A design guide for poly propylene

P P DESIGN GUIDE.pdf

Equivalent Alloy steels

Elastic Spring back

When an electronic connector is formed, the base metal must be transformed from flat strip into a complicated, three dimensional part. This requires permanent deformation of the base metal. However, most connector materials are chosen due to their resistance to permanent deformation. Naturally, this tends to complicate the fabrication process. This conflict between manufacturability and required performance can best be seen in elastic springback.

When a component is formed, the stamping tool bends the metal into a certain angle with a given bend radius. Once the tool is removed, the metal will spring back, widening the angle and increasing the radius. The springback ratio is defined as the final angle after springback divided by the initial stamping angle (Figure 1).
In order to understand springback, it is necessary to look at a material’s stress-strain curve.

When a bend is being formed, the material is deliberately over-stressed beyond the yield strength in order to induce a permanent deformation. When the load is removed, the stress will return to zero along a path parallel to the elastic modulus (Figure 2). Therefore, with some exceptions, the permanent deformation will usually be less than the designer intended deformation of the strip. The springback will be equal to the amount of elastic strain recovered when the die is removed.
It is also important to note that the stress is highest at the top and bottom surfaces of the strip and falls to zero at the neutral axis of the bend, roughly in the middle of the strip.
Therefore, most of the stress in the interior of the strip is elastic and only the outer surfaces undergo yielding. The interior of the strip would like to straighten out the bend when the load is removed while the outer edges tend to resist straightening. The bend will not return to a zero stress state, but instead will spring back to an equilibrium point where all internal stresses balance. This is why forming operations induce residual stress in the material.

Several variables influence the amount of springback that is seen in a bend. A material with a higher yield strength will have a greater ratio of elastic to plastic strain, and will exhibit more springback than a material with a lower yield strength. On the other hand, a material with a higher elastic modulus will show less springback than a material with a lower elastic modulus. Figure 2 shows that the unloading stress-strain curve would be shifted toward less springback if it had a higher slope. In addition, the R/t ratio of the bend will come into play. A sharp bend will concentrate the stress more than a gradual bend, resulting in more plastic strain. Therefore, smaller R/t ratios will result in less springback.

There are several methods to deal with springback. The first is to experimentally
determine how much tighter the forming bend must be to allow the material to springback to the desired bend angle. Another mechanical solution is to coin the outside of the bend in order to introduce compressive stress on the outer fibers, which balance out the tensile stresses created during forming operations. At very small R/t ratios, this may even result in negative springback, where the final angle will be tighter than the stamped angle.
However, this is a very severe forming operation, which may make the strip more likely to fracture during forming.
The four variables that affect springback can also be used in an effort to control it. For instance, a material with a high modulus may be used to reduce springback. This will also result in increased contact force. A lower yield strength material may be used, but will result in a lower performance connector, since the lower yield strength limits the amount of stress that the connector can withstand. Strip thickness may be adjusted. However,bearing in mind this age of miniaturization, most connectors are progressing towards thinner strip, which will result in more springback. A smaller bend radius can be used to reduce springback. This requires a material with better formability.
For any given application, springback must be experimentally determined. The following
example may serve as a guide. The four variables which govern springback can be
combined into a single, non-dimensional variable as shown in Figure 3. During a series of 90º V-block formability tests, the springback angle was measured for a number of common connector materials. The springback ratio of each test was plotted against the non-dimensional variable. For every spring connector alloy tested, the results all fell on the same curve. The equation of that curve is shown in Figure 3. This means once the springback is calculated for several materials and R/t ratios, springback behavior can be extrapolated for any other connector alloy. Note: the equation shown is valid only for 90º V-block plane strain bends, and will not be representative of actual bends in the field.
Springback will occur in virtually every bend formed on a connector. It cannot be eliminated or predicted without experiment, but can be mitigated by careful material selection. For a new part configuration, trial and error is still necessary to determine how much springback will occur. If the bend is outside the specified tolerance, either the tool configuration or the
material must be changed to bring the connector back in spec.

