Ulas Yaman

• Professor
• Professor (Associate) at Middle East Technical University

We report on 3D printing of artifacts with a structured, inhomogeneous interior. The interior is decomposed into cells defined by a 3D Voronoi diagram and their sites. When printing such objects, most slices the printer deposits are topologically the same and change only locally in the interior. The slicing algorithm capitalizes on this coherence a...

Two-dimensional curve offsets have a wide application area ranging from manufacturing to medical imaging. To that end, this paper concentrates on two novel techniques to produce planar curve offsets. Both methods, which are based on mathematical morphology, employ the concept that the boundaries formed by a circular structuring element whose center...

For the purpose of generating 2D curve offsets used in 2.5D machining, four new methods based on morphological operations on different mathematical entities are presented in this paper. All of the methods, which lend themselves for parallel processing, exploit the idea that the boundaries formed by a circular structuring element whose center sweeps...

This paper presents a direct command generation technique for digital motion control systems. In this paradigm, higher-order differences of a given trajectory (i.e. position) are calculated and the resulting sequence is compacted via data compression techniques. The overall method is capable of generating trajectory data at variable rates in forwar...

Micro drilling of aerospace alloys is a challenge considering the material properties, geometrical complexities and the technical requirements. Water Jet Guided Laser (WJGL) machining is a novel process used in several industries. The primary advantage of the process is its combination of precision and cooling, which increase the quality in the mac...

Purpose This study aims to thoroughly examine the milling process applied to fused filament fabrication (FFF) parts. The primary objective is to identify the key variables in creating smooth surfaces on FFF specimens and establish trends about specific parameters. Design/methodology/approach In this study, PLA and ABS samples fabricated by FFF are...

This study investigates how varying cell size affects the mechanical behaviour of photopolymer Triply Periodic Minimal Surfaces (TPMS) under different deformation rates. Diamond, Gyroid, and Primitive TPMS structures with spatially graded cell sizes were tested. Quasi-static experiments measured boundary forces, representing material behaviour, ine...

Material extrusion additive manufacturing (MEAM) has revolutionized the production of complex designs while minimizing the amount of effort required due to its simple production pipeline. However, MEAM naturally comes with a well-known trade-off; higher build resolution often tends to enhance the product quality at the cost of a slower build rate....

Path planning algorithms are utilized in various fields to improve the efficiency of the defined tasks. Regarding extrusion based additive manufacturing (AM) technologies, an optimized path performs the same task in less time with higher surface quality and better mechanical properties. This paper proposes a continuous path planning algorithm for d...

This article investigates the mechanical behavior of polyamide and carbon fiber‐reinforced (CFR) polyamide structures produced by Fused Filament Fabrication. CFR improves solid polyamide's tensile strength and modulus by more than 200% and 800%, respectively. The enhancement is highest in the parallel raster due to the alignment of the fibers in th...

Metal Fused Filament Fabrication is an Additive Manufacturing method of manufacturing metal parts by using filaments composed of metal powders encased in plastic binders. It is advantageous for manufacturing parts with complex geometries using a wide range of materials, including stainless steel, copper, tool steel, nickel alloys, and titanium. Whe...

The polymer parts fabricated by Fused Filament Fabrication (FFF) process deteriorated noticeably in terms of dimensional accuracy due to the thermal processes during the fabrication and cooling phases. Commonly, researchers tend to concentrate on modifying the CAD model or fabricating the parts larger than the nominal then post-processing the artif...

Additive Manufacturing (AM) is a rapidly developing set of methods with lots of benefits. This technology promises fast, cheap and lightweight fabrication for the antennas and waveguides. Different AM technologies such as Fused Filament Fabrication (FFF), Stereolithography (SLA), Material Jetting and Powder Bed Fusion are used to fabricate antennas...

In this study, a novel approach is proposed to enhance the performance of the parts optimized by Solid Isotropic Material with Penalization (SIMP) method. SIMP is a topology optimization method that aims the optimum distribution of material in a design domain subjected to predefined loads, constraints and boundary conditions. The method forces ever...

Waterjet-guided laser machining is a novel process used for precision cutting and drilling of various materials and geometries. There are many noise factors in the process affecting the laser beam characteristics, namely the effective cutting length and laser power in the waterjet. Although these variables are mainly set by the laser and waterjet p...

Laser drilling is a preferred method to make cooling holes on gas turbine parts. Although it is a fast process, there are some quality issues. Waterjet guided laser (WJGL) is a hybrid process, in which a laser beam is coupled with and guided through thin cylindrical waterjet. Pressurized water in this novel process provides focusing, cooling and cl...

The paper gives a detailed review of the approaches adopted for embedding information into/onto additively manufactured parts. The primary purpose of this paper is to review all the techniques adopted for embedding information, highlight notable trends and improvements in these works, and provide design and manufacturing pipelines to realize most o...

