THE SOCIETY OF PLASTICS ENGINEERS – SOUTHERN CALIFORNIA SECTION

Presidents Message

January 2019 • No 2

A new year brings in new reasons to become involved with SPE! Whether your goal is to become more engaged with the local plastic community, promote your company, or to broaden your plastic knowledge – we are here to help you achieve these goals.

The Southern California section is looking forward to hosting another successful year of engaging technical programs, fun golf outings, and networking opportunities.

We will be kicking this year off with our 2nd Medical Plastic MiniTec on February 4th. On behalf of SPE’s Southern California Section and Medical Plastic Division, we invite you join us for a day of technical talks, table top exhibits, posters, and networking. We have received an immense amount of support for this event and I want to thank all our sponsors.

Sincerely,Ashley SpittleSouthern California SPE President

A one day conference where 14 presentations from the industry will discuss the latest developments in the area of medical plastics.

A one day conference where 14 presentations from the industry will discuss the latest developments in the area of medical plastics.

Sponsors

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SAVALIA BUYS PERFORMANCE ENGINEERED PRODUCTS

November 5, 2018 By Roger Renstrom  Plastics industry entrepreneur Dennis Savalia scored his largest acquisition Nov. 2, buying Performance Engineered Products Inc. in Pomona, Calif.

PEP becomes Savalia’s sixth purchase of a plastics processing business in three southern California counties in the past 20 months.“I keep in touch with people. Relationships are very important,” Savalia said about his purchasing practices. “People know me and approach me. It helps me to grow my own business and deal with customers as well.”Savalia acquired PEP from the estate of Carl Joseph Dispenziere Sr. Terms were not disclosed. Dispenziere founded PEP in Los Angeles in 1979 and moved the business to Pomona in 1981. He died in 2011 at the age of 77.

Savalia intends to consolidate his five smaller businesses within PEP’s leased 50,000-square-foot facility during the next six months.“We have an option on additional space” adjacent to the existing Pomona quarters, he said.

Savalia has assumed the duties of CEO and president at PEP.

PEP’s previous CEO, Kevin Rafferty, has committed to help for a few months during the transition and remain available as a consultant, as needed.

Rafferty, a business transition and turn-around specialist, joined PEP in January 2013 as CEO, and says he returned the plastics business to profitability within four months of his arrival.PEP operates 30 injection molding machines — 13 Toyo, 10 Selex, four Arburg, two vertical Engel and one Cincinnati — with a clamping force ranging from 28-390 tons.

Savalia operates a total of 24 presses of 60-825 tons at his other California sites, Honor Plastics and Molding Inc. in Ontario and Kowalski Molding Service Inc. in Riverside.

“My goals are to reach $12 million in 2019 and $15 [million] to $18 million in a couple of years,” Savalia said in a telephone interview.PEP recorded sales of about $6 million for the fiscal year ended Oct. 31, 2018. Savalia projects 2018 sales of about $4.5 million for the five other businesses.

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We can help you choose the right robot system and even design a gripper to match your molds. Contact MSI TEC for more info and to schedule a demo.

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PEP employs 32, with primary end markets in the of automotive, electrical/electronics, appliances and consumer products, aerospace and non-invasive medical industries .

Savalia’s investments are located in San Bernardino, Los Angeles and Riverside counties.In 2017, Savalia acquired Honor Plastics from James and Susan Prior and Pearce Plastics Inc. in Pasadena from the estate of Woodrow Wilson Pearce in March; Precision Plastic Concepts Inc. in Rancho Cucamonga from the estate of Frederick Fitzgerald in July and Kowalski Molding Service Inc. and its machine shop from Stanley Kowalski in November. Savalia had operated the Kowalski facility on a rental basis for two months.In March 2018, he added Target Molds Inc. of Baldwin Park, which does business as Target Molds & Plastics, from Frank and Antoinette Grower.

