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Oleksandr Nechyporenko

Worm gearboxes – reliable or not?

  Worm gearboxes are probably the most common type of gearboxes in industrial segment. And while some operators of worm gearboxes use them and only them, considering this type of gearboxes as a cost-effective solution to their tasks, others consider them unreliable and try to avoid them in every way.

  So why are there completely different opinions about this product?

  Practically every production process at each enterprise is unique and two absolutely identical productions do not exist. Even using the same serial equipment in different enterprises, there can be different ambient temperatures, different operating modes and, of course, there will be different mechanics and adjusters... Therefore, from our point of view, all happy equipment operators are alike and every unhappy - unhappy in its own way.

  Let's try to figure out how an opinion can be formed about a particular product, using the example of a worm gearbox. In enterprise A, the task is to install a drive for the gate opening mechanism. It works quite rarely, performing a dozen open-close cycles per day and the operator buys and installs an inexpensive worm gearbox of dubious origin. And it will work, or more correctly, it will stay installed long enough. His operator will be satisfied with an economical solution, claiming that he does not have problems with cheap worm gearboxes and he does not understand why he should pay more.

  A real and absolutely positive operating experience.

  Armed with such a response, backed up by the seller’s statement “why pay more” unmistakably played on natural human feelings, enterprise B installs on its production the same gearbox on the raw materials conveyor. It seems there is same drive power, the same gearbox, the same gear ratio, but the gearbox began to heat up, oil leaks appeared - and these were only the forerunners of its sudden breakdown ...

  A real and absolutely negative operating experience.

  And if to take a closer look? Then we will find out that in enterprise B the ambient temperature from comfortable +20°С has increased to +40°С, the operating mode has become almost continuous, the engine starts have become overloaded. All this turned out to be a real quality test for a worm gearbox and not everyone will pass this test.

  This is how a different, but each time a PRIVATE opinion about worm gearboxes is being formed.

  What is our opinion about this matter?

  We are sure that a high-quality European worm gearbox is a good and budget-oriented solution to the basic tasks of reducing the rotational speed and increasing the torque. As well as for the conveyor at the enterprise B on condition of its correct selection.

  However, we’d like to note a number of restrictions, where the use of a worm gearbox is not recommended:

  1. If the gearbox works with a high frequency of loaded start-stops, if there are shock loads, if a small gap in the shaft is needed, we recommend that you consider using a bevel helical gearbox.
  2. If the gear ratio of your gearbox is higher than i = 40 ... 50, then it is necessary to remember about the effect of self-braking of the worm gear.
  3. With a rotation speed of up to 20 ... 30 rpm and a torque of 1000 Nm (motor power from 4 kW), we select other, more efficient solutions, both in economic terms and in terms of energy saving.

  Among the important components of a high-quality worm gearbox, we recommend to pay  attention to the following:

  1. The grinding quality of the worm shaft which provides high efficiency, long service life and helps to reduce the heating of the gearbox.
  2. Constructive and precise manufacturing of the worm pair, which provides high contact endurance and a significant gearing resource.
  3. Sealings that correspond to the heating temperature of the worm gearbox and eliminate the flow of oil.
  4. High-quality oil with a viscosity of at least 320 VG, which ensures correct lubrication of the gearbox throughout its service life
  5. 100% quality control of each manufactured product.

  We’d like to note that one of the world manufacturers known to us has been producing such gearboxes for 60 years now and is the absolute leader on the European market.

  And which worm gearboxes do you prefer? Waiting for your answers in the comments.