Despite the rapid growth in the past decade, the industrial adoption of additive manufacturing has not still been achieved due to certain limitations. A recent trend to alleviate its inherent drawbacks is to integrate additive manufacturing with secondary production techniques. Indeed, hybrid additive manufacturing solutions may help overcome the c...

A novel design and manufacturing pipeline for Additive Manufacturing is presented. The architecture of the pipeline is motivated by the observation that the conventional pipeline is unnecessarily complex. Most of the time, only a small set of programming steps suffices for 3D design and manufacture. In particular, the proposed method requires no co...

This article describes the control of a rotary inverted pendulum utilizing on–off-type cold gas thrusters as the actuators, which have high similarities with thruster actuated spacecrafts with slosh dynamics. The study is completed in three phases. Firstly, a Pulse Width Modulator (PWM) design method is utilized to obtain quasi-linear thrust output...

We propose a method for extracting auxetic patterns from meshes for fabrication by modifying the existing mesh primitives directly and fully automatically. This direct approach is novel in the sense that most of the fabrication-oriented surface tiling methods introduce additional primitives, such as curve networks in an interactive semiautomatic fr...

Water jet guided laser overcomes the adverse effects of conventional laser cutting and drilling processes, such as heat-affected-zone, spatter, burr formation, etc. Pressurized water in this novel process provides focusing, cooling and cleaning on the cut region, eliminating undesired side effects of the laser. The process is nowadays used in energ...

In this study, a topologically optimized part is remodeled with microstructures to increase its strength-to-weight ratio. Firstly, the Solid Isotropic Material with Penalization (SIMP) method is applied on the selected part. The SIMP method finds the optimum material distribution in a design domain and creates solid-void formations whose densities...

Laser Micro Jet (LMJ) is a hybrid process combining laser and water-jet. The technology is commonly used for micro drilling operations. A problem of laser drilling is not being able to stop the cutting effect of the laser beam after breaking through the material and causing damage inside the parts. A potential solution is to study the process param...

Within the scope of this study, machine codes are generated to fabricate topologically optimized parts directly, conveyed to the design and fabrication pipeline, utilizing 3 dimensional printers employing Fused Deposition Modeling type of additive manufacturing method. As the additive manufacturing industry advanced, topology optimization methods b...

Dimensional accuracy of parts manufactured by Fused Deposition Modelling (FDM) greatly suffers from the shrinkage problems of the available polymer materials. This paper proposes a constructive idea for resolving the shrinkage issues and explains how shrinkage could be managed by interior geometry of the artifacts fabricated on desktop 3D printers....

Coverage of an area is required for a large variety of robotics and manufacturing applications, such as environment monitoring, home cleaning, search and rescue operations, machining, delivery, additive manufacturing and even for 3D terrain reconstruction. In this work, we present highly flexible algorithms that can be used for coverage and graph t...

Fused filament fabrication technology provides the opportunity to produce complex objects with sophisticated interior features. Here, extruding variable bead widths for desktop 3D printers is presented in order to improve resolution and to decrease the build time. In the proposed method, the cross-section is continuously varied according to the geo...

General design approaches are related with and inspired by natural examples. Since evolution itself pushes beings to their full potentials in the most efficient way, it is important for us to understand, observe and mimic the nature itself. In this study, naturally inspired internal structures are constructed by using hollow Voronoi cells and model...

Additive Manufacturing (AM) facilitates the production of intricate objects despite its weakness in attainable part quality and fabrication speed compared to the conventional manufacturing methods. To alleviate the problems arising as a natural outcome of AM methods, hybrid technologies become viable options by employing concurrent manufacturing pr...

Quick Response (QR) codes have been utilized in various fields of manufacturing after their introduction to the automotive industry. Due to their error correction algorithms, they have advantages over the other coding schemes. Various information regarding the parts can be stored into these QR codes, which are conventionally printed on the labels o...

Modifying the interior structure of the artifacts improves not only the strength of the parts but also the dynamic responses of them which can be tuned according to the resonance frequencies of the mounting platforms. Additive Manufacturing (AM) approaches are the finest solutions for the fabrications of these parts with structured interiors. In th...

This paper proposes a novel approach to generate patterned indentations for different additive manufacturing methodologies. Surface textures have many practical applications in various fields, but require special manufacturing considerations. Beside conventional manufacturing processes, additive processes have also been utilized in the last decade...

Curve offsets are utilized in different fields of engineering and science. Additive manufacturing, which lately becomes an explicit requirement in manufacturing industry, utilizes curve offsets widely. One of the necessities of offsetting is for scaling which is required if there is shrinkage after the fabrication or if the surface quality of the r...

In the scope of this study, an alternative automated method to the conventional design and fabrication pipeline of 3D printers is developed by using an integrated CAD/CAE/CAM approach. It increases the load carrying capacity of the parts by constructing heterogeneous infill structures. Traditional CAM software of Additive Manufacturing machinery st...

An interior design methodology to compensate for the shrinkage in the holes of artifacts fabricated with desktop 3D printers employing fused deposition modeling process is presented in this study. In the conventional way of compensating, the initial geometry is scaled according to the predictive and statistical models so that the critical dimension...

