The choice between ball screw and timing belt is determined by which properties are most important for your linear drive. Do you need to prioritize accuracy or speed? Do you have limited space? Is it important that the application requires minimal maintenance? We go through some characteristics that differentiate the ball screw and the timing belt.
Strengths and weaknesses
There are several different areas where the properties of the ball screw and the timing belt are important for the linear movement. Depending on the application requirements, they have different advantages. Simply put, the ball screw is good if you need high repeatability, stiffness and power, while the timing belt is good if you need high speed and long movements.
Precision
In terms of precision, the ball screw is better than the timing belt. It normally has a small backlash,but it can be eliminated and thus come down to thousandths of a millimeter. It also has high repeatability with the exact same position every time. Timing belts in some cases have a backlash, but generally a so-called "tight cog" used, which eliminates this.
In the end, however, there will always be a lower precision on a toothed belt drive as it has a much larger feed per revolution and therefore becomes sensitive to backlash and loosening in the driving motor and gear. But above all, the stiffness in a timing belt is significantly lower than in a ball screw, so the actual precision becomes very sensitive to which loads affect the driven part.
Accuracy
The accuracy is well defined for the ball screw and is selectable in different classes to about 0.05 mm per meter. For the timing belt, it is more difficult to specify the pitch accuracy. As a guideline, one can assume roughly 1 mm deviation per meter.
Speed
If you need high speed or fast acceleration, the timing belt is best suited. The ball screw can handle a maximum of 1 m/s, while the timing belt can reach up to 4 m/s without any limitations. It has higher acceleration, but in return slightly less accuracy.
Stroke length
The timing belt offers a significantly longer stroke than the ball screw, which generally reaches its maximum limit around 5-6 meters and up to 10 meters if you are prepared to sacrifice some performance.
Maintenance needs
A ball screw needs to be lubricated regularly and it is important to be careful about this. A ball screw can go through many millions of revolutions in a week and without proper lubrication it can wear out relatively quickly. However, an encapsulated ball screw needs to be lubricated less often. A toothed belt drive, on the other hand, is relatively maintenance-free, especially when you often choose to oversize the bearings for the pulleys in order to make them maintenance-free over a very long period of time.
Load capacity
A ball screw provides higher power and is more compact, which means that it works well, for example, in processing machinery or machining tools, where space is limited and the need for high power is great.
Security
A ball screw can be perceived as safer than a timing belt. But if the balls are destroyed or lost for some reason, it will fall freely. For safety-critical applications, ball screws with return mechanisms in metal are therefore primarily chosen, and in case of personal safety requirements, you can supplement with a redundant safety nut. Belt drives can feel unsafe, but properly dimensioned and pre-tensioned it has enormous strength. In general, the breaking strength is a factor of 10 higher than the recommended linear load. The first thing that happens in case of large overloads is that the belt cogs over and there is a risk of damage to the teeth of the belt. Even the timing belt wheels can be damaged if this happens several times.
