Description of the device and operating principle of the glue gun

The unpredictable behavior of the heating element in a Chinese glue gun has become the talk of the town. The service life, according to information from Internet users, varies from a few seconds after switching on to five years of proper operation. About the power of the heating element, we came across statements ranging from “virtually does not heat at all” to “heats quite satisfactorily.” This was the reason for the curiosity that arose, which prompted me to buy, first, an inexpensive Chinese glue gun for the purpose of “opening it and looking.” That is, thoroughly familiarize yourself with the design of the device, and that’s all. I didn’t take any glue sticks; I probably won’t need them.

Application area

Various materials are glued together with a glue gun:

• cardboard;
• ceramics;
• glass;
• plastic;
• metal, leather;
• tree;
• cork.

The pistol is indispensable in the household. Options for its use are presented in the table.

Design and principle of operation

During operation, the gun is held by the handle. On top is the barrel, which includes all the elements of the device.

When the device is turned on, the heating element located in the heating chamber is heated. A heating stick touches it, which melts at a temperature of 105-210 degrees. With its further supply, excess pressure is created, and the molten glue is pushed out through the nozzle.

Body and handle of the product

The handle is hollow. Only wires pass through it, and a trigger is installed on the side. The housing houses the entire device. It is made of plastic with a low degree of thermal conductivity. This is due to heating of internal parts.

The weight of the device is 300 g. After turning it on, the device should only be positioned vertically. You can’t lift it with its nose up and put it on its side. This is due to the presence of molten glue inside it.

There is a platform at the bottom of the handle, and a folding pad is fixed in front of the body. The gun is mounted on these support points.

Feeder

When you press the trigger, which can be carousel or slide, the force is transferred to the ring pusher. This structural element is in direct contact with the rod. The rotating ring grabs the rod and pulls it towards the heating element.

The ring pusher is the weak element of the system. If there is even a slight defect, the rod may slip through the ring.

Guide coupling

The part is made of heat-resistant rubber. One side of it is put on the heating chamber, and the other side is inserted with a glue stick.

The coupling performs 2 functions:

1. It keeps the molten mass of glue from flowing into the body of the device.
2. Creates temperature uniformity. In its absence, during downtime, the rod would begin to melt in front of the heating chamber.

This is another weak point of the pistol. If heated, the rubber may tear when trying to rotate the rod.

Heating chamber

Externally, it is a tube in which the heating element is located. Some types of devices have two heating elements built in. In this case, heating of the rod occurs not only in the end part, but also on the sides.

The performance of the equipment depends on the size of the chamber and the power of the heating elements. This design unit is the most reliable. If used correctly, the likelihood of it breaking is very small.

Nozzle

An exiting stream of glue is formed in this element. Nozzles come in direct flow and with a valve. With the first option, the heated glue moves by gravity. The dosage is ensured by the feeding mechanism. With high fluidity of the glue, it begins to come out constantly. This is a disadvantage because of its large losses.

A spring-loaded ball is built into the nozzle with a valve, blocking the hole. Opening occurs under the influence of excess pressure when the glue is heated. The channel is never completely blocked by the ball. This is so that when overheated, excess glue can leak out on its own.

A protective cap is installed on the outside to avoid burns. Depending on the type of gun, nozzles can be stationary or removable. Each nozzle has its own channel thickness. Attached with a threaded connection. Replacement is carried out only when the device is warm, otherwise the hardened glue will not allow this to be done.

Review - analysis of the cheapest 20W heat gun

I continue the series of reviews of tools for the home craftsman. In this review, we look at, disassemble and study the ancestor of 3D printers - a 20-watt glue gun. Is it really 20 watts, can 20 watts melt hot glue and what is inside it? In terms of popularity of use, the heat gun comes right behind blue electrical tape, and it’s not for nothing that the gun is also blue. You can quickly repair toys with a heat gun; it sticks well to plastic and can be used 10 minutes after gluing. You can make your own refrigerator magnets or set up a workspace by gluing a bunch of tool magnets onto a shelf. You can fix the wires in the connectors. This is a smaller version of the heat gun - for 7mm rods. There are larger options, perhaps if you need to glue a lot and often the larger option is preferable. The smaller option is completely enough for me.

The heat gun is over a year old, so it looks like this. I bought it for $5.74, the account was closed for abuse, so now in the title there is a link to the cheapest option that I found.

Purchase Confirmation

Stored in a camera box, it also contains rods and glue residues that can be reused.

The gun can stand on a surface, for this there is a stand and a cut on the handle. The stand is fixed in two positions and there are two versions of the stand, they often send either one randomly, I don’t see the difference. But I prefer to hang it or place it with the nozzle up because the glue flows. For perfectionists, there are heat guns with a valve for $10+.

On the side of the gun there is an LED indicating whether it is turned on (very convenient when the socket is broken) and a power button.

The stated power is 20 watts. I turn it on - after turning it on it immediately shows about 60 watts, the power drops quickly, I didn’t have time to take a picture of the maximum speed. After heating, consumption stabilizes at 7 watts

The glue in the gun warms up for about 5 minutes, after heating the temperature of the spout is about 130 degrees. The hot tip of the gun can be used to touch up and shape the already applied glue.

