In the most prevalent create, the information is sealed from a die of your desired shape as well as a flat stationary steel plate engrossed in a brass or aluminum liner. The shaped electrode, too, is usually manufactured from a brass strip a few inches high, as thick because the seal wanted and fastened to some plate placed on the press ram. What type and measurements of press, shaped electrode and reduce platen will, naturally, rely on the specified application.
To some degree these factors are independent of merely one another, for instance, a greater current or maybe more pressure is not going to necessarily lessen the sealing time. The type and thickness of material as well as the total are from the Container Tracker determine these factors.
When you switch on the ability, the material heats up and its particular temperature rises, naturally, as being the temperature rises, heat is carried out off from the dies along with the air until a stat of warmth balance is reached. At this time, the quantity of heat generated throughout the plastic material remains constant. This temperature, indicating a sort of equilibrium condition between the heat generated along with the heat loss on the seal must be on top of the melting reason for the plastic.
This is the time required (measures in seconds or fractions of this) to reach 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 (less than .004″) lose heat so rapidly that it becomes tough to seal them. Using this we are able to observe that, overall, thicker materials require more heating efforts and less power than thinner materials. Furthermore, it had been learned that certain poor heat conductors which 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 fantastic in improving the seal.
The usual heating period ranges in one to four seconds. To reduce failures, we advise that the timer determining the heating cycle ought to be set slightly higher than the minimum time found needed for an excellent seal.
The electrodes provide the heating current to melt the information along with the pressure to fuse it. Generally, the lower the strain the poorer the seal. Conversely, a greater pressure will usually produce a better seal. However, a lot of pressure can result in undue thinning out from the plastic material and also in an objectionable extrusion over the sides from the seal. Arcing might be caused because of the two electrodes moving closer to each other thus damaging the plastic, the buffer and / or possibly the die.
To get high pressure but prevent the above disadvantages, s “stop” around the press restrains the moving die within its motion. This is certainly set to avoid the dies from closing completely when there is no material between them. This also prevents the die from cutting completely throughout the material and as well gives a seal of predetermined thickness. Every time a tear-seal form of die is used, the stops are certainly not set on the press, since a thinning from the tear seal area is wanted.
To insure a uniform seal, the appropriate pressure needs to be obtained at all points from the seal. To insure this, they grind the dies perfectly flat and held parallel to one another inside the press. They have to also rigidly construct the dies to prevent warping under pressure.
Power essential for an effective seal is directly proportional towards the part of the seal. Moreover, thicker materials require less power than thinner materials because thinner materials lose heat to the dies more rapidly. Our sealability calculator shows the most area of the seal obtainable with every unit. However, keep in mind these figures are calculated for concentrated areas. The sealable area will be less for too long thin seals and then for certain materials which are challenging to seal.
When starting a new sealing job, the first test should be with minimum power, moderate some time and medium pressure. In case the seal is weak, you should increase power gradually. For greatest freedom from burning or arcing, the power should be kept as little as possible, consistent with good sealing.
The dies needs to be held parallel to make even pressure in any way sections. If there is a lot of extrusion or if perhaps the seal is way too thin, the press sealing “stop” needs to be used. To set the stop, place half the complete thickness of material to be sealed in the lower plate. Close the press and adjust the stop-nut finger tight. Then insert the total thickness of material from the press and make up a seal. Look into the result and reduce or enhance the “stop” as required.
When the seal is weak at certain spots, the dies are not level. The leveling screws ought to be checked and adjusted. If these adjustments continue to be unsatisfactory, the die may need to be surface ground.
After making many seals, the dies then warm-up substantially as well as the some time and power might require readjustment after a few hours of operation. To get rid of 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 throughout the material may occur. Arcing could also occur as soon as the material to be sealed has different thickness at various areas of the seal or where die overlaps the edge of the material. In these instances, there could be arcing from the air gaps in between the material and also the die. Enhancing the power can sometimes remedy this.
Arcing might also occur as a consequence of dirt or foreign matter around the material or dies. To avert this, care must be taken to keep your material and also the machine clean.
Sharp corners and edges on dies could also cause arcing. The die edges should invariably be rounded and smooth. When arcing occurs, the dies should be carefully cleaned and smoothed with fine emery cloth. Never try and seal material which has previously been arced.
Because they are now making sealing electrodes larger and more complex, it is vital that no damage due to arcing occurs in the die. Although dies are repairable, losing production time sea1 repairs could be prohibitive.
We supply all Thermatron equipment with arc suppression devices. The purpose of this device is always to sense the possibility of an arc then switch off the R.F. power before a damaging arc may appear. Before full production runs are made, usually a sensing control (which may be set for various applications and sealing areas) is preset. The Container Tracker fails to prevent arcing but senses the arc, then shuts off the power that prevents injury to the die.
As being an option, an Arc Suppressor Tester could be included in 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 called a Buffer. You attach this to just one or both dies to insulate the fabric being sealed from the die. This may several things: it lowers the high temperature loss in the materials for the dies; it compensates for small irregularities in the die surface and could help to make a great seal even if your die will not be perfectly flat; it decreases the tendency to arc when too much effort or pressure is utilized. Overall, it can make 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) can be used successfully in most cases. A strip of cellulose or acetate tape followed the shaped die works extremely well with very effective results.