A Review on Machine Learning Models in Injection Molding Machines

One of the most suitable methods for the mass production of complicated shapes is injection molding due to its superior production rate and quality. The key to producing higher quality products in injection molding is proper injection speed, pressure, and mold design. Conventional methods relying on the operator’s expertise and defect detection techniques are ineﬀective in reducing defects. Hence, there is a need for more close control over these operating parameters using various machine learning techniques. Neural networks have considerable applications in the injection molding process consisting of optimization, prediction, identiﬁcation, classiﬁcation, controlling, modeling


Introduction
Injection molding is one of the widely used manufacturing processes for manufacturing plastic products [1]. More than 30% of the weight of all plastic products is manufactured using the injection molding process. Besides plastic products, injection molding is mainly used in the automotive, medical, and electronics industries [2]. High production rate and quality are some of the significant advantages of injection molding. e finished products from injection molding require minor finishing operations, which is another advantage [3]. However, the equipment used in injection molding can be quite expensive and sophisticated, so injection molding is not suitable for small-scale production [4][5][6][7].
Injection molding is melting plastic consisting of two types of thermoplastic polymers and thermosetting polymers. e machine injects the pressure onto the mold cavity that fills and solidifies the molten plastic to produce an end product. A whole injection molding process consists of three stages that are filling, postfilling, and mold opening. Some of the interesting properties of plastic are as follows: transparency, ability to make complex sizes and shapes quickly, ability to integrate with other materials easily with an excellent thermal and electrical insulator, lightweight, and anticorrosion. Some of the issues regarding the quality are flow marks, volumetric shrinkage, jetting, weld lines, flash, sink marks, dimension shrinkage variation, and warpage. Recently, neural network and machine learning have grown drastically to solve problems that will possibly occur in the injection molding process to improve its characteristics [8][9][10][11].
Injection molding consists of four stages: filling stage, holding stage, cooling stage, and demolding stage [12]. e material is fed into the injection molding machine and is then heated. e molten material is forced under pressure into the mold and then cooled and hardened inside the mold. It is then ejected out of the mold. e cycle starts from the filling stage and ends at the demolding stage. As shown in Figure 1, a significant portion of the total time is taken by the cooling and recovery stage. Many industries are working on reducing the cooling time by implementing modifications in mold design [13]. Cooling channels in mold helps to reduce the cooling time and decrease the cycle time. More production cycles can be completed by decreasing cycle time, improving the industry's productivity [14]. Injection molding is prone to defects, and some of the common defects are flow lines, weld lines, flash, and sink marks. Injection speed, pressure, and mold design are essential in reducing defects [15]. Most of the defects are caused by improper injection pressure and temperature control. So, control over these parameters is crucial in reducing defects [16]. Traditional methods rely on the operator's expertise and conventional defect detection techniques. ese techniques are unreliable and time-consuming, and hence they increase the lead time and reduce the industries' productivity. So, there is a need for faster monitoring [17]. Implementing machine learning techniques in injection molding can be a better alternative to traditional methods. Although establishing a machine learning network can be expensive, it is profitable in the long run. Machine learning techniques can also be used in optimizing the mold design to reduce the cooling rate and improve the quality of the final product [18][19][20].
Machine learning is an excellent application in the present era, which provides systems the ability to automatically learn and improve from previous training given to them without being explicitly hard coded or programmed. Machine learning explicitly emphasizes the computer program's improvement, which runs the data, using it for their learning.
A significant intention of machine learning is to allow the systems or computers to learn correctly without any human intervention. is review intends to accumulate all the ML models implemented in injection molding.

