Thermoforming Optimization Leads to Bottom Line Savings for Thermoformers: How to save up to 24% in cost!

Transcription

1 Thermoforming Optimization Leads to Bottom Line Savings for Thermoformers: How to save up to 24% in cost! William Karszes, PhD, OCTAL, Roswell, Georgia Mohammed Razeem, OCTAL, Dallas,TX Jerome Romkey, GN, Chester, Nova Scotia SUMMARY: Thermoforming is the process of forming a flat sheet into a shaped part or parts. The basics are to heat the sheet, form the material and then trim the finished parts away from the unwanted sheet. OCTAL Petrochemicals manufactures polyethylene terephthalate, which when compared to APET, processes faster and requires less thickness to achieve product performance. GN thermoformers of Chester, Nova Scotia have designed a new thermoforming machine (DX-series) for APET trays that increases efficiency and reduces waste. The combination of the new DX machine from GN and PET Sheet from OCTAL, trade name DPET, leads to a potential savings of up to 24%. This is real bottom line potential savings without changing pricing! OCTAL s singular focus on DPET sheet responds to the converging global trends of consumer lifestyles that increasingly demand convenience packaging, and the growing need for effective product merchandising requiring impact packaging. OCTAL; advanced process technology and state-of-the-art converting equipment is used to manufacture DPET sheet. The basis of this new material is to have a polyethylene terephthalate, which processes faster and requires less thickness to achieve product performance. OCTAL has developed a more uniform product meeting the thermoformers demand while maintaining the lowest carbon footprint in the market. GN thermoformers new thermoforming machine (DX-series) for APET trays increases efficiency and reduces waste. How a machine is designed to accomplish these tasks may vary, however, one wants to accomplish these steps in an economical manner to maximize the profitability to the processor. Within this paper we explore two different types of machines. One is distinguished by the heating of the plastic by conduction of heat into the plastic from a heated platen. This process is defined as contact heat method (GN-DX series). The second process is where the heat is introduced into the sheet by electromagnetic waves or radiant heat called the radiant heat method. The source of the radiant heat may be varied and the control scheme is varied between the two processes. GN machines are based on the contact heat method. This paper will not go into the technical details of each process, but is written to compare the economics of the two processes. Also within this study we examine the effects of a specific material DPET (OCTAL) on the economics of the process.

2 The two companies developed cost models, and experiments were carried out in GN laboratories and in field trials to confirm the basis of the cost models. Furthermore, the use of GN s machine and OCTAL s DPET lowers the amount of energy used in the thermoforming process. Thus, the combination of these two new technologies creates huge savings potential for the thermoformers not only in bottom line savings, but also in overall energy efficiency. INTRODUCTION: A new-patented process has been developed by OCTAL Petrochemical to produce APET (amorphous polyethylene terephthalate) sheet. The new process has been created to produce a new sheet specifically for the thermoformer. The new product trade named DPET was trialed in GN laboratory in Chester, Nova Scotia. The new material was tested against RPET and regular APET. The purpose of the tests was to develop a cycle that produced a well-formed part of like clarity. During experiments a new GN machine was also tested (GN s DX series). The test results showed DPET had a faster cycle time, was more efficient and could be run with lower clamping pressure. OCTAL and GN have developed costing models for thermoformed trays. The two models are presented and compared. The models are then used to show savings to the thermoformer when using DPET and GN machines. Based on the costing models up to 24% bottom line savings can be added to thermoformers using the new DX machine and DPET. Moreover, DPET has 2 main advantages; higher speed and also tight tolerance, which allows for lower weight packaging. The cost models allow the processor to explore their own possible saving. Both models lead to the same answers. The GN model allows one to investigate processing cost, investment cost and return on investment. The most important finding of the model is that 50% less waste on GN thermoformer can lower customer total production cost by approximate 12%. The study shows that investment costs plus return on investment is important but not so much as the waste. The OCTAL model treats only the processing cost. Furthermore, thermoformers customers are demanding cost containment while requiring more environmentally friendly products. Thermoformers need to have new innovative technologies not only to contain cost but also to reduce their carbon footprint as legislature points to tougher standards. OCTAL commissioned PIRA (Printing Industry Research Association) to conduct a streamlined comparison of carbon footprint of DPET against APET and rpet. The results of the study are shown in table 1 below.