Know About STEP

STEP Application Protocols

A list of the STEP Application Protocols (AP) as of June 2004 is given in Fig.2. The ability to support many protocols within one framework is one of the key strengths of STEP. All the protocols are all built on the same set of Integrate Resources (IR's) so they all use the same definitions for the same information. For example, AP-203 and AP-214 use the same definitions for three dimensional geometry, assembly data and basic product information. Therefore CAD vendors can support both with one piece of code.

Part 201 Explicit Drafting
Part 202 Associative Drafting
Part 203 Configuration Controlled Design
Part 204 Mechanical Design Using Boundary Representation
Part 205 Mechanical Design Using Surface Representation
Part 206 Mechanical Design Using Wireframe Representation
Part 207 Sheet Metal Dies and Blocks
Part 208 Life Cycle Product Change Process
Part 209 Design Through Analysis of Composite and Metallic Structures
Part 210 Electronic Printed Circuit Assembly, Design and Manufacturing
Part 211 Electronics Test Diagnostics and Remanufacture
Part 212 Electrotechnical Plants
Part 213 Numerical Control Process Plans for Machined Parts
Part 214 Core Data for Automotive Mechanical Design Processes
Part 215 Ship Arrangement
Part 216 Ship Molded Forms
Part 217 Ship Piping
Part 218 Ship Structures
Part 219 Dimensional Inspection Process Planning for CMMs
Part 220 Printed Circuit Assembly Manufacturing Planning
Part 221 Functional Data and Schematic Representation for Process Plans
Part 222 Design Engineering to Manufacturing for Composite Structures
Part 223 Exchange of Design and Manufacturing DPD for Composites
Part 224 Mechanical Product Definition for Process Planning
Part 225 Structural Building Elements Using Explicit Shape Rep
Part 226 Shipbuilding Mechanical Systems
Part 227 Plant Spatial Configuration
Part 228 Building Services
Part 229 Design and Manufacturing Information for Forged Parts
Part 230 Building Structure frame steelwork
Part 231 Process Engineering Data
Part 232 Technical Data Packaging
Part 233 Systems Engineering Data Representation
Part 234 Ship Operational logs, records and messages
Part 235 Materials Information for products
Part 236 Furniture product and project
Part 237 Computational Fluid Dynamics
Part 238 Integrated CNC Machining
Part 239 Product Life Cycle Support
Part 240 Process Planning


Each Application Protocol includes a scope describing its purpose, an activity diagram describing the functions that an engineer needs to perform within that scope, and an Application Requirement Model describing the information requirements of those activities. These information requirements are then mapped into the common set of Integrated Resources and the result is a data exchange standard for the activities within the scope.

The ultimate goal is for STEP to cover the entire life cycle, from conceptual design to final disposal, for all kinds of products. However, it will be a number of years before this goal is reached. The most tangible advantage of STEP to users today is the ability to exchange design data as solid models and assemblies of solid models. Other data exchange standards, such as the newer versions of IGES, also support the exchange of solid models, but less well.

STEP led the way with three dimensional data exchange by organizing an implementation forum for the CAD vendors so that they could continually improve the quality of the solid model data exchanges. The history of this success is relatively interesting because it show that the initial reluctance of vendors to implement user-defined standards can be overcome with enough perseverance.

At first, in 1996, there was a significant body of opinion that solid model geometry data could not be exchanged between systems using a neutral standard. However, in 1997 Ford, Allied Signal and STEP Tools, Inc. demonstrated the first successful data exchange of 3D geometry using STEP. Once this basic capability had been demonstrated a pilot project, called AeroSTEP, was organized by Boeing and its Aircraft engine vendors to test the first translators by exchanging data about where an engine fits onto the airframe. This project started out by exchanging simple faceted models but eventually demonstrated the exchange of models with great complexity.

The AeroSTEP project made it clear that STEP data exchange of solid model data was both feasible and valuable. As a result, vendor neutral implementation forums were formed in Europe, the Far East and the USA and the quality of the translators was raised to the level that allowed anyone, including ordinary users in small organizations, to use STEP for data exchange of solid models after about 2001.