Injection Molding
Injection molding is a manufacturing process in which molten material is injected into a mold to produce parts ( Figure 2) [22]. Different materials can be molded into desired shapes using injection molding. Some widely used materials are polyvinyl chloride (PVC) (Figure 3), nylon, polyamide, polyester, and acrylic [23]. Except for aluminum and magnesium, almost all metals can be molded using the metal injection molding process. e adherent oxide film on the surface of aluminum and magnesium powder hinders the sintering step in the molding process. Titanium alloys, low alloy steels, cobalt alloys, and stainless steel are widely used in metal injection molding. So, injection molding offers an excellent material choice.
One of the significant advantages of injection molding is its higher production rate [24]. e injection process can be automated, and as a result, the production capacity can be tremendously improved. Usually, injection molding is utilized in the production of smaller parts [25]. More extensive parts required more giant molds and more material to fill the mold, impacting its production rate and efficiency. So, the speed of injection molding depends on the size and complexity of the mold. Labor costs are also drastically reduced due to the automation of injection molding. Another advantage of injection molding is that complex parts can also be molded. us, injection molding offers design flexibility [26]. Injection molding is capable of producing accurate parts, maintaining good dimensional stability. So, as a result, the scrap resulting from production is meager [27]. Since injection molding is mainly used to produce parts from nonbiodegradable materials like plastics and polymers, keeping the scrap rate minimum is essential. e postproduction or finishing work required after production is also low as high dimensional stability is maintained, and surface finish is also good.

Steps in Injection Molding.
e main parts of an injection molding machine are mold, clamping unit, hydraulic system, control system, hopper, cooling channels, injection unit, and drive unit. Injection molding consists of four stages.   Advances in Materials Science and Engineering From Figure 4, in the first stage, the material is heated until it is melted, and it is then injected into a mold under pressure. Material is fed from the hopper and is then melted [28]. A screw is used to transfer the molten material to the injection site. e melted material takes the shape of the mold, and it is allowed to cool to solidify the material [29]. Different methods are used in the preparation of ceramic powders and metallic powders. Carbonyl synthesis, highpressure water atomization, and atomization using gas are standard methods for preparing metal powders. e median particle size obtained from these three processes is shown in Table 1.
e purity of gas atomized powder is superior to those prepared using water atomization [33]. Silicon nitride is obtained by nitriding of silicon, and aluminum oxide is obtained from the leaching of bauxite. Different chemical methods are used in the manufacture of ceramic powders. In general, ceramic powders are finer than metal powders. Finer powders offer better strength in comparison to coarse powders. Binders are used to provide easy separation from mold and retain the shape and strength of the part formed [34]. e majority of the defects occur during the molding or injection phase. Injection pressure, mold temperature, and mold complexity are significant factors that affect the quality of the produced parts, so to reduce defects and improve the   Advances in Materials Science and Engineering 3 quality of the produced parts, reasonable control is required over these parameters. Hardened steel, aluminum, and beryllium-copper alloys are used for manufacturing molds. Steel is used for making molds that require a longer lifespan, but it is comparatively expensive [35]. Ejection gap, cooling circuit design, and allowances are considered while designing the mold. A good surface finish is required in the core, cavity, and runner. Pressure is applied continuously by the screw, which melts the material and injects the molten material into the mold [36]. e screw of the injection molding machine moves forward at a slower rate, and the injection rate is also slower. As the material starts to cool down and solidify, the gate solidifies. After this, the screw of the injection molding machine moves back to its original position [37]. To compensate for shrinkages and ensure the quality of the final product, the holding pressure is maintained for some time after the material in the mold completely solidifies. About 60% of the total cycle time of injection molding is in the cooling phase, as shown in Figure 1 [38]. Cooling channels are provided in the mold design to accelerate the cooling process. Incomplete cooling produces defective parts and is not suitable for the application. e mold release or demolding is the next and final stage in injection molding. When the mold reaches a particular value, the mold is opened by the clamping unit for extracting the final product. Improper molding methods result in uneven surface stress and product deformation. So, the method of the demolding has to be chosen carefully. Stripper plate demolding and ejector demolding are the most widely used demolding methods [39]. When ejector pins or pressurized air cannot remove a part from the mold core, a stripper plate is used. A stripper plate is utilized to push the part from the injection mold core, and complete contact is made between the outer parts of the part and the stripper plate for the injection process. It is more reliable than ejector pins or pressurized air, and it is usually used for thin-wall injection molding. Incomplete molding can increase cycle time, incur high costs, and waste material. After demolding, one cycle of injection molding is completed. Usually, a cycle time can vary from a couple of seconds to a couple of minutes.
Many injection molding processes are widely used for different sets of applications, as shown in Table 2 [33]. e most commonly used injection molding techniques are thermoplastic injection molding and metal injection molding [40]. ermoplastic injection molding plays a vital role in manufacturing products from plastic and polymers, whereas metal injection molding is mainly used for automotive and electronic applications [41]. e other commonly used injection molding processes are gas-assisted injection molding, microinjection, and thin-wall injection molding. ese molding techniques find their use in medical, electronics, and telecommunication fields.
ere are various parameters to consider while choosing the desired injection molding process for a particular application [24]. Some factors to consider are production capacity, product size, design considerations, and cost of operation and materials.
Injection molding also has certain disadvantages [42]. Designing and modeling injection molding components take much time, and it is a complex process. One such complicated process is designing the mold. Mold design is critical to the accuracy and finishing of the final product, and hence much time is invested in this process. So, this leads to a temporary increase in lead time and hence affects the industry's productivity [43]. e equipment and necessary apparatus are pretty expensive compared to other manufacturing processes. So, injection molding is not suitable for small-scale production. Also, there are limitations in the size of the product because it is challenging to manufacture large-size products. High tool cost and design cost are incurred in the manufacture of large-sized products, and hence it is not feasible. So, these are some of the limitations of injection molding.