In this study, the Solid Isotropic Material with Penalization (SIMP) topology optimization method is employed on the artifacts via keeping the penalization factor as unity. When the penalization is not carried out, the finite elements of the artifact have intermediate material densities. These density values are then used as the thicknesses of the...

In this study, we propose an Algorithms-Aided Design (AAD) approach to shift the center of gravity of 3D printed artifacts to a predefined location by creating a heterogeneous internal structure utilizing the same type of material. When the conventional design and fabrication pipeline of 3D printers and additive manufacturing machinery is employed,...

This paper presents a novel method for generating image projections required for Digital Light Processing type 3D printer systems where the entire cross-section of the printed object is directly formed via projecting the image onto a vat of photopolymers. The cross-sections (i.e. slices), which are initially represented as bitmap images, are compre...

The latest industrial revolution, Industry 4.0, is encouraging the integration of intelligent production systems and advanced information technologies. Additive manufacturing (AM) is considered to be an essential ingredient in this new movement. In this paper, a comprehensive review on AM technologies is presented together with both its contributio...

This paper presents a new command generation technique titled VEPRO for computer controlled production machinery. In this method, the tool trajectory is described by a high-level scripting language that enables parametric representations of complex work-piece geometries. The interpreted script is then employed to generate the interpolation data req...

Additive manufacturing (AM), in other words 3D printing, is becoming more common because of its crucial advantages such as geometric complexity, functional interior structures, etc. over traditional manufacturing methods. Especially, Fused Filament Fabrication (FFF) 3D printing technology is frequently used because of the fact that desktop variants...

This paper proposes an alternative approach to improve the dimensional accuracy of the holes manufactured with Fused Filament Fabrication desktop 3D printers. As opposed to the state of the art techniques, where they scale the input geometric designs according to their predictive and statistical models, the proposed method modifies the interior of...

This study develops a novel command generation paradigm for desktop fused filament fabrication 3D printers. In the conventional approach, designed artifact in CAD software is saved as an STL file, which is still a de-facto file standard in the field, and then imported into the CAM software of the corresponding 3D printer. After adjusting the printi...

As a part of a “lab-at-home” education paradigm for control engineering courses, this paper proposes (and elaborates) a novel hardware-in-the-loop simulator with 3D animation capabilities. The developed software, which can be tailored to simulate any dynamic systems in non-real-time, is designed to work in conjunction with a control hardware. In th...

This study focuses on an integrated software and hardware platform that is capable of performing (real-time/non-real-time) hardware-in-the-loop simulation of dynamic systems, including electrical machinery, CNC machine tools. In this approach, once the dynamics of the plant to be controlled is defined via C++ language, the resulting code is cross-c...

This paper focuses on a direct command generation technique for Computer Numerical Control (CNC) machine systems. In this paradigm, higher-order differences of a given trajectory (i.e, position) are computed and the resulting data are compacted via data compression techniques. As a part of the command generation scheme, the paper also introduces a...

This paper focuses on a novel command generator for servo-motor drives to be used as an integral part of their motion controllers. The method, which incorporates a new data compression algorithm, is capable of generating trajectory data at variable rates. In this paradigm, higher-order differences of a given trajectory (i.e. position) are first com...

Polymorphic robotic systems, which are composed of many modular robots that act in coordination to achieve a goal defined on the system level, have been drawing attention of industrial and research communities since they bring additional flexibility in many applications. This paper introduces a new polymorphic robotic system, in which the detection...

This paper presents a comprehensive comparison of several real-time motion controller topologies implemented on a field programmable gate array (FPGA). Controller topologies are selected as proportional-integral-derivative controller with command feedforward, sliding mode controller, fuzzy controller, and a hysteresis controller. Controllers and ot...

This study focuses on advanced direct command generation paradigms that can be easily incorporated to modern servo-motor drive systems. As an alternative to conventional methods, two new command generation techniques are proposed in this paper. In the first method, higher-order differences of a given trajectory (i.e. position) are computed and the...

This paper presents an embedded control system course for graduate-student education / research. This course, which is to provide hands-on-experience, employs " lab-at-home " approach where the students are expected to design and implement various embedded control systems at home rather than a formal lab environment. With the utilization of a PC so...

zetçe Bu makalede ayrık zamanlı kontrol teorisi üzerine verilen derslerdeki teorik bilgilerin uygulamaya konulmasına dair bir "Evdeki Laboratuvar" yöntemi dahilinde öğrencilere sunulabilecek, gerçek doğrulukla benzetim gerçekleştiren "Cadmus" adlı yazılım paketi tanıtılmıştır. Öğrenciler sahip oldukları bilgiler ışığında, mikrodenetleyici içeren bi...

In this study, universal motion command generator systems utilizing a Field Programmable Gate Array (FPGA) and an interface board for Robotics and Computer Numerical Control (CNC) applications have been developed. These command generation systems can be classified into two main groups as polynomial approximation and data compression based methods....