[Wallerawang]

Hello Guys
Could someone please let me know the difference between the Active and Passive Probes please. I think I understand how the passive ones work with the 3 pins resting on 6 balls (correct me on this if I'm wrong) but how do the Active Probes work?
Thanks
Steve

[David Bord]

One is normally closed(Passive) and the other normally open. The Active is a higher quality and more accurate, however i believe the passive probe is still more accurate than the Tormach. If you are using it infrequently then the passive is a more economical choice, and what I purchased. Its very nice for the $.

As I understand it, the active wont need to have the contacts cleaned after thousands of actuations... think automotive points from old cars.

David

[BAMCNC.COM]

If you own a Passive Probe and a Electronic Tool Setter, you have to invert one of the inputs when you switch back and forth.

Just some info.

[Wallerawang]

Thanks for the information guys - now I am wondering what is the actual switching mechanism is in the active probes - is it some sort of electronic gizmo or something else?
Thanks
Steve

[gjvander]

Active probes often times have strain gauges mounted on a beam. Electronic circuit excites the gauges and monitor threshold change to indicate touch. This method is used by Renishaw probes (not sure if all them use it).

Geo

[gjvander]

Here is a link that shows Renishaw's method:

RENGAGE? technology

[bobeson]

The only significant difference between the Tormach "active" probe and the Tormach passive probe is $1,003.50.
Otherwise, you get some bling, the claim of "sealed electronics", light-up-on-contact LEDs, and a coiled wire.

They both use "kinematic" mounts with fundamentally the same approach to triggering, and the same fundamental susceptibility to "lobing" artifacts from variances in pre-trigger travel as a function of angle-of-approach. I don't know what the fabrication quality differences translate into as far as measurable differences between the two probes, but I'd expect it to be fairly small. I own an older model of the "active" probe, but I only use it for Z-setting now, since it's been abused by software bugs too much for reliable horizontal triggering (bugs in both my Gcode and Tormach's Mach3 code).

If I had a chance to evaluate the two current offerings side-by-side, assuming money was no object (as if!), then I would choose whichever proved to allow me to calibrate it most easily, and to remain in calibration. These factors would easily trump the blinky LED and claims of sealed internals (who uses coolant with a probe in the mill spindle?), regardless of the money. If you do think the extra $1,003.50 needs justification before spending, no way would I get the active probe. Get the passive probe and a Haimer zero-master analog and some extra tips for both, along with spare edge-finders for when all else fails, and you're good to go.

[gjvander]

I agree. The passive probe gives me 0.1 mil repeatability when I do edge finding two or three times in a row. Not sure it makes sense to spend more for the active if the passive is that good already.

Geo

[Wallerawang]

Thanks everyone - I think I'll get the passive version.
Steve

[Wallerawang]

Thanks everyone - I think I'll get the passive version.
Steve

[underthetire]

Active probes often times have strain gauges mounted on a beam. Electronic circuit excites the gauges and monitor threshold change to indicate touch. This method is used by Renishaw probes (not sure if all them use it).

Geo

They have both. Strain or LVDT types use less force to measure, and are more accurate, also much more expensive. It's a good probe for CMMs or really high precision equipment.

[BAMCNC.COM]

I like my cheap Enco led edge finder. I've only used the Tormach passive 1 time, its just sits there, I could zero 5 times manually with the cheap led light indicator before the Tormach one could do it once. (hooking up cable, swapping input because I use the Electronic tool setter the most)

[mike sr1]

I like my cheap Enco led edge finder. I've only used the Tormach passive 1 time, its just sits there, I could zero 5 times manually with the cheap led light indicator before the Tormach one could do it once. (hooking up cable, swapping input because I use the Electronic tool setter the most)

I would like a probe as well, but am wondering how much I would use it. I use an axial dial indicator that rotates in the spindle, seems to work fine for me as I mostly indicate centers of holes, the parts are within a few tenths when machined, it was only 80 bucks or so, much cheaper way to go for me....

[MFchief]

I have found that I use my probe much more than in the past since I constructed a small bracket on the face of the mill. I leave the probe plugged in all the time and it only takes seconds to put it into use. This is easy for me since I don't have any other tools, such as a tool setter, which use the aux socket.

Terry

Attachment 188528

[bobeson]

I use an axial dial indicator that rotates in the spindle, seems to work fine for me as I mostly indicate centers of holes

Ah yes, I forgot to mention how useful a coaxial dial indicator can be also. In fact, I use my Blake co-axial dial indicator probably more than any other X/Y position setting tool, now that I've grown accustomed to planning datums at hole centers.

I'm quite fond of my Blake model, and I've heard others say it compares very well to the generic versions, but I haven't personally used any others, so I dunno what the cost difference buys you. I'd guess, like mike sr1 posted, that you will find even the cheap models quite useful.

In response to mike sr1, I'll say that you will find the most utility with a probe vs. indicator when you are able to take advantage of programmed functions for repetitive locating. For example, I used mine for checking the precise dimensions of rough-cutoff stock in a multi-part fixture, and then could automatically adjust the number of roughing passes I took, too avoid too thin or too thick initial cuts. Also, you can use wizards to perform tricky things, like finding the center of radius of an arc segment, which can be pretty difficult to do with an indicator, depending on the specific details. I grew rather fond of picking off all 3 axis of my vise jaws as a reference datum with one programmed function, but I make do without now that my probe is iffy.