Savalia has consolidated and absorbed the Pearce, Precision Plastic and Target operations at Honor’s 22,000-square-foot facility in Ontario,

and each of those identities will come under the PEP banner. The Honor and Kowalski business names are also being phased out.

Previously, Pearce had occupied 30,000 square feet, Precision Plastic 10,000 square feet and Target 12,000 square feet. The Kowalski operation continues temporarily in its own facility pending its relocation to Pomona.

Now, Savalia’s operations employ a total of 60 including two mold makers at Honor Plastics and one at Kowalski Molding.

Previously in Southern California, Savalia, 54, held positions as general manager and vice president of Hi-Rel Plastics & Molding Inc. in Riverside and vice president at Tri-Star Plastics and Molding Inc. in Anaheim. Reprinted with permission from the Nov. 12 print issue of Plastics News, copyright 2018 Crain Communications Inc.

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A one day conference where 14 presentations from the industry will discuss the latest developments in the area of medical plastics.Monday, February 4, 2019

Sheraton Park Hotel atthe Anaheim Resort1855 S Harbor BlvdAnaheim, CA 92802

Schedule of Events:

7 – 7:45amRegistration and Continental Breakfast

7:45 – 8am Keynote Speaker

8am – 7pmTabletop Exhibition

8am – 5pm All Day MiniTec(Lunch and Breaks Included)

5 – 7pmCocktail Reception and Poster Session (Included in Registration)

Register to Attend:MiniTec (Advanced): $125 MiniTec (On-site): $175

Info & Online Registration:www.4spe.org/MedPlasticsMinitec

Contact:Ned LeMasterp: 608-402-3268 e: ned.e.lemaster@dupont.com

Ashley Spittlep: 562-217-1377 e: aspittle@ethorn.com

Morning Session on New Materials & DesignKeynote SpeakerVipul Davé – Johnson & Johnson

Polymer excipient technology for extended release of APIGreg Moakes and Don DeMello – Celanese

Materials and process technology solutions for designing connected medical devicesManish Nandi – SABIC

Biodegradable/Resorbable Polymers: Recent Themes and Challenges in the Medical Device Industry Rob Klein – Stress Engineering Services

Friction-reducing Materials for Medical DevicesBob Hergenrother - BioCoat, Inc.

Design Considerations for Medical Plastics with CAE & FEAAlan Wedgewood & Helga Kuhlmann - DuPont

Medical Device Plastics and Adhesives - A Design Approach JoAnne Moody Zeta Scientific LLC

Compounding via Twin Screw Extrusion for 3D FilamentsCharlie Martin - Leistritz

Panel Discussion - Topic to cover Materials and Chemical Resistance to Cleaning

Afternoon Session on Processing & ApplicationsModifications to Medical Cooling and Vacuum Tanks to Minimize Water Issues from Bio-Films, Endotoxins and Pyrogens Bob Bessemer – Bessemer Consulting/ConAir

Considerations for Extruding Water Sensitive PolymersChristian Herrild – Teel Plastics

Scientific Screening Methods for Medical Polymers Demonstrating Compatibility with Drugs and DisinfectantsTom Meehan – Eastman Chemical

Influence of Stabilizers on Property Retention of Thin Wall TubingChris Moran – Compounding Solutions

Miniaturized medicine on the riseDonna Bibber - Isometric Micro Molding

Long-Acting Implants: Design for Durable Drug Delivery Seth P. Forster – Merck

Development of Guidance for the Interconnectibility between Vial Container Closure Systems and Vial Transfer DevicesNaresh Budhavaram – Eli Lilly

Reception and Poster Session(Includes Cocktails and Hors d’oeuvures)

TABLETOP EXHIBITOR OPPORTUNITIES AVAILABLE

Showcase Your Company!

• Registration Fee - $750• Registration includes 1 admission• Company name recognition published

in promotions and on event signage!• Booth setup 7 - 8am; requests for

electricity accepted

SPONSOR OPPORTUNITIES AVAILABLE Company Name Recognition published in

promotions and displayed on signage!