Defects in Injection
Molding. Injection molding is also prone to defects like any other manufacturing process [44]. e majority of the defects can be mitigated by redesigning the molding process and following design guidelines [45]. Commonly observed defects in injection molding are flow lines, weld lines, flash, and sink marks. e causes and prevention of these defects are listed in Table 3.
From Table 3, it can be seen that most of these defects can be eliminated if we have reasonable control over the operating parameters of the injection molding process. So, to establish a reasonable control on operating parameters, we need to implement specific machine learning techniques into the molding process.
Flow lines are lines or patterns appearing on the final product, and they are usually off-toned in color. Small craters formed in dense areas of the final product are called sink marks [45]. ey are mainly caused by the improper gate and runner design and inadequate cooling time. Condition in which thin surface layers form on the surface of the part due to the presence of contaminants is called surface delamination. Weld lines are similar to flow lines, but they appear similar to a plane than a line when compared to flow lines. ey are caused by improper bonding and low injection pressure and speed [46]. Non-uniform cooling of mold causes warping, creating internal stresses within the part and resulting in distortions. When mold is subjected to high injection pressure and high screw speed, it can degrade the mold's material, which can cause discolorations in the final product. is type of defect is called a burn mark [16]. Traditional methods of inspection of the parts include visual inspection and various destructive and non-destructive tests. However, the main problem with these techniques is that they are inefficient and rely on the operator's experience. It is time-consuming and increases the product's production cycle, affecting the productivity of the industries [47]. Online monitoring can offer a better alternative than conventional methods. It utilizes machine learning techniques in defect detection, and it is more efficient and improves the industry's productivity. e initial cost of an online monitoring system can be pretty expensive, but they are profitable in the long run [48].

Machine Learning Models
Machine learning algorithms are mainly categorized into supervised and unsupervised.

Supervised Learning.
ese algorithms can predict the future or unknown data based on their learning in the previous training. e comparison will be made with the expected output and output that the machine has generated, and then the model can be changed accordingly [49].

Unsupervised Learning.
ese algorithms are quite the opposite of the supervised learning algorithms, where they will not be trained to classify, but these will get inference from a function and describe the unlabelled dataset [50]. e following is the list of widely used machine learning algorithms. e following algorithms can be used for most of the data problems.