Application.

The rods come in different colors, different compositions and for different temperatures. There is a lot of water on this subject on the Internet; usually the most popular rods melt at about 100 degrees and are soft at 80. Accordingly, their scope of application is limited. It seems that information about the composition of the rod and its melting point can only be found on the packaging, if there is one. You can fix the wires in the connectors, you can simply create connectors - the temperature is low and the glue can be easily formed with wet fingers. Also, the connection with hot-melt adhesive is detachable - the parts can be heated and unstuck.

Well, let's see what's inside after several years of use. I unscrew a few screws and the gun disassembles into two halves.

Inside you can see wires, again fixed with hot glue, a key, an LED, a trigger with a rod feeding system and a rod heating chamber. There is no glue inside, the gun is clean inside. The glue in the heating chamber is heated by an element that is held in place by a spring. Pressed through some kind of piece of iron with a triangular profile.

At the entrance to the chamber there is a silicone tube, it is fixed with a spring and sealant. The output is a silicone ring. I disconnect the heating element, let's see what's inside.

It is insulated with something similar to Kapton. Several layers of insulating material. Underneath there are two plates and a piece of something that has a cold resistance of 3.7K

This heating element is quite fragile, almost crumbling in your hands.

I collect all its pieces together under the plates, fix them with Kapton, then the old insulating material and again with Kapton. The entire sandwich fits normally in its original place.

I added a temperature sensor, it warms up to 144 degrees.

Using a proprietary power regulator from Viessmann (just a triac regulator inside) you can lower the temperature of the glue. Melts at approximately 80 degrees. But I would recommend more, thinner glue sticks better.

I definitely recommend the gun. One minus of the gun is that the glue leaks if you place it with the nose down. I just put it with the nose up. Someone will buy a gun with a valve, but the glue seems to press harder because of the valve and it is several times more expensive.

Differences between glue sticks

When gluing surfaces, rods with a diameter of 7 and 11 mm are most often used.

They have the following characteristics:

1. The material is characterized by high bending strength;
2. The length of the rods reaches 300 mm;
3. Stored at room temperature;
4. Visually transparent;
5. Bonds a large number of materials.

There are also varieties of flowers:

• White. Used for gluing plastic, ceramics, tiles.
• Black. Good adhesion to carpets and leather.
• Yellow. Used for gluing paper products and wood.

The following colors are available for making crafts: red, green, blue, pink. Some rods contain shiny elements - they are used for decoration.

Power selection

Depending on the power of the device, the amount of time spent melting the glue is less. However, other factors should also be taken into account. If there is a large heating chamber and low power of the heating element, heating will occur slowly. But if final heating is ensured, then energy consumption will be reduced and there will be no risk of overheating. A powerful heating element in a small chamber will not provide such savings.

If the power of professional devices is 300-500 W, then at home 30-150 W is enough. If there is a shortage of molten glue, you will have to wait for a new portion to appear. Some devices are equipped with a temperature sensor. At the beginning of operation, there is maximum heating with a power consumption of up to 200 W. Subsequently, the economy mode is activated - 15-40 W.

At home, it is better to purchase a low-power device. Within 3-5 minutes. it will warm up, and then the heating will stabilize. The pursuit of power is justified only among professional workers, where long hours of daily work are required.

Work process

When gluing surfaces, you should work quickly, because the molten mass hardens quickly. To do this, the points to which gluing will be carried out are marked in advance.

The work process is presented step by step in the table.

After the entire rod has been used up, a second one is inserted, which pushes out the remains of the first. To separate the glued surfaces, this place is well heated.

If during operation it is necessary to change the color of the rod, and the gun has already cooled down, then it is turned on for 1 minute. Then the old rod is unscrewed and the new one is charged. The remains of the old one are pushed out by pressing the trigger.

Glue gun diagram

And now the melting chamber with a heating element installed on it appeared to the eye. Looks like a small jet turbine.

The clamp and thrust pad have been removed. Here is the heating element itself. I note that at the installation site it lay flat, in the center and was in direct contact with the body of the melting chamber with only one of its planes.

I unwrap the rather careless packaging - an insulator. Inside there is simply a miniature ceramic heating element and two contacts for supplying 220 volts to it.

I took a closer look at the heater and rang the two sides with a multimeter. They call, but not everywhere. The darkening visible in the photo at the bottom is present on all sides and completely covers the adjacent end side. It doesn't ring. This is a ceramic coating on top of the heating element. Designed for direct contact with the body of the heating chamber and transfer of heat generated by the heater, without placing a dielectric spacer between them. This spraying is the dielectric gasket. It became clear that the heater was installed incorrectly by the manufacturer. He was lying on his side, and was also wrapped three times in insulating material. According to the existing dimensions of the heaters, 4 of them will fit on the installation site.

Guided by common sense (as far as God has given), I began to correct the manufacturer’s “jambs”. The dimensions of the contacts were brought into line with the dimensions of the ceramic heater. Exactly in length, and 1 mm less in height.

I made a millimeter-long bend at a right angle to prevent the contact from sliding down onto the body of the heating chamber.

