Who wears shoes made of lead?
igu-blog-adm | 24. February 2022
The TV commercial for the Soda Streamer presents it perfectly. Who wants to carry anything heavy nowadays? One of the things using PET bottles as an alternative to glass bottles aims at is weight. The sustainability of the two solutions will be discussed at a later time.
“The fact is that it takes energy to move mass. That energy can take the form of fuel, electricity, or your own muscle power. That’s why we don’t wear shoes made of lead!”
So it is also important to reduce weight in machine and equipment design and in automation. Every excess gram increases energy requirements or slows movement. The law of inert mass applies.
The textile industry, e.g., uses linear bearings that must be moved at speeds of over 20m/s, in some cases at a frequency of over 100Hz, with accelerations of more than 6m/s2. This can be done only with little dead weight.
It should be easy for one person to handle and move portable laboratory or kitchen equipment. Equipment that must be frequently lifted must not exceed 10kg. The weight limit for occasional lifting is 15kg. (Source: German Federal Minister of Labour and Social Affairs/German Load Handling Regulation (Lastenhandhabungsverordnung, or LasthandhabV)
How can I make a design lighter? The easiest way is with material selection. Plastics and aluminium are five times and two and a half times lighter than steel, respectively. The more flexible shape of the plastic offers even more weight advantages.
This can be taken into account during linear guide selection. Linear guide systems can move on anodised aluminium with your plastic sliders. Optimal weight distribution ensures that the slider leaves no traces on the aluminium. You may be familiar with this effect from skis or snowshoes. Lots of surface area, little surface load, little danger of collapse – and also a reason for staying in a prone position when approaching someone who has fallen through the ice.
For technical reasons, recirculating ball bearing guides cannot be moved continuously on aluminium rails. Under load, point contact for individual balls would leave marks in the surface and damage the ball guide. The maximum surface pressure on the soft aluminium is too great – the hard anodised layer is very thin and can be compared with a chicken egg, or more specifically, with the egg shell. Hard shell – soft core!
How important is it to you to reduce weight? What do you value? I would like to hear your arguments and counter-arguments …
Stefan Niermann – igus GmbH