- TITLE:
DESIGN AND BUILD HIGH PRECISION SLA 3D PRINTER
- AUTHOR(S):
P. Ikonomov, A. Wyman, S. Rawale
- ABSTRACT:
The goal of this research was to build a high precision 3D printer to be able to produce high-
resolution biological structures. We designed, build from scratch, and tested 10 microns resolution
SLA 3D printer to create high precision structures with complex 3D external and internal spaces.
The laser moves on predefined paths on X and Y- axes to cure resin, layer by layer, and then moves
up on the Z-axis for each subsequent layer until the part is produced. The 3D printing process
utilizes a three-axis platform with motion resolution of +/-5 microns and curing laser with diameter
10 microns to enable curing of the resin and building of thin walls and cavities not possible with
other 3D printer technology. Furthermore, this 3D printer increases the accuracy and finished
surfaces of the printed structures. The printing is controlled by CNC system, providing simultaneous
motion in all three axes using stepper motors and preloaded ball screws. We had built several FDM,
SLA, and SLS 3D printers and CNC machines, which experience helped us to achieve a design with
desired high resolution. The 3D printer serves as a foundation for future research to print high
precision parts such as biocompatible bone structures.
- PAGES:
46-
- DOWNLOAD:
DESIGN AND BUILD HIGH PRECISION SLA 3D PRINTER
- TITLE:
INVESTIGATION OF LIGHT INTENSITY OF WIRELESS LED LIGHT CURING UNITS
- AUTHOR(S):
G. Georgiev, Ts. Dikova, V. Panov
- ABSTRACT:
In recent years, LED light curing units (LCUs) have become the main source of light for the
polymerization of resin based composites (RBCs). Various factors can affect the normal functioning
of LCUs, one of which is the battery charge of the wireless models. The aim of this study is to
evaluate the stability of the light intensity of different brands of wireless LED LCUs by measuring it
from a fully charged to a fully discharged battery. For this purpose 10 new different fully-charged
wireless LED LCUs are used. Light intensity is measured with a digital radiometer. For each unit,
the number of curing cycles of 20 s until full battery drop is determined as well as the change in light
intensity with increasing the number of cycles (N) and decreasing the battery life (%). It has been
found that for some devices (LY-C240, SK-L029A, CV-215, OSA-F686C, Xlite4, D-Light Duo) the
light intensity is lower than specified by the manufacturer, which may cause incorrect determining of
the optimal polymerization time. In six of the examined models - Bluephase N, D-Light Duo, LY-
C240, Demi Plus, I-LED 2500 and Elipar Deep Cure S, the light intensity is stable and independent
of the battery life. In the other devices (SK-L029A, CV-215, Xlite4, OSA-F686C), the battery
discharge causes a decrease in light intensity. It can be concluded that dentists have to periodically
measure the light intensity of their LCUs and regularly recharge them, especially in battery-
dependent models
- PAGES:
40-
- DOWNLOAD:
INVESTIGATION OF LIGHT INTENSITY OF WIRELESS LED LIGHT CURING UNITS
- TITLE:
TECHNOLOGICAL FEATURES IN FABRICATION OF Co-Cr DENTAL ALLOY BY SELECTIVE LASER MELTING
- AUTHOR(S):
Tsanka Dikova
- ABSTRACT:
The process of selective laser melting (SLM) is an alternative to the conventional technologies
and can be used to solve many of their problems. During SLM process, an object is produced directly
from a virtual 3D model by melting a metal powder layer by layer using a laser. Incorrectly selected
process parameters can lead to defects decreasing the details quality.
The purpose of the present paper is to analyze the peculiarities of the production of dental Co-Cr
alloy by SLM method and to propose technological regimes for manufacturing of fixed partial
dentures with high density. Four-component dental bridges are used as samples, which are made of
Co212-f ASTM F75 alloy using SLM 125 machine. The accuracy and structure of the specimens are
investigated by OM and SEM. The influence of technological parameters of the SLM process on the
quality of the details is analyzed.
It is found that in order to ensure high accuracy of the constructions, it is necessary to make
changes in the dimensions at the stage of the virtual model, as the corrections are the same on all
axes. Optimal technological parameters - laser power and scanning speed are calculated and
proposed, which provide a dense structure and high mechanical properties of the details,
manufactured of Co-Cr dental alloy by SLM method with the equipment used. The results of this
study will be useful for successful implementation of the SLM equipment in dentistry for production
of high quality Co-Cr constructions.
- PAGES:
34-
- DOWNLOAD:
TECHNOLOGICAL FEATURES IN FABRICATION OF Co-Cr DENTAL ALLOY BY SELECTIVE LASER MELTING
- TITLE:
FINITE-ELEMENT MODELING AND OPTIMIZATION OF THE DEEP ROLLING PROCESS WITH A TOROIDAL ROLLER IN ALUMINUM ALLOY 2024-T3
- AUTHOR(S):
G. V. Duncheva, T. P. Atanasov
- ABSTRACT:
In this article the deep rolling with toroidal roller of cylindrical specimens made of 2024-T3high-
strength aluminum alloy was studied and optimized in terms of the useful residual axial stress
distribution. For this purpose, a planned numerical experiment was conducted, based on developed
3D finite element model of the process being studied. The surface layer constitutive model was
defined in accordance with the flow stress concept. The governing factors are the radius of roller
curvature, the feed rate, and the burnishing force magnitude. The objective functions are the residual
axial stresses in the middle of the surface being treated and the average velue of the residual axial
stresses in a depth of 0.5 mm from the surface. In order to study the objective functions, dispersion
analysis (ANOVA) and regression analysis were performed. Based on the obtained regression
models, the process optimization was conducted. As a result, the governing factors values providing
the maximum intensive and deep zone with useful residual axial stresses were defined.
- PAGES:
3-
- DOWNLOAD:
FINITE-ELEMENT MODELING AND OPTIMIZATION OF THE DEEP ROLLING PROCESS WITH A TOROIDAL ROLLER IN ALUMINUM ALLOY 2024-T3
- TITLE:
COMPREHENSIVE MODEL OF THE MICRO-HARDNESS OF DIAMOND BURNISHED 41CR4 STEEL SPECIMENS
- AUTHOR(S):
V. P. Dunchev
- ABSTRACT:
Diamond burnishing (DB), based on severe plastic deformation of the surface layer, improves
the surface integrity (SI) of metal components and thus, enhances their operating properties. The
micro-hardness is one of the mechanical characteristics of the SI. The increased micro-hardness due
to DB is a precondition for improved wear and fatigue crack resistance of the treated component.
The article presents a comprehensive experimental mathematical model which predicts the micro-
hardness distribution in depth from the surface depending on the diamond insert radius and
burnishing force. The selection of the significant governing factors is based on previous study. The
experimental model is based on a fourth-order one-dimensional polynomial whose variable is the
depth and the coefficients are functions of the two governing factors
- PAGES:
25-
- DOWNLOAD:
COMPREHENSIVE MODEL OF THE MICRO-HARDNESS OF DIAMOND BURNISHED 41CR4 STEEL SPECIMENS