Linear Regression.
It is used to predict the values of one variable based on the values based on other variables. A variation in guessing is called a dependent variable. A variable that we use to predict other variables' values is called an independent variable. For example, we use linear regression for understanding that test performance could be predicted based upon the updated timing of how to use tobacco based on smoking time [51].

Logistic Regression.
Logistic regression is a supervised learning set of rules using binary type troubles. ough "regression" contradicts classifying the point of interest here in the phrase, logistic refers to the logistic feature doing the classification assignment on these algorithms. Logistic regression is an easy and productive algorithm, and that is why it is usually utilized as much as binary class obligation. Customer churns, e-mail spamming, and website and advert click prediction are few examples wherein logistic regression offers a practical answer. A base about logistic regression is the logistic function, also known as sigmoid function, which takes into any of the actual value numbers, mapping it to the values between zero and one [52].

Decision Tree.
A decision tree classifier is a nonparametric supervised learning algorithm that can be used for classification and regression. A tree is a piecewise constant approximation.
e main element of the decision tree classifier is its ability to separate intricate, complex, and dynamic decision-making processes into an assortment of less complex decisions and, along these lines, provides a solution that is simpler to interpret [53].
3.6. SVM. Support vector machine intakes data points and generates the maximum marginal hyperplane (MMH) that best separates the tags. A line can be an example of MMH in 2 dimensions which can be called as the decision boundary.
is decision boundary classifies both sides of lines with different classes [54].  Lens, sensors, and optical instruments [33] in-wall injection molding Food packaging, telecommunication applications, and medical applications [33] ermoplastic injection molding Plastic industry, medical, electronics, and automotive applications [33] Advances in Materials Science and Engineering 3.7. Naive Bayes. Naive Bayes is a supervised set of rules used for type responsibilities. erefore, it is known as the Naive Bayes classifier. Naive Bayes assumes that capability is independent of each difference; there is no correlation among features. However, that is not the case in actual lifestyle. e naive assumption about capabilities is not correlated which is why the set of rules is called naive [55].

KNN.
e K-nearest neighbor (KNN) is a nonparametric classification method, which is easy yet powerful in the vast majority of the cases. e algorithm has a significant dependency on the value of K. In practice, for every unseen instance, its K-nearest neighbors within the training set are first of all recognized. From that point forward, the dominant occurring class on this produced neighborhood set of K elements is recognized as a label set for the unseen instance. Predicting was achieved consistently with most of the people classes. Similarly, KNN regressions take mean values about five close factors.
3.9. K-Means. K-means clustering is a vector quantization method that seeks to partition n observations into k clusters, with each observation belonging to the cluster with the closest mean cluster centres, which serves as the cluster's prototype. As a result, the data space is partitioned into Voronoi cells. Squared Euclidean distances are minimised by K-means clustering within cluster variances [57].

Random Forest.
In this machine learning algorithm, a combination of tree predictors is used to predict the output data. ese trees depend on the value of a random vector which is sampled independently and with similar distribution for all the trees in the forest. ese are also called decision forests for classification and regression by constructing a multitude of decision trees at training time [58].
A neural network is a subset of machine learning (ML) and is the core of deep learning. Neural networks are also called artificial neural networks or SNN. is neural network is mainly inspired by the human brain and how the neurons send the signals to each other. e artificial neural networks consist of three components: the input layer, the hidden layer, and finally the output layer. e neural networks mainly rely on the training data for learning and improving their accuracy over time [53,[59][60][61][62].
(1) Single-layer feed-forward network: in the singlelayer feed-forward network, there will be two layers: the input layer and the output layer. In the input layer, computations are not done, so they will not be counted. When different weights are applied to the input nodes, the cumulative effect for each node is taken, and the output layer is formed. (2) Multilayer feed-forward network: the multilayer feed-forward network has a hidden layer and does not directly contact external layers. Having more hidden layers makes the neural network computationally stronger. (3) Single node with its feedback: in the single node with its feedback, the output could be directed back like input to the same layers or the preceding layer node resulting in a feedback network. Recurrent networks are the feedback networks with a closed loop. (4) Single-layer recurrent network: recurrent neural network is a subset of an artificial neural network in which the connections between the nodes form a directed graph with sequence. e neural network will exhibit dynamic behavior for a time sequence. e single-layer recurrent network will use the internal state or memory to process the input sequences. (5) Multilayer recurrent network: the processing output element may be directed to the processing element in the same and preceding layers in the recurrent multilayer network. e same task is performed for all sequence elements, and the output depends on previous computations. e main feature of RNN is the hidden state that captures information about the sequence.

