Mass production

Introduction

Mass production is the production of large amounts of standardized products, including and especially on production lines. The concepts of mass production are applied to various kinds of products, from fluids and particulates handled in bulk (such as food, fuel, chemicals, and mined minerals) to discrete solid parts (such as fasteners) to assemblies of such parts (such as household appliances andautomobiles).

Nowadays the main problems of mass production are:

1. Impossibility to load production line;
2. With the lack of mechanization and automation of labor, work in the production line is characterized by monotony, great intensity and turnover of workers;
3. Significant capital investments for the organization of mass production; 
4. Reliability of the equipment is not very high;
5. Frequent changes of types of products, due to technological progress.

The object of the work is to design a production line that produces vertical sleeve hole with gloss on one side. So, the main tasks of the project are:

1. Explain the advantages and disadvantages of mass production;
2. Calculate technical and economical parameters of the production line;
3. Build the graphics that shows the results of calculations.

 

 

 

 

 

 

 

1. Output data

According to the objective the production line should produce vertical sleeve hole and gloss on one side.

Table 1.1 - List of manufacturing operations and characterization of the equipment

№ of operation	Operation name	Equipment
		Equipment sign	Wholesale Price, UAH	Engine power, kW	Dimensions mm	Occupied area, m2
1.	Handling of enterance	2Н135	28675	4	2535×825	4,25
2.	Broach hole	7Б55У	149110	18,5	4070×1600	26,05
3	Turning	1И611П	166315	3	1790×670	8,83
4.	Mechanical milling cutter	6Р80	57350	3	1600×1875	14,3
5.	Boring holes Ø20	2Н125	22940	2,5	2350×785	3,59
6.	Locksmith treatment	Locksmith treatment	11470	-	1000×800	4,1
7.	Washing	Washing	17205	0,5	950×750	3,6
8.	Heat treatment	Heat treatment	34410	4	1020×950	6,2
9.	Internal grinding	3К227А	206460	4	2815×1900	24,07
10.	External grinding	3А-110В	177785	1.5	1600×1670	17,03

The minimum wage for the current period is 1147 UAH.

 

 

Table 1.2 - Duration of process operations

Indicators		# of operation	Category of work		Value
The annual output (Nр), units./year.					57000
The complexity of operations (tшт i), min./unit		1	3		7,13
		2	5		2,26
		3	5		10,81
		4	6		5,77
		5	3		3,88
		6	2		2,89
		7	1		2,06
		8	4		5,85
		9	6		9,52
		10	6		4,84
Net weight of item, kg/unit.					6,66
Consumption rate of metal, kg/unit. (НВМ)					5,661
Complexity of manufacturing the product norm – kg/unit					55,01

During determination of the rate of metal consumption we’ve used the coefficient 0,85. The complexity of manufacturing the product was got by summarizing of the values of the complexity of manufacturing operations.

 

 

 

 

2 Designing of a production line in machining

2.1 Features and benefits of the mass production

As it was said in the Introduction: mass production is the production of large amounts of standardized products, including and especially on production lines. 

Mass production have several advantages before traditional production.

The economies of mass production come from several sources. The primary cause is a reduction of nonproductive effort of all types.  In mass production, each worker repeats one or a few related tasks that use the same tool to perform identical or near-identical operations on a stream of products. The exact tool and parts are always at hand, having been moved down the assembly line consecutively. The worker spends little or no time retrieving and/or preparing materials and tools, and so the time taken to manufacture a product using mass production is shorter than when using traditional methods.

The probability of human error and variation is also reduced, as tasks are predominantly carried out by machinery. A reduction in labour costs, as well as an increased rate of production, enables a company to produce a larger quantity of one product at a lower cost than using traditional, non-linear methods.

However, mass production is inflexible because it is difficult to alter a design or production process after a production line is implemented.

So in a nutshell, the advantages of mass production over traditional are following:

1. continuity of work;
2. the principle of parallelism;
3. easy to plan production process;
4. regular output;
5. reduce the time of production.

2.2 Calculation of the tact (τ) of the production line

The tact is the indicator of work of production line.

Tact is the time between release of two products on the production line.

The tact of the streaming line is defined by the formula:

τ = , (2.1)

Where:

Fdob - Day Fund-time (8h2) · 60 = 960 min., with 8-hour working day in two shifts;

BP - regulated time spent on maintenance of machine, take Bp = 60 min.;

Ndob - daily release program, units.

 τ = (960 - 60) /227= 3,96 min. / unit.

The daily release program is calculated by the formula:

, (2.2)

Where:

Np - given year program production, units.;

nrd - the number of working days in a year (365-104-10)= 251 days

Ndob = 57000/251 = 227 units.

 

2.3 Calculation of equipment, loading and degree of synchronization of operations

Calculation of the amount of equipment for each operation conducted by the formula:

, (2.3)

Where:

 nri - estimated number of machines on and one-operations units.;

tшт - an artificial time and th operation, min.;

τ - tact of streaming line, min. / units.

n_р1= 7,13 / 3,96 = 1,8 units.                    n_пр1 =2 units

n_р2= 2,26 / 3,96 = 0,57 units.                    n_пр2 =1 unit.

n_р3 = 10,81 / 3,96 = 2,73 units.               n_пр3 =3 units

n_р4 = 5,77/ 3,96 = 1,46 units.                  n_пр4 =2 units

n_р5 = 3,88/ 3,96 = 0,98 units.                    n_пр5 =1 unit

n_р6= 2,89 / 3,96 = 0,73 units.                  n_пр6 =1 unit

n_р7 = 2,06 / 3,96 = 0,52 units.                  n_пр7 =1 unit

n_р8 = 5,85/ 3,96 = 1,48 units.                    n_пр8=2 units.

n_р9= 9,52/ 3,96 =  2,4 units.                   n_пр9=3 units.

n_р10 = 4,84/ 3,96 = 1,22 units             n_пр10=2 units.                     