NOTES TO GUIDE THE DESIGNER ON PRESS TOOL DESIGN

1. These notes' are to guide the designer, to design a practical press tool, to get an acceptable component from the tool and are very valuable points, to produce a perfect tool design drawing.
2. The press tool designer should keep these points in mind or should refer to these notes, before starting a fresh press tool design.
3. Depending upon the type of press tool, to be designed for the particular operation/stage of the components, the designer shall apply the relevant points of these notes.
4. These notes are grouped under the following headings of the tool design. .
A. Most important press dimensions to be considered,
B. Miscellaneous notes to the designer,
C. Planning and layout,
D. Punches and Dies,
E. Cutting clearance,
F. Shearing and shear,
G. Locating of work,
H. Shedders and strippers,
J. Progressive and automatic tools,
K. Compound and combination tools,
L. Forming and drawing tools,
M. Tool materials and craftsmanship,
N. Die try-out and operation.
A. MOST IMPORTANT PRESS DIMENSIONS TO BE CONSIDERED:
5. Before starting a tool design, the designer should know the specifications of the press on which the tool shall be used during the production run. The following factors of the press specification must be considered:
5.1 SHUT HEIGHT WITH/WITHOUT BOLSTER AND BOLSTER PLATE THICKNESS,
5.2 ROLL FEED HEIGHT,
5. 3 SHANK DIAMETER AND LENGTH,
5.4 HOLE IN PRESS BED/BOLSTER (WIDTH AND LENGTH),
5. 5 STROKE LENGTH AND ITS STEPS -DETAILS LIKE FIXED OR ADJUSTABLE STROKE,
5.6 DOES GATE GO UP IN TO THE WAYS? GATE-TOP RAM,

5.7 IF THE GATE GO UP IN TO THE WAYS, CHECK THE OPENING BETWEEN THE WAYS,

5.8 WHICH WAY SHOULD DIE FEED?
5 .9 TONNAGE OF THE PRESS,
5.10 ADDITIONAL HOLES FOR CLAMPING PUNCH HOLDER TO THE TOP RAM (GATE),
5.11 TAPPED HOLE CENTERS IN PRESS BOLSTER-TEE-SLOT POSITIONS AND ITS SIZE,
5.12 THE DISTANCE ABOVE THE BOTTOM OF THE STROKE WHERE THE PRESSURE FIRST OCCURS,
5 .13 ANY ADDITIONAL PRESSURE REQUIRED DUE TO ATTACHMENTS SUCH AS THE BLANK
HOLDER, IRONING WRINKLES OR STRETCHING THE MATERIAL IN DRAWN WORK,



5.14 DIE CUSHION DETAILS AND ITS MOUNTING POSITIONS.PRESSURE TRANSFER PINS POSITIONS IN THE BED/BOLSTER.
B. MISCELLANEOUS NOTES TO THE DESIGNER:
6. SHOULD PART BE MADE PROGRESSIVE OR COMPOUND –This should be given due consideration before proceeding with the die layout. In general, precision stampings can be made more accurately in compound dies.
7. LAY-OUT CORRECT FOR BURR SIDE -many stampings have a right burr side, which the part print may not specify. This point should be checked before starting the die lay- out.
8. STARTING AND AUTOMATIC STOPS -Care should be taken in establishing the position of starting stops to avoid cutting half slugs or blanks.
9. BACKING UP PUNCHES WITH SIDE STRAIN -Punches cutting on one side only should be heeled, the heel entering the die for support before any cutting takes place. The same condition may arise with forming or shaving or bending punches. Shaving on one side only should be avoided and a forming punch, which has all the pressure on one side, must be backed up solid in some manner. Dowels as a rule, are not sufficient.


