Partial Automation

There does seem to be another question begging. So many of the carrots in the two tails of the distribution are in the trouble areas (clogging or wrong-end chopping) that it appears that the automated in-feeder is not doing a satisfactory job. In the real processing plant from which Case study 3.5 was drawn, this was precisely the case (except that the vegetable was okra, not carrots). The reliability of the product forced the process engineers to compromise and use a partially automated work station. Space for human operators on both sides of the shaker tables was provided so that vegetables that are seen to fall incorrectly could be turned over manually before entering the chopper area.

Partial automation is not limited to food processes where product variability is the chief problem. Orientation and alignment of various kinds of products and machine parts may require intelligent vision or some sophisticated capabilities which in a given manufacturing process maybe infeasible either technically or economically. Partial automation, where the worker and machine each do their parts according to their capabilities is an alternative that should not be overlooked by the automation engineer. This website has considered the problem of moving the material or piece parts position for processing or assembly. Although the operations have been seen to be complicated and some even ingenious but none has resulted in useful change to the process itself. Parts feeding and orientation was without doubt important but we are now ready to consider the automation of machines that process or assemble these parts into useable products.

The success of an assembly automation project depends not so much on the achievable motions of industrial robots handling product parts as it does on the tiny subtleties of positioning and orienting of piece parts for assembly.  Sometimes these detailed problems can be avoided by preserving parts orientations to begin with, either during their manufacturing or at the vendor’s site for purchased parts. Lab automation news has an example video and case study of a partial automation device.

Given that parts orientation must be accomplished, clever mechanical devices are required for this purpose with the principal representative being the vibratory bowl with parts selectors in the discharge track. Those parts that the bowl system is unable to select and orientate correctly are rejected back into the bowl for a retry. The rejected parts are not lost; generally, the only things lost are time and production rate. The amount of decrease in production rate from rejection of mis-oriented parts is related directly to the efficiency of the vibratory bowl and part selector track. The overall efficiency of the system can be quantified from the matrix of individual rejecter probabilities along the selector track. High production rates are necessary, vibration rate can be sped up with corresponding higher feed rates up to a point. The science of orientation and feeding applies not only to small metal parts, but also to plastic bottles, moldings, castings, and even food products. Food products present special problems for automation engineers due to the variation in item sizes and shapes.