• Corporate: $1000 (includes 2 admissions) • Lunch Sponsor: $500 (2 available)• Breakfast Sponsor: $400 (2 available)• Break Sponsor: $100 (5 available)• Reception Sponsor: $300 (2 available)

4

A one day conference where 14 presentations from the industry will discuss the latest developments in the area of medical plastics.Monday, February 4, 2019

Sheraton Park Hotel atthe Anaheim Resort1855 S Harbor BlvdAnaheim, CA 92802

Schedule of Events:

7 – 7:45amRegistration and Continental Breakfast

7:45 – 8am Keynote Speaker

8am – 7pmTabletop Exhibition

8am – 5pm All Day MiniTec(Lunch and Breaks Included)

5 – 7pmCocktail Reception and Poster Session (Included in Registration)

Register to Attend:MiniTec (Advanced): $125 MiniTec (On-site): $175

Info & Online Registration:www.4spe.org/MedPlasticsMinitec

Contact:Ned LeMasterp: 608-402-3268 e: ned.e.lemaster@dupont.com

Ashley Spittlep: 562-217-1377 e: aspittle@ethorn.com

Morning Session on New Materials & DesignKeynote SpeakerVipul Davé – Johnson & Johnson

Polymer excipient technology for extended release of APIGreg Moakes and Don DeMello – Celanese

Materials and process technology solutions for designing connected medical devicesManish Nandi – SABIC

Biodegradable/Resorbable Polymers: Recent Themes and Challenges in the Medical Device Industry Rob Klein – Stress Engineering Services

Friction-reducing Materials for Medical DevicesBob Hergenrother - BioCoat, Inc.

Design Considerations for Medical Plastics with CAE & FEAAlan Wedgewood & Helga Kuhlmann - DuPont

Medical Device Plastics and Adhesives - A Design Approach JoAnne Moody Zeta Scientific LLC

Compounding via Twin Screw Extrusion for 3D FilamentsCharlie Martin - Leistritz

Panel Discussion - Topic to cover Materials and Chemical Resistance to Cleaning

Afternoon Session on Processing & ApplicationsModifications to Medical Cooling and Vacuum Tanks to Minimize Water Issues from Bio-Films, Endotoxins and Pyrogens Bob Bessemer – Bessemer Consulting/ConAir

Considerations for Extruding Water Sensitive PolymersChristian Herrild – Teel Plastics

Scientific Screening Methods for Medical Polymers Demonstrating Compatibility with Drugs and DisinfectantsTom Meehan – Eastman Chemical

Influence of Stabilizers on Property Retention of Thin Wall TubingChris Moran – Compounding Solutions

Miniaturized medicine on the riseDonna Bibber - Isometric Micro Molding

Long-Acting Implants: Design for Durable Drug Delivery Seth P. Forster – Merck

Development of Guidance for the Interconnectibility between Vial Container Closure Systems and Vial Transfer DevicesNaresh Budhavaram – Eli Lilly

Reception and Poster Session(Includes Cocktails and Hors d’oeuvures)

TABLETOP EXHIBITOR OPPORTUNITIES AVAILABLE

Showcase Your Company!

• Registration Fee - $750• Registration includes 1 admission• Company name recognition published

in promotions and on event signage!• Booth setup 7 - 8am; requests for

electricity accepted

SPONSOR OPPORTUNITIES AVAILABLE Company Name Recognition published in

promotions and displayed on signage!

• Corporate: $1000 (includes 2 admissions) • Lunch Sponsor: $500 (2 available)• Breakfast Sponsor: $400 (2 available)• Break Sponsor: $100 (5 available)• Reception Sponsor: $300 (2 available)

The 2019 SPE Golf Tournament for Education was a huge success. The tournament was held at the spectacular Sierra La Vern country club. The day was gorgeous as the heat wave broke and the temperatures were comfortable. The course was

groomed and ready for our tee off. The course is fair to players. Those who take safe shots are rewarded with good but average results. Those who take more ambitious shots are often rewarded, but an errant shot is punishing. The tee boxes were festooned with sponsor’s signs. We want to give thanks for the sponsors as they make the Scholarships and student admissions to our events possible.

