to each other thus damaging the plastic, the buffer and / or even the die.
To obtain high-pressure nevertheless stay away from the above disadvantages, s “stop” about the press restrains the moving die in the motion. This really is set to stop the dies from closing completely should there be no material between the two. 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 can be used, the stops are not set on the press, since a thinning from the tear seal area is wanted.
To insure a uniform seal, the right pressure should be obtained at all points in the seal. To insure this, they grind the dies perfectly flat and held parallel to each other in the press. They have to also rigidly construct the dies in order to avoid 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 on the dies more rapidly. Our sealability calculator shows the maximum section of the seal obtainable with every unit. However, be aware that these figures are calculated for concentrated areas. The sealable area will probably be less for very long thin seals and also for certain materials which can be challenging to seal.
When starting a new sealing job, the initial test needs to be with minimum power, moderate some time and medium pressure. In the event the seal is weak, you should increase power gradually. For greatest freedom from burning or arcing, the ability must be kept as little as possible, consistent with good sealing.
The dies must be held parallel to produce even pressure in any way sections. If you find a lot of extrusion or maybe if the seal is just 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 full thickness of material in the press making a seal. Examine the result and reduce or boost the “stop” as required.
When the seal is weak at certain spots, the dies usually 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 heat substantially and also the some 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. Usage of heated platens is desirable when performing tear seals applications.
Should you not have the 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 where die overlaps the edge from the material. In these instances, there may be arcing inside the air gaps between your material as well as the die. Enhancing the power can occasionally remedy this.
Arcing can also occur as a result of dirt or foreign matter about the material or dies. To avoid this, care has to be taken up keep the material as well as the machine clean.
Sharp corners and edges on dies could also cause arcing. The die edges should be rounded and smooth. When arcing occurs, the dies must be carefully cleaned and smoothed with fine emery cloth. Never try to seal material containing previously been arced.
Because they are now making sealing electrodes larger and more complex, it is vital that no damage because of arcing occurs about the die. Although dies are repairable, the losing of production time sea1 repairs could be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The function of this product is usually to sense the potential of an arc and then switch off the R.F. power before a damaging arc may appear. Before full production runs are manufactured, commonly a sensing control (which may be set for various applications and sealing areas) is preset. The Fleet Management is not going to prevent arcing but senses the arc, then shuts off the power that prevents problems for the die.
As an option, an Arc Suppressor Tester might be included with the unit, 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 a single or both dies to insulate the material to get sealed through the die. This will many things: it lowers the temperature loss from the materials for the dies; it compensates for small irregularities in the die surface and could help make a great seal even if the die is not perfectly flat; it decreases the tendency to arc when a lot of time or pressure can be used. Overall, it makes a better seal with less arcing. Buffer materials should have a very 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) may be used successfully typically. A strip of cellulose or acetate tape adhered to the shaped die may be used with very effective results.