PROCESS PLANNING

 

PROCESS PLANNING

 

Process planning is defined as a systematic procedure of developing and determining an economical method or series of methods by which a product can be successfully manufactured in a given time.

 

Tooling is a part of production engineering so process planning plays an important role in selecting proper equipment and tooling. This also specifies that application and operation in such a manner that the end product will meet all the requirements stipulated in the specification. At the same time the process will be performed as minimum cost and maximum profitability.

 

REQUIREMENTS IN PROCESS PLANNING

The following principle data and information are required to plan a manufacturing process.

1.     A brief description of the job to be manufactured which clearly and comprehensively defines its service function.

2.     Specification and standard that stipulate the service function.

3.     Working drawings of the job with complete specification.

4.     Data on the quantity of the parts to be manufactured in a period.

5.     Total quantity of space parts required for unit.

6.     Equipment, capacity of tools and data of all other equipments necessary including manpower.

7.     Date of starting and date of delivery.

              Above all these requirements it is important to have a good knowledge of machining sequences and their capabilities.

             The process planning followed in tool making may be summarized as follows:

First a good design is prepared and passed on to planning and toolmaker. Then the manufacturing of parts, which are to hardened, are given more priority and they are sent to heat treatment. In the due time the other parts such as bolster plate are finished. At the same time it is important to design and manufacture the electrode if they are any. After heat treatment the process of EDM starts along with bench work. Finally the parts will be ready for assembly.

 

PROCESS PLAN SHEET

Process plan sheet is a detail record where all information’s relating to different operations to manufacture is listed in a tabular form known as analysis sheet. The character of a process sheet will depend mainly on the scale of production of the degree of importance of the product being manufactured.

 

PLANNING OF OPERATION SEQUENCE

The following points should be considered while planning the sequence of operations.

a)           List of available machines.

b)           Accuracy and surface finish required.

c)            Convenience in operating the machine tool.

d)           Capacity of the machine tool.

e)             Performance of operation is economical or not.

 

CHECK LIST FOR MOULD PIECE PART

a)                Is the piece part drawing approved?

b)                Whether all the notes pertaining to job are clear?

c)                 Is the type of plastic material indicated?

d)                Is the function, location and use of piece part understood?

e)                 Can any changes be recommended to make a simplest of better pieces?

f)                   Are the numbers of cavities correct?

g)                Can these tolerances be maintained?

h)                Are the dimensions given including or excluding shrinkage?

i)                   What shrinkage factor should be used?

j)                   Has the parting line be approved?

k)                 Is the runner location correct?

l)                   Is the gate location correct?

m)              Will the piece hang on the injection side?

n)                Is the ejection mechanism sufficient?

o)                  Has the polish be specified?

 

MOULD

A)   The mould parting line chosen is most efficient for operation and construction is of mould?

B)   Is the capacity of adequate strength to resist internal cavity pressure?

C)   Have the materials for core and cavity and other parts been specified?

D)  Whether ‘O’ rings, springs etc. are provided wherever necessary?

E)   Has the mould been properly marked for identification?

F)   Are the dimensions on the prints are the same as the dimensions on the mould?

 

MACHINE

A)   Is the weight of the sum of moulding, runners, sprue is within the shot capacity of press?

B)   Is the clamping pressure of the machine sufficient for projected area of the moulding and runners?

C)   Will the mould pass between the machine tie bars?

D)  Do the clamping arrangements for the mould suit the platen boltholes?

E)   Is the length of work of mould and shoot weight within the capacity of the machine?

 

CONSTRUCTION

A)          Is the mould free from horizontal flash?

B)          Does the ejection assembly provide sufficient support to prevent distortion under cavity pressure?

C)          Can all the parts be dismantled and separated in the event of break down or modification?

D)         Are all necessary parts hardened?

E)          Is the ejection stroke sufficient to clear the moulding?

F)          Have sufficient ejectors been provided to prevent distortion cranking or sticking of the mouldings?

G)         Is the ejection assembly suitable for particular machine ejector systems?

H)         Have adequate cooling system been provided?

I)             Is the cooling too close or too distant from mould surface?

