Production Technology of Agril. Machinery 3(2+1)

LESSON 22. CASE STUDY OF MANUFACTURING OF WEEDERS

The manual welders are mostly manufactured by small scale manufactures who doesn’t have adequate facilities and complete know-how about the material, heat-treatment and production process to maintain proper specifications. Efficient working of the welders and specially the performance of critical components like blade depends a lot on proper material and manufacturing process.

The manufacturing procedure and techniques to be adopted by the manufacturer shall depend on many factors of which few have been listed below:

i. The status and facilities available with the manufacturers

ii. Material of construction and its availability

iii. The volume of production and batch size

iv. Precision, tolerance and clearances permissible

Fabrication of good quality hand tools at small scale industry level shall be possible only with simple manufacturing processes by taking into consideration the local availability of raw material and by adopting standard parts whenever possible.

3.1 Case study

A case study on batch  production of CIAE Twin Wheel hoe and PAU Wheel hoe was taken up to develop the production design and the process for standardization, keeping in view the facilities available with small scale manufacturers.

Twin wheel hoe (fig.2) PAU Wheel hoe (fig.3) where redesigned and jigs-fixtures and die-punchers were developed for product improvement and reduction in fabrication time. Time requirement for fabrication of various components was also studied to determine the actual labour cost. Based on the study, a project profile for batch production of weeders was also prepared.

3.2 Redesigning of weeders

The existing weeders were redesigned, without disturbing the functional performance to facilitate the batch production. The changes made in weeders are as detailed below:

3.2.1 CIAE Twin Wheel Hoe Weeder (fig.1)-Old design, (fig.2) - Modified design

3.2.1.1 Frame:

In earlier design this part used to be made of ISI section. This was replaced by ISF section to make the use of die possible for cutting and to reduce the length of welding.

3.2.1.2 Height Adjuster:

This component in old design was made of ISF section and given curvature by manual hammering and then welded to the frame, thus consuming lot of labour. This was replaced by detachable height adjuster, which is lighter and easy to fabricate with the help of jigs and dies.

3.2.1.3 Axle:

The earlier design had fabricated axle, which required operation on lathe. This was replaced by standard bicycle axle thus completely eliminating the time devoted on turning.

3.2.1.4 Blade:

The old design had blade made of two uniform pieces welded together at centre to form one piece. It was observed that the think cutting edge of the blade used to get damaged during welding. The design improvement in this case was replacement of two pieces by single piece thus eliminating the welding and the probability of damage to cutting edge.

3.2.1.5 Wheel bush:

Wheel bush was used to fabricate from 20 dia. round bar, which required turning to make inner diameter of 10 mm and parting on lathe. Operation on lathe was completely eliminated by replacing this bush by BSW hexagonal nut of equivalent size.

3.2.2 PAU Wheel Hoe Weeders (Fig.3)

The only component redesigned in PAU wheel hoe was handle frame support. This component in the original design was made of tube section of 18 dia. The tube section required cutting on lathe/hack saw and subsequently forging of ends to weld the same properly in position. During welding the tube section requires precise current setting and skill in welding to avoid formation of holes. To overcome this problem, the tube section was replaced by flat section. This flat section was cut on shearing cum punching machine in triangular shape and welded in position without any difficulty. The time required in fabrication and welding was reduced thus.

3.3 Identification of Production Process for different components:

The production process for each component was identified considering the facilities generally available with the small scale industries. The details of production process of each component are as detailed below:

3.3.1 Twin Wheel Hoe

3.3.1.1 Wheel:

A fixture (fig.4) was designed to bend the round bar to form a wheel rim. Another fixture was designed to weld wheel rim, bush and spokes to form wheel sub-assembly.

3.3.1.2 Axle:

The earlier design was provided with an axle fabricated by turning 20 round bars. This was replaced by standard bicycle axle, thus completely eliminating the time devoted on fabrication of axle which was 18 man-min.

3.3.1.3 Frame:

Frame in the earlier design was made of angle section which was used to cut on power hack saw. This was replaced by flat section which was cut on fly press with the help of die and again bent on fly press with the help of another die. Thus the time required in fabrication was reduced to 35 man-min in comparison to 26 man-min with the earlier method. For welding the fork arm, fork base and axle together a fixture was designed.