10. INDICATE CLASS OF WORKMAN SHIP -Some working surfaces can be left as they come from furnace or machine and some should be ground and some lapped or stoned. The designer should indicate what is required.
11. SELECTION OF PROPER STEELS -To day there are steels for every purpose and some thought should be given to what is expected of the die, what material is being punched or formed and choose the best material for the particular job.
12. SPRING STRIPPERS: -Make the spring stripper of ample width and length to provide room for additional springs if necessary. Also make it thick enough to properly take care of the stripper bolts which some times loosen up. If some of the punches are to be guided in the stripper, it must be supported on guide posts/pillars and accurately held in line. When punches are not guided in the stripper, ample clearance must be allowed around all the smaller punches to avoid the possibility of their being thrown out of line. If they are one or two good sturdy punches in the die, fit the stripper close to these punches (0.001" to O. 005" clearance) and allow 0.010" to 0.015" clearance on the smaller punches.
13. HIGH NESTS FOR HAND FED SECOND OPERATION:- If possible, make locating nests 3 to 4 times the blank thickness with the top well rounded to receive the part. The proper condition here will increase production 10% to 25%.
14. PROVISION FOR WEAR ON FORMING TOOLS:- Some forming dies wear fast from the abrasion action and usually provision can be made to adjust or replace this portion at little, if any, added cost.
15. STRIPPER WELL DOWELLED:- In some dies, the stripper is depended upon to do a lot of heavy guiding and it is easy to overlook the importance of large dowels to keep the stripper from shifting.


16. INDICATE HARDNESS:- Having each part the proper hardness is important. Frail parts must be drawn back perhaps to Rockwell 55C and other parts possibly should be left as high as 65C. "
17. CONSIDER LENGTH OF PILOTS: - pilots must be long enough to accurately locate the strip before any punch starts cutting or trimming or forming otherwise their purpose is defeated.




18. STAMP THE FEED DISTANCE ON THE DIE:- This dimension should be plainly stamped on roll feed jobs to save the set-up man the trouble of checking it up.
19. GIVE INSTRUCTION ON THE ASSEMBLY DRAWING TO STAMP THE FOLLOWING DETAILS:- These details should be stamped on the tool bolster plate, to assist the tool shop personnel to maintain the tool and for easy follow up of the production.
19.1 TOOL ORDER NUMBER
19.2 COMPONENT NAME AND DRG NUMBER,
19.3 MATERIAL, STRIP WIDTH,
19.4 SHEET THICKNESS AND TOLERANCE,
19 .5 CLEARANCE,
19 .6 REQUIRED TONNAGE,
19.7 DETAILS OF PRESS ON WHICH THE TOOL SHALL BE LOAD
19 .8 TOOL DESIGN DRAWING NUMBER,
19 .9 SHUT HEIGHT OF THE TOOL,
19.10 ROLL FEED HEIGHT,
19.11 PITCH OF STAGE FOR PROG TOOL.
20. Always check the die drawings with part prints to make certain that the tool will produce the part correctly, relation of grain direction to forms, shear forms, embossments, spurred holes, blanking pressure required and strength of fragile projections.
21. Dimension the detail drawing with information in the form required by the toolmaker, so that he has a minimum amount of translation to do, in understanding the tool design drawing.
22. As soon as the design of a die is decided upon order material/arrange to issue the material details to planning, so that there are no unnecessary delay. Order try-out material at the same time.
23. Always confirm to customers/company's specification for the type of tool construction, kind of steel, die set standard if possible and standardized sizes of die sets.
24. Whenever possible, specify the standard parts as per the international nomenclature/standards and other parts of the tool should be referred as per the standard nomenclature followed in national/international standards for tools.
25. Design all tool parts so as to be easily removable with minimum of disassembly.