J)            Is the cooling too close or too distant from mould surface?

K)          Are the runners of sufficient size used?

L)           Has the sufficient opening provided between the halves to allow the extraction of mouldings?

M)        Do the spherical nose radius and cylindrical nozzle meet with the spherical seating on the sprue bush?

N)          Have mould lifting bolts holes been provided?

 

MANUFACTURING PROCESS

Manufacturing is a process of making the raw material into a finished product according to the planned drawing.

Manufacturing process is classified in two groups.

a)           Conventional manufacturing process.

b)           Non-conventional manufacturing process.

Manufacturing of injection mould mainly consists of:

1)           Mould box manufacturing.

2)           Manufacturing of core and cavity.

 

MANUFACTURING OF MOULD BASE

A mould base is an assembly of top plate, bottom plate, pillars and bushes; cavity plate, core plate, core back plate, ejector plate and ejector back plate.

 

TOP PLATE

Item No                          : -01

Material                         :-C-45

Raw material size1                   :-470X260X40

Finished size                   :- 460X250X35

 

Milled keeping 0.5mm excess for grinding with right angle to each of the surfaces. Thickness should be ground for proper seating of plate on which top surface butts on fixed platen of machine and the bottom side with cavity plate. A bore diameter of 50mm+0.1mm is done in the top surface for seating of locating ring. Three M5 screw holes are done to clamp the locating ring and the same setting a hole of dia. 25 for depth of 12mm is done for seating of sprue bush. A bore of dia36 H7 X 4 holes are done for seating of pillars and anchor pieces. M12X4 relieved holes are done for the screws to clamp the cavity plate to the top plate, which are transferred from cavity plate to the top plate. M8relived holes are done for screws to clamp the wedges.   The sides of the plate are chamfered with 5 X 45º to avoid the physical injuries.

 

BOTTOM PLATE

Item No                   :- 02

Material                  :- C-45

Raw material           :- 470X260X40             

Finished size           :- 460X25X35

 

The material is first milled right angle to each of the surfaces with 0.5mm grinding allowance. Thickness is ground because, the bottom surface will be clamped to machine platen and top is fixed to spacers. A hole of dia 40 is drilled to accommodate the ejector rod from the machine. Four relief holes for M16 screws are done so that it should hold pillars and core plate with spacer and core back.Dia M8reliufe hole for holding the core holder plate. The side’s plate is chamfered with 5 x 45º to avoid physical injuries.

 

GUIDE PILLAR

Item No.                  :-04  

Raw material size    :-Ø40X160 

Finished size           :- Ø36X155

        Material                 :- 17Mn1 Cr95

HRC                       :-CHDN52-55 HRC

It is a cylindrical part, which give alignment to the top half and bottom half of the tool with a sliding fit in the guide bush. Turning is done between centers keeping 0.5mm grinding allowance. After heat treatment it is inspected and ground on a cylindrical grinding machine to the finished size. Among four guide pillars three pillars are grinded to 36H7/g6 fit with the guide bush and have a dia36H7/k6 fit in the cavity plate. And one pillar is grinded to achieve 35H7/g6fit with guide bush for fool proofing. An entry lead of 10 degree is provided for easy entry and radius of R3 is done to provide an entry into guide bushes.

 

GUIDE BUSH

Item No.                  :- 05

Raw material size    :- Ø50X 140        

Finished size           :- Ø42X60

Material                  : -17Mn1 Cr95.   

  HRC                     :-CHDN 52-55 HRC

It is a cylindrical part, which give alignment to the top half and bottom half of the tool with a sliding fit in the guide pillar. Turning is done keeping 0.5mm grinding allowance. After heat treatment it is inspected and ground on a cylindrical grinding machine to the finished size. 36H7/g6 fit with three guide pillar and 35H7/g6  fit with one pillar and has a dia42H7/k6 fit in the liners

CORE HOUSEING

Item No.                  :-  03

Raw material size    :- 430X210X

Finished size           :- 420X210X36

Material                  :- C-45   

HRC                       :-  20-25 HRC

A milling operation of all the sides is performed with 0.5mm grinding allowance.DIA45H7X4 holes done in cnc milling for to house the sleeve bush to slide the sleeve.dia12H7relife hole for return pin. And M6X8 taping hole for clamping the wear plate.M10X4taping hole and Dia8H7X4 NOS dowel done for housing liners..M6X8mm relieve hole is done from bottom side for ball catch. Four holes of M16 are done for holding core plate with bottom plate...   All the edges are chamfered to be safe against the cuts.