Discussion: ML Implementations and Outcomes
As technology advances, more advanced injection molding types are invented. Some of the examples include metal injection molding and ceramic injection molding. In metal injection molding, powdered metals are fused with alloys of relatively softer metals injected into the mold. Gas-assisted injection molding and water-assisted injection molding are used when the molding parts are very thick and in cases where making hollow parts is necessary to save both cycle time and maintain high product quality. Even existing injection molding processes are also developed to improve performance. For example, in plastic injection molding, new resin formulations are developed to improve the strength and decrease the weight of the product. Many injection molding tools are also developed, which can improve the quality of the products. ese tools use machine learning to improve the precision and accuracy of the final products. e paper's main focus was on the algorithm used, AI model taxonomy, depth layer sizes, training time, testing time, dataset, framework, core language, interface, advantages, and disadvantages. Based on the algorithm used, classification was done if it was a supervised or unsupervised algorithm. Depth layer size is found to determine the number of layers and the number of neurons in the hidden layers for the most optimized result. Dataset size is also considered to determine if the amount of input training data was sufficient or not to the model to give the most accurate results and predictions. e framework and software also considered which software gives the best visualization and correct prediction of the results. It was found that the most used software programs were MATLAB and 6 Advances in Materials Science and Engineering C-MOLD. At last, the advantages and disadvantages of the model proposed in the research works are given to date to help the future models to be analyzed accurately and chosen for the right task based on the requirements met by their advantages and disadvantages. In machine learning, supervised learning ( Figure 5) is when the machine will be trained on input data using labels to be given or predict the output with the required accuracy. e scheme like the supervisor or a teacher first teaches the student how to solve and then makes the student more accurate. After training, the model is then tested on test data, which is a part or subset of the training data in different ratios. Since the machine is already trained, it gives the output more reliability. e method in [63] gave the best output by predicting the perfect time when the machine should be changed to minimize damage cost by getting trained using multiple supervised algorithms, compared with other obtained results from various research works shown in Table 4.
Unsupervised learning ( Figure 6) is a section of machine learning used in many real-world problems in which the labels are not mentioned, and the hidden patterns from the dataset should be found out. e model by itself tries to generate a pattern from all the datasets without supervision. Based on the similarities in the dataset, the machine tries to find common elements and group or cluster those data together. is method is similar to how a normal human being learns on his or her own. e method in [72] shows the best results using unsupervised cluster analysis that finds the molds wearing out and predicts in real-time, and it has an excellent early warning system which predicts before they wear out and cause trouble.
e comparison of such models with other obtained results from various research works is given in Table 5.
Reinforcement learning (Figure 7) is a segment of machine learning where the machine learns the classification of the dataset by the trial and error method like getting rewards for giving correct output and penalties for wrong output to the machine. Using this concept, the model finds how it should be doing a task to maximize rewards and minimize penalties by starting with random data trials. e paper [77] used reinforcement learning by predicting the operating conditions and molding conditions in a short period and performing molding with less consumption power, compared with other obtained results from various research works shown in Table 6. e artificial neural network ( Figure 8) is a segment of artificial intelligence used to simulate or replicate the working of human brain functionality. e ANN consists of processing units that contain inputs and outputs. rough the input, the ANN learns and then produces the required output. e method in [43] gives the best result using ANN by predicting high accuracy and recommending the injection molding process condition on the real and correct time in fix material condition. Table 7 compares research works done in ANN implementation in injection molding.
Backpropagation algorithms (Figure 9) are rules used to guide artificial neural networks (ANNs). It is the most basic block in the neural network. is algorithm can effectively train the neural network by chain rule technique. e backpropagation performs a back pass after every forward pass, which adjusts the model parameter. Here, the method in [13] using the backpropagation algorithm predicts the faults even with less important variables than desired, causing an ANN system to diagnose faults that can be successfully built, compared with other obtained results from various research works shown in Table 8. e hybrid algorithms in the artificial neural network use different algorithms like swarm optimization, greedy gradient, and backpropagation and combine them to get an improved hybrid algorithm for prediction. e research works have shown that using the hybrid algorithm for ANN gave high process reliability. ey are cost-effective due to reduced production costs and high-quality parameters. Here, the method in [18] gave the best result by predicting the parameters ideally at the test run without consuming and wasting many resources, compared with other obtained results from various research works shown in Table 9.
A genetic algorithm ( Figure 10) is a segment of neural network algorithms which are based on nature-inspired property of natural selection. It is a subset of evolutionary computation.
is tedious process follows the Darwinian theory. is algorithm's main advantage is that it is faster and efficient than many traditional methods and has an excellent list of solutions rather than just one solution. In the papers using many parameters and increasing the search space, the genetic algorithms fit the best. e method in [108] gives the best result using genetic algorithms by taking the time needed to determine the starting process parameter for injection molding which could be significantly reduced compared with other obtained results from various research works shown in Table 10.
Recurrent neural networks ( Figure 11) are a subset of neural networks mainly used for their sequential data algorithm in the famous Apple Siri and the Google search by voice. It contains an internal memory due to which it can remember its inputs that help significantly solve the Advances in Materials Science and Engineering  Advances in Materials Science and Engineering