35th annual SPE Golf TournamentJune 21, 2018

Sierra La Vern Country Club

The tournaments are a shotgun start were everyone started at the same time at different holes. Prior to the start, SPE served a continental breakfast. There are free balls at the range and putting greens to sharpen up the eye. The tournaments are a scramble format. This makes each foursome a team. Everyone hits a tee shot. The best ball is used, this continues for each shot of the round. The team with the lowest score wins the event. This year’s winner had a score of -6.

After a pleasurable round, we adjourned to the banquet room where we were greeted with a great lunch with a choice of steak or salmon, cooked to perfection. At the luncheon, we awarded the winners prizes for the event. There is always raffle for great prizes which were donated by players. We then adjourned to go back to the office the take care of any issues of the day. All in all, this was not a bad way to spend a day. What can be better, Golf, good friends, a great lunch and supporting our scholarship program.

We want to thank all the players, Tee sponsors, Raffle donors and the Sierra La Vern Country club for being such great host.

We will do it again next June. See you there.

AbstractFor cold runner molds, the pack and hold times are optimized by conducting a gate freeze study (or gate seal study) where the part weight is recorded as a function of the pack and hold times. When the gate freezes the part weight remains constant with increasing pack and hold times. A second or so is added to the lowest value of time where the part weight stays constant and this number is taken as the total time for the setting of the pack and hold times. However, in hot runner systems or in valve gated systems the gate area always has molten plastic and therefore the above method does not produce acceptable results. A method for optimizing this value in hot runner systems or valve gated systems is proposed based on the Cosmetic and Dimensional Process Window concept that was introduced by the author in an earlier paper. This was followed up with experimental results.

IntroductionThe process of thermoplastic injection molding consists of melting the plastic and injecting it into a mold that set at a lower temperature than the plastic melt temperature. The plastic cools down to take the shape of the cavity and form a part. The part is then ejected out of the mold. During the melting of the plastic pellets the volume of the plastic increases, a homogeneous mass of the melt is formed and this melt is injected into the mold where the volume of the melt reduces as it cools to form the part. It is this reduction in volume (or shrinkage) that determines the final size of the molded part. The final shrinkage is not easily predictable since it is easily influenced on a number of molding parameters. Molding process validations therefore call for a number of procedures to be followed to find the most robust areas of each processing parameter and optimize these parameters.

These validation procedures can be broken up into the 6-Step Study (or the Scientific Molding Studies) and Design of Experiments [1]. The 6-Step Study consists of (i) The Viscosity Study (ii) The Cavity Balance Study (iii) The Pressure Drop Study (iv) The Cosmetic Process Window Study (v) The Gate Seal

Study and (vi) The Cooling Study. The 6-Step studies are done to determine the robust areas of the process for the given physical condition of the mold; its ability to withstand packing pressures, venting efficiency, cooling capability and other features. During the second part of the validation the technique of Design of Experiments is used. The process parameters are varied within the windows determined during the 6-Step Study and the effect of each of these is process parameters is determined. The optimum process is selected based on the analysis.

The complete filling phase consists of three phases: injection, pack and hold. The injection phase, the pack phase and the hold phase make up the filling phase. In the injection phase, the mold cavity is filled with molten plastic at a rate such that the plastic does not cool down to its no-flow temperature before it reaches the end of fill. It is also important that the plastic temperature difference within the filled cavity is not large. Therefore the injection phase is relatively a fast filling phase. If the gate is closed or shut off at the instant when the cavity is completely filled, as this plastic cools down it will shrink causing voids or sinks in the part. To compensate for this shrinkage additional material should be injected into the mold following the injection phase and therefore the gate must still remain open. This is called the packing phase. If the gate freezes off prematurely, then this compensation cannot take place and the parts will result in being underpacked having a visual defect such as sink or loss of surface texture. There is also be an effect on the shrinkage value and without the required amount of plastic in the cavity the shrinkage is higher resulting in an undersized part. The third phase is called the holding phase which starts once the required amount of plastic has been injected into the cavity. When the required amount of plastic has been injected inside the cavity, the molten plastic is still under pressure and can bleed out of the cavity if the pressure is released. Therefore a certain amount of pressure is applied such that no plastic is injected into the cavity but the pressure is sufficient to keep the pressurized plastic inside the cavity. This is called the holding phase. During this phase, the plastic does not get in nor get out of the cavity. The pressure is held till the gate freezes off preventing any flow of the plastic