3 As per study conducted by PIRA for OCTAL; DPET TM has a carbon footprint 27.6% lower than APET and only 0.2% higher than 50 % RPET OCTAL s process for producing DPET is more energy efficient and has the lowest carbon footprint for APET on the market. When compared to APET and rpet, DPET has a carbon footprint 27.6% lower than APET and only 0.2% higher than 50% RPET (50% RPET+50% APET) assuming that no energy is carried on from the post consumer waste. But practically that s not the case. A certain amount of energy is carried on from post consumer waste. In such a case DPET has 20% less carbon footprint than 50% RPET. EXPERIMENTAL PROCEDURE: Rolls of APET, RPET and DPET were tested in the GN laboratory. All materials were 16 mil (or 400 microns) (nominal). The material was formed into trays with a four to one draw ratio. A six-cavity mold was used. The criterion was to develop a DPET cycle time and then optimize the cycle. The criteria were both the relative clarity and formation of the part. A panel of three judged relative clarity and, formation was judged by a trained GN technician. DPET was first trialed using the standard APET cycle time. Preheats and cycle time were then adjusted to optimize the cycle time. The clarity and formation of parts were ranked at each change. Once an optimum cycle was obtained the recipe was noted. In this trial the formation of the part was always good however; the loss of clarity was noted if the temperature/time was pushed beyond optimum. The surface temperature was then measured using temperature strips. The temperature was noted to be approximately 100 o C. The cycle time for DPET was noted to be 4.08 seconds. Contact heat thermoformers generally run slower than radiant heat thermoformers however low waste of contact heat system reduces part cost and material usage. Once optimization was obtained, a 10-minute trial of DPET was run. The material ran without any trouble over this period of time. GN agreed this was adequate time to prove the stability of the material and machine. The machine was left idle for over an hour and the DPET cycle was run again. The machine produced good parts on the second cycle and again had no trouble during the 10-minute run time. As a further test for reproducibility a second roll of DPET was mounted on the machine from a different cycle in the same production lot of DPET. Again the material produced good parts on the second cycle and performed well throughout the cycle test.

4 As a final trial, the original DPET roll was remounted on the machine; the trial was run to determine how fast DPET could be run. The cycle time was reduced to 3.32 seconds with good parts being formed. RPET was then mounted on the machine. The first trial was run at the DPET settings. The resultant parts were well formed, but showed significant haze. The cycle time and temperatures were adjusted to obtain the clearest parts. The clearest parts were obtained when the preheat temperature was reduced and the dwell increased. The overall optimum cycle time for RPET was determined to be 4.43 seconds. The surface temperature was tested and found to be approximately 96 o C. The results of this test showed RPET cannot adsorb heat as fast as DPET and retain clarity. APET was mounted on the machine and optimized per the same procedure as outlined. The results were a cycle time of 4.42 seconds for APET. Again the trial shows APET cannot adsorb heat as fast as DPET and retain clarity. Other trials at GN had been run using 20 mil DPET and the results were essentially the same with DPET running faster than either RPET or APET. The average cycle time will vary with gauge and part configuration. DPET runs consistently 10% faster than the APET and RPET. A trial was run at a commercial thermoformer on a GN machine. Starting with the standard cycle time we improved the cycle time by over 10%. The cycle time was not running at standard at the time of the trial. At the end of the trial we had decreased the cycle time greater than the 10% over standard. The check of the surface temperature at optimum showed a value of between 98 o C and 100 o C. Feedback from customers in the field has overwhelming confirmed the results. Use of DPET on the GN machines will lead to shorter cycle times. GN MACHINE: GN has developed a new thermoforming machine (DX Series), which is more efficient than previous models. The DX series are servo driven, have increased tonnage for cutting longer knife lengths of PET sheet, has adjustable stripping point to assist in reducing cross web scrap and can handle larger rolls of sheet. The new DX thermoformer reduces the cost per part. In conjunction with the DX line GN has also developed a tool specific platen, which can increase cycles per minute by 20 to 30 COST MODELS: Two cost models were developed, one by GN and the other by OCTAL; the two models basically present the same results. More information concerning machine costs is incorporated into the GN machine The aim of this model is to compare three different materials APET, DPET and RPET on GN machines (contact) versus radiant machines. Table 2 represents variables that are common to all materials.

5 Table represents, variables that are used to run the cost model. The above variables are used for the example model in this article. The user has to enter a certain set of data to run the model as shown in table 3. To show an example of how the model works we have taken a case of 2,000,000 trays of dimension 252x110 mm with a gauge or thickness of 250 microns (APET sheet) and a total of 10 trays per cycle. As explained earlier DPET has a gauge control of ±1% and also a 3% more efficiency, which is incorporated in the calculation. In the third field; input, cycles per minute for APET sheet. From test conducted at GN we know that APET runs at cycles per minute. The cycles per minute of other materials are calculated based on test results at GN labs. The user can opt to run the model either on contact machine (GN) or radiant machine. For example purpose we have opted for contact heat. Based on the type of machine the scrap plus waste and energy consumption rows will change. For contact heat the skeletal waste and scrap is 11% else it is 25% and for energy consumption its 6.8 KW else it is 70 KW. The model is based on two contact machines versus one radiant machine; this is to level the throughput of both the machines. An additional process waste of 5% using APET and RPET is included in the model as per test results from GN labs. Other data that need to be entered by the user include cost of labor, cost of raw material, cost of scrap and cost of electricity per Kwh.

6 Screenshot of the model input page, where the user feeds in the variables to run the model. After entering the data in the input fields the model gives an output based on the type of machine opted. (Results for this example is shown in table 4.)

