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Research Papers

Prediction of Cutting Time When Crosscutting Rounds, Pipe, and Rectangular Bar With a Gravity Fed Portable Bandsaw

[+] Author and Article Information
Amrit Sagar

Department of Mechanical Engineering,
Tufts University,
200 College Avenue,
Medford, MA 02155

Thomas P. James

Department of Mechanical Engineering,
Tufts University,
200 College Avenue,
Medford, MA 02155
e-mail: thomas.james@tufts.edu

1Corresponding author.

Manuscript received April 13, 2013; final manuscript received September 10, 2013; published online January 3, 2014. Assoc. Editor: Eric R. Marsh.

J. Manuf. Sci. Eng 136(2), 021001 (Jan 03, 2014) (12 pages) Paper No: MANU-13-1161; doi: 10.1115/1.4025565 History: Received April 13, 2013; Revised September 10, 2013

Portable bandsaws are gaining in popularity for their use on remote jobsites to efficiently cut structural materials such as bar, pipe, and channel. Some of their increased popularity is due to the recent introduction of high watt-hour lithium ion batteries, which has further improved the portability of bandsaws by making them cordless. However, with cordless bandsaws, knowledge of cutting rates becomes more important as battery runtime limits productivity. Unlike industrial cutoff bandsaws that typically have feed rate control, the cutting rate of portable bandsaws is determined by operator applied pressure and gravity. While some research has highlighted the cutting mechanics of bandsaws and related wear processes, there is a lack of progress in the area of predicting cutoff time as a function of sawing parameters, such as applied thrust force, blade speed, workpiece material properties, and geometry of the cross section. Research was conducted to develop and experimentally verify a mechanistic model to predict cutting rates of various cross sectional geometries with a gravity fed portable bandsaw. The analytical model relies upon experimental determination of a cutting constant equation, which was developed for a low carbon steel workpiece cut with an 18 teeth per inch (TPI) blade. The model was employed to predict crosscutting times for steel rounds, squares, and tubes for several conditions of thrust force and blade speed. Model predictions of cutting time were in close agreement with experimental results.

FIGURES IN THIS ARTICLE
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Copyright © 2014 by ASME
Topics: Blades , Cutting , Pipes , Thrust , Band saws
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References

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Figures

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Fig. 1

Portable cordless bandsaw with 18V lithium ion battery (Model 2629-22, Milwaukee Electric Tool Corporation, Brookfield, WI). Tool weight with battery is approximately 4.6 kg (10.1 lb).

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Fig. 2

Two dimensional schematic representation of the bandsawing process. Each tooth cuts one zone on the workpiece by moving one pitch distance, p.

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Fig. 3

Asymmetric cross section showing the difference in lever arms, L1 and L2, from the pivot point, which creates different thrust forces, F1 and F2, along the mean length of the cutting line (dashed line)

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Fig. 4

Asymmetric cross section and related nomenclature used in the derivation of a cutting constant that is dependent on length of cut. The length of the cutting lines (horizontal dashed lines) are defined by the area function g(x), whereas the midpoint of the cutting lines is defined by the area function h(x).

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Fig. 5

Depiction of cross cutting a square bar that is tipped at an angle θ, such that the lines of cut defined by g(x) are constantly changing in length

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Fig. 6

Crosscut section of a pipe showing three cutting zones and the variation in cutting length, L1, L2, etc., as the blade enters the workpiece (zone 1)

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Fig. 7

Portable bandsaw used for verification experiments of predicted cross cutting times. The gravity fed saw rotates freely about a fixed pivot axis. Thrust force applied to the workpiece is controlled by a custom counterweight system.

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Fig. 8

Cutting time for successive crosscuts of a 19.05 mm square steel bar with two 18 TPI blades (thrust force = 71.9 N, blade speed = 1864 mm/s). An initial break-in period is followed by a steady cutting rate.

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Fig. 9

Determination of the cutting constants, K, for 1018 steel bar of various widths (18 TPI Blade, blade speed = 1823 mm/s, thrust force = 49.8 N). Error bars represent plus and minus one standard deviation. The solid line represents the cutting constant equation.

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Fig. 10

Experimental and predicted crosscut times for a steel square bar tipped at an angle θ to the blade. Error bars represent plus and minus one standard deviation from mean crosscut time.

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Fig. 11

Verification of analytical model when crosscutting steel rods (O.D. = 19.05 mm) and pipe (O.D. = 19.05, I.D. = 9.50 mm) for various conditions of blade speed and thrust force: (a) Round bar, speed = 1823 mm/s, (b) round bar, thrust force = 49.8 N, (c) pipe, speed = 1516 mm/s, and (d) pipe, thrust force = 69.8 N

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Fig. 12

The length of cut per tooth changes rapidly as a function of crosscut depth for pipe sections (outer radius = 25.4 mm, wall thickness = 6.5 mm)

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