Saturday, December 2, 2023

Design for Manufacture for Injection Molding - Important Points

2023 BEST E-Book on #IndustrialEngineering. 

INTRODUCTION TO MODERN INDUSTRIAL ENGINEERING.PRODUCT INDUSTRIAL ENGINEERING - FACILITIES INDUSTRIAL ENGINEERING - PROCESS INDUSTRIAL ENGINEERING.  Free Download.

https://academia.edu/103626052/INTRODUCTION_TO_MODERN_INDUSTRIAL_ENGINEERING_Version_3_0 


Lesson 250 of IEKC Industrial Engineering ONLINE Course Notes.

Engineering in Industrial Engineering -  Machine work study or machine effort improvement, value engineering and design for manufacturing and assembly are major engineering based IE methods. All are available as existing methods.


Milacron Servo Injection Molding Machine.

Milacron’s servo injection molding machines offers energy efficiency, reliability, precision, and product versatility. The reduced energy use reduces the heat load on the factory and reduces maintenance and operational costs over the life of the machine.

https://www.milacron.com/products/injection-molding-machines/servo/

Product Design for Manufacture and Assembly, Third Edition

Geoffrey Boothroyd, Peter Dewhurst, Winston A. Knight

CRC Press, 08-Dec-2010 - Technology & Engineering - 712 pages

https://books.google.co.in/books/about/Product_Design_for_Manufacture_and_Assem.html?id=W2FDCcVPBcAC 

Note: It is important to read the books by Boothroyd to understand the full method of DFMA. The DFMA method is to be combined with Value Analysis and Engineering to do product industrial engineering. In the note only attempt is made to make readers aware of issues raised and solutions proposed by DFMA method.

8. Design for Injection Molding 339
8.1 Introduction 
8.2 Injection Molding Materials 
8.3 The Molding Cycle 
8.4 Injection Molding Systems 
8.5 Injection Molds 346
8.6 Molding Machine Size 351
8.7 Molding Cycle Time 
8.8 Mold Cost Estimation 359
8.9 Mold Cost Point System 367
8.10 Estimation of the Optimum Number of Cavities 369
8.11 Design Example 372
8.12 Insert Molding 374
8.13 Design Guidelines 375
8.14 Assembly Techniques 376
References 379 


Design for Injection Molding


Injection molding technology is a method of processing predominantly used for thermoplastic polymers. It consists of heating thermoplastic material until it melts, then forcing this melted plastic into a steel mold, where it cools and solidifies. The increasingly sophisticated use of injection molding is one of the principal tools in the battle to produce elegant product structures with reduced part counts.


Injection molding technology is a method of processing predominantly used for thermoplastic polymers. It consists of heating thermoplastic material until it melts, then forcing this melted plastic into a steel mold, where it cools and solidifies. The increasingly sophisticated use of injection molding is one of the principal tools in the battle to produce elegant product structures with reduced part counts.


The most common types of molds used in industry today are (1) two-plate molds, (2) three-plate molds, (3) side-action molds, and (4) unscrewing molds.

MOLD COST POINT SYSTEM

The main cost drivers are given. For each cost driver, there are associated graphs or tables to be referred to for determination of the appropriate number of points. The mold manufacturing cost is determined by equating each point to one hour of mold manufacture.

(i) Projected Area of Part (cm2)

Equations provide points for the size effect on manufacturing cost plus points for an appropriate ejection system,

(ii) Geometric Complexity

—identify complexity ratings for inner and outer surfaces according to the procedure. 

—Apply Eq.  to determine the appropriate point score

(iii) Side-Pulls

—identify number of holes or apertures requiring separate side-pulls (side cores) in the molding operation.

— Allow 65 points for each side-pull.

(iv) Internal Lifters — Identify number of internal depressions or undercuts requiring separate internal core lifters. — Allow 150 points for each lifter.

(v) Unscrewing Devices — Identify number of screw threads that would require an unscrewing device. — Allow 250 points for each unscrewing device.

