In the most typical create, the material is sealed between a die of your desired shape plus a flat stationary steel plate engrossed in a brass or aluminum liner. The shaped electrode, too, is generally made of a brass strip 1 or 2 inches high, as thick since the seal wanted and fastened to some plate placed on the press ram. What type and measurements of press, shaped electrode and lower platen will, obviously, depend upon the specified application.
To some extent these factors are independent of merely one another, for instance, a more substantial current or more pressure will not necessarily reduce the sealing time. The type and thickness of material and also the total are of the electronic seal device determine these factors.
As you may start up the energy, the content heats up and its particular temperature rises, naturally, because the temperature rises, heat is carried out off with the dies along with the air until a stat of heat balance is reached. At this moment, the quantity of heat generated inside the plastic material remains constant. This temperature, indicating a kind of equilibrium condition between the heat generated as well as the heat loss on the seal has to be higher than the melting reason for the plastic.
It will be the time required (measures in seconds or fractions of this) to achieve this melting point defined as the “heating time”.
The warmth loss is of course greater with thinner material and fewer with thicker material. Indeed, very thin materials (less than .004″) lose heat so rapidly that this becomes hard to seal them. From this we could notice that, overall, thicker materials require more heating time and less power than thinner materials. Furthermore, it absolutely was learned 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, for example, are perfect in increasing the seal.
The standard heating period ranges from a single to four seconds. To reduce failures, we advise that this timer determining the heating cycle needs to be set slightly higher than the minimum time found essential for a great seal.
The electrodes give you the heating current to melt the content along with the pressure to fuse it. Generally, the less the pressure the poorer the seal. Conversely, an increased pressure will most likely produce a better seal. However, excessive pressure can lead to undue thinning from the plastic material and in an objectionable extrusion over the sides from the seal. Arcing could be caused because of the two electrodes moving closer to one another thus damaging the plastic, the buffer and / or even the die.
To get high-pressure nevertheless steer clear of the above disadvantages, s “stop” around the press restrains the moving die in the motion. This really is set to prevent the dies from closing completely if you find no material between the two. And also this prevents the die from cutting completely with the material and simultaneously provides a seal of predetermined thickness. Every time a tear-seal type of die is utilized, the stops will not be set in the press, since a thinning of your tear seal area is wanted.
To insure a uniform seal, the proper pressure must be obtained at all points from the seal. To insure this, they grind the dies perfectly flat and held parallel to each other inside the press. They should also rigidly construct the dies in order to avoid warping under pressure.
Power essential for an excellent seal is directly proportional towards the part 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 most portion of the seal obtainable with every unit. However, bear in mind that these figures are calculated for concentrated areas. The sealable area will be less for too long thin seals and for certain materials that are tough to seal.
When establishing a new sealing job, the very first test should be with minimum power, moderate some time and medium pressure. When the seal is weak, you need to 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 has to be held parallel to make even pressure in any way sections. If you find too much extrusion or if perhaps the seal is way too thin, the press sealing “stop” must be used. To set the stop, place half the entire thickness of material to be sealed around the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the complete thickness of material in the press and make a seal. Look into the result and minimize or increase the “stop” as required.
If the seal is weak at certain spots, the dies are certainly not level. The leveling screws ought to be checked and adjusted. If these adjustments will still be unsatisfactory, the die may have to be surface ground.
After making many seals, the dies then warm-up substantially and the some time and power may require readjustment after several hours of operation. To reduce readjustment, they equip many machines with heated upper platens to pre-warm dies to operating temperatures. Use of heated platens is desirable when conducting tear seals applications.
If you do not make the various adjustments correctly, arcing with the material may occur. Arcing could also occur when the material to get sealed has different thickness at various parts of the seal or the location where the die overlaps the advantage in the material. In these cases, there can be arcing in the air gaps involving the material as well as the die. Improving the power will often remedy this.
Arcing can also occur as a consequence of dirt or foreign matter around the material or dies. To avoid this, care has to be come to retain the material and also 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 must be carefully cleaned and smoothed with fine emery cloth. Never make an effort to seal material containing previously been arced.
As they are now making sealing electrodes larger plus more complex, it is important that no damage because of arcing occurs on the die. Although dies are repairable, the loss of production time sea1 repairs can be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The function of this device is usually to sense the opportunity of an arc and after that turn off the R.F. power before a damaging arc can occur. Before full production runs are produced, normally a sensing control (which is often looking for various applications and sealing areas) is preset. The Fuel sensor does not prevent arcing but senses the arc, then shuts off of the power that prevents problems for the die.
Being an option, an Arc Suppressor Tester can be put into the device, 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 called a Buffer. You attach this to 1 or both dies to insulate the information being sealed from your die. This may many things: it lowers the temperature loss from the materials to the dies; it compensates for small irregularities within the die surface and may help to make a great seal even if the die will not be perfectly flat; it decreases the tendency to arc when a long time or pressure is used. Overall, it will make a much better 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) can be utilized successfully typically. A strip of cellulose or acetate tape followed the shaped die can be used with successful results.