Utvärdering av tillverkningsmetoder för svarvbommar

Sammanfattning

On today’s competitive market, it is difficult to achieve profitability

trough high prices on manufactured products. Profitability must be obtained

through low manufacturing costs, high quality and short lead times. One of

the companies on the market is Sandvik Coromant, manufacturer of tools and

chips for metal cutting.

This master thesis investigates the methods of manufacturing for boring

bars at the manufacturing unit GVH4 at Sandvik Coromant in Gimo, Sweden.

Currently the boring bars are manufactured with two different methods, one

where the iron bar is hardened and annealed before further processing and

one where the hardening and annealing is executed after most of the

processing. The location of the hardening and annealing in the

manufacturing process will affect the different manufacturing steps and

also the material flow in the factory. With a value-flow analysis, the

differences in material flow of the two manufacturing methods have been

analysed. The value-flow analysis resulted in a mapping of the production

lead-times, facts about the manufacturing steps, material flow and

information flow. Trough a study of how the differences in cycle-times in

the manufacturing steps are affected by the choice of manufacturing method

and by economic calculations with an activity-based viewpoint, an analysis

has been made to determine the method of choice.

To obtain information interviews have been carried out with the personnel

at the concerned departments. Observations of the flow of material and

buffer stocks were carried out, at the same time the amount of products in

work were calculated. The necessary facts for the economical calculations

have been collected from the companies? economical follow-up. In some cases

where the follow-up has been obscure the writers have been compelled to

make there own calculations of the cost in these areas.

The result of the value flow analysis became a descriptive map over the

current material- and information flow. From this analysis it has been

determined how the production led times varies between dependent on the

choice of manufacturing method. In conclusion: there is no substantial

difference in led times between the two methods with today’s production

setup. Measurements of the cycle-times have shown interesting facts about

the time for increasing value of the products in the production.

The measurements of cycle-times and the activity analysis of the

production, has resulted in an economical calculation showing that

processing before hardening and annealing is preferable, from an economic

point of view. The investigation has shown that difference in total cost

choosing this method, is about 6 %. If future increase in production volume

is expected, the investigation has also shown that the preferred method is

the one where the hardening and annealing is executed after processing.

This is because a greater amount of boring bars can be manufactured before

costly investments in production equipment become necessary.

Furthermore, during the investigation it has become increasingly evident

that there are some limitations in today’s economical follow-up regarding

analysis of where and why resources are consumed in the production. The

structure of the accountancy has limitations when it comes to examining

possible economic consequences followed by changes in the production.

The gathered material about quality aspects has resulted in a listing of

quality aspects that are of importance for the choice of manufacturing

method. Some of the quality aspects indicate that the implementation of

hardening and annealing before processing is impossible for some products:

this is due to requirements concerning hardness of the product. Finally,

suggestions of areas to be further investigated before choosing

manufacturing method have been made.