(vi) Surface Finish/Appearance — Refer to Table identify the appropriate percentage value for the required appearance category. — Apply the percentage value to the sum of the points determined for (i) and (ii) to obtain the appropriate point score related to part finish and appearance.

(vii) Tolerance Level — Refer to Table  to identify the appropriate percentage value for the required tolerance category. — Apply the percentage value to the geometrical complexity points determined for (ii) to obtain the appropriate point score related to part tolerance.

(viii) Texture — If portions of the molded part surface require standard texture patterns, such as checkered, leather grain, etc., then add 5% of the point scores from (i) and (ii).

(ix) Parting Plane — Determine the category of parting plane from Table and note the value of the parting plane factor, to obtain the point score from Equation . To determine the cost to manufacture a single cavity and matching core(s) the total point score is multiplied by the appropriate average hourly rate for tool manufacture.

DESIGN GUIDELINES

Several have published design manuals or handbooks need to be consulted for designing injection molding components. Information can be obtained from them on the design of ribbed structures, gears, bearings, spring elements, etc.  Du Pont, G.E. Plastics Division, or Mobay Corporation and other plastics manufacturers provide design information associated with their engineering thermoplastics.

Generally accepted design guidelines are listed below. 

1. Design the main wall of uniform thickness with adequate tapers or draft for easy release from the mold. This will minimize part distortion by facilitating even cooling throughout the part. 

2. Choose the material and the main wall thickness for minimum cost. Note that a more expensive material with greater strength or stiffness may often be the best choice. The thinner wall this choice allows will reduce material volume to offset the material cost increase. More important, the thinner wall will significantly reduce cycle time and hence processing cost. 

3. Design the thickness of all projections from the main wall with a preferred value of one-half of the main wall thickness and do not exceed two-thirds of the main wall thickness. This will minimize cooling problems at the junction between the projection and main wall, where the section is necessarily thicker. 

4. If possible, align projections in the direction of molding or at right angles to the molding direction lying on the parting plane. This will eliminate the need for mold mechanisms. 

5. Avoid depressions on the inner surfaces of the part, which would require moving core pins to be built inside the main core. The mechanisms to produce these movements (referred to in mold making as lifters) are very expensive to build and maintain. Through holes on the side surfaces, instead of internal depressions, can always be produced with less expensive side-pulls. 

6. If possible, design external screw threads so that they lie in the molding plane. Alternatively, use a rounded or rolled-type thread profile which can be stripped from the cavity or core without rotating. In the latter case, polymer suppliers should be consulted for material choice and appropriate thread profile and depth. 

In addition to these general rules, design books should be consulted for design tips and innovative design ideas. 

 REFERENCES 

1. Dewhurst, P., and Boothroyd, G., Design for Assembly in Action, Assembly Eng., January 1987. 

2. Rosato, D.V (Ed.), Injection Molding Handbook, Van Nonstrand Reinhold, New York, 1986. 

3. Sown, J., Injection Molding of Plastic Components, McGraw-Hill (UK), 1979. 

4. MacDermott, C.P., Selecting Thermoplastics for Engineering Applications, Marcel Dekker, New York, 1984. 

5. Bernhardt, E.G. (ed.), Computer-Aided Engineering for Injection Molding, Hanser Publishers, Munich, 1983. 

6. Design Handbook for Dupont Engineering Polymers, E.I. du Pont de Nemours and Co. Inc., 1986. 

7. Farrell, R.E., Injection Molding Thermoplastics, Modern Plastics Encyclopedia, 1985-86, pp. 252-270. 

8. Khullar, P., A Computer-Aided Mold Design System for Injection Molding of Plastics, Ph.D. Dissertation, Cornell University, 1981. 

9. Gordon Jr., B.E., Design and Development of a Computer Aided Processing System with Application to Injection Molding of Plastics, Ph.D. Thesis, Worcester Polytechnic Institute, Worcester, MA, November 1976.

