Capabilities

• Compound viscosity
• Application pressure
• Nozzle orifice diameter
• Nozzle orifice length
• Needle lift
• Chuck speed

The compound viscosity is controlled by the compound manufacturer to predetermined specifications. However, it can be significantly effected by changes in application temperature. Some compounds respond differently to changes in temperature. These viscosity properties and the proper application temperature should be discussed with the compound supplier.

The application pressure is also extremely important in controlling compound film weights. A constant pressure is critical when maintaining film weight. Fluctuations in air pressure to a water based compound pot can drastically effect compound film weight. Worn compound pumps and pumps which generate pressure surges can have a significant effect on film weight.

Let us assume, for the sake of this discussion, that compound viscosity and pressure are under tight control. Changes in nozzle orifice diameter and/or orifice length can effect the compound pressure and subsequently the application weight. For example, if the compound application weight is to high and, when subsequently lowered, control of pressure and placement is lost, then a change to a smaller orifice nozzle or to a different style of nozzle having a longer lead may improve the application. Conversely, if the weight and placement are acceptable, however the pressures are excessively high causing pumps to wear and seals to leak, a change to a larger diameter or shorter lead may help.

The distance the needle is lifted out of the nozzle seat can drastically effect film weight and placement. Typical lift is 0.040 to 0.060 inches. Distances of more than 0.060 can cause excessive wear on seals in the compound gun and have an effect on compound placement. The further the needle had to travel to seat in the nozzle, the longer the nozzle will dispense compound. Changes in needle lift also effect the number of turns lining by increasing or decreasing the overlap of the turns.

Compound placement can also be effected by chuck speed. Many times, a high film weight needed to get good cutedge placement can be lowered and the proper placement achieved by increasing chuck speed. The ease of changes in chuck speed varies with the type of end liner used.

As one can readily see, there are several ways to achieve changes in film weight and placement. F & H Nozzle Specialists offers its customers over twenty years of nozzle and needle manufacturing experience and twenty five years of end sealant application technology. If we can be of any assistance with your application problems, please do not hesitate to contact us.

We, at F & H, have concerns about the method of lapping the nozzle to the needle in our customers' facilities.

Listed are some of the many factors which effect the quality of lapping a nozzle and needle.

• The skill of the individual doing the lapping
• The lack of proper alignment equipment
• The type of lapping compound used
• The labor cost of lapping

Because of the concerns, F & H offers our customers lapped sets produced in our manufacturing plant by our skilled personal and our precise equipment. These lapped sets are then marked and packaged individually.

It is our recommendation, if lapping is required, that it be done by F & H. We have found that more damage can be done to a nozzle and needle by lapping in our customer's plant than any benefit gained.

We cannot stress strongly enough, when nozzles are changed for any reason, the needle should also be changed. Poor lining results may occur when a new nozzle is used with a worn needle tip. At this time, seals should also be checked and replaced if worn.

These flow matched sets are produced by utilizing a very precise air flow gauging instrument. Large quantities of nozzles are checked by air flow and separated into groups of equal flow rate. The required sets are then selected from these matched groups.

Most flow matched nozzles are used on either four or six station rotary lining machines. When using flow matched sets, all stations should be changed at the same time, including needles, since the nozzle orifice changes due to wear caused by needle impact and abrasive compounds. It is a recommended practice to change full sets of nozzles and needles even when not using flow matched sets for the same reasons. A new nozzle will have a smaller orifice of several thousandths of an inch and dispense less compound at the same pressure setting. Used needles may not match the new nozzles and create problems as well.

Many times a liner mechanic will attempt to overcome this condition by making a needle lift adjustment to compensate. However, when the needle lift is adjusted on only one station to correct for film weight, the compound placement is also effected. The number of turns lining is changed by increasing or decreasing the overlap resulting in non-uniformity of ends from station to station.

There are other situations which can cause erratic compound weights and placement in addition to needles and nozzles. Close attention should be paid to worn linkage, springs, seals, etc.