Error compensation for thermally induced errors on a machine tool Page: 4 of 20
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
Abstract
Heat flow from both internal and external sources and temperature of the
environment create machine deformations, resulting in positioning errors between the tool
and workpiece. If the error can be predicted from a reasonable number of inputs, it can then
be removed in real time by the machine controller. Although much research is currently
being performed in the field of thermal error compensation, there is no industrially accepted
method. There are many possible input-output correlations, and the models can be
established empirically, analytically, or by some combination of these. I have selected a
simple model that linearly relates discrete temperature measurements to the deflection. The
largest barrier to the success of this type of model is how to (1) locate the temperature
sensors and (2) determine the number of required temperature sensors so the model is
robust enough to perform under varying operating conditions. This research develops a
method to determine the number and location of temperature measurements. The approach
assumes that adequate knowledge of the temperature distribution completely determines the
deflection at any instant in time, so the model is not time dependent. An advantage to this
approach is that warm-up and cool down situations can be represented by the same model
as steady state conditions. Furthermore, the model is based on the analytical solution to
thermally induced deflections.
Introduction
Machine deformation is caused by a varying temperature field throughout the
machine due to changing operating conditions. The cause-effect relationship is pictorially
represented in Figure 1. The most complex model first relates the operating conditions to
the imposed heat flows. The heat flows are used to determine the temperature field and the
temperature field is then used to determine deformations. Finite element analysis is a useful
tool to determine the model. However, in practice this method has not been successful
because the output is very dependent on the particular boundary conditions.
Simpler models relate experimentally measured deformations to measured inputs.
The form of the model can be analytically determined or purely empirical. There are three
types of inputs that can be considered: (1) operating conditions, (2) heat flows, and (3)
temperature field. A model based on heat flows or temperature fields measures discrete
locations. Difficulties with these approaches are (1) where to measure the input and (2)
how many inputs are required. The number and location of inputs may vary as the
operating conditions change. A model based on operating conditions is usually very
complex. Furthermore, models using either heat flow or operating conditions as inputs are
time dependent due to the thermal capacitance of the machine structure.
Upcoming Pages
Here’s what’s next.
Search Inside
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Krulewich, D.A. Error compensation for thermally induced errors on a machine tool, report, November 8, 1996; California. (https://digital.library.unt.edu/ark:/67531/metadc689526/m1/4/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.