Plastic Mold Steels
NAK80
Technical Center:
In this section we will feature answers to commonly asked questions. Check
back often, as this page is regularly updated.
International Mold Steel specializes in pre-hardened mold and tool steels
that are considered to be the finest available in the market place today.
Because of their unique and homogenous make-up, deviation in hardness or hard
spots is a thing of the past. When machining these materials it will become
immediately apparent that much faster metal removal rates can be achieved.
Machining
Pre-hardened Mold and Tool Steels for PX5 and NAK55
In a recent independent tool study, it was determined that International Mold
Steel products can be machined up to twice as fast as conventional 30 R.C. P-20
material and still show equal or less cutting tool wear.
The machine used was a heavy-duty vertical milling machine equipped with #50
taper tool holders.
The cutting tool was a 4-inch in diameter and 8-octagon shaped T.I.N. coated
carbide inserts at a positive rake. Cutting depth was .150 inches. At 400
surface feet per minute we were able to cut up to .025 inches per insert or .200
inches per revolution of cutter. Even at this rate we were getting 22 to 25
minutes of 'tool life' before the insert had to be indexed.
Material Removal Rates
Consider this: material removal rate during this time span in approximately 300
pounds of steel. It showed that we could remove a lot of steel with moderate
surface feet but a heavy chip load. Once again, the clean make-up of the
material made this possible.
To Calculate Surface Feed
Surface speed is usually given in feet per minute. It is the distance (in feet)
that the outermost cutting edge of a rotating tool (circumference) covers in the
span of 1-minute.
To understand how this translates into spindle speed, or revolutions per
minute (rpm) that the cutting tool is revolving, review this example:
Example:
Surface feet 400 feet per minute Diameter of cutting tool is 4 inches.
Revolutions per minute (rpm) if cutting tool is ____
Equation:
C = Surface feet per minute (feet) D = Diameter of cutting tool (inches) R =
Revolutions per minute of cutting tool (rpm)
R = (C x 12) = (400 x 12) = 4800 = 382 rpm
(D x Pi) (4 in. x 3.14) 12.56
If you need to know surface feet per minute and the cutter diameter and
spindle speed is known, you will have this equation:
C = Pi x D x R = 3.14 x 4 x 382 =
400 sf.
12 12
To Calculate Chip Load
Chip load is the amount of materials (in .001 inches) that each cutting flute
or cutting insert of a rotating tool removes.
Chip load is calculated by dividing the distance of the table travel or feed
per minute in inches by the spindle speed of the machine. This will give you the
distance the cutter traveled in one revolution. This number is then divided by
the number of cutting flutes or inserts.
Example:
Spindle speed is 450 rpm. Table travel or feed rate is 60 inches per
minute. Number of flutes or cutting inserts is 6.
Equation:
R = Spindle speed (rpm)
I = Number of cutting flutes or inserts
S = Distance of feed rate or table travel in inches.
C = Chip load
| |
( |
S
R |
) |
( |
60
450 |
) |
|
. |
| C = |
= .13333 |
= .0222 |
| |
I |
|
6 |
|
To Calculate Feed Rate
S = C x I x R =
S = .0222 x 6 x 450
To find rpm of spindle or R with chip load and feed rate known:
R = S = 60
= 450 rpm
I x C 6 x .0222
|