11. Ballman, P., and Shusman, R., Easy Way to Calculate Injection Molding Set-Up Time, Modern Plastics, McGraw-Hill, New York, 1959.

13. Dewhurst, P., and Kuppurajan, K., Optimum Processing Conditions for Injection

Molding, Report No. 12, Product Design for Manufacture Series, University of Rhode Island, Kingston, February 1987.

14. Schuster, A., Injection Mold Tooling, Society of Plastic Engineers Seminar, New York, September 30-October 1, 1987.

15. Sors, L., Bardocz, L., and Radnoti, I., Plastic Molds and Dies, Van Nostrand Reinhold, New York, 1981.

16. Archer, D., Economic Model of Injection Molding, M.S. Thesis, University of Rhode Island, Kingston, 1988.

18. Reinbacker, W.R., A Computer Approach to Mold Quotations, PACTEC V, 5th Pacific Technical Conference, Los Angeles, February 1980.


Designing Plastics Parts for Assembly - The pioneering development of the IBM ProPrinter.

Designing Plastics Parts for Assembly, Preface 1st Edition, by Dr. Peter Dewhurst, Department of Industrial and Manufacturing Engineering,

University of Rhode Island, November, 1993

https://www.ets-corp.com/lectures/dppa/p1th.htm

Process Design of Injection Molding System for Umbrella Handle Based on Moldflow

ICIIP 2019: Proceedings of the 2019 4th International Conference on Intelligent Information ProcessingNovember 2019 Pages 146–150https://doi.org/10.1145/3378065.3378093

https://dl.acm.org/doi/10.1145/3378065.3378093

Injection molding design: 10 critical considerations for designing high-quality molded parts, part one
https://www.plasticstoday.com/injection-molding/injection-molding-design-10-critical-considerations-designing-high-quality-molded

Design for Manufacturing Course 5: Injection Molding - DragonInnovation.com
9 Dec 2014
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https://www.youtube.com/watch?v=jx5_gO9LTf8
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Design Guidelines for Extrusion and Injection Molding
NPTEL
https://www.youtube.com/watch?v=I4PptmWppUE

Injection Molding - 2.008 Design and Manufacturing II - MIT Course Page
https://course2008.mit.edu/injection-molding


DFMA Injection moulding
https://news.ewmfg.com/blog/manufacturing/dfm-design-for-manufacturing

Protolabs Injection Molding Facility in Plymouth, Minn. Recognized as Smart Factory Lighthouse


Global Lighthouse Network Recognizes Protolabs as Leader in Fourth Industrial Revolution
Posted On September 27, 2021 By Protolabs

Protolabs injection molding facility in Plymouth, Minn. has been inducted into the World Economic Forum’s Global Lighthouse Network, recognizing our industry leading efforts to implement Fourth Industrial Revolution (4IR) technologies.



The digital manufacturer becomes one of  10 U.S. companies so far honored by the World Economic Forum for industry advancements through manufacturing technology

Protolabs’ injection molding facility was recognized for its transformation as a prototype provider to now a full production provider through the implementation of 4IR technologies connecting its e-commerce experience to the shop floor. Its end-to-end connection—termed the digital thread—enables the technology-driven manufacturer to provide production lead times in as fast as one day, instead of two to three months with traditional manufacturers.

The 4IR technologies recognized by the World Economic Forum include Protolabs’ interactive e-commerce quoting system with automated design for manufacturability (DFM) analysis, its automated mold design and toolpathing programs, and its digital process controls and inspections. The prevailing theme with those technologies is the overall reduction in manual processes—both for Protolabs and its customer—due to strategic implementation of automation. That automation then drives significant customer value like product innovation, speed to market, supply chain risk reduction, and a multitude of other benefits.

