A paper: Cutting, by ‘Pressing and Slicing,’ of Thin Floppyslices of Materials Illust

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kel_aa

Joined
Oct 1, 2004
Messages
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This is a technical paper. There are differential equations and graphs. Like cheese, in the paper title, it'll be an acquired taste. But I'm sure some will like it.

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Cutting, by ‘Pressing and Slicing,’ of Thin Floppyslices of Materials Illustrated by Experiments on Cheddar Cheese and Salami
A. G. Atkins, X. Xu, G. Jeronimidis

Abstract
Why it is easier to cut with even the sharpest knife when ‘pressing down and sliding’ than when merely ‘pressing down alone’ is explained. A variety of cases of cutting where the blade and workpiece have different relative motions is analysed and it is shown that the greater the ‘slice/push ratio’ E given by (blade speed parallel to the cutting edge/blade speed perpendicular to the cutting edge), the lower the cutting forces. However, friction limits the reductions attainable at the highest E. The analysis is applied to the geometry of a wheel cutting device (delicatessan slicer) and experiments with a cheddar cheese and a salami using such an instrumented device confirm the general predictions.

The server is really crappy. But isn't that the general state of the internet these days? I haven't fully absorbed the research material yet, but it was delicious.
http://www.uploading.com/files/M7EOHXS0/Slicing.pdf.html
 
that is the most scientific and constrained use of the word floppy that I have ever seen
 
Thanks for the link, straightforward explanation of the influence of a draw by a simple energy summation. If you look at the total work done then it is obvious that more work from a draw will equal less work needed on the push and it is much easier to frame out a lot of these situations considering energy vs forces.

-Cliff
 
shouldn't this really be highly dependent on edge finish? It seems that the smoother the finish, the less damage done to the cut material. At an extreme, if the edge were microscopically perfect, and very low friction on the draw, the material wouldn't 'see' that the blade was moving, would it?
 
The viewpoint is taken that there is no deformation of the material and that all the energy provided is used to expand the crack infront the the edge. This is how fracture toughness is defined (by the author), the amount of energy necessary to propogate a crack at a constant speed through a material. There are a large number of constraints noted, a more expanded viewpoint has been taken by a number of other authors such as :

"In this paper, based on the analysis of the applied cutting force and the internal stresses in compression cutting, the influence of the material properties (deformation and fracture toughness) on the cutting force is explained. Using this formulation, the authors provided a method to describe the sharpness of a blade and experimentally demonstrated its applicability. Based on the material properties and knife sharpness properties, the required force to realize compression cutting can be predicted."

From :

http://www.actapress.com/PaperInfo.aspx?PaperID=22980

-Cliff
 
"In this paper the theory has been limited to cases where the offcut is very thin and thus floppy, and therefore stores no elastic energy. The analysis may, however, be extended to the situation where the offcut is permanently deformed either by bending, or by shear, and will be presented elsewhere."

Cliff, you do a good and quick summary service. It took me two readings to understand the paper. I guess the other paper elsewhere should be found.

Have you read that specific paper you linked? Are you collecting these sort of papers?

As long as this is a thread on cutting mechanics, here is another:

Knife Slicing of Wood Across the Grain
T.A. Martin, H. McCallion
Abstract
This paper investigates a method for slicing thick pieces of wood across the
grain using a sharp steel knife, and it demonstrates the effectiveness of the knife slicing process at an experimental level. In order to highlight the key parameters facilitating or hindering the thick slicing process, several factors affecting the cutting forces and the cut surface quality have been studied; the blade geometry, the effect of friction, the cutting speed, the boundary load constraints and the wood moisture content. The results indicate that a large proportion of the cutting force may be related to the wedging action of the blade in the wood. Therefore, significant reductions in the cutting energy can be achieved by optimising the blade shape. A simple homogeneous strain
model has been developed which quantifies the cutting forces in terms of the blade angle and the blade surface friction. The results from this theoretical model are compared with the experimental findings and discussed in relation to methods for improving the cutting technique.

http://www.uploading.com/files/T3OGX06C/woodcuttingacross.pdf.html
 
A small reduction in the cutting force is observed when the applied end pressure is
increased. This finding seems contradictory to intuition. If friction plays a major role in
determining the cutting force, one would expect a compressive stress, applied at
infinity, to add to the shear traction on the blade. However, it is not obvious how this
compressive stress is distributed around the blade. It may favour fracture across the
grain and inhibit splitting along the fibres. This phenomenon can only be verified b
developing a better understanding of the stress distribution in the wood.
Click to expand...

funky.....
 
kel_aa said:
Are you collecting these sort of papers?
Click to expand...

Yes, I want to both introduce this type of research into the cutlery community and as well show that a lot of that work has been done in detail by lay people, how of course don't use the same language, but will often explore the same processes and make the same conclusions. For example :

http://www.cutleryscience.com/articles/sharpness_review.html

Of course published papers will attempt to make something seem very complicated but at a basic level physics is very simple and you can summarize anything in a few simple words. If you can't then you don't understand it. The equations and such are just to frame out the implementation and provide the logical support and predict conclusions in a definate manner.

-Cliff
 
I couldn't find a copy of "Modeling Compression Cutting of Biomaterial for Robot Control" but here is a later paper by the same authors.

Cutting, ‘by Pressing and Slicing’, Applied to Robotic Cutting Bio-materials,
Part I: Modeling of Stress Distribution, and
Part II: Force during Slicing and Pressing Cuts

Debao Zhou, Mark R. Claffee, Kok-Meng Lee, and Gary V. McMurray

Part I Abstract

Bio-material cutting, such as meat deboning, is one the most
common operations in food processing. Automating this process
using robotic devices with closed-loop force control has shown
some promise. The control of the force trajectory directly relates
to the internal stress in the material being cut, and must provide
enough force to initiate the cut. The ability to model the stress
distribution in the bio-materials being cut would provide a better
understanding of the influencing factors and help predict the
required cutting force for the design of the cutting mechanism
and for automating the cutting operations. This research is
presented in two parts: part I models the stress distribution when
a blade acts on the bio-material and part II discusses the
principles of biomaterial cutting. Starting with modeling a point
force in the normal and tangential direction on the boundary of a
semi-infinite body, an analytical expression for the stress tensor
has been obtained and simulated using direct integral method.
This paper provides the theoretical basis for explaining the
cutting phenomena and predicting the cutting forces, a topic to
be presented in Part II.

Part II Abstract

The applications of robotics are becoming more and more
common in non-traditional industries such as the medical
industry including robotic surgery and sample microtoming as
well as food industry that include the processing of meats, fruits
and vegetables. In this paper, the influence of the blade edgeshape
and its slicing angle on the cutting of biomaterials are
formulated and discussed based on the stress analysis that has
been presented in Part I. Through modeling the cutting force, an
optimal slicing angle can be formulated to maximize the feed
rate while minimizing the cutting forces. Moreover, the method
offers a means to predict cutting forces between the blade and
the biomaterials, and a basis for design of robust force control
algorithms for automating the cutting of biomaterials.


http://www.sharebigfile.com/file/48294/McMurrayPartI.pdf.html

http://www.sharebigfile.com/file/48298/McMurrayPartII.pdf.html
 
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