Suhas Kulkarni, FIMMTECH Inc., Vista, CA, USA

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OPTIMIZATION OF PACK AND HOLD TIMES FOR HOT RUNNER AND VALVE

GATED SYSTEMS IN INJECTION MOLDING

into or out of the cavity. Some molding machines have the option of controlling the packing speed. For this research work the molding machine selected did not have this capability. The topic will be discussed in a future paper.

The end of the injection phase can be controlled either by screw position, injection time, hydraulic pressure or cavity pressure. The screw position control is the most commonly used technique. The end of the pack and hold phases are controlled by time. A typical graph with its variables is shown in Figure 1. In case of cold runner molds, the process of optimization of the pack and hold phases is relatively simple. A graph of Part Weight versus Time is generated. See Figure 2. When the gate freezes off the part weight remains unchanged. The time that is required to freeze off the gate is called the gate freeze time. For additional stability and robustness an additional second or so is added to this value and is used as the setting on the injection molding machine. This would be the total time for the pack and hold phase. In most parts satisfactory results are obtained using a single pressure for pack and hold phases and therefore there is only one setting for pressure and one setting for holding. In some cases the differentiation must be done and the gate seal time above should be an addition of the pack time and the hold time. The author has been researching into the differentiation of the pack and hold phases. Some data has been generated and will be presented in future papers. For the scope of this paper, we will consider that the pack pressures and hold pressure are both of the same value and will use the commonly used terminology and call the two parameters as hold pressure and hold time.

When the mold is a hot runner mold there is a small land in the gate area that will freeze off. Before this land is the hot runner system and therefore the plastic is always molten. On the other side of this land is the cavity wall that is thicker and so is molten during the filling phase. On both sides of this gate the pressure is high enough to keep the plastic flowing (in either direction depending on which side has greater pressure). The absence of the static pressure prevents the gate freeze. Therefore the above technique of gate freeze for cold runner molds does not produce expected results. When the mold is a valve gated mold, a valve opens and closes a pin thus opening or closing the gate. The timing of the valve is controlled by a setting on the controller. A combination of the holding pressure and the timing on the valve gate

determine the part quality. Too little time or pressure could underpack the part whereas too much time or pressure can overpack the part. Therefore in case of a hot runner mold or a valve gated mold the right combinations of time and pressures needs to be found.

The Concept of the Cosmetic Process Window (CPW): The Cosmetic Process Window is defined as the limits of the considered molding parameters between which cosmetically acceptable parts can be molded [1]. The CPW and the related concepts described below are based on the concept of the Molding Area Diagram (MAD) introduced in the Injection Molding Handbook [2]. Dimensions are not considered in the CPW. A bigger cosmetic window assures a robust molding process and increases the chances of achieving the required dimensions with better process capability. See Figure 3 where the two parameters considered are holding pressure and melt temperature. The Concept of the Dimensional Process Window (DPW): The Dimensional Process Window is defined as the limits of the considered molding parameters between which dimensionally acceptable parts can be molded [1]. The DPW is always a subset of the CPW. See Figure 4 that shows the DPW for the same data from Figure 3.