By implementing manufacturing automation and Industrial IoT technologies like this, Protolabs is able to unlock new levels of sustainability and efficiency for itself and its customers

About Protolabs

Protolabs is the world’s leading provider of digital manufacturing services. The e-commerce-based company offers injection molding, CNC machining, 3D printing, and sheet metal fabrication to product developers, engineers, and supply chain teams across the globe. Protolabs serves customers using in-house production capabilities that bring unprecedented speed in tandem with Hubs, a Protolabs Company, which serves customers through its network of premium manufacturing partners. Together, they help companies bring new ideas to market with the fastest and most comprehensive digital manufacturing service in the world.

Protolabs Automated Design Analysis & Consultative Design Service for Injection Moulding


Already well known in the industry for our automated design for manufacturing analysis via our digital quoting platform, we have now launched an injection moulding consultative design service, to help you find the best manufacturable solution.

Our automated design analysis takes your CAD and typically within a couple of hours provides feedback on whether your design is manufacturable. It also helps identify any particularly challenging features and provides suggestions on how to improve manufacturability. You can submit your part for analysis and quote as many times as you want, at no cost.

The new complementary consultative design service allows you to take advantage of our engineers' experience in injection moulding, to help you optimise your solution. Whilst our quoting platform will check your design is possible, you may also need the critical thinking of an experienced person to find the best solution, whether it be support with a particularly complex geometry, trying to find a solution for a text requirement, or even help in cost cutting ideas to ensure your part is within budget.
https://www.protolabs.co.uk/automated-design-analysis/




One of IndustryWeek's four Best Plants 2022 winners

Protolabs Injection Molding Facility
Plymouth, Minnesota
Employees: 450
Square Footage, Manufacturing: 140,000
Primary Products: Injection molding
Start-up date: 2014
Achievements: Automated digital twin, Recognition as a WEF Global Lighthouse Network plant, 16.4% reduction in scrap and rework costs within past 3 years, digital process control reduced parts non-conformance by 45%, increased large injection molding capacity by more than 50% in the past 3 years.
https://www.industryweek.com/resources/industryweek-best-plants-awards/article/21248819/pushing-the-limits-of-prototyping-speed-at-protolabs-injection-molding-facility

Role of People in The Fourth Industrial Revolution Factories
January 7, 2022 | McKinsey Podcast.
Participation of Protolabs CEO
https://www.mckinsey.com/capabilities/operations/our-insights/the-fourth-industrial-revolution-will-be-people-powered

Proto Labs, Inc. (PRLB) CEO Rob Bodor on Q1 2021 Results - Earnings Call Transcript
May 06, 2021 
https://seekingalpha.com/article/4425169-proto-labs-inc-prlb-ceo-rob-bodor-on-q1-2021-results-earnings-call-transcript

Protolabs: the changing face of digital manufacturing
By Harry Menear
May 19, 2020
https://businesschief.com/leadership-and-strategy/protolabs-changing-face-digital-manufacturing


 4/27/2018 
‘Digital Manufacturing’ at Protolabs Evolves from Prototyping to ‘On-Demand’ Short Runs
Today its “digital manufacturing” model is accelerating from rapid prototypes and first-run production parts to “on-demand” short-run manufacturing.
https://www.ptonline.com/articles/digital-manufacturing-evolves-from-prototyping-to-on-demand-short-runs

David Greenfield
14 June 2016

Digital thread: Essentially, the term refers to digitizing every aspect of product development and manufacturing —from design through production—to enable full access to every relevant piece of data associated with the product for tracking, quality assurance, troubleshooting and maintenance.
https://www.automationworld.com/products/software/article/13315564/the-digital-thread-on-display





How Proto Labs Is Building The Factory Of The Future
Hollie Slade, Forbes Staff
Oct 15, 2014
https://www.forbes.com/sites/hollieslade/2014/10/15/how-proto-labs-is-building-the-factory-of-the-future/ 

The Digital Thread on Display
The production processes at Proto Labs exemplify the digital thread concept in low-volume, custom manufacturing.











Ud. 2.12.2023, 15.9.2022,  23.8.2022
Pub 16.12.2021




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