 

CAVITY PLATE

Item No.                            : -   02        

Raw material size              : - 415X215X35mm                

Finished size                     : - 410 X210X30mm

Material                            : - C-45   

HRC                                 : - 20-25 HRC

A milling operation of all the sides is performed with 0.5mm grinding allowance. Eight small profile pockets of size5.08H7 X11.88H7X 30 is done in wire cut machine, for inserting  the    cavity pin. Dia15H7X4Holes alose done in wire cut machine for  inserting The cavity insert. two slots sige of 240x25x30 machining in  cnc machine for inserting the wedges block. Four holes of dia 35k6 with dia42x6 machining for aligning piller.M14 taping hole for clamping the top plate.dia12H7 with collar dia 20x7are drilled at an angle of 22degree for cam pin. at a centre of the plate dia 16H7hole done for spruebush.        

 

EJECTOR PLATE

Item No.                 :-   08         

Material                 :-    C-45 

        Raw material size   :-   415X128X22           

        Finished size           :-  410X122X20

        HRC                        :-  20-25 HRC

The size is maintained in milling machine with grinding allowance of 0.5mm. After that grinding is done. six M8 holes are drilled and tapped to fix the plate to the ejector back plate. Drilling and boring holes for guiding ejector guide bush of dia26H7.  Four relief holes of dia12H7 with counter bore of dia20 are done for return pins. A boring is done for the sleeve bush the bore size is dia 35H7x4holes. A chamfering of 5 x 45º is done to avoid injuries.

 

EJECTOR BACK PLATE

Item No.                   :-   09       

Material                  :-   C-45 

Raw material size   :-   450X335X26  

Finished size          :-   446X330X26

        HRC                       :-  20-25 HRC

The sizes are maintained in milling. The purpose using this plate is to retain the ejector pins. Two holes of dia26H7 is drilled and reamed to fit the ejector bush along with counter bore of dia 34 for depth of 5mm. The relieved holes for M8 screws and counter bores are also done. It is chamfered to 5x 45º to avoid cuts and injuries.

SPACERS

Item No.                  :-   07        

Raw material size   :-   450X130X60

Finished size           :-  446X126X56

Material                  :-  C-45   

        HRC                        :   20-25 HRC

They are machined to size and ground. The four relief holes are done for M16 screws holes for clamping purpose. Grinded to the finished size. All the sharp edge are chamfered to avoid injury.

 

MANUFACTURE OF CYLINDRICAL PARTS

All cylindrical parts are pre machined on lathe keeping 0.5mm allowance for grinding. But locating ring is completely finished in lathe only. The other parts are sprue are sprue bush, return pins, guide pillar aligning bushes, rest pins, feet buttons, etc.

 

All the above which are made up of OHNS (T110 W2 Cr1) material are heat treated and then ground to required dimensions.

 

HINTS FOR PURCHASING RAW MATERIAL & STANDARD ITEMS

RAW MATERIAL

1       A careful study of current market status should be made before buying anything

2       Make a complete list of different materials required.

3       While purchasing do not overlook the raw material size to the finishing size.

STANDARD ITEMS

While purchasing STD items like ejector pins, screws etc buy some extra numbers for easy replacement in case of damages. Inspections should be done whether they are in given tolerances. Keep them in a clean place by applying a thin film of oil.

 

CORE AND CAVITY INSERTS

After heat treatment they are inspected for required hardness. The hardness may vary between 46-48HRC

.