3.3.1.4 Blade:

In this case the material spring steel was replaced by mild steel. Spring steel blade was made into two pieces and welded to form one piece. This also required annealing, machining, hardening and tempering. The mild steel blade was made in one piece, machined and carburized for giving hardness. With this, identification the quality of the blade improved and also the time required in fabrication was reduced to 12 man-min from 16 man-min required for spring steel blade. A die-punch (Fig.5) was designed to make one piece blade from mild steel sheet. A fixture was also designed for bevelling edges of blade on shaping machine. 

3.3.1.5 Tyne :

A fixture (Fig.6) was designed and developed to bend tyne in a definite curvature. The tyne is required to be heated before subjecting to bending on the fixture.

3.3.1.6 Height Adjuster:

For height adjuster also a die for bending and a jig for drilling 4 holes were designed. In the earlier production process these adjusters were given curvature by manual hammering and welded to the frame permanently. In the existing method, the height adjusters were made detachable and the production process involved the use of jigs for drilling and dies for bending. In this case also the labour requirement reduced to 7 man-min from 14 man-min.

3.3.2 PAU Wheel Hoe

3.3.2.1 Wheel :

Fixture (Fig.4) for bending rim of twin wheel hoe was incorporated with provided for adjusting the same to the size of PAU weeder rim. An extra disc with 380 mm diameter was designed which can be mounted on the same fixture to make it suitable for PAU wheel rim.

3.3.2.2 Handle Frame:

A die forging the ends of handle frame was designed. Another die for making U-notch on the forged ends with the help of fly press was also designed.

3.3.2.3 Fork :

U-notch on the ends of form a rim was made by using a die. A fixture for welding form arms and form base was designed.

3.3.2.4 Tyne :

A fixture for bending tyne in particular radius was designed. The tyne need be heated before subjecting to bending on fixture.

3.3.2.5 Depth control plate :

Depth control plate was drilled with 8 nos. of 80 holes on a jig. A jig containing buttons for clearance for smooth removal of cut material had been designed.

3.3.2.6 Blade :

Bending of blade was carried out on press brake. A fixture was designed to bevel edges of blade on shaper. A fixture was also designed for welding blade, tyne and depth control plate together.

3.4 Production Process of weeders :

Table 1shows the detailed production process for twin wheel hoe weeder. Material used for each component and the time taken in fabrication of each is also detailed in the table. The production process also contains the sequences of operation followed and the machine used for each component.

Table – 1 : Production Process and time for fabrication of Twin Wheel Hoe

Component & Process	Material and Machine	Time (Man-Min)
A. Wheel Sub-Assembly
1 Rim	ISRO 100
a.   Straightening	Straightening die	12.00
b.  Shearing	Shearing cum punching	0.40
c.  Straightening	Hammering	4.00
d. Bending	Die	3.00
e. Welding	Arc	2.00
f. Final straightening	Forging hammer	0.60
2.   Spokes	ISRO 10 0/
a. Straightening	Straightening die	5.00
b.Shearing	Shearing cum punching	2.00
c.Straightening	Hammering	3.00
3.   Bush	Nut 7/16’’
a. Turning	-
b. Welding(Rim, spoke & Bush)Fixture		10.00
4.    Axle	Standard Bicycle Axle
a. Step turning	-	-
b. Parting	-	-
c. Drilling	-	-
Subtotal		42

 

 