K-MEANS
Un-Supervised Learning APRIORI Clustering Figure 6: Unsupervised learning. Complete data are not fed into models [72] sequential data problems. In the research by Nagorny et al. [113], the recurrent network gave the best result by showing the best performance about the LSTM layer architectures, compared with other obtained results from various research works shown in Table 11.

Summary and Conclusions
For reducing defects in injection molding, control on operating parameters is required [48]. ese operating parameters include injection speed and pressure, mold temperature, and mold design [16]. Traditional defect detection methods are unsuitable for detecting defects and controlling operating parameters. ey mostly rely on the operator's expertise, and they are unreliable at times and are not efficient [47]. We can establish reasonable control over the operating parameters with machine learning techniques and reduce errors. One such application of machine learning techniques is in mold design [14]. e mold design takes a great deal of time, and it is a very complex process. Mold design can affect the quality and strength of the final product. Machine  Figure 7: Reinforcement learning. Easily possible to adjust operating conditions and molding conditions in a short period and perform molding with less consumption power NA [77] Advances in Materials Science and Engineering  Reliably predicts the fiber orientation of the long fiber compression molded composite NA [78] learning can be applied in designing and optimizing mold design. It helps to save a lot of time and preproduction delays [47]. e initial setup cost for implementing machine learning to injection molding can be costly, and it is not suitable in low production applications [2]. However, in high production, applications can be profitable in the long run and improve productivity [118][119][120][121][122][123]. However, in injection molding, there is a constraint on the size of the product. For manufacturing large products, the equipment required is costly and takes a lot of floor space. So, it is not feasible for the manufacture of large products [20,[124][125][126][127].
ese are some of the significant conclusions that can be drawn from the recent research works which may benefit researchers: (1) Machine learning algorithms can be used in injection molding processes, starting from the molding process until the final step stages. (2) Multiple regression equations that were obtained through design of experiments can help the requirement of many train datasets for ANN. (3) Machine learning counters the drawback of the simulation by reducing repetitive processes significantly and reducing substantial computational power, amount, and time, which replaces the need for professionals to interpret results that again help in the implementation. (4) e most commonly used simulation programs were MATLAB and C-MOLD.    [83] 14 Advances in Materials Science and Engineering loading of feedstocks consisting of blends Not able to detect a critical solid loading enabling the attainment of a significant reduction in lead times for a particular feedstock [37] Advances in Materials Science and Engineering 15 Determines the total number as hidden layers; the neuron on every hiding layer was the trial-error process. e selected neural network might be the best and may not be the best. Sensitive studies about a cost relating feature in a product the cost might be challenging. [91] 16 Advances in Materials Science and Engineering  [23] Advances in Materials Science and Engineering  [103] 18 Advances in Materials Science and Engineering  [107] Advances in Materials Science and Engineering (5) Neural network is a perfect model that can be used in the modeling complex interactions among many inputs and outputs along with high prediction with excellent accuracy. (6) e only drawback is the need for a good amount of training data and computational power, time, and cost. (7) e best selection of the hidden layer architecture is not correctly decided because it fails for other applications. (8) A minimal quantity of datasets has been used by many during training. Large datasets should be used to avoid overfitting. (9) e neural networks can be applied for many applications like control, identification, modeling prediction, optimization, monitoring, and classification. (10) ANN can be used to develop a reverse process model effectively. (11) e best predictor was Gaussian process regression with the highest coefficient of determination of 0.995. (12) Even the multiple linear regression is a simple model structure, and it did not perform worst on many datasets.

