Influence of Process Parameters on Sheet Lamination Method-based 3D printing: A Review

. Additive manufacturing of carbon fibre reinforced thermoplastic composites” provides us advantages to create lightweight structures with great strength and stiffness over traditionally developed carbon fibre manufacturing techniques, because of enhanced design freedom. This paper is a summary of scholarly sources on Additive manufacturing. This study is a summary of state-of-art techniques this study allows us to identify gaps in the existing research, and also discusses the results of the study and the conclusions derived from it.


Introduction
This study points which are model of FFF based composites using a hot press can greatly improve the tensile and flexural properties of FFF composite parts by decreasing the void content.The action of pressure and heat operation to the manufactured continuous CF/PA6 composites and accomplished to minimize the porous content from 12.3% to 6.0%, which enhanced the flexural characteristics [1,2].The impact of pressure application on microstructural and mechanical properties of previously made composite techniques are deeply studied in this papers.The interdependence of porosity level and the quantity of pressure used has been identified.The increment in application of pressure impacted in lowering the voidity, that also enhanced the stiffness and strength of the final parts [3,4,5].Rapid prototyping of components posess high obstacles namely the less material availability and a high porosity percentage in the manufactured parts.Additive Manufacturing of components at present include less hardness and high porous content compared to fabricated parts with conventional techniques because of the bad compaction of successive layers [6,7].The use of compaction at the time of Rapid prototyping of continuous CFRP, which minimized the porosity content and enhanced the tensile and flexural characteristics of manufactured parts.The void fraction is also minimized from 10.0% to 3.0%, moreover the tensile strength is improved to 24.2% with the application of hot compaction [8].Actually, high pressure and heat application is not practical to store such FFF shaped component.High content of voidness is quite general in Fused Filament Fabrication continuous composites of fibres because of the resulting of the triangular shaped gaps in between the manufactured models [9,10].The papers [11,12,13] mentioned that the shortage of compaction in an FFF process occurred a twelve-percentage porous nature in the middle of the layers by Markforged approach.In discontinuous fibre composites, mechanical properties are not good in comparison with fibre composites (continuous).Blok (2018) accomplished one % of validity for the nylon composites reinforced with short carbon because of less volume fraction.[14,15,16] noticed that the void volume percentage in FFF built fibre of carbon reinforced with ABS parts were shown as sixteen percent and twenty seven percentage without fibrous content.With the increase in fibre content, tensile strength of the parts increased starting at 35 MPa till 65 Mpa.High fibrous content will cause of build failure because of occurrence of nozzle clogging.This explained the effect of trade-off in processability and characteristics in the way of choosing of continuous type or discontinuous type fibres.The characteristics of the components are improved due to the length of the fibres, the processability is decreased in the material [17,18].Previously manufacturing methods utilized autoclave devices or heated rollers to enhance the combination of successive layers that will increase the mechanical performance of components.At present there is no useful pressure applied in rapid prototyped composites [19,20]).By the use of pressure, heat the sheets are melted combinedly for specific polymers.Rather than sintering, it joins the sheets using ultrasonic welding [19].Company is producing the best laminate sheets in India.The reason why I am saying this because, they have huge varieties of decorative laminates.Along with that It is a decorative laminate sheet that is generally used as an overlay over wooden furniture.[21,22].Here the manufactured short ABS reinforced with carbon fibre composites that acquired tensile strengths of 74.0 to 39.05Mpa and stiffness of 2.19 to 5.89Gpa respectively for multiple raster geometries [23,24].The component had 4.18% to 8.54 % void levels.However, for lamination of sheet processes, it can greatly improve the overall strength and component stiffness of the discontinuous fibre reinforced polymer parts by combining the layers.This gives us the stronger inter-laminar bonding, causing small sized air gaps [25].

Sheet Lamination Method
The Sheet lamination method involves manufacturing of sheets of material through bonding.At present "Laminated Object Manufacturing" is used to manufacture polymer composites with fibre reinforcement known as "Selective Lamination Composite Object Manufacturing".This method follows both subtractive approach and additive approach.Sheet reinforcement with fibre are slashed with ultrasonic blade.After that pressure and heat is applied on the sheets to form a bond and finally a 3D object is made.One more method is such as a Inkjet printer is utilized to print a carbon fibre layer and thermoplastic powder is deposited on the substrate layer, At the end sandblaster is used to remove unwanted portion of powder layers.The parts produced by CBAM are ten times more strong compared to those parts manufactured using other 3D printing techniques.[

Procedure
The required sample is fabricated by Sheet Lamination (SL) 3D printing manufacturing technique, similar to Composite Based Additive Manufacturing.The carbon fibre filament is introduced into a 3D printing machine.After a carbon fibre gets fused and becomes liquid it is printed as per the geometric model, a thermoplastic powder (PA2200 nylon powder) is deposited on the first layer.Then, the excessive powder left over is squeezed out, from the cross-section of the printed geometrical shape.Further all the steps of layer have been printed, a heat treatment is carried out to completely observe that all the layers are combined together and powder is fully melted.At the end sandblasting operation is carried out to remove the unnecessary particles in the samples.

Materials
Materials for additive manufacturing are those that can be utilised to create desired items using additive manufacturing technology.Various kinds of materials are offered in the market.We require an technique to manufacture materials by adding layer by layer utilising CAD 3D models for all material types for the industries.This section goes into great length on various materials and their corresponding 3D printing methods.

