## Curve by equation (again)

## Curve by equation (again)

(OP)

Refering to back to a previous thread regarding creating a curve by equation. After sorting out my problems with basic mathmatics I eventually got something similiar to what I was after, however I am a bit confused as to how pro is treating the values in the equations.

If I use microsoft excel to plot the curve according to a set of parameters I get one result, then i use pro with exactly the same equation and parameters I get a differnt result. It is as if the units are different.

Can any body shine any light on this matter

kind regards

Dav

If I use microsoft excel to plot the curve according to a set of parameters I get one result, then i use pro with exactly the same equation and parameters I get a differnt result. It is as if the units are different.

Can any body shine any light on this matter

kind regards

Dav

## RE: Curve by equation (again)

If you could give us a little more background on how you have this setup thus far in Pro/e. I would assume you are using a graph and trajpar to help with the curve?

Best Regards,

Heckler

Sr. Mechanical Engineer

SW2005 SP 2.0 & Pro/E 2001

Dell Precision 370

P4 3.6 GHz, 1GB RAM

XP Pro SP2.0

NIVIDA Quadro FX 1400

o

_`\(,_

(_)/ (_)

Do you trust your intuition or go with the flow?

## RE: Curve by equation (again)

for an explanation of the shape

/* ENTER TOOL STEP OVER

SO = 0.5

/* EMPIRICAL VALUE TO CORRECT SHAPE ERROR

SF = 0.0175

/* ENTER PROFILE ALLOWANCE

PA = 0.1

/* ENTER TOOL CUTTER DIAMETER

CD = 10

/* ENTER SLOT WIDTH

SW = 12.7

/* ENTER NUMBER OF REVOLUTIONS

N = 100

A = ( ( SO * SF ) / 3.141592654 ) / 2

B = ( ( SW - ( 2 * PA ) ) - CD ) / 2

x = ( A * ( t * N * 360 )) - ( B * sin ( t * N * 360 ) )

y = ( B * cos ( t * N * 360 ))

z = 0

The curve is going to act as tool path for milling cutter to follow. If you use the same equations in Excel but remove the 'SF' term, you get what I think is the correct result, however when enter it in pro you get the wrong result. This is why I have added the 'SF' term in the equation for 'A'

Cheers

Dav

## RE: Curve by equation (again)

I don't know if this will help (or if it's even correct).

/* (b > a) PROLATE CYCLOID

/* (b = a) CYCLOID

/* (b < a) CURTATE CYCLOID

/*

/* Curve originates on csys.

/* Extends +x (mainly for Prolate), +y.

/*

/* --------------------------------------------------------------------

ra = 4 /* radial segment a.

rb = 4 /* radial segment b.

/* Describe the reference circle center total translation; e.g. circumference.

c_ref = 2 * PI * ra

/* Describe the position of ref circle center as a function of t.

x_ref = t * c_ref

/* Describe reference circle, radial vector rotation at that (t) point.

ref_angle = 360 * (x_ref / c_ref)

/* Describe the angle with respect to csys.

/* (Initial vector direction is 6 o'clock ref csys.)

angle_wrt_csys = 270 - ref_angle

/* Define point rb x,y with respect to ref circle center (at t).

rbx_ref = rb * cos(angle_wrt_csys)

rby_ref = rb * sin(angle_wrt_csys)

/* Describe point with respect to csys.

rbx = x_ref + rbx_ref

rby = rb + rby_ref /* reference circle origin is x = 0, y = rb.

/* Assign the values.

x = rbx

y = rby

z = 0