ExperimentalThe plastic material used for the experimentation was Terluran GP22 manufactured by BASF. The mold was a customer supplied mold from Distinctive Plastics, Vista, CA. The mold had 2 identical cavities with a hot runner system with direct gating into the part. The molding machine had a clamping force of 90 Tons with a barrel capacity of 5.5 oz of Polystyrene. The screw diameter was 40 mm. The molded parts were dimensionally measured 2 hours after they were ejected from the mold. The time was sufficient for the parts to achieve thermal stabilization to room temperature and achieve dimensional stabilization. A Mitutoyo drop indicator had the capability of measuring in inches only and had a least count of 0.001 inches or 0.0254 mm. The parts were therefore measured in inches and the measurements were later converted into millimeters. The DOE analysis was done with the help of the Nautilus software from FIMMTECH Inc.

ProceduresA two cavity mold that was in production to mold a screen for a fluid based technology product was chosen for the study. The melt temperatures were set to 230 deg C and the mold temperatures were set to

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40 deg C. The injection speed was optimized via the in-mold rheology study and was set to 90 mm/sec. The shot size and the transfer position were set such that the cavity filled about 97% of final weight in the injection phase. A final profiled slower injection speed of 25 mm/sec was also used to help the consistency to the transfer to the hold phase. The cooling time was set to 20 seconds based on a required cycle time of 40 seconds. The cooling time would need to be optimized once the hold time and hold pressure was established. For the start of this experiment, the hold time and the hold pressure were set to zero. In other words the hold phase was completely absent. The screw charge delay time was set to 7 seconds and the back pressure was set to 6.9 bar. A template to generate a cosmetic process window was prepared. The x-axis corresponded to the holding time and the y-axis corresponded to the holding pressure. Such a template is called a Visual Inspection Template (VIT). A filled out and completed VIT is shown in Figure 5. A red square represents a part with a defect at lower pressures (sink, short, etc.), a red triangle represents a part with a defect on the higher end of the pressures (flash, overpacked parts, etc.) and a green circle represents a part that was cosmetically acceptable.

With the above settings the molding was started. Due to the absence of the hold phase and the shot size and transfer position was set to fill the part only about 97%, the parts that were molded were short. As the first set of sub-experiments the holding time was set at 4 seconds. Starting with a hold pressure value of 27.6 bar (400 psi) parts were molded from 27.6 bar to 96.6 bar (1400 psi) in steps of 13.8 bar (200 psi). The data was input into the VIT as per the guidelines mentioned above. At the holding time setting of 4 seconds all the parts had sink. Similarly, the holding time was increased and tested in the range from 5 seconds to 10 seconds in steps of 1 second and the data was collected and recorded in the VIT. The pressure values tested were from 27.6 to 96.6 bar. The completed VIT is shown in Figure 5. The defect on the lower pressures was sink and on the higher side was flash in the screen area.

This filled out template now represents the Cosmetic Process Window Diagram or CPW diagram for the hot runner mold under consideration.The next step is to establish a process for the required dimensions. Dimensional optimization is done using the technique of Design of Experiments (DOE) [1]. Since DOE requires the parts to be molded at the corners of the process limits, parts molded at these

limits must first be cosmetically acceptable. Therefore a rectangle must be inscribed inside the CPW such that at the corners of this rectangle the molded parts will be cosmetically acceptable. Looking at Figure 6 several such rectangles can be inscribed in the VIT (Figure 5). The holding pressure should pack out the whole part but should never overpack the part or the gate area. A judgment must be made based on the part thickness and flow length to evaluate if during the longer holding times if the plastic is being truly packed out towards the end of fill and/or the thick areas or is it only packing out the gate area of the part. Results from a flow analysis software could help out in such evaluations. In the present case there can be three such windows represented by the numbers 1, 2 and 3. Based on the geometry of the part that was used in this experiment Window 3 was chosen.

Once the CPW was determined, this data is to be used for performing a DOE. To keep matters simplified for understanding the concept of optimization, the holding pressure and the holding time were the only two factors that were studied. A two level DOE for each factor was considered. Standard validation protocols will demand for additional factors such as mold temperature, melt temperature, cooling time and so on. In a previous paper [3] the author has written about the selection of these factors.