Component & Process	Material and Machine	Time(man-Min)
B. Handle Sub-Assembly
1.Handle	IST 25 0/
a. Turning	Lathe	0.80
b. Bending	Pipe bending	5.00
2.Handle Frame	Its 25 0/
a. Turning	Lathe	1.00
b. Drilling	Drill	2.00
c. Welding (Handle & Handle Frame)	Fixture	6.00
Sub-Total		15
C. Frame Sub-Assembly
1.Frame Arm	ISF 25 X 5
a. Straightening	Hammering
b. Shearing	Shearing cum punching
c. Straightening	Hammering
d. Shearing	Fly press
E. Drilling	Drill
f. Bending	Fly Press
2. Fork Base	ISF 25 X 5
a. Straightening	Hammering	0.50
b. Shearing	Shearing cum punching	0.40
c. Straightening	Hammering	0.50
d. Welding (form arm & base)Arc		6.00
4.Height Adjuster	ISF 30 X 3
a. Straightening	Hammering	1.00
b. Shearing	Shearing cum punching	0.50
c. Straightening	Hammering	1.00
d. Drilling	Drill(Jig)	3.00
e. Bending	Fly Press	2.00
f. Welding fork & height adjuster	--	--
Sub-Total	--	24
D. Blade Sub-Assembly
1.Tyne	ISSQ 16
a. Shearing	Power Hack Saw	3.00
b. Bending	Hammering	1.50
2. Blade	MS Sheet 3 mm
a. Annealing	--	--
b. Shearing	Power Press	1.00
c. Shaping	Shaper	5.00
d. Welding	--	--
d. Bending	Press Brake	0.50
f. Heat treatment	Carburizing	3.50
g. Welding (Blade & Tyne)	Arc	2.00
E.U-Clamp Sub –Assembly
1.U-Clamp	ISF 30 X 5
a. straightening	Hammering	1.00
b. Shearing	Shearing cum punching	0.50
c. Straightening	Hammering	0.50
d. Slot cutting	Power Press	0.50
e. Drilling	Drill	1.00
f. Bending	Die	1.00
g. Nut welding	Arc	2.00
2.Bush	IST 14 0/
a. Parting	Lathe	1.00
3.Scarper	ISRO 12 0/
c.Straightening	Hammering	0.50
b. Shearing	Shearing cum punching	0.40
c.Straightening	Hammering	0.20
d. Forging	Hammering	2.00
e. Welding (bolt & bush)	Arc	1.00
Sub-Total	Say	28
F. Derusting & chipping	Manual	3.00
G. Primer Coating	Dipping	4.00
H. Paint Coating	Dipping	5.00
I. Assembling	Manual	5.00
Grand Total		129

Fabrication of wheel hoe weeder with the modified method (with tooling aids) took 2.15 man hour for fabricating one unit in comparison to 3.32 man-h  with the existing method (without tooling aids).Thus the saving in labour in case of modified method was 1.17 man-h i.e.35

As far as saving in material is concerned, the twin weeder fabricated with modified method weighed 1.5 kg less. The saving in material has been achieved by replacing heavier sections with lighter section. The replacement has been yield not only material saving and reduction in weight but the ease in fabrication as well. Time consuming operations like manual bending of height adjusters, fabrication of axle on lathe etc. have been completely eliminated.

3.5  Project Profile

1. Product : Twin Wheel Hoe & PAE Wheel Hoe

It is proposed to manufacture two different designs of wheel hoe weeds. Twin wheel hoe and PAU wheel hoe. Wheel hoe weeders has been in great demand for weeding operation, Wheel hoe weeders has got advantage over traditional khurphi in respect of labour, time and drudgery in weeding operation.

2. Production target :  Twin Wheel  Hoe - 2000 units per annum

                                       PAU Wheel Hoe   -  1500 units per annum

The workshop will have facilities to fabricate 2000 units of Twin Wheel hoe and 1500 units of PAU wheel hoe weeders in a year.

3. Land & Building : Constructed shed of 1500 sq. ft. and  open area of 1500 sq.ft.

The shed is proposed to be taken on rent  @Rs.3000/- per month

4. Machinery requirement:

SI. No.   Machine & Description	Quantity	Approx. cost
1.           Spanner Set	4	1000/-
2.           Hand tools kit	2	1000/-
3.           Anvil	2	5000/-
4.           Arc welding et, 600 amp	1	25000/-
5.           Pillar drill, 13 mm	1	20000/-
6.           Fly press, 20 t	1	20000/-
7.         Power hack saw, 12’’ blade	1	10000/-
8.         Abrasive cut off machine	1	10000/-
9.         Mechanical pipe bending machine	1	5000/-
10.      Tooling	1 set	15000/-

     TOTAL                                                           112000/-

In finalizing the machinery requirement care has been taken to keep the expenditure on machinery as low as possible. A new entrepreneur can start the workshop with minimum machinery as a detailed in the table above. Owing a lathe will be too expensive, as a such as abrasive cut of machine has been proposed which  can be used for cutting various sections like angle, rod,flat,pipe etc.Similarly Owing a power press will also be not economical, considering the size of sections involved in farbrication.It will be underutilized always. A fly press will be enough to meet out the fabrication requirement. For the components involving press work and heat treatment etc. Like in case of fabrication of blade, it is proposed that the same can be got done outside on contract basis.

