In the most typical put in place, the fabric is sealed between a die from the desired shape as well as a flat stationary steel plate engrossed in a brass or aluminum liner. The shaped electrode, too, is usually made from a brass strip a few inches high, as thick since the seal wanted and fastened to your plate installed on the press ram. What type and dimensions of press, shaped electrode and reduce platen will, of course, depend upon the required application.
At some level these factors are independent of merely one another, for instance, a larger current or more pressure does not necessarily lessen the sealing time. What type and thickness of material and also the total are of your Container Tracker determine these factors.
As you activate the power, the information gets hot as well as its temperature rises, naturally, because the temperature rises, heat is carried out off from the dies and also the air until a stat of warmth balance is reached. At this time, the amount of heat generated in the plastic material remains constant. This temperature, indicating a kind of equilibrium condition between your heat generated and the heat loss towards the seal must be higher than the melting point of the plastic.
This is basically the time required (measures in seconds or fractions on this) to reach this melting point considered the “heating time”.
The high temperature loss is of course greater with thinner material and less with thicker material. Indeed, very thin materials (lower than .004″) lose heat so rapidly it becomes very difficult to seal them. Out of this we could see that, overall, thicker materials require more heating some time and less power than thinner materials. Furthermore, it had been learned that certain poor heat conductors that do not melt of deteriorate easily under the impact of high frequency can be used as buffers. Bakelite, Mylar, silicone glass and Teflon, by way of example, are fantastic in enhancing the seal.
The standard heating period ranges in one to four seconds. To lessen failures, we advise that this timer determining the heating cycle ought to be set slightly over the minimum time found necessary for a great seal.
The electrodes supply the heating current to melt the information as well as the pressure to fuse it. Generally, the less the strain the poorer the seal. Conversely, a higher pressure will normally generate a better seal. However, excessive pressure can result in undue thinning out of the plastic material and in an objectionable extrusion down the sides from the seal. Arcing could be caused as a result of two electrodes moving closer to one another thus damaging the plastic, the buffer and / or even the die.
To have high pressure and yet steer clear of the above disadvantages, s “stop” on the press restrains the moving die in the motion. This can be set in order to avoid the dies from closing completely when there is no material between the two. This too prevents the die from cutting completely through the material and simultaneously offers a seal of predetermined thickness. When a tear-seal form of die is utilized, the stops are not set in the press, since a thinning from the tear seal area is wanted.
To insure a uniform seal, the appropriate pressure must be obtained at all points of your seal. To insure this, they grind the dies perfectly flat and held parallel to each other in the press. They need 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 towards the dies more rapidly. Our sealability calculator shows the utmost portion of the seal obtainable with each unit. However, bear in mind that these figures are calculated for concentrated areas. The sealable area is going to be less for very long thin seals and for certain materials which are challenging to seal.
When establishing a new sealing job, the initial test needs to be with minimum power, moderate some time and medium pressure. When the seal is weak, you should increase power gradually. For greatest freedom from burning or arcing, the ability should be kept as low as possible, consistent with good sealing.
The dies must be held parallel to produce even pressure whatsoever sections. If you find a lot of extrusion or maybe the seal is just too thin, the press sealing “stop” ought to be used. To create the stop, place half the total thickness of material to be sealed about the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the entire thickness of material inside the press making a seal. Examine the result and reduce or enhance the “stop” as required.
When the seal is weak at certain spots, the dies will not be level. The leveling screws ought to 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 time as well as power may require 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 doing tear seals applications.
If you do not create the various adjustments correctly, arcing with the material may occur. Arcing may also occur when the material to be sealed has different thickness at various areas of the seal or where die overlaps the edge in the material. In these instances, there might be arcing from the air gaps between the material along with the die. Boosting the power will often remedy this.
Arcing can also occur because of dirt or foreign matter about the material or dies. To avoid this, care should be taken to keep the material and the machine clean.
Sharp corners and edges on dies might 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 make an effort to seal material which includes previously been arced.
As they are now making sealing electrodes larger and a lot more complex, it is essential that no damage because of arcing occurs about the die. Although dies are repairable, the loss of production time sea1 repairs could be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The function of this gadget is usually to sense the chance of an arc and after that switch off the R.F. power before a damaging arc can take place. Before full production runs are produced, normally a sensing control (which is often set for various applications and sealing areas) is preset. The Container Tracker will not prevent arcing but senses the arc, then shuts away from the power that prevents harm 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 with a thin layer of insulating material termed as a Buffer. You attach this to one or both dies to insulate the material to become sealed in the die. This may several things: it lowers the heat loss from your materials on the dies; it compensates for small irregularities within the die surface and may even help to make an effective seal even if your die is just not perfectly flat; it decreases the tendency to arc when a lot of time or pressure is used. Overall, it will make a greater seal with less arcing. Buffer materials should have a very good heat resistance and high 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 many instances. A strip of cellulose or acetate tape followed the shaped die may be used with highly effective results.