difference between up milling and down milling | Up Milling and Down Milling| Basic Milling cutting
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What is difference between up milling and down milling?
What is the up milling?
What are the advantages of up milling?
Why up milling is preferred over down milling?
Milling is one type of conventional machining process primarily for generating flat or stepped surfaces. In peripheral milling, cutting velocity is imparted by rotating the milling cutter about a fixed horizontal axis; whereas, the feed rate is imparted by moving the workpiece (basically worktable) against the rotating milling cutter. Since both cutting velocity and feed rate are vector quantities, so based on their mutual directions, peripheral milling can be classified into two groups—up milling and down milling. Each of them has specific advantages and disadvantages, as illustrated below. Various similarities and differences between up milling and down milling are given in table format in the following sections.
Up Milling Down Milling
In up milling, cutter rotates against the direction of table feed. In down milling, cutter rotates along the direction of table feed.
Chip load on teeth (or uncut chip thickness) increases gradually from zero at the point of engagement to maximum at the point of disengagement. Chip load on teeth (or uncut chip thickness) decreases gradually from maximum at the point of engagement to zero at disengagement.
Here tooth experience gradual loading as contact starts with zero chip load. Here tooth experience impact loading as tooth engages suddenly with maximum chip load.
With horizontal axis milling machine, cutting force in up milling mode is directed upward, and thus it tends to lift off the workpiece from the worktable. Accordingly, rigid and expensive fixture is required for firmly mounting the workpiece. In down milling mode, the cutting force is directed downward, and thus it tends to press the workpiece rather than lift off. So cheaper fixture can be employed.
Thin workpiece samples, if machined using up milling mode, may get distorted due to upward cutting force. Chances of distortion of thin workpiece samples are less with down milling mode if proper support in bottom is provided.
Due to gradual buildup of chip load in up milling, heat generation is also high. So there exists a tendency of chip welding with the teeth. Tendency of chip welding is less in down milling but chip re-deposition on finished surface occurs frequently that may degrade quality of finished surface.
Burr is formed only on unfinished surface ahead of the tool feed; however, majority of such burr is removed in the subsequent passes. Burr is formed at finished surface in opposite side of the tool feed. Thus these burrs are not removed automatically. This leads to degraded cutting quality.
At the beginning of engagement, teeth rub with lay or feed marks on the machined surface. This improves surface finish. No such rubbing action takes place, and thus lay marks remains intact on the machined surface.
Besides improving surface finish, rubbing during engagement may result in undesirable work hardening owing to significant heat generation. Chance of work hardening is minimal with down milling.
In up milling mode, no chipping action occurs on teeth of the cutting tool due to gradual contact. Accordingly, tool wear rate is relatively low. Due to impact loading at engagement, chipping occurs and it may cause notch wear. Thus tool wear rate is high.
___________________________________________________________________________
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Up milling and down milling,Difference between up and down milling,difference between up milling and down milling,difference between up milling and down milling with sketch,up milling operation,up milling,down milling operation,down milling,up milling and down milling,up milling and down milling animation,up milling and down milling difference,up milling and down milling process,milling process,up milling and down milling diagram,learn engineering,ekeeda
#mechanicalmagicmechanicallearningtutorials,
What is difference between up milling and down milling?
What is the up milling?
What are the advantages of up milling?
Why up milling is preferred over down milling?
Milling is one type of conventional machining process primarily for generating flat or stepped surfaces. In peripheral milling, cutting velocity is imparted by rotating the milling cutter about a fixed horizontal axis; whereas, the feed rate is imparted by moving the workpiece (basically worktable) against the rotating milling cutter. Since both cutting velocity and feed rate are vector quantities, so based on their mutual directions, peripheral milling can be classified into two groups—up milling and down milling. Each of them has specific advantages and disadvantages, as illustrated below. Various similarities and differences between up milling and down milling are given in table format in the following sections.
Up Milling Down Milling
In up milling, cutter rotates against the direction of table feed. In down milling, cutter rotates along the direction of table feed.
Chip load on teeth (or uncut chip thickness) increases gradually from zero at the point of engagement to maximum at the point of disengagement. Chip load on teeth (or uncut chip thickness) decreases gradually from maximum at the point of engagement to zero at disengagement.
Here tooth experience gradual loading as contact starts with zero chip load. Here tooth experience impact loading as tooth engages suddenly with maximum chip load.
With horizontal axis milling machine, cutting force in up milling mode is directed upward, and thus it tends to lift off the workpiece from the worktable. Accordingly, rigid and expensive fixture is required for firmly mounting the workpiece. In down milling mode, the cutting force is directed downward, and thus it tends to press the workpiece rather than lift off. So cheaper fixture can be employed.
Thin workpiece samples, if machined using up milling mode, may get distorted due to upward cutting force. Chances of distortion of thin workpiece samples are less with down milling mode if proper support in bottom is provided.
Due to gradual buildup of chip load in up milling, heat generation is also high. So there exists a tendency of chip welding with the teeth. Tendency of chip welding is less in down milling but chip re-deposition on finished surface occurs frequently that may degrade quality of finished surface.
Burr is formed only on unfinished surface ahead of the tool feed; however, majority of such burr is removed in the subsequent passes. Burr is formed at finished surface in opposite side of the tool feed. Thus these burrs are not removed automatically. This leads to degraded cutting quality.
At the beginning of engagement, teeth rub with lay or feed marks on the machined surface. This improves surface finish. No such rubbing action takes place, and thus lay marks remains intact on the machined surface.
Besides improving surface finish, rubbing during engagement may result in undesirable work hardening owing to significant heat generation. Chance of work hardening is minimal with down milling.
In up milling mode, no chipping action occurs on teeth of the cutting tool due to gradual contact. Accordingly, tool wear rate is relatively low. Due to impact loading at engagement, chipping occurs and it may cause notch wear. Thus tool wear rate is high.
___________________________________________________________________________
Welcome to My YouTube Channel
MODI MECHANICAL ENGINEERING TUTORIALS.
This channel is Containing of fundamental concepts of Mechanical engineering.
In some videos passing trick of subjects of engineering, passing tricks for GATE,PSU,UPSC,GPSC etc…. examinations.
Subscribes, like and share
In My Channel Easy explanation about more Mechanical engineering concepts, which are really helps you in your future.So,
Subscription Link: @modimechanicalengineeringt8780
Prof. Mayur S. Modi
Up milling and down milling,Difference between up and down milling,difference between up milling and down milling,difference between up milling and down milling with sketch,up milling operation,up milling,down milling operation,down milling,up milling and down milling,up milling and down milling animation,up milling and down milling difference,up milling and down milling process,milling process,up milling and down milling diagram,learn engineering,ekeeda
5 سال پیش
در تاریخ 1398/12/01 منتشر شده
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