What if the pressure of a pump is so high that spindles wear out too quickly”?
This question was faced by a supplier of innovative analysis systems used in laboratories. Together with manufacturer Thomson, Eltrex Motion developed a ball screw with exactly the right load rating and the right variation and deviation to tackle this challenge.
When analyzing samples, we often think of a laboratory technician who takes extensive time to look at a blood sample, for example, through a microscope. However, a manual process with a pipette is not sustainable when thousands of samples per day are involved. Then an automated process is necessary.
The systems of a Dutch customer of Eltrex Motion are used for this. This company supplies, among other things, (U)HPLC systems that serve as a front-end for Liquid Chromatography Mass Spectrometry (LC/MS) instruments. A 'robot' (the autosampler) then offers the liquid samples to a detector that analyzes the sample.
Separate substances under pressure
The liquid samples can, for example, consist of beer, coffee or cannabis. Through the analysis, the suppliers of these products find out whether the desired ingredients are present in the correct proportions. High Performance Liquid Chromatography (HPLC) is a technique that is used to separate and identify the different substances.
For even better separation, Ultra High Performance Liquid Chromatography (UHPLC) can also be used. The biggest difference with HPLC is that UHPLC works with much greater pressure. For example, the UHPLC pump from the aforementioned Dutch supplier of analysis systems offers a maximum working pressure of 1300 bar. With HPLC solutions the pressure is usually about 250 bar.
High demands on the spindles
That high pressure does place a higher load on the pump parts, including the spindles. “Normal spindles are not made for that pressure. Spindles with two or three revolutions then wear out too quickly," says a team manager from the Dutch manufacturer of analysis systems.
“The spindles must run without problems for at least five years,” the team manager continues. “In addition, it is important that the spindles ensure that the pump pumps the liquids with a stable flow, otherwise you will get an incorrect analysis result.”
Design for a high load rating
With these principles in mind, an engineering process was started together with Eltrex Motion, with which the company has had a close relationship for years. “To achieve a higher load rating, we added more bullets, ultimately using more ball orbits.”
To achieve the correct variation and deviation for high accuracy and problem-free operation, Eltrex Motion enlisted the help of the spindle manufacturer. “We went to the manufacturer with a measuring setup in the suitcase. It was immediately clear to them which parts of the spindle they produce are and are not suitable for us. We are now assured that we always have a spindle with the correct variation and deviation.”
Joint steps have also been taken within the supply chain. The spindles sometimes take weeks to arrive, for example because they are transported by ship. During that period, rust formation is lurking. A problem that the Dutch manufacturer of analysis systems sometimes had to deal with in the past. “Thanks to the correct packaging method, we no longer encounter that problem.”
Steps in the collaboration 
In addition to spindles, Eltrex Motion now also supplies the couplings between the spindles and the drives of the UHPLC pump. “For the time being, we assemble the spindles together with the drives in the pump ourselves. And we press a bearing onto the spindles together with the coupling, as it were. We are now looking into whether Eltrex Motion can supply the sub-assembly of the spindle with the rotational bearings and couplings for us in series. Eltrex Motion is growing with us in every respect.”
For more information: info@eltrex-motion.com
Nederlands