Based on the selected CPW (Window 3) the DOE matrix is shown in Table 1. Parts were molded at the 4 settings in Table 1 and were measured for dimensions. The dimensional requirement on this part was for the overall length and was specified at 126.80 +/-0.07 mm. The analysis was carried out with the DOE module of the Nautilus Software. The results are shown in Figure 7 through Figure 10 (pages 8-9).

Results and DiscussionsThe results from the Cosmetic Window studies are shown in Figure 6. Based on these, the DOE limits and experiments were planned. Figure 7 to Figure 10 are the results from the DOE. Figures 7 and 8 show the Dimensional Process Windows for cavity 1 and

Table1: DOE Matrix based on the Cosmetic Process Window

Expt No Hold Time (sec) Hold Pressure (bar)1 10 69.0

2 10 41.43 6 69.04 6 41.4

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2 respectively. Solid green contour lines are used for cavity 1 and dotted contour lines are used for cavity 2. The green lines represent the combination of the setting where the parts are dimensionally acceptable and the red lines are where the parts are not dimensionally acceptable. Dimensional Process Windows inside which the parts will be dimensionally acceptable can now be drawn inside these windows. One must evaluate individual cavities to begin with but must then overlay the two cavities on top of each other to evaluate the Composite Dimensional Process Window [1]. Such a window is shown in Figure 9 for the above experimental data. This figure takes both the dimensions into consideration. Process robustness is the goal of every molder and therefore it is best that the center of the above window (Figure 9) is taken at the process settings. Based on the window, a holding pressure of 55 bar and a holding time of 7.0 seconds was chosen as the process settings. Varying the holding time from 6.2 to 7.5 seconds between 43.5 to 63.5 bar will still produce dimensionally acceptable parts. This is an indication of a robust process and will therefore produce parts not only to specifications but also with improved statistical process capability. Again, several Dimensional Windows are possible here. On molding machines, the extent of pressure variation is higher than time variation and therefore maximizing the pressure window is always preferred [3].

Conclusions and RemarksThe above procedure was described for hot runner molds but can easily be extended to molds with valve gated systems. The procedure remains the same and is in fact slightly simpler since the valve pin shuts off the gate eliminating the true hold phase from the original discussion of the pack and hold phase.

The above mold had gone through an iteration for steel adjustment resulting in an acceptable process window. During the first iteration the mold was incapable to mold parts to dimensional specification consistently. The cosmetic process window was large but the dimensional process window was extremely small. Considering both cavities the molding process was not robust making it statistically not capable either.

There are other parameters that also must be considered for the DOE. To keep matters simple for understanding only two factors and one dimension was considered. Composite dimensional windows for multi-dimensions and cavities must be considered.

Optimization of holding pressure times for hot runner molds has always been an area of trial and error. The

procedure described above is a scientific way of determining the holding pressure and time in case of hot runners and valve gated systems. The procedure also evaluates and demonstrates the robustness of the process and the ability to mold parts consistently. The procedure was simplified to one pressure only as a holding pressure but users must try and apply the technique for optimizing pack and hold pressures. A combination of the concepts of the 6-Step Study, Cosmetic Process Window, Dimensional Process Windows and DOEs must be applied [4]. A future paper will cover some of this as an extension to this paper.

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Figure 1: Speeds, Pressures and Times involved in the Injection, Pack and Hold phases (for a position controlled transfer into pack and hold).

Figure 2: Gate Freeze Study for Col Runner Molds

Figure 3: The Cosmetic Process Window

(Continued on page 9)

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Dimensional Process Window:Holding Time 6.2 to 7.5 secHolding Pressure 43.5 to 63.5 bar

Selected Process Settings:Holding Time 7.0 secHolding Pressure 55.0 bar

AcknowledgementsThe author wishes to thank the staff of Distinctive Plastics of Vista, CA, USA for their constant support during the experimental phase of this research. A special mention is due for Tim Curnutt, President of Distinctive Plastics for his insight on the subject of injection molding during the numerous discussions the author has had with him.

