In the most frequent put in place, the material is sealed from a die in the desired shape and a flat stationary steel plate engrossed in a brass or aluminum liner. The shaped electrode, too, is normally made from a brass strip a few inches high, as thick because the seal wanted and fastened into a plate mounted on the press ram. The type and dimensions of press, shaped electrode and lower platen will, obviously, rely on the required application.
To some degree these factors are independent of just one another, for instance, a greater current or higher pressure does not necessarily decrease the sealing time. What type and thickness of material and also the total are of your Container Tracker determine these factors.
When you switch on the ability, the content gets hotter and its temperature rises, naturally, as the temperature rises, heat is conducted off throughout the dies along with the air until a stat of warmth balance is reached. At this moment, the amount of heat generated in the plastic material remains constant. This temperature, indicating a kind of equilibrium condition involving the heat generated and the heat loss on the seal needs to be on top of the melting reason for the plastic.
This is 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 much less with thicker material. Indeed, very thin materials (less than .004″) lose heat so rapidly it becomes very difficult to seal them. Out of this we can easily observe that, overall, thicker materials require more heating efforts and less power than thinner materials. Furthermore, it was found out that certain poor heat conductors that do not melt of deteriorate easily within the impact of high frequency can be used buffers. Bakelite, Mylar, silicone glass and Teflon, by way of example, are great in boosting the seal.
The standard heating period ranges in one to four seconds. To reduce failures, we propose the timer determining the heating cycle must be set slightly over the minimum time found necessary for a great seal.
The electrodes provide the heating current to melt the content as well as the pressure to fuse it. Generally, the less the pressure the poorer the seal. Conversely, a higher pressure will often create a better seal. However, excessive pressure can lead to undue thinning out from the plastic material as well as in an objectionable extrusion along the sides from the seal. Arcing might be caused due to two electrodes moving closer to one another thus damaging the plastic, the buffer and / or perhaps the die.
To get high-pressure and yet avoid the above disadvantages, s “stop” around the press restrains the moving die in their motion. This really is set in order to avoid the dies from closing completely if you find no material between them. This too prevents the die from cutting completely through the material and simultaneously provides a seal of predetermined thickness. Each time a tear-seal sort of die can be used, the stops will not be set on the press, since a thinning of your tear seal area is wanted.
To insure a uniform seal, the proper pressure has to be obtained whatsoever points of your seal. To insure this, they grind the dies perfectly flat and held parallel to one another within the press. They need to also rigidly construct the dies to avoid warping under pressure.
Power necessary for an effective seal is directly proportional for the portion 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 utmost area of the seal obtainable with every unit. However, be aware 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 hard to seal.
When establishing a new sealing job, the first test must be with minimum power, moderate time and medium pressure. If the seal is weak, you need to increase power gradually. For greatest freedom from burning or arcing, the strength should be kept as low as possible, consistent with good sealing.
The dies needs to be held parallel to generate even pressure in any way sections. When there is a lot of extrusion or if the seal is way too thin, the press sealing “stop” must be used. Setting the stop, place half the whole 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 making a seal. Look into the result and reduce or raise the “stop” as required.
When the seal is weak at certain spots, the dies will not be level. The leveling screws needs to be checked and adjusted. If these adjustments remain unsatisfactory, the die may have to be surface ground.
After making many seals, the dies then heat substantially as well as the some time and power might need readjustment after a few hours of operation. To eliminate readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Use of heated platens is desirable when doing tear seals applications.
If you do not make your various adjustments correctly, arcing throughout the material may occur. Arcing can also occur once the material to be sealed has different thickness at various aspects of the seal or in which the die overlaps the advantage in the material. When this happens, there can be arcing within the air gaps between the material and also the die. Boosting the power can often remedy this.
Arcing might also occur because of dirt or foreign matter around the material or dies. To prevent this, care has to be delivered to keep your material and the machine clean.
Sharp corners and edges on dies may also cause arcing. The die edges ought to always be rounded and smooth. When arcing occurs, the dies needs to be carefully cleaned and smoothed with fine emery cloth. Never attempt to seal material which has previously been arced.
Since they are now making sealing electrodes larger and a lot more complex, it is essential that no damage on account of arcing occurs around the die. Although dies are repairable, the losing of production time sea1 repairs might be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The function of this piece of equipment would be to sense the opportunity of an arc then switch off the R.F. power before a damaging arc can occur. Before full production runs are produced, usually a sensing control (that may be set for various applications and sealing areas) is preset. The Fuel sensor is not going to prevent arcing but senses the arc, then shuts away 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 way of a thin layer of insulating material referred to as a Buffer. You attach this to just one or both dies to insulate the content being sealed from your die. This will a number of things: it lowers the warmth loss from your materials on the dies; it compensates for small irregularities in the die surface and could help make a good seal whether or not the die is just not perfectly flat; it decreases the tendency to arc when a long time or pressure is used. Overall, this makes a much better seal with less arcing. Buffer materials should have a very good heat resistance and voltage breakdown. Of many materials used (Bakelite, paper, glassine, Teflon, glass Mylar, silicone, fiberglass, etc.). Bakelite (grade xx about .010 to .030 inches thick) may be used successfully in many instances. A strip of cellulose or acetate tape adhered to the shaped die can be utilized with very effective results.