MAIN CORE INSERT

Item No.                         :- 25

Material                         :-H13(OS)  

Raw material size            :- dia35X215mm

Finished size                   :- dia31X208

HRC                               :- 46-48HRC

Quantity                         :- 4NO

CORE forms internal profile of the component, at first it is pre machined on lathe machine and keep allowance 0.5 for harnding. At center of the core insert M5taping for clamping the core sub inset, in back side dirll8x170mmdrilling for baffle cooling hole they are sent for heat treatment. After coming from heat treatment all the dimension are maintained with reference to tooling hole. And first sent for cylindrical grinding to mateine exact sige .finally profile sparking for core sub insert are finished on EDM  using electrode roughing and finishing living spark gap. Totally two electrode are sparked. After completing all machining core is Inspected as per drawing. 

MAIN CAVITY INSERT

Item No.                                   :- 26

Material                          :-H13(os)   

Raw material size            :- dia 32x55

Finished size                   :- dia30x50

HRC                               :-  46 - 48 HRC   

Quantity                         :- 4NO

          The insert has an H7/k6 fit with the cavity plate. This cavity insert forms the outside profile of the component. First it is pre machining on lathe machined ground living0.5mm for cylindrical grinding .in center1.5mm drill for wire entry hole, and it sent for  heat treatment. After coming from heat treatment first send for wire cut for wire cutting the hole size of 3k6for inserting the cavity sub insert. And sparking the collar dia 6x3mm depth. All machining process are completed the cavity inserts are sent to the inspectioning the cavity as per drawing.

 

SUB CORE INSERTS

Item No.                :- 27

Material               :-OHNS)

Raw material size:- Ø8x30mm

Finished size       :- Ø6.38x25.5mm    

Hardness            :- 50-52HRC

Quantity             :- 4NO

The material used is OHNS.

         This is pre machined on turning with 0.5mm grinding allowance on all dimensions. In back side M5 taping for clamping in the main core insert .And It  sent to heat treatment. After coming from heat treatment dimensions of the sub core insert maintained by cylindrical grinding.

.

SUB CAVITY INSERTS

 Item No.                 :-   30

Material                            :-H-13(OS) 

Raw material size    :-  Dia8X60mm

Finished size           :- Dia6X 55.8mm

HRC                       :-45-485HRC

Quantity                 :-   4NOS

          This is pre machined on turning with 0.5mm grinding allowance on all dimensions. Then sent to heat treatment. After coming from heat treatment dimension3K6X55.8mm are maintained as per size. dia1.36and 0.5radius is matiane in profile grinding machine. . All machining process are completed the cavity inserts are sent to the inspectioning the cavity as per drawing..

 

SUB CAVITY INSERTS

Item No.               : 31

Material              :- H-13(OS)

Finished size       :-  68X11.88X5.08mm     

HRC                   :-  50-52HRC

Quantity              :- 8NOS                                     

     The material used is H-13(OS)

This insert is directly blanked out from wire cut .In first setting the fitting size68X11.88X5.08h6 mm was done and in second setting radius profile was done. This insert H7g6 fit in cavity plate.

 

MANUFACTURING OF SLIDERS

Item No.                :-  36

Material               :-          HDS

Raw material size :-   312X72X65mm

Finished size         :- 308X70X60mm            

Hardness             :- 50-52HR

Quantity             :-2NOS

Slider is used for side profiling with cam pin actuaction.The material used is HDS. This is pre machined on milling with 0.5mm grinding allowance on all dimensions. After grinding slider was moved to rough profiling on Cnc milling. After cnc job was moved to milling for angular drilling at an angle of 20 degree and angular milling by tilting spindle to an angle of 22 degree. After that Rectangular circuit cooling hole done as per drawing.M5X4Taping is done for clamping the wear palate. Then slider was sent to heat treatment. After treatment slider was ground and all the dimension are maintained as per drawing and angular grinding was also done ,and then job was moved to finish cnc, and then to EDM  for profile sparking in four position in one slider using electrode of roughing and finishing achieve  projection profile. .After completing all machining slider is inspected as per drawing.

 

ELECTRODES

The flat insert pressed inside the core insert provides a square opening inside the component. It matches with with the depth of the component resulting in the square profile inside the component. It is first milled and then ground to the required size.