26. Consider in the design, the safety and the relation of efficiency to fatigue of the press operator.





27. On detail drawings vitally important working dimensions must not mingle with less important details like location of screws, spring holes, dowels etc.
C. PLANNING AND LAYOUT:
28. Always determine if a more satisfactory design can be obtained by the use of an inverted tool.
29. Draw/Drawing tools are usually inverted.
30. The blank usually follows the shape of the punch.
31. On a blanking tool, the burr is to wards the punch i.e. the clearance shall be given to punch dimension in the case of a blanking tool.
32. Burrs from piercing and contouring are on the same side of the blank taken from a compound tool.
33. In progressive tools, the burrs of the piercing and the blank profile are on the opposite sides.
34. A compound piercing and blanking type of tool is usually to be preferable to a progressive type tool for the same operation.
35. If the part drawing of a blank calls for a close flatness, it is preferable to design an inverted blanking tool instead of a conventional design.
36. On complicated forms always use a template to check the parts and the layout of the punch and die.
37. It is often good practice to use a shaving tool after a blanking tool operation on heavy stock to get clear, sharp edges and to hold close tolerance and to get perfect right angle edge through-out the thickness of the' sheet.
38. Shaving tools as the name implies, are used to remove the die roll or rough edges caused by the shear fracture or break through characteristics in blanking tools. In effect, the shaving tool action is a trimming or squaring up action. Shaving tools are similar to blanking or piercing tools, except little or no clearance is left between the punch and die. Usually no shear is added to either the punch or the die. Often it is necessary to shave a blank only at important functional areas.



39. The amount of metal to be removed by a shaving operation is proportional to the blank thickness and varies with the stock. From 8 to 10% of the thickness of mild steel stock is a good average. For two shaving allow 10% and take off 2/3 with the first and 1/3 with second operation.
40. SHAVING DIRECTION: 1'he cutting direction for a shaving operation should be the same as the cutting direction of the previous cutting operation i.e. for shaving a blank profile, the burr side of the blank should face the shaving punch.
41. STRIPPING IN SHAVING: - Be certain that stripping provisions are adequate. The amount of stripping force required in shaving operation may be double or even triple the force required for equivalent blanking or piercing type of cutting operation.
42. When the thickness of the stock is more than 3mm, it is preferable to have more than one sharing operation. The No. Of shaving operation also depends on the profile to be shaved and the cleanliness of the cut band and the needed accuracy of the profile of component.
43. CLEARANCE BEFORE SHAVING: -cutting clearance for the prior cutting operation (before shaving operation) should be made at least normal or larger than normal if necessary. Most common error is to use too little cutting clearance for those cutting operation, which precede shaving operation.
44. CLEARANCE IN SHAVING: Cutting clearance for shaving dies may be practically non-existent. It is common practice to use fits between punches and die opening which are as close as possible without interference. However, in cases where the shave allowance is quite large, a cutting clearance (in shaving) equal to 5 percent of the shave allowance will be generally acceptable.
45. ALLOWANCE FOR SHAVING:- The width of the scrap web removed by the shaving operation is the shave allowance.
A -Shave allowance for the first shave or for single shave operation
A1 -Shave allowance for second shave operation
T -Stock material thickness
C -cutting clearance used for previous cutting operation (prior to shaving)





For steel A = C+O-O4T A = o.075mm mini
Al=c/2 Al= o.035mm mini
For Brass, Copper, German silver
A = 2c A = o.075mm mini
Al = C Al = o.035mm mini.
46. RECOMMENDED SHAVING CLEARANCE:
First shaving clearance = 5% of first shaving allowance
First shaving allowance = A = c+o.04T
T -Stock thickness
C -Piercing or blanking clearance in % of sheet thickness prior to shaving.
Second shaving allowance = Al = c/2

Second shaving clearance = 5% of second shaving allowance.
47. PINCH TRIMMING: Pinch trimming (should be done) can be attempted, when the sheet thickness of the material is less than 1.5mm (1/16”)



48. DRAWING OF SHEETS: In drawing of sheets, the blanks holder pressure is normally considered between 10 to 20% of the drawing load.
49. DRAWING PRESSURE: To find out the drawing pressure in draw tools, the formula is: -
= (Yield points + ultimate tensile strength) cross sectional area
2
50. DRAWING SPEED: Drawing speed shall depend on the material that is to be drawn. Normally 30 feet per minute is considered for steel material. For brass material the draw speed can be little more i.e. 40 feet per minute draw speed can be considered.

