Towards improvement of geometrical quality for manual assembly parts

Geometrical variation affects all mass-produced products. This variation will lead to deviations from the nominal design of the product both in terms of aesthetical and functional properties.<br /><br /> Geometrical variation originates either from the manufacturing of the parts or from the assembly process. In order to minimize the effect of variation robust design principles are often used.<br /><br />In early product development the majority of the properties in the system solutions are fixed and to change these later in the product development will be costly. In order to verify the system solution (locating scheme and tolerances), different simulation techniques are used to predict the behavior of the product. This is done using virtual tools, for example Computer Aided Tolerancing (CAT). In order to gain confidence for such tools it is very important that the simulation results are accurate and that they capture all factors that influence the product.<br /><br />In this thesis the focus has been on geometry assurance and CAT simulations for products that are manually assembled. Although many things can be automated, in the automotive industry most of the final assembly is performed by humans and nothing suggests that this will change. Since humans are quite different from robots’ other factors need to be taken into consideration when designing products that are to be manually assembled. <br /><br />The research presented in this thesis reports current issues and problems when performing geometry assurance, robust design and CAT simulations during product development of manual assembly products. In the thesis it is shown that the level of manual assembly complexity affects costs of poor quality, failure rate and geometrical quality.<br /><br />A simulation tool, is developed that simulates the robustness of an assembly both with consideration to sensitivity to variation and level of manual assembly complexity. The tool is implemented in a CAT system, RD&amp;T.<br /><br />Finally, a number of existing research gaps are identified for further research

Criteria for Assessment of Basic Manual Assembly Complexity

AbstractTough competition force companies to develop and increase their product assortment in order to maintain their market share. This has resulted in numerous product variants with more features and build options. The complexity and risk of quality errors will increase. Managing complex product and installation conditions will result in distinct competitive advantages. Research has shown that sustainable and more cost-efficient assembly solutions can be obtained by proactive improvement of the working environment and installation conditions for the operators. Significant reduction of costly corrective measures can be made. The objective of this paper was to demonstrate criteria for proactive assessment of manual assembly complexity, which have been developed and verified in several studies. A further objective was to clarify and quantify included criteria as far as possible to enable a more general application in manual mass production of complex products

Variation Analysis considering manual assembly complexity in a CAT tool.

Virtual geometry assurance is a key component of today´s product development. Much of the virtual geometry assurance is done in Computer Aided Tolerancing (CAT) tools. Earlier research has shown that manual assembly complexity influences the geometrical quality of the product and that assembly tolerances are seldom used in CAT simulations for manual assembly parts. In this study a method for including manual assembly complexity in variation analysis in CAT is introduced and discussed.The method has been tested and implemented in a CAT tool using a real industrial case with promising results

The DNA polymerase of bacteriophage YerA41 replicates its T-modified DNA in a primer-independent manner

Yersinia phage YerA41 is morphologically similar to jumbo bacteriophages. The isolated genomic material of YerA41 could not be digested by restriction enzymes, and used as a template by conventional DNA polymerases. Nucleoside analysis of the YerA41 genomic material, carried out to find out whether this was due to modified nucleotides, revealed the presence of a ca 1 kDa substitution of thymidine with apparent oligosaccharide character. We identified and purified the phage DNA polymerase (DNAP) that could replicate the YerA41 genomic DNA even without added primers. Cryo-electron microscopy (EM) was used to characterize structural details of the phage particle. The storage capacity of the 131 nm diameter head was calculated to accommodate a significantly longer genome than that of the 145 577 bp genomic DNA of YerA41 determined here. Indeed, cryo-EM revealed, in contrast to the 25 angstrom in other phages, spacings of 33-36 angstrom between shells of the genomic material inside YerA41 heads suggesting that the heavily substituted thymidine increases significantly the spacing of the DNA packaged inside the capsid. In conclusion, YerA41 appears to be an unconventional phage that packages thymidine-modified genomic DNA into its capsids along with its own DNAP that has the ability to replicate the genome.Peer reviewe

The DNA polymerase of bacteriophage YerA41 replicates its T-modified DNA in a primer-independent manner

