                                     

02/04/96        SHopcoST version 2.0

Machine Capacity:                                  

The purpose of this document is to provide the user with data
on some of the factors, which determine Machine Capacity and
Machining Time for SHopcoST 2.0. 

The energy required to cut a material is a product of cutting
speed and cutting force. By determining how much cutting energy
is required to remove material, it can be determined at what
horsepower level the machine is functioning. The method for
determining the horsepower level is the power constant for
various materials and conditions. The power constant alone does
not determine the cutting energy, but provides a proven method
for computing the power at the motor.  

The factors which do not influence the Power Constant are:
1. The Cutting Speed.
2. The Depth of Cut.
3. The Cutting Tool Material.

The factors which influence the Power Constant are:
1. The Material Hardness.
2. The Feed Rate.
3. The Rake Angle of the cutting tool.
4. Tool Wear, or the condition of the cutting edge.
5. Chip Breaker.
6. Cutting Fluid. (low cutting speeds)

1. THE MATERIAL HARDNESS:
At present Shopcost version 2.0 includes seven different types of
materials and various Brinell hardness levels.

Plain Carbon Steel- Low, Medium or High carbon content from
80 to 360 Brinell Hardness.

Free Machining Steel- American Iron and Steel Institute values
are given from 1108 to 1151, and their hardness.

Alloy Steels- American Iron and Steel Institute values are given
from 1330 to 8740, and their hardness.

Gray Cast Iron- 100 to 240 Brinell Hardness.
Alloy Cast Iron- 150 to 250 Brinell Hardness.
Tool Steel- 175 to 400 Brinell Hardness.
Stainless Steel 150 to 250 Brinell Hardness.         
  




2. THE FEED RATE:

Feed rates from .001 to .060 are given, and reflect the feed in
inches per revolution for turning or chipload per tooth for
milling.

Example: A turning operation of .018 inches per revolution,
requires the cutting tool to move at .018 thousandths of one inch
per 1 revolution of the part.  

Example: A milling operation of .005 chipload per tooth, will
produce a chip of that given thickness, depending on the feedrate
in inches per minute. Chip thickness effects the life of the
milling cutter.  


3. THE RAKE ANGLE OF THE CUTTING TOOL:

The rake angle can be disregarded, but with this software, the
rake angle of the tool is based on a positive 14 degrees. Using a
rake angle that is more positive reduces the power required by
one percent per degree. Using a rake angle that is more negative
increases the power required by one percent per degree. 


4. THE TOOL WEAR FACTOR:

The tool wear factor comes into to play when you see one of the
two screens in the turning or milling operations:   

  What type of turning operation is it. ?
         
         Finish Turning(lightcuts)
         Normal rough and semi-finish turning
         Extra-heavy duty rough turning
                
  
  What type of milling operation is it. ?

         Slab milling
         End milling
         Light and medium face milling
         Extra-heavy duty face milling
                                  
In both cases, the cutting speed will decrease and the horsepower
requirement will increase, as you go from a Normal or Medium
operation to an Extra-heavy duty operation. Really all it's doing
is allowing a condition for sharp tools or expected tool wear.
Try a few experiments to see what I mean, while programming in
the same values except here.





Behind the scenes: 

If your planning a turning operation, and your inserts have been
indexed or your tooling is sharp, you could Enter 1 for Finish
turning(Lightcuts). By entering 1, you have programmed in the
best possible condition of your tooling, and your cutting speed
will increase slightly, but won't demand more horsepower.  
Try not to use this technique much of the time, because if
you're running a lot of parts, it's best to use an operation
which describes the type of tool wear to be expected from that
operation.  
 

5. CHIP BREAKERS:

Chip breakers may reduce the power needed to cut the same
material, but has not shown to be true or false.


6. CUTTING FLUID:

Some cutting fluids may reduce the power needed at lower cutting
speeds, but could be counter-productive for high-speed
applications. High-speed, high-temperature cutting, tends to
promote better shear flow and thus reduces the cutting force and
power needed. 

                  
Actual Capacity:

Based on the attributes that you give, such as feed, depth of cut
and cutting speed for starting conditions, it will compute how
much cutting energy is needed at the tool, and how much 
horsepower the machine needs, with the following efficiency
rating: 

90% efficiency rating for a direct belt drive.
75% efficiency rating for a back gear drive.
75% efficiency rating for a geared head drive. (middle) 
70% efficiency rating for a oil-hydraulic drive (low)


Behind the scenes:

If you have a gear driven machine that you feel is higher than 75
percent, and closer to 90% efficient, then go with the belt
drive. These values are based on averages only, and may not
reflect the rating of your machine, but usually their close. 

Actual capacity then is the required HP needed to machine the
part, with the values given.   




Available Capacity:

Based on how much horsepower is actually needed to produce the
part, we'll get a relationship between actual and potential
capacities. The difference between what's needed, and what your
machine has to offer, are the available capacities.

Available capacity is the max. machining performance, that your 
motor will allow, for the values given.


Metal Removal Rates:

From the actual and available capacities, we can determine the
rate of metal removal (cu.in.\min). The MRR is shown at the
bottom of each bar graph, just above the HP ratings. Would you
say that MRR has minimum and maximum values?, not always, because
you could over-shoot the capacity of your machine, and end up 
with an actual MRR that's greater than what your machine can
deliver. The MRR values are a range between two capacities, which
are the actual and available respectively.   


Machining Time:

In the final modules of Shopcost, we can compute the Machining
Time for turning or milling, based on the two capacities we've
produced. The purpose of the Machining Time function here is to
utilize the range of our capacities, therefore, Shopcost 2.0 will
only consider the roughing cycle in it's determination for
machining time.

What the Machining Time feature does consider:

1. The least required or actual horsepower needed to machine the  
   part.  

2. The best performance or available capacity that your machines  
   motor can give.

3. The amount of material to be left for finishing.

4. The time it takes to return the tool, feed in and begin        
   another pass, from multiple passes, which are based on the     
   machinists own estimation of a single pass. 
            
    
                                      







What the Machining Time feature does not consider:

1. The finish cycle, which would include a tool change,
   on a manual machine, or indexing the tool changer.

2. The time required to index the insert, or sharpen the tool as  
   a result of excessive tool wear or chipping.

3. Drills, Taps, Boring bars or other tools which would require   
   changeover time from a turning or milling operation.

4. The time required to load and unload the parts.


If you want to make any suggestions as to improving Shopcost 
for future use, please feel free to do so. Included with the 
program, are my e-mail and mailing street address. 

Their are several help files built in, but their only in
places that would benefit from them.

Their Hasn't been a discussion about the Round and Bar stock
components of the program, because I hope their self-documenting.

Shopcost 2.0 was written with a combination of "C" "C++" and
Object oriented programming. It stands now at 48 modules and
compiled 63k lines. The project was mostly developed on weekends
using Borland Turbo C++ 3.0., with many sources of information.  


Shopcost 2.0
author: John Scheldroup     
home:   406 E. 9th St. Superior, WI 54880
email:  jschel@aol.com

have a nice day