This is how the contacts assembled with the heater began to look (top view).

The assembly resistance (located inside the clothespin) turned out to be 6 kilo-ohms. It immediately became clear that the 20W declared by the manufacturer would not be even close to being confirmed.

Exactly according to the dimensions of the ceramic heater, I cut out two copper plates 2 mm thick. It is necessary to somehow fill the void at the installation site and take heat from the sides of the heater.

The cut was made to allow the sides to be compressed. This will add reliability in holding the heater in place and is intended to improve heat transfer.

Sectional installation diagram. In the figure there are gaps between the individual components, but in a real assembly there should not be any.

Assembly completed. The heater without a gasket stands on a designated plane (end) covered with dielectric coating, with current-carrying contacts on the sides, then four layers of mica on three sides (taken from an old burnt soldering iron), and copper plates on the sides. The seal is the insulator on the right made of asbestos. I had a piece on hand and it seemed that it would be more reliable.

Here you can see that the sides are already pressed against the copper plates and hold the entire assembly, the ceramic heater is directly in contact with the wall of the heating chamber, and the electric. contacts are far from her.

The last thing to put in place is the clamp. The junction of the wires with the contacts must be insulated with ceramic insulators or something that fully replaces them.

After assembly, the first thing I did was measure the current consumption. When turned on, within a few seconds, there is a gradual current jump of 80 - 120 - 210 mA, then a sharp jump down - 20 mA. Mains voltage 225 - 230 volts x 0.02 A = maximum 4.6 W. And on the front panel of the gun, in plain sight, there is a nameplate indicating a power of 20 W. The glue gun will actually have the stated power if you install 4 heating elements. However, let’s not dream, but rather look at the video of the heating dynamics of a correctly assembled and installed (in my opinion) heating element.

Safety rules at work

To avoid injury during work, you must adhere to the following safety rules:

1. According to the instructions, the duration of continuous operation should not exceed 30 minutes. Then the device turns off and cools down.
2. It is prohibited to turn on the equipment without a rod.
3. The cable location should always be at the rear.
4. After the gun has warmed up, do not touch the nozzle or glue. This may cause skin burns.
5. It is not allowed to carry out work with wet hands or in a room with a high level of humidity.
6. Upon completion of work, the device is placed on the stand in a vertical position. In a horizontal position, glue may leak into the body.

Emerging problems and solutions

The main problem in operation is the uncontrolled flow of glue, even with the trigger released.
The reasons and solutions are as follows:

1. If the device does not have a thermostat, then the heating does not always correspond to the marking of the rod. In this case, it needs to be replaced. The problem is also solved by the presence of a valve in the nozzle.
2. The rod is clamped. It needs to be moved back.
3. There is a gap between the rod and the heater. Its diameter is made with a high degree of accuracy. If the specified size is 11.2 mm, then reduction to 11 mm is not allowed. This is a marriage. In the heating chamber, due to the pressure difference, a reverse flow of glue occurs. The defective product needs to be replaced.
4. Defect in the manufacture of the pistol. During breaks between work, a plug should be inserted into the nozzle. For example, a toothpick.

Other breakdowns and their solutions:

1. No glue movement. The reason is that the gun is clogged. To do this, it is disassembled and cleaned. During operation, you need to monitor the nozzle and prevent glue from sticking around it.
2. If the power source is a battery, then its energy is not enough to heat the glue. In this case, the device is heated at the charging station.
3. If the design is cheap, the pusher may get stuck in the softened rod. It is necessary to turn off the device to cool down.
4. If it is not possible to apply a dot to the surface, the glue stretches in the form of a thread, then the rods should be placed in the refrigerator for a while.

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Working with a rod without a gun

If there is a rod, in the absence of a gun, you can glue the surfaces, but the quality will be low.

There are 2 ways:

1. Insert the refill into the body of the ballpoint pen. After warming up, you can start working. The disadvantages include the need for constant heating.
2. Apply a drop of glue to the match near the head of the sulfur or cut off a circle of the rod, cut along the diameter to the middle and put it on the match. Then set the head on fire, the glue will melt - and you can start working.

Using a glue gun is a progressive technology. In addition to ease of use, high quality gluing is obtained. The speed of hardening is also attractive. The main thing is to properly master the art of work and comply with all safety requirements.

Do-it-yourself hot glue gun repair

A hot glue gun is a very convenient tool for home crafts, but sometimes it fails and the heating element is damaged.

I managed to restore the functionality of this device...

To repair a hot-melt glue gun, I used a posistor from the kinescope demagnetization system of an imported color monitor as a heater (TVs also have a similar part).

To work you need to prepare:

• small Phillips screwdriver;
• hacksaw or grinding machine;
• file;
• soldering iron;
• posistor from the color picture tube demagnetization system;
• PVC electrical tape;
• FUM tape;
• a strip of copper foil;
• mica;
• tester, multimeter or ohmmeter (to monitor insulation resistance).

Description of pistol repair

We disassemble the gun: unscrew and tidy up the screws, unsolder the leads from the damaged heater, remove the heat block, remove the bracket holding the heater, carefully disassemble the heater, preserving the insulating film if possible.