Process Plan Solution

Process Plan Homework Solution

Please note that these answers represent only one possible way to manufacture this component

are a variety of feasible and correct answers.

Features:

1. Use a flat end mill to clear out the required material, possibly using larger endmills where

possible (multi

Another option: use peripheral mills to machine away material. Again, multip

used, but the smallest would need to be 0.100”.




Use a flat end mill to clear out the required material, possibly using larger endmills where

possible (multi







possible (multi-tool strategy). Could be done on a manual or CNC three




are a variety of feasible and correct answers. Tool images are from McMaster.com.


tool strategy). Could be done on a manual or CNC three




Tool images are from McMaster.com.













tool strategy). Could be done on a manual or CNC three-axis mill.

Another option: use peripheral mills to machine away material. Again, multiple widths could be

Please note that these answers represent only one possible way to manufacture this component; there


axis mill.

le widths could be

; there

le widths could be

2. Fixture the work piece as shown and use a 3/16” flat end mill to create the slot. Could be done

in a manual or CNC mill.

3. Use a 3/16” center

bottom. You could also spot drill and drill the hole first to remove most of the material, but

would need to finish with the flat end mill.

±0.002”, particularly if usin

Fixture the work piece as shown and use a 3/16” flat end mill to create the slot. Could be done


Use a 3/16” center



±0.002”, particularly if usin



Use a 3/16” center-cutting flat end mill to create the hole s



±0.002”, particularly if using an end mill.


cutting flat end mill to create the hole s



g an end mill.


cutting flat end mill to create the hole s


would need to finish with the flat end mill. Reaming is likely not required to hold a tolerance of

g an end mill.


cutting flat end mill to create the hole since it needs to have a square


Reaming is likely not required to hold a tolerance of


ince it needs to have a square




ince it needs to have a square






4. Use a letter ‘I’ drill (0.272” diameter)to create the hole, after spot drilling! Then, use a 5/16

tap to create the threads. The hole could be cut on a drill press or

done manually.

5. This is a tricky f

need to use a T

approach through either the slot (#2) or the threaded hole (#4, do this before tappi

don’t damage the threads). Because this feature is an odd diameter, you need to use circular

interpolation to create the surface, limiting you to a CNC mill (

to buy a custom tool of the correct diameter and use a

Things to consider if mass producing:

• Create a custom form tool for feature #1

• Create custom tooling (correct diameter) for #5

• Set up a CNC mill to both drill and tap #4

• Consider having a near

features. This would eliminate all of the rough machining and thus reduce overall machining

time. Consider the time and material savings versus the cost of tooling for forging.

Use a letter ‘I’ drill (0.272” diameter)to create the hole, after spot drilling! Then, use a 5/16


done manually.

This is a tricky f

need to use a T






Create a custom form tool for feature #1

Create custom tooling (correct diameter) for #5

Set up a CNC mill to both drill and tap #4

Consider having a near





done manually.

This is a tricky feature to create because it is more than a half

need to use a T-slot cutter (so that the shaft is much smaller than the cutting head) and









Consider having a near-net shape component (i.e. forging) made, then f





eature to create because it is more than a half

slot cutter (so that the shaft is much smaller than the cutting head) and









net shape component (i.e. forging) made, then f





eature to create because it is more than a half














eature to create because it is more than a half-circle. To cut this feature, you




interpolation to create the surface, limiting you to a CNC mill (or you could spend more money

to buy a custom tool of the correct diameter and use a manual mill).





tap to create the threads. The hole could be cut on a drill press or mill, and the tapping can be

circle. To cut this feature, you




or you could spend more money

nual mill).

net shape component (i.e. forging) made, then finish machine the critical




mill, and the tapping can be



approach through either the slot (#2) or the threaded hole (#4, do this before tapping so you



inish machine the critical



Use a letter ‘I’ drill (0.272” diameter)to create the hole, after spot drilling! Then, use a 5/16-24

mill, and the tapping can be


ng so you



inish machine the critical


Comments from grading the submissions:

