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MEC130 > Producing Shapes > Flashcards

Producing Shapes Flashcards

1
Q

What are the 3 types of basic milling?

A

Slab milling
Face milling
End milling

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2
Q

For up milling, what does the smoothness of a generated surface depend on?

A

The sharpness of the cutting edges

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3
Q

What’s broaching used for?

A

To machine internal and external surfaces i.e. holes (circular or irregular) or keyways

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4
Q

Describe the process of face/end milling

A

The cutter is mounted on a spindle having an axis of rotation perpendicular to the workpiece surface

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5
Q

For up milling, what factors contribute to a poor surface finish?

A

Slide-Cut mechanism results in poor surface finish

Chips can also be carried onto the newly machined surface contributing to a poorer (rougher) surface finish

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6
Q

Describe backlash

A

Backlash refers to the “play” or excessive amount of clearance between the machine hand wheel screw and the nut attached to the machine table or slide

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7
Q

Name the processes used to produce shaped parts

A 
Milling
Planing
Shaping
Broaching
Sawing
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8
Q

For slab milling, what is the equation for the allowances for approach?

A

La = ((D^2)/4 - (D/2 - dc)^2)^(1/2)

La = allowances for approach, D = Diameter of cutting tool, dc = depth of cut

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9
Q

For up milling, what are the drawbacks of the sliding mechanism?

A

Sliding action causes work hardening on the material and can dull the cutting edges

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10
Q

For an end mill cutting steel, what should the depth of cut be?

A

No more than 1 half of the diameter of the tool

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11
Q

Describe the broach tool

A

Has multiple teeth, with each tooth standing slightly higher than the previous tooth
Uses a single pass to machine the workpiece
The feed per tooth is the change in height of two successive teeth called rise per tooth (RPT)
Has cutting teeth (made up of roughening teeth and semi-finishing teeth) and finishing teeth

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12
Q

Describe shaping

A

Cutting tool moves across fixed workpiece in one direction

Used to produce parts much like planing but the parts are much smaller

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13
Q

What is the feed of the table (fm) related to and what are its units?

A

Related to the amount of metal each tool removes per minute

inches per min

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14
Q

What is the main downside to down milling?

A

Backlash

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15
Q

What are the methods of producing surfaces for milling (i.e. not categories of milling)?

A 
Up milling (conventional milling)
Down milling
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16
Q

What can a metalworking planer produce?

A

Accurate, flat surfaces

Various cross-sections with grooves and notches along the length of the workpiece

17
Q

What are the 2 construction options for planing machines?

A

Double-housing planer

Open side planer

18
Q

Describe sawing

A

Cutting operation with a blade consisting of many small teeth
Each tooth removes a small amount of material
Unlike broaching uses many passes to finish machining

19
Q

For all milling processes, what is the equation for cutting speed?

A

Ns = Vc / (pi*D)

Ns = Cutting speed, Vc = Cutting Velocity, D = Diameter of cutting tool

20
Q

Describe the process of down milling

A

The cutter rotation is in the same direction as the feed rate
Chips decrease in thickness as the tooth rotates through the workpiece
Teeth engage at a specific point where the depth of cut is at maximum
No slide-cut mechanism so tool life is longer BUT increased load on tooling and machine
Chips are carried away from the cutting surface so cannot impair surface finish
The cutter pulls a workpiece towards itself and pushes the workpiece down onto the table
Cutting force tends to hold workpiece against machining table so lower clamping force is sufficient

21
Q

What is the most common type of construction for a milling machine?

A

Column-knee construction

22
Q

For face/end milling, what’s the overrun equal to?

A

When W < D/2:
Lo = La = (W(D-w))^(1/2)

WhenW >= D/2
Lo = La = D/2

23
Q

For slab milling, what is the equation for cutting time (t)?

A

t = (L + La) / fm

t = cutting time, L = length of cut, La = allowance for approach, fm = feed of the table

24
Q

What’s the general equation for material removal rate (MRR)?

A

MRR = Removed volume / Cutting time

25
Q

Describe the process of up milling

A

The cutter rotates against the feed direction of the workpiece
Chips increase in thickness as the tooth rotates through the workpiece
Depth of cut starts at zero and increases
Tooth initially slides along the surface until the pressure on the material is enough to start cutting
The cutter pushes the workpiece away and lifts it from the table (tends to loosen the workpiece from a holding device, a higher clamping force is required)

26
Q

For all milling processes, what’s the equation for material removal rate (MRR)?

A

Removed volume = L x W x dc
Therefore
MRR = W x fm x dc

L = length of cut, W = width of cut, dc = depth of cut, fm = feed of table

27
Q

What’s an advantage of planing and shaping?

A

Cheap, compared to milling and grinding

28
Q

For face/end milling, what’s the equation for cutting time (t)?

A

t = (L +La +Lo) / fm

L= Length of cut, La = Allowance for approach, Lo = Overrun, fm = feed of the table

29
Q

How are the depth of teeth, land behind cutting edge and the radius of the gullet related to pitch?

A

Depth of teeth: D = 0.4P
Land behind cutting edge: L = 0.25P
Radius of gullet: R = 0.25P

30
Q

What is the depth of cut equal to for broaching?

A

The sum of RPT

31
Q

Describe the process of peripheral/slab milling

A

The axis of cutter rotation is parallel to the machining surface of the workpiece

32
Q

For all milling processes, what is the equation for the feed of the table (fm)?

A

fm = ft x n x Ns

fm = feed of the table, ft = feed per tooth, n = number of teeth, Ns = Cutting speed

33
Q

What are planing and shaping often used for?

A

To produce large dies and other tooling

34
Q

For broaching, define the pitch

A

The distance between 2 successive teeth

MEC130 (8 decks)

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