Process Parameters Influence
The process parameters influence on microstructural properties and mechanical characteristics of CFRP composites has been extensively researched in the literature.The optimal quantity of pressure and temperature application time was shown to greatly reduce void content Within this approach, the process of hot press gives us the required heat, pressure to make small component; nevertheless, the factors chosen determine the end part qualities.The printed layer is coated with powder, this quantity is determined by an amount of ink used.Printing factors can influence the resolution of a desired shape as well as the adherence of the layers.Three criteria were chosen based on these considerations: pressure level, time under compaction and areal density of ink.When compared to other parameters, pressure has the lowest p-value for influencing final component qualities.To maximise both flexural and tensile qualities, the peak amount of pressure is desired.Because of compact layers, the part thickness is reduced, concluding in a larger volume percentage of fiber and lesser porosity.Figure 4 depicts tensile characteristics and porosity are related, the relationship between volume fraction and porosity.Every point depicts one of the experimental data sets.The strength and modulus of elasticity of pieces drop as porosity rises, demonstrating a clear link.The biggest drawbacks of the composite technique in AM is creation of voids within the components .This technique was projected to have a high level of void creation due to the several circumstances that may end up in the air trap inside the nylon powder and layers.

Fig5. Load vs Displacement graphs [19]
As a second key component after pressure, it is discovered as the ink areal density printed has a critical influence in powder volume adhered to substrate.With the rise in droplet number, the powder amount which may be utilised as a mixing agent, ending in thicker finished components.The powder weight for each ink level confirmed this.Fig6.Tensile stress vs Tensile strain [22] However, for a rise in the binder quantity owing a greater droplets might reduce the volume fraction as the finished component volume increases, while the number of fabrics of carbon fibre (reinforcement) employed remains constant.To improve the volume fraction of fibre by forming bond within the layers of fabric, the appropriate ink volume must be determined.For each set the deposition of ink per unit area printing is shown in Fig. 6, determined by dot spacing, size of droplet.It is observed that the settings of printing with low, medium have distinct drops, but use of more ink has large droplets.

Fig10. Porosity content under Scanning Electron Microscope [2]
There will always be some porosity or faults in the finished item, just as there will be in conventionally created materials, and additive manufacturing is no exception.There are a number of post-processing techniques available to seal internal pores and obtain near 100% density in additive manufacturing material, each of which raises the component price while providing minimal advantage to mechanical qualities.Engineers must think critically about real-world component requirements and how detailed characterization of their process and material may be leveraged to achieve the optimal balance of microstructure, characteristics, and cost for a specific application.However, like with traditional materials, the goal is to limit overall porosity and describe the material's behaviour and reaction to that predetermined level, while also providing a procedure to flag any unanticipated fault levels.Developers, such as GE Additive, create themes and parameter settings that achieve 99.5% density in parts on a regular basis, a far cry from what the technology was capable of 15 years ago.The levels of additional porosity are now much lower than in traditional casting procedures.

Results
Table2 : Percentages of Fibre volume fraction and porosity of the samples for each experiment set.

Discussion
The data show that the amount of pressure, compaction time, and areal density of ink printed on the substrate during the CFAM process all have a significant impact on the porosity content and carbon fibre volume fraction of short CFRP composites.Because of the reduced porosity inside the sample, the Fibre Volume Fraction of the samples increases as the amount of pressure and compaction time increases, improving the mechanical properties.Tensile properties were connected to flexural strength and stiffness.

Conclusion
The study clearly suggests that the products manufactured using Sheet lamination method provides greater strength and less porosity.It can be understood that in SLM method printing time will be reduced, but post-processing is necessary,Integration as hybrid manufacturing systems is possible, it involves simple material handling During the layering step, OEM components like as sensors, cables, and so on can be embedded into the part.Sheet lamination process is quite inexpensive due to the usage of basic materials.No need of supporting structures in AM technology equipment.Full-color printing -LOM/SDL can print in all colours.The material condition does not change during or after the procedure in various sheet lamination processes.In general, composites of AM perform poorly when compared to classical composite fabrication.Traditional high-quality composites generally contains much lower than 1% porosity; AM composite production processes must be improved to achieve such densities.Polymers reinforcements with fibres usually employed in additive manufacturing might enhance mechanical qualities while also increasing overall porosity inside the component.The CFAM method achieves a low porosity content (1.5%) and a content of fibre volume (15%).In comparison to injection moulding and Lamination of Nylon(PA2200) components with UTS of 25 MPa to 40 MPa, the inclusion of Nylon-12 with fibres in the CFAM methods enhanced the properties of the material till 97 MPa.balanced property profile of multifunctional material.Nylon powder can be used as a matrix material as it has high stiffness and strength, excellent chemical resistance, good long-term consistency strong selectivity and detail resolution a variety of finishing options.

Fig2:
Fig2: Steps involved in manufacturing [2] Conferences ICMPC 2023 https://doi.org/10.1051/e3sconf/202343001251251 430 Table1 : 3D Printing Material Comparisons [source: Google] Constituent materials combined to form a Composite with different chemical, physical properties.When compared to single material properties, composites have improved mechanical, physical, and chemical properties.Composites have a wide range of applications these days, including manufacturing, electronics, aerospace, biomedical, structural, sporting, wearable, and automobiles, among others.Recent research has been successful in the fabrication of a wide range of composites, and there are many different types of composite materials available, some of which are also commercially available.Particle reinforced composites, natural fiber-reinforced composites, synthetic fiber-reinforced composites, nanomaterial reinforced composites, ionic polymer metal composites, graphene-based composites, and lightweight cellular composite which are most usually world known and also the best examples of composites.