- How an automatic light filter works
- Functions and adjustment
- Darkening degree
- How to check the mask upon purchase
- Optimal headband design
- Shield shape
With the advent of auto-darkening masks, many welders began to use them exclusively for ease of use. However, “chameleons” are not at all universal, the frustration of working with them usually stems from the wrong choice. So let’s choose the right welding helmet..
How an automatic light filter works
Welding helmets provide excellent eye and face protection while keeping both hands free. And if a chameleon is installed as a light filter, the problem of blind ignition of the arc disappears forever, and the comfort of work goes to a completely different level..
The auto-shading filter is designed like a monochrome LCD display, but there are many more layers. In fact, these are several polarizing films, interposed with thin transparent plexiglass, an ultraviolet filter and one light filter with static dimming, usually yellow or light green. Automatic light filters are manufactured according to the EN 379 standard, if the chameleon does not have such a mark, then it is better to refuse to buy such a mask.
When voltage is applied, the liquid crystals of polarizing films are rearranged, and the filter is less likely to transmit light. A large number of films are required for effective shading, regardless of the angle of incidence of light. Note that at low temperatures, the standard switching time of several tens of microseconds can increase by a factor of 2–3..
Such a filter device requires an external power source. It can be either built-in or removable. The latter is more preferable: if the chameleon starts to malfunction, then replacing the battery in many cases solves the problem. However, having disassembled the inner panel of the light filter, it is enough just to get to the control board and replace the lithium “tablet”.
The built-in control board helps to change the degree of filter shading, adjust its sensitivity and other parameters. There is a rather rare variety of fully automatic masks that do not imply adjustment and switching modes. Automatic triggering does not always work as it should, and therefore often such a purchase becomes a waste of money.
Functions and adjustment
The ability to switch modes of operation for a chameleon is extremely important. Let’s say you’ve finished a seam and want to clean it with an angle grinder in order to apply another, protective one. Instead of removing the mask, putting on your goggles and then doing these manipulations in reverse order, you can desensitize with a slight flick of your finger to perform stripping, and then switch the mask back to welding mode. Even with static darkening, the workpiece will be quite clearly visible, while the face will remain under reliable protection from sparks. In some masks, this adjustment is implemented by a vernier that adjusts the sensitivity of the optical sensor, while there is a separate switch for the grinding mode.
It is also possible to adjust the dimming off delay. It often happens that the arc disappeared for a moment and re-ignited, or welding is carried out with frequent separation. If at this moment it was necessary to switch the light filter, there is a high probability of catching the “hare”. It is not particularly dangerous for the eyes, but due to the high contrast of the flash, visual acuity will noticeably decrease for a while. The chameleon switch usually has two delay positions – LONG and SHORT, in more advanced chameleons there is a third MEDIUM position.
The switches can be located either on the inside of the visor or outside on the mask body. This is of fundamental importance only if you understand well the principle of the chameleon and use the advantages of automatic masks in your work constantly. Otherwise, there is a high probability of knocking down the settings by careless movement..
Finally, each welder can choose the optimum shade level based on personal preference. The DIN scale provides for shade levels from 5 to 15, while masks are adjusted mainly in the range from 9 to 13. The higher the index, the darker the filter will be when turned on..
The shading depth of the filter is a matter for a separate discussion. In addition to the individual preferences of the welder, the type of welding, arc power and working position play a role here..
The degree of shade 13 according to DIN is practically a dull shadow and either a plasma cutter or a magnesium torch can significantly “pierce” the light filter. In electric arc welding, this mode is almost never used, because even the weld pool looks like a dull dot, not to mention the surroundings. Therefore, in the MMA and MIG-MAG mode, the regulator is usually set to position 11–12. At the same time, the deeper the darkening, the higher the likelihood that the glare reflected behind the back and the sun shining in the back of the head will interfere with normal operation. Just because they are brighter than filter visibility.
Shade levels 9 and 10 are used for TIG welding or when working with an acetylene torch. Good visibility of the details may also be needed when applying cosmetic sutures with coated electrodes. The eyes do not suffer from increased brightness (UV protection is built into the filter), but visual acuity will drop for a while.
The darkening of the filter is uneven in different areas – stronger in the center and weaker at the edges. This difference is most noticeable in filters with a diagonal of more than 3-4 inches, if a similar phenomenon occurs in smaller glasses – this is a sign of a very mediocre product quality.
How to check the mask upon purchase
To check the mask when buying it is not at all necessary to have a welding machine on hand. The mask is triggered not only on bright light sources, but also on a sudden change in the illumination level. The mask should switch when the head is turned sharply towards a brightly glowing object, such as the sun, a silicon lighter or a regular light bulb.
In the low sensitivity mode, switching will most likely occur, but the filter will turn off after a couple of moments. In normal sensitivity mode, you can check if the standard shutdown delay values are convenient and how wide the dimming range is..
A new mask must be tested in real work immediately after purchase. The point is that differences in the filter design always affect the image quality. The deeper the shading, the more likely bright objects will appear hazy and washed out. Approximate data on the quality of visibility and distortions can be extracted from the cipher – four numbers separated by a slash. The smaller the first two digits, the less the filter distorts the proportions and clarity of the object. The third number indicates the degree of unevenness of shading over the entire area of the filter, the fourth – how many units on the DIN scale the shading changes depending on the angle of incidence of light.
Optimal headband design
Agree that it is incredibly convenient when the mask can not be removed from the head at all during work, only to raise the shield while preparing the parts. To a large extent, this possibility depends on the device of the belt for fixing the mask on the head..
First and foremost, adjusting the circumference of the skull. The knob is located at the back of the head. The most convenient scheme for its operation is to press, crank and release, blocking from accidental cranking. In this case, the mask does not have to be pulled over the head with effort: the belt is put on freely, then pulled up, when removed, everything happens in the reverse order.
The front and top of the belt should have a soft lining, preferably with sticky fasteners for removal and washing. This will prevent the belt from chafing your forehead and will keep dripping sweat out. The location of the plastic straps varies greatly among individual masks, do not hesitate when choosing to try on several options to find the most comfortable one for the shape of your head. It is better if the head belt has adjustable elements, a third elastic belt for support in the lower part of the back of the head can be a good addition.
The futuristic look of most masks is not a design perversion. Convenience and safety during work largely depends on the shape of the flap..
A wide projection at the very bottom of the facepiece is designed to direct the exhaled air downward so that the inside of the mask does not fog up in cold weather. At the same time, from the outside, this protrusion should be as streamlined as possible so that harmful vapors from the weld pool do not penetrate under the mask..
In the raised position, the mask should be as low as possible, otherwise you will cling to it for every doorway or lamp. It is optimal if the mask can be securely fixed not in the fully raised position, but strictly horizontally. It depends on the quality of the screw connections with which the shield is attached to the head harness. Ease of use is largely determined by these elements: due to poor quality, the screws can loosen themselves, which is why the mask will constantly fall and interfere with performing minor actions between welding sessions.
The material of the shields is lightweight acrylic, less often carbon plastic. The latter is preferable in terms of strength and heat resistance. Do not forget that the face of the mask must be covered with a special transparent membrane to which sparks do not stick. The mask must have one or two of these replaceable membranes.