Feature 1-

Most people suggested using end milling to create this geometry, and realized that an end mill � � 0.1"

is required for the smallest slot. Some people suggested using this same end mill for all of the

machining. While you could technically do this, consider the following:

Material removal rate (MRR) is the product of tool velocity, cut depth, and cut width. Cut width is

proportional to tool diameter, and maximum cut depth is often some fraction of a tool diameter, thus

also proportional. Tool velocity (feed rate) is the product of number of flutes, spindle speed, and feed

per tooth (fpt). Feed per tooth is limited by your tool diameter (i.e. as you get very small tools, the tool

will not support the loads of high fpt). Thus, MRR is a function of three variables that are at least

somewhat dependent on tool diameter and �� .

There is also a trade off to be considered – changing tools costs time (and time = money). Thus, a

balance needs to be struck between MRR of multiple tools and tool changes. In this simple part, you

should realize that using a very small tool will require considerable time to rough out a relatively large

volume and a tool change (or several!) would be warranted.

Feature 2-

The easiest way is to end mill this from the end so that a flat end mill can be used. Second option,

though less ideal, would be to use a ball end mill. Some people suggested drilling a hole at the radius of

the slot, then end milling out the remainder from above (this would require two setups!). Others

suggested the opposite – mill, then drill the radius (but you should never try to use a drill to ‘finish’ part

of a hole that is already half gone – this is what mills are for!).

Feature 3-

Most common mistake was not realizing that this hole has a flat bottom. You can’t use a normal drill to

create this feature!

Feature 4-

Most people got this one. Points were usually lost for not realizing that 5/16 thread requires drilling a

hole smaller than 5/16 – if you drill at full size, there is nothing left to form threads from! I was hoping

you would specify tool sizes, but this is the only question where I docked points for not specifying the

correct size.

If you were actually making this part, you would want to create the threads after machining feature 1,

so that you are tapping a through-hole (avoid blind hole tapping if at all possible).

Feature 5-

See solution. This is a difficult feature to make. Tool path planning is a fascinating geometric problem –

be sure you pay attention to geometry (including collisions!) when you’re choosing tools.

A note from all 5 features:

If you can use a standard vise (with parallel jaws) to hold a part, DO IT! Many people drew exciting and

exotic clamping systems (exiting & exotic = $$$) – there just isn’t any need for these. You didn’t lose

mega-points for this, but I made a note.

Some people need to rotate their minds by either 30 or 90 degrees. A lot of effort went into figuring out

how to hold a hexagon by its corners – recall that the same hexagon has three pairs of parallel faces that

are quite conducive to clamping! A similar amount of effort went into holding the sides of the hexagon

to drill/mill feature 3, while forgetting that the work piece has two nice flat faces at either end.

All of these features can be made on a 3-axis mill, which is what makes it one of the most versatile

machines in the shop. While it may not be optimal (for each feature) to use a mill, consider the benefits

of only needing a single machine to make a part. You didn’t lose points for suggesting a variety of

machines.

Changes if making 100’s

Here, I was looking more for the why’s of a changing process, not necessarily “I’d do steps 1-3-2-4-5”.

Things that got you points:

• Setup reductions

• Custom tooling (absorb the cost of tools over many parts)

• Considering automation (i.e. a CNC mill) (absorb the cost of NC programming over many parts,

coupled with significant labor reduction)

Things that show you are thinking:

• Considering a net shape process

• Considering talking to the designer and figuring out which tolerances they really care about (and

remember this yourself if you are designing something!)

Things that will run your shop out of business:

• Buying a 5 axis machine to do this part. When you buy a five axis machine, you are paying for

precision positioning capability at any angle imaginable. On this part, you only need to precisely

position at three different orthogonal angles. You would be far ahead to use a $30,000 three-

axis HAAS and a $1000 Chic vise that can rotate, versus a $150,000 5 axis machine.

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Process Plan Solution