Videojet Technologies Inc. is relied upon by food and pharmaceutical manufacturers to provide them with machines for laser-marking, printing, and coding. The machines are used to code their products in order to ensure that they are safe, easily traceable and fresh. The company has in decades installed numerous case coding, thermal ink jets (TIJ), continuous ink jets (CIJ), laser marking units, and thermal transfer overprinting among other products globally. The engineers in the company have been struggling to come up with a cart which is appropriate for use in printers for coding. This article discusses how linear actuators have revolutionised the designs of printers from the Videojet company.
In normal circumstances, as each sub-assembly moves between work station on the production line, a printer is supposed to go together with it. Upon completion of his job, the assembler prints out a work order using a printer. Traditionally, it was required by the operating process that tri-level carts be used to transport all items between workstations. However, there was usually no adequate shelf space for secure storage of the sub-assemblies resulting to them being hand delivered and occasionally being lost.
The other problem that faced them was the fact that it was not possible to adjust the cart’s height. The engineers contemplated buying the height adjustable ones to replace the carts, but such carts would need manual adjustment which would consume a lot of time, and also cause hardships to the smaller operators when using the carts for heavy products.
The next option was electrical carts equipped with automatic height adjustment. Their limitation was that, their height adjustment could not completely cater for all assemblers and they were costly.
The final decision was to try and make their own cart. They encountered another problem of coming up with a lifting column which could satisfy the height difference between the assemblers.
The engineers embarked on some research which led them to the LC200 column made by Thomson Industries Inc. according to John Forster who is the Videojet principal manufacturing engineer, it has a low retracted-length-to-stroke-length-ratio which seamlessly accommodates operators from less than 5ft to greater than 6ft, adding that the custom cart integrates electrostatic discharge shield and hold the sub-assemblies. It has a lifting column which raises from a collapsed state to total extension along a sole linear axis.
Figure 1: Lifting column (source)
It has a telescopic leadscrew driven by a geared DC motor that runs silently and offers high load capacity with least current intake.
Figure 2: Geared DC motor (source)
At any column height, the engineered polymer bushings deliver a high moment load capability. It is equipped with dynamic braking which guarantees short and reliable stops. An integrated load-holding brake locks the system in position in case of power cut.
Figure 3: load-holding brake (source)
The column is made of extruded aluminium and also has end-of-stroke-limit switches and do not need any repairs. There is an optional encoder that allows for synchronous operation of multiple columns, however, in this single-axis application, it was not required.
Foster explained that, at any one time they use a maximum of 25 carts. And with the sub-assemblies moving with the printers, chances of mistakes are fewer, their first pass yield has gone up and a lot of time is saved in the rework process. He hopes that very soon they will mount their test stands on carts. Which will be double the number of lasers testable within the existing space.