5. Raw Material requirement:

     This has been calculated from the manufacturing drawings of both the weeders.

S.NO.	MATERIAL	Qty	Unit Weight	Qty by weight (kg)	Rate (Rs./kg)	Approx. Cost
1.	ISRO 12	200m	0.89	178	17	3000
2.	ISRO 10	7500m	0.62	4650	17	79000
3.	ISRO 6	3225m	0.22	710	17	120000
4.	IST 40	32 m	-	-	90 per m	3000
5.	IST 25	5400 m	-	-	20 per m	108000
6.	IST 18	3450 m	-	-	16 per m	55200
7.	IST 14 , 2 thick	45 m	-	-	30 per m	1400
8.	ISSQ 16	38 m	2.01	765	17	13000
9.	ISSQ 12	480 m	1.13	542	17	9200
10.	ISF 65  X 5	102 m	2.5	255	17	4300
11.	ISF 30 X 5	260 m	1.2	312	17	5300
12.	ISF 30 X 3	420 m	0.7	294	17	5000
13.	ISF 25 X 5	2530m	1.0	2530	17	43000
14.	ISF 20 X10	1200 m	1.6	1920	17	32600
15.	MS Sheet 3mm	36 sq.m	24.70	890	22	19600
16.	Standard axle	3675 nos.	-	-	20	15000
17.	Nut bolts	500 kg	-	-	30	15000
	Total (say)					480000

Note The quantity includes 5 & 10 % allowance towards wastage on account of scrap/rejection for purchased & sheet metal parts.

6. Manpower:                              

S.No	Description	Man Days	Rate (Rs/man-days)	Amount
1.	Supervisor  or   Entrepreneur	300	100/-	30000/-
2.	Skilled technician	600	100/-	60000/-
3.	Unskilled worler	600	70/-	42000/-

                                      Total                                                                    132000/-

7. Miscellaneous   expenditure (20% of rows material):      Rs.96000/-    (Say)

This also includes expenditure on contract services like press work, shaping work, heat treatment etc.

 8. Total working capital (Monthly basis)                   

i.   Rent of building                                                 :    Rs.3000/-

ii. Cost of raw material                                            :    Rs.40000/-

iii. Overhead expenditure                                         :    Rs. 8000/-

iv. Salary                                                                :    Rs.11000/-

                      Total                                                            :  Rs. 62000/-

9. Essential working capital (for 3 months)          :  Rs. 186000/-

10. Total project cost

i. Cost of machinery                                         :   Rs.112000/-

ii. Essential working capital                               :   Rs.186000/-

           Total                                                    :   Rs.298000/-

11. Production     Cost 

i.    Annual   Working Capital                         :     Rs.744000/-

ii.   Depreciation                                           :     Rs. 11200/-

iii. Interest on capital from bank @ 14%          :     Rs. 31300/-

          (75% of project cost)

            Total                                                :  Rs.786500/-

12. Profit from  unit :

i. Scale proceed:

   Twin  wheel  hoe  2000  units  @ Rs.250 /-  each        :        Rs . 5,00,000 /

   PAU   wheel  hoe   1500   units  @ Rs. 300 / - each     :        Rs . 4,50,000

ii. Profit ( scale proceed –production  cost )                    :        Rs.1,63,500/-

iii. Monthly profit (Say)                                                 :        Rs .13,625/-

13. Break Even Point :

14. Pay back period  :

15. Return on  investment  :  

3.6 Suggestion 

Entrepreneur  should install  the  minimum  machinery  required  and for  machine  specific jobs like press work , heat treatment etc..,  he should get the work done from outside on contract basis .

Reference:

Uday R.Badegaonkar, Case study of Manufacturing of Weeders , Scientist (SG), Central Institute of Agricultural Engineer, Bhopal