(Continued from page 8)

(Continued on page 10)

Figure 4: The Dimensional Process Window Figure 8: Contour Plot for Cavity 2, Dimension: Length

Figure 5: Visual Inspection Template Figure 9: Composite Contour Plot for Cavity 1 & 2, Dimension: Length

Figure 6: Possible Cosmetic Process Windows

Figure 7: Contour Plot for Cavity 1, Dimension: Length

Figure 10: Dimensional Process Window for Cavity 1 & 2, Dimension: Length

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Clarence’s life was a life lived to its fullest. I first met Clarence in December of 1985 when our church group was having a hay ride and caroling. Clarence brought his son and daughter to the event and we became good friends. He had just gone to work for Team Losi and was looking for an assistant in the Engineering department, Clarence offered me the position. I turned him down the first time because I thought the RC industry was just a fad and would go away. Little did I know that it was world- wide competition. When Clarence offered me the job the second time, I accepted and was never sorry for making the change. Clarence taught me so much about molding and plastics.

Clarence was SPE Southern California Section President 1995-1997. When I lost my mother in 1996 Clarence encouraged me to join SPE to give me something to do and help me move on. He was so right, I took over the Section Secretary

position and we were always busy with not only our branch, we also traveled to Orange County and San Diego to support both branches with their functions.

In 2000 when Team Losi was sold to Horizon Hobby we moved from Chino to Ontario. Clarence was very busy with the Engineering Department solving problems of mold design and best materials to use for their projects. Clarence also went to China and Taiwan for the company and even taught a class in the different materials we needed for our products and how to mold them.

Clarence was always the go to person for engineering problems. Even some of our molders would call him to come to their facility to solve a molding issue. Clarence was always willing to help where needed. In 2001 I was SoCal Section President and served until 2003. Because we worked together Clarence was always there to give me a guiding hand and answer questions when I did not understand protocol of the section. I will always be grateful for his guidance.

I know that everyone who had the opportunity to know Clarence and work with him will have fond memories and stories of their own. Clarence will be missed by all and forgotten by none.

By Doreen Beghtol

Clarence Giles Smith Jr.April 25, 1945 – December 15, 2018

HASCO – the leading internationally agile supplier of metric modular standard components and accessorieswith a large number of innovations fortool and mold making since 1924.

www.hasco.com

HASCO America Inc.270 Rutledge Road, Unit B, Fletcher, NC 28732 USAToll Free 877-427-2662, quotes.america@hasco.com

References1. Kulkarni S, Experimental determination of the

Aesthetic, Dimensional and Control Process Windows using the technique of Design of Experiments in Injection Molding, ANTEC 2009, Society of Plastics Engineers.

2. Rosato Dominic & Rosato Donald, Injection Molding Handbook, 1986, Van Nostrand Reinhold Company, Inc., USA.

3. Kulkarni S, Selection Of Parameters And Levels For Design Of Experiments In The Injection Molding Process Development ANTEC 2011, Society of Plastics Engineers.

4. Kulkarni S, Robust Process Development and Scientific Molding, 2010, Hanser Publications, Germany.

(Continued from page 9)

BASF Plastic AdditivesHoneywell PE WaxHORN FiberglassHuber Flame Retardants and Calcium CarbonateImerys Minerals

INHANCE HDPEKing Industries SilanesNYCO MineralsVertellusZeeospheres Ceramics

HORN, an IMCD company, is your first choice for best-in-class technologies, specialty chemicals and plastic additives. The technical sales experts on its Advanced Materials team serve suppliers and customers with unmatched formulation expertise, innovative problem solving capabilities and superior customer service.

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advanced@ethorn.com • 800.442.4676 • www.ethorn.com

LOCAL INFORMATION ON RESOURCES AND EDUCATION AVAILABLE TO PLASTICS PROFESSIONALS.

1142 S. Diamond Bar Blvd. #926Diamond Bar, CA 91765