7 If the same model is run for radiant heat the results are as shown in table 5. Screenshot of the output for the model based on the type of machine opted and variables used in the sample model input page. RESULTS: This study is based on models created by GN for their thermoforming machine (DX Series) and OCTAL for their DPET sheet. These models compare GN s contact technology machines versus European radiant heat technology the new GN transport system on the DX line can save 0.13% of material. This reduces scrap and cost of production. DPET is manufactured to a tighter gauge tolerance then all other commercial sheet products. DPET is manufactured to a caliper tolerance of ± 1%. This tight tolerance leads to savings as thinner gauges can be specified. (as shown in figure 1) Additionally it was estimated that tighter caliper leads to 3% higher efficiency during forming and 5% less process waste than its competitors.

8 OCTAL S DPET TM has a caliper control of ± 1% when compared to ± 5% caliper control of competitors. Running the cost model we know that the weight of one 252x 110 mm APET tray weighs gms whereas the same tray in DPET weighs gms. Thus the ± 1% tight tolerance helps in reducing the weight of formed part by about 9%, which results in reducing the cost of total production. The tight tolerance enables uniform heating and cooling of sheet during forming, resulting in faster throughput, reducing process waste, increased efficiency and reduces production hours. Reducing production hours (Figure 2) reduces cost of labor by about 9%. Graph comparing DPET, APET AND RPET on GN s new machine is shown in Figure 3. The graph compares the various costs involved in production of APET, RPET and DPET TM Sheet. The graph clearly indicates that DPET TM will cut cost for thermoformer.

9 GN machines are smaller in size when compared to its competitors. This results in a lower capacity. Therefore to balance the equation we have used TWO GN machine versus one radiant machine in the model. The cost of 2 GN thermoformers is usually comparable to the cost of one European radiant thermoformer. In addition the tooling for GN machines is 25 % - 50% cheaper than radiant machines as shown in Figure 3. Tooling for GN machines is 25 % - 50% cheaper than radiant machines.

10 Figure indicates that DPET can run 8% faster than APET and 7% faster than RPET. The cycle time for DPET, APET and RPET are 4.08, 4.42 and 4.43 respectively. This means that DPET can run 8% faster than APET and 7% faster than RPET as seen in Figure 4. Gn s competitors produce around 6200kilos of scrap whereas GN along with DPET produces only 2,299 Kilos of scrap. Hence new GN machines along with DPET produce about 63% less scrap/waste and reduce cost of electricity by 78% to form parts when compared to radiant machines. This will reduce the cost of raw materials to about 16% as seen in Figure 5.

11 New GN machines along with DPET reduce cost of electricity by 78% to form parts when compared to radiant machines. This will reduce the cost of raw materials to about 16% A total savings of 24 % is achieved when running DPET on GN machine versus APET or RPET on radiant machine. On running the cost models we see that there is a cost savings of $4585.Using DPET, versus RPET, and savings of $4551 when comparing DPET, versus APET on GN machines. This implies that customers can save about 12 % on cost of production. Comparing GN s machine with radiant there is a total saving of about 13%. A cost

12 savings of $10240 is achieved upon running DPET on GN s machines versus APET on radiant machine, and savings of $10,200 when compared to RPET on radiant machine. Hence a total savings of 24 % is achieved as seen in Figure 6. MODEL SUMMARY: Thus it can be concluded that a thermoformer using OCTAL s DPET along with GN s machine would be able to reduce scrap, cost of raw material, cost of electricity, cost of labor, production hours and increase throughput. ENERGY CONSUMPTION: GN s DX machines use 6.8 KWs to run. In the model radiant units use 70 KWs to run. Using the models we find the following comparisons: (Table 2) Comparing energy consumptions when running APET and DPET on GN machine versus radiant machines. The data above is for two GN machines and one radiant machine. This is to match the throughput of both the machines. Results and Discussion: Trials at GN laboratory have shown that DPET can be run faster than APET or RPET. Figure 7 shows the results of experimentation. This data has been confirmed by trial on GN machines run by commercial thermoformers.

13 Comparing cycle times for DPET, APET and RPET on GN s DX machine. Indicates that DPET runs faster. Comparing production hours when running DPET, APET and RPET on GN machines. Faster cycle time reduces production hours

14 DPET can take more heat and retain clarity. This factor is due to the DPET process and the customization by OCTAL for the thermoformer. While APET and RPET can be run at faster cycle times the overall clarity cannot be maintained. If clarity is not an issue then DPET can be run faster than competitive materials and form parts at faster speeds. The new DX series from GN are efficient, and as shown in the cost models the combination of the machine and material lead to a potential of 24% over radiant machines. This savings represents bottom line profit for the processor. Using this combination also saves energy. The GN machine has a 78% energy savings in addition to the 27.6% lower carbon footprint for DPET when compared to APET. ** To obtain copies of cost models please contact Mohammed Razeem - mrazeem@octal.com Jerome Romkey - marketing@gnplastics.com