Nri is rounded to the first or next higher integer - get adopted npri number of machines.

Loading equipment ηзi also define for each i-th operation by the formula:

 , (2.4)

η_з1 =( 1,8/2) * 100% = 89,95 %  

η_з2 =( 0,57/1) * 100% = 57%                 

η_з3 =( 2,73/3) * 100% = 90,9%                 

η_з4 =(1,46/2) * 100% =72,8%                          

η_з5 = (0,98/1) * 100% = 98 %                          

η_з6 = (0,73/1) * 100% = 73%                          

η_з7 = (0,52/1) * 100% = 52%                          

η_з8 = (1,48/2) * 100% = 73,8%                         

η_з9 = (2,4/3 )* 100% = 80%                          

η_з10 = (1,22/2) * 100% = 61%                        

Loading of equipment for specific operations should not exceed 85 - 90% for creating of the reserve of the equipment to ensure the smooth operation of the production line. If the calculations would be higher than 85 - 90%, we should increase the number of machines.

For effective work of the equipment at the production line the level of loading of the machine should exceed 60-70%

Table 2.1 - Calculation of equipment on the production line (A):

№		Operation name	tштi, хв.	nрi,шт.	nпрi, шт.	ηзі, %	tштi/nпрi	Degree of sinhronization Сі
1		Handling of entrance	7,13	1,8	2	89,95	3,565	0,202
2		Broach entrance	2,26	0,57	1	57	2,26	-0,238
3		Turning	10,81	2,73	3	90,9	3,603	0,215
4		Boring entrance Ø20	5,77	1,46	2	72,8	2,885	-0,027
5		Locksmith treatment	3,88	0,98	1	98	3,88	0,308
6		Washing	2,89	0,73	1	73	2,89	-0,026
7		Heat treatment	2,06	0,52	1	52	2,06	-0,306
8		Internal grinding	5,85	1,48	2	73,8	2,925	-0,014
9		External grinding	9,52	2,40	3	80	3,173	0,07
10		Handling of enterance	4,84	1,22	2	61	2,42	-0,184
		Total	55,01	13,88	18	74,84	29,662

Average loading of equipment is calculated by the formula:

, (2.5)

where m - number of operations.

= 13,88/18 = 0,77

Degree of non synchronization of operations is calculated by the formula:

, (2.6)

where - working tact on i operation;

- Average working tact of streaming line.

Average tact of the production line is found according to the formula:

= 29,66/10 = 2,966

 

С₁ = (3,565– 2,966)/ 2,966=0,202

С₂  = (2,26- 2,966)/ 2,966= -0,238

С_3а   =(3,603- 2,966)/ 2,966=0,215              

С₄   =(2,885- 2,966)/ 2,966= -0,027

С₅   =(3,88- 2,966)/ 2,966= 0,308

С₆  =(2,89- 2,966)/ 2,966= -0,026       

С₇ =(2,06- 2,966)/ 2,966= -0,306

С₈ =(2,925-2,966)/ 2,966 = -0,014     

С₉ =(3,173- 2,966)/ 2,966 = 0,07      

С₁₀  =(2,42- 2,966)/ 2,966 = -0,184

On the basis of the results we’ve got, we can plot the following graphics:

 

 

Figure 2.1 - Graph of synchronization of the operations

Figure 2.2 - Graph of loading of equipment for the operations

 

According to the level of synchronization the type of production line is determined. Organization of work and choose of transport means depends from the type of the line.

If at all operations the degree of desynchronization does not exceed 10%, then this line is synchronized continuous-flow. If at least one of operations exceeds the specified value, then this line should be called  unsynchronized

 

2.4 Equipment Selection

Selection of equipment in practice carried out simultaneously with the design process. This often guided by existing warehouse equipment. When selecting equipment in the project consider the following:

. 1) the ability to install and machining parts on a machine. For this the size of the details and macine are compared. For drilling machine, such as the basic size is diameter - maximum diameter drilling. For lathe - the height of the centers and the distance between the centers. The radius of details may not exceed the height of the centers and the length of detail - the distance between the centers;

2) the cost of the machine, we must use equipment with less price.

Choosing of the tools usually have to hold pricelist wholesale prices for machine tools.

 

 

 

 

 

 

 

 

 

 

 

 

Table 2.2 - Statement of equipment on the production line:

Operation Name				Model of machine	Overall dimensions of machine, mm			Quantity of machines	Price, UAH.		Engine power, kW
									One item	Total	One machine	Total
1				2Н135	2535×835		2		28675	57350	4	8
2				7Б55У	4070×1600			1	149110	149110	18,5	18,5
3				1И611П	1790×670			3	166315	498945	3	9
4				6Р80	1600×1875			2	57350	114700	3	6
5				2Н125	2350×785			1	22940	22940	2,2	2,2
6				Bench press	1000×800			1	11470	11470
7				Washing	950×750			1	17205	17205	0,5	0,5
8				Heatequip	1020×950			2	34410	68820	4	8
9				3К227А	2815×1900			3	206460	619380	4	12
10				3А110В	1600×1670			2	177785	355570	1,5	3
Total								18		1915490		67,2