Yersinia phage YerA41 is morphologically similar to jumbo bacteriophages. The isolated genomic material of YerA41 could not be digested by restriction enzymes, and used as a template by conventional DNA polymerases. Nucleoside analysis of the YerA41 genomic material, carried out to find out whether this was due to modified nucleotides, revealed the presence of a ca 1 kDa substitution of thymidine with apparent oligosaccharide character. We identified and purified the phage DNA polymerase (DNAP) that could replicate the YerA41 genomic DNA even without added primers. Cryo-electron microscopy (EM) was used to characterize structural details of the phage particle. The storage capacity of the 131 nm diameter head was calculated to accommodate a significantly longer genome than that of the 145 577 bp genomic DNA of YerA41 determined here. Indeed, cryo-EM revealed, in contrast to the 25 angstrom in other phages, spacings of 33-36 angstrom between shells of the genomic material inside YerA41 heads suggesting that the heavily substituted thymidine increases significantly the spacing of the DNA packaged inside the capsid. In conclusion, YerA41 appears to be an unconventional phage that packages thymidine-modified genomic DNA into its capsids along with its own DNAP that has the ability to replicate the genome

Vulnerabilities in prevention and treatment of malnutrition – the role of the electronic patient journal

publishedVersio

Towards improvement of geometrical quality for manual assembly parts

Geometrical variation affects all mass-produced products. This variation will lead to deviations from the nominal design of the product both in terms of aesthetical and functional properties.\ua0Geometrical variation originates either from the manufacturing of the parts or from the assembly process. In order to minimize the effect of variation robust design principles are often used.In early product development the majority of the properties in the system solutions are fixed and to change these later in the product development will be costly. In order to verify the system solution (locating scheme and tolerances), different simulation techniques are used to predict the behavior of the product. This is done using virtual tools, for example Computer Aided Tolerancing (CAT). In order to gain confidence for such tools it is very important that the simulation results are accurate and that they capture all factors that influence the product.In this thesis the focus has been on geometry assurance and CAT simulations for products that are manually assembled. Although many things can be automated, in the automotive industry most of the final assembly is performed by humans and nothing suggests that this will change. Since humans are quite different from robots’ other factors need to be taken into consideration when designing products that are to be manually assembled. The research presented in this thesis reports current issues and problems when performing geometry assurance, robust design and CAT simulations during product development of manual assembly products. In the thesis it is shown that the level of manual assembly complexity affects costs of poor quality, failure rate and geometrical quality.A simulation tool, is developed that simulates the robustness of an assembly both with consideration to sensitivity to variation and level of manual assembly complexity. The tool is implemented in a CAT system, RD&T.Finally, a number of existing research gaps are identified for further research

What are the obstacles and needs of proactive ergonomics measures at early product development stages? - An interview study in five Swedish companies.

Despite health and safety legislation and ergonomics regulations for several years many Swedish companies are still unable to effectively prevent the consequences of poor ergonomics. Corrective measures are often made (too) late when employees complain and work-related disorders have already occurred. Besides, several studies have shown that poor ergonomics result in deteriorated assembly quality and reduced productivity and that late measures are often costly. Other studies have proven that design engineers are often unaware of design consequences and do not know how to apply ergonomics principles in new product and production design. Therefore, the purpose of this study was explore what is required to improve the situation. One way to find out was to ask engineers involved in product and production development. Thus, 64 engineers in design and manufacturing engineering in five Swedish companies were interviewed about ergonomics conditions related to quality and productivity issues. In general, their answers unexpectedly demonstrated a fairly good awareness of the implications of poor assembly ergonomics but also that appropriate product and production design methods and tools to prevent these are missing. 58 of the respondents thought that poor ergonomics can result in reduced product quality. 47 stated that profitability calculations are necessary for changes of poor ergonomic solutions. 37 said that ergonomics risks are accepted due to lack of appropriate calculation methods. Altogether, many suggestions emerged for how to improve product and production design methods and tools in order to achieve more complete and sustainable manufacturing solutions

A model for calculation of the costs of poor assembly ergonomics

In product development there are many design requirements to meet and often tough project budgets to keep. Requirements that are considered not profitable will often be neglected, which affects assembly ergonomics. The objective of this study was to develop a calculation model for application in practice that enables calculation of costs of poor assembly quality related to assembly ergonomic conditions. The model is meant to be used by engineers and stakeholders in the design or redesign of manual assembly solutions. For that purpose, manual assembly tasks of 47061 cars at high, moderate and low physical load levels were analyzed with respect to assembly-related quality errors and corresponding action costs during production and on the market. The results showed that ergonomics high risk issues had 5-8 times as many quality errors as low risk issues and the earlier these were found the less were the action costs. The action costs for errors that were discovered late in assembly were 9.2 times more costly compared to early repair of errors in the factory. The action costs for quality errors that were found and corrected on the market were further 12.2 times more expensive to correct compared to actions taken in the factory. Examples are shown of how to apply the calculation model that was developed based on the obtained quality data. Relevance to industry: Both ergonomics and quality issues can be proactively solved through simultaneous risk assessment in early product development and hereby late reactive action costs can be greatly reduced