Advances in Materials Science and Engineering
(13) K-nearest neighbor astonishingly produced results below expectation as compared to rest of the algorithms studied (14) Some other algorithms like neural networks, support vector machine, and decision tree have average predictive quality.

Future Directions
e future directions to guide the researchers ahead are as follows: (1) e future work for this review concentrates on applying the different methodologies in machine learning and neural networks to many different types of machine data comprising contrasting values. In the future, more machine learning techniques may be made which are best suited for a particular injection molding machine for corresponding variables that gives the best results after analyzing with different test datasets. e self-made customized learning model might give a better result for a particular injection molding machine and its parameters. In this manner, future work might be continued on this review. (2) In the future, the model's scalability should be taken into consideration. e study's main aim was to find the prediction models that can find out good and bad   [111] Advances in Materials Science and Engineering 21 Effectively helps engineers determine the final optimal process parameter setting Multiresponse process parameter design problems [112] 22 Advances in Materials Science and Engineering values for injection molding parameters. Many different parameters have been taken into consideration while feeding the models with data, and multiple machine learning models, including supervised and unsupervised learning, have been considered. eir outputs were compared with respect to the best and worst predictions to find the best models that give the most accurate results.
While feeding and training the model, the dataset ratio should be balanced between several good and bad parts. e data size should also be considered; it should not cause overfitting or underfitting, which might result in wrong predictions in the future. (3) For the future, the work can concentrate mainly on integrating more and more factors or parameters affecting the performance of injection molding Few results of reverse mapping deviation which is more significant than 10% machines. It is strongly believed that the optimization strategy is effective. Many materials might be included in the future, and different molds might also be used for the workpieces to give a great application where automated machines are primarily used in the industries. More stress can be given on the parameter optimization and the tolerance design, which are essential activities related to quality; by considering different molds, the scalability of the model increases. (4) In the future, the work corresponding to this review study can prepare or generate various kinds of learning models and algorithms. It includes the complete implementation of machine learningbased models or artificial intelligence-based models or control systems to manufacture different objects using injection molding. It should also involve the validation part of the injection molding machine with different kinds of data (including the edge cases and exceptions) and experiments that make the model complete for usage in terms of prediction and validation of the injection molding machine output using given process control parameters.

Disclosure
Senthil Kumaran Selvaraj and Aditya Raj are first authors.

Conflicts of Interest
e authors declare that they have no conflicts of interest.

Authors' Contributions
Senthil Kumaran Selvaraj and Aditya Raj contributed equally to this study.