51. HARDENED BACK PLATE: When the compressive stress of the punch (behind the shoulder of punch) on the top bolster plate increases beyond 24.5 kg/mm2 (35000 psi), the designer should provide a (52 RC) hardened back plate behind the punch holder. Keep a minimum of 6mm thick back plate.
52. SPRING ACTUATED STRIPPERS: If the stock or strip is thin(less than 0.5mm), it is good practice to use movable strippers (spring actuated floating stripper) which simultaneously act as a blank holder that firmly grip the stock or strip during cutting. This especially true, when the cutting contour (profile) is irregular.
53. BACK TAPER IN DIE: For thin strip or stock, a back taper of 1/20 right from the die surface, has been found to give good results. The cutting angle 'B' is then large enough to allow sufficient re-sharpening without appreciable change in size of the blank.

Hyperthreading in autocad

Hi guys i thik this may be useful for you .

The autocad can be enabled hyperthreading this will be used while redraw,regen,zoom in zoom out and pan, I felt increase in speed while working with large die designs of size more than 30MB

The command is Whipthread set its value to 3,in many cases i seen it is set to 1 (the value makes it off).

This will be felt only when your processor is hyperthreaded (like I3,I5 etc.,)

Warpage

1. Moisture in the granules
2. Feed system too small
3. Wrong gate position
4. Hold time too short
5. Wrong melt temperature
6. Wrong tool temperature
7. Poor surface finish
8. Problems with hot runners
9. Warpage
10. Mould deposit

Partially crystalline substances such as POM (acetal), PA (nylon), PBT and PET (polyesters) tend to warp far
more than amorphous ones. This point should be taken into consideration already when designing moulds and
mouldings. If this is not done, it is almost impossible to rectify at a later stage. This article discusses the
causes of warpage and steps that can be taken to prevent and reduce it.

What are the main causes of warpage?

Shrinkage is relatively high in partially crystalline materials and is influenced by a number of factors. In the
case of unreinforced materials, warpage is greatly influenced by wall thickness and mould surface temperature.
It follows that major differences in wall thickness and unsuitable mould temperatures will cause the moulding
to warp. Totally different shrinkage characteristics will be evident in the case of glass fibre reinforced
materials, due to orientation of the glass fibres. The effect of wall thickness differences on shrinkage is
relatively slight. Here, the main cause of warping is the difference between fibre orientation longitudinally and
at right angles to the direction of flow. Warpage is essentially due to wall thickness distribution, gate location,
flow restrictions and by-passes, as well as the inherent rigidity of the moulded part.
These different causes of warping, depending on whether the material is fibre-reinforced or not, frequently
result in contrary warping phenomena in the same part.

How can warpage be prevented?

Unreinforced materials require uniform wall thicknesses. Melt accumulations should be avoided as far as
possible. Multi-point gating can be used to achieve a high pressure gradient and thus reduce shrinkage
differences to a minimum. The mould heating system should be designed so that heat is dissipated as evenly as
possible
With glass fibre reinforced materials, the symmetry of the moulded part is as important as uniform wall
thickness. Asymmetrical parts hinder melt flow and thus orientation, and eventually cause warpage. In the case
of asymmetrical parts it is therefore necessary to achieve a balance by incorporating blind cores at the mould
planning and design stage. The position of the gate is also important – every by-pass and every weld line is a
potential cause of warping.

What possibilities are open to the moulder?

Assuming that the moulded part, the gate and the mould have all been correctly designed, the moulder can
control warpage up to a point via the holding pressure and mould temperature. The use of several heating
circuits to optimise heat dissipation is normal practice.
In the case of reinforced materials, changing the injection rate or lowering the mould temperature is a slight
help. If the possibility of subsequent warpage has not been foreseen at the mould and moulded part design
stage, this cannot be subsequently rectified by modifying moulding conditions.

Cooling channels caculations

Thermal conductivity for Different materials

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Know more recyle symbols

Hai guys here is the Design data for plastic Engineers

This book tells about plastics properties and processing methods
Design_Data_for_Plastics_Engineers.pdf

A design guide for poly propylene

P P DESIGN GUIDE.pdf

Good american phrases

Its really funny !!!!!!!
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Bending calculations

This holds good and its results are practically good i also experienced it!!!!!!
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Direct download of AUTOCAD 2008

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Here are the meanings for recycling symbols in plastics components