[gjvander]

For example, I used mine for checking the precise dimensions of rough-cutoff stock in a multi-part fixture, and then could automatically adjust the number of roughing passes I took, too avoid too thin or too thick initial cuts.

Would you mind posting a snippet of code to show how you do that?

Geo

[bobeson]

Would you mind posting a snippet of code to show how you do that?

Sure, although I've gotta warn you that it's kinda hard to read. This particular code was picked quickly from a big messy pile of old code; don't rely on it in to be bug-free! Also note that my style of using conditional execution branching causes fits for mach3's preview window, so the display is wonky, but the code executes as intended. This particular part doesn't have the math included for the roughing-cut adjustments, but if you can figure out what the code here is doing, you can figure out how to use the appropriate measurement to implement this pretty easily.

(*** BEGIN COPYRIGHT NOTICE.   {7 text lines, including these two delimiting lines}          ****)
(*** E2K 16-slot fixture wrapper, Copyright 2009, E2K Engineering, Inc. All rights reserved. ****)
(*** Permission granted for limited private reuse of this code in whole or part, provided    ****)
(*** this entire copyright notice remains prominently included in all derived files.         ****)
(*** Republication of this code, or portions thereof, is prohibited without authorization.   ****)
(*** For republishing rights or commercial reuse permission, contact [email protected]        ****)
(*** END COPYRIGHT NOTICE.     {7 text lines, including these two delimiting lines}          ****)


(*** This file is used as a generic template for designs cut on the)
(*** E2K 16-slot fixture )

( This parameter table is used to describe the EPM-1 16-part fixture )
( This fixture consists of two rows [along x] of 8 columns [along y])
( of parts, each held about 1 inch apart, with variances for mount holes, etc.)

(IsHere?  X origin     Y origin     Z origin )
 
(initial table fixture offsets with nominal values)

#800 = -.1  #801 =  0.0  #802 = 0.0   #803 = 1.9
#810 = -.1  #811 =  0.0  #812 = 1.95  #813 = 1.9
#820 = -.1  #821 =  2.0  #822 = 0.0   #823 = 1.9
#830 = -.1  #831 =  2.0  #832 = 1.95  #833 = 1.9
#840 = -.1  #841 =  4.0  #842 = 0.0   #843 = 1.9
#850 = -.1  #851 =  4.0  #852 = 1.95  #853 = 1.9
#860 = -.1  #861 =  6.0  #862 = 0.0   #863 = 1.9
#870 = -.1  #871 =  6.0  #872 = 1.95  #873 = 1.9
#880 = -.1  #881 = 10.0  #882 = 0.0   #883 = 1.9
#890 = -.1  #891 = 10.0  #892 = 1.95  #893 = 1.9
#900 = -.1  #901 = 12.0  #902 = 0.0   #903 = 1.9
#910 = -.1  #911 = 12.0  #912 = 1.95  #913 = 1.9
#920 = -.1  #921 = 14.0  #922 = 0.0   #923 = 1.9
#930 = -.1  #931 = 14.0  #932 = 1.95  #933 = 1.9
#940 = -.1  #941 = 16.0  #942 = 0.0   #943 = 1.9
#950 = -.1  #951 = 16.0  #952 = 1.95  #953 = 1.9


(*********** Here is the main code section of the program ***********)

(**** First we probe the fixture to find out where everything is located ****)

m6 t99 g43 h99
#100 = 0  (the current fixture number is the main index loop variable)
M98 P100 L16 (probe all of the 16 fixtures)
   (*** Now we have a table of parameters giving part fixture offsets ***)

(**** Next switch to 1/4" end mill and rough cut the top half of each part ****)

M6 T3 G43 H3  (select 1/4" 4-flute HSS end mill)
m3 s1450 f14 m8
g04 p4
#100 = 0
M98 P400 L16 (cut top half of each part with 1/4" mill)

(**** Now make pretty finishing cuts with the chamfering tool ****)

m6 t15 g43 h15 (switch to indexed chamfering mill)
m3 s742 f4 m8
g04 p4
#100 = 0
M98 P440 L16 (run chamfer tool once around each part)

(**** That's it for now*****)
m5 m9
g00 z 4

M30


(*************** Here are the subroutines that do all the real work *********)

(****************************************************************************)

O100  (probe for part location and store origin and presence info)

#201 =  [800 + #100 * 10]  (table row index for nominal locations of current part)
#301 =  [600 + #100 * 10]  (table row index for measured results of curent part)
#101 = #[#201 + 1] (get nominal part x left, in fixture coordinates)
#102 = #[#201 + 2] (get nominal part y front, in fixture coordinates)
#103 = #[#201 + 3] (get nominal part z top, in fixture coordinates)

g00 z [#103 + 0.3] 
g00 x [#101 - 0.2] y [#102 + 0.25] 
g00 z [#103 - 0.3]
g31 x [#101 + 0.1] f 5
g00 x [#101 - 0.15]

(Determine whether part is present by comparing probe result with destination)
(if we are within 0.005 of our probe destination, then no trip)
(set the result in parameter 3 as zero for part not present, or one for present)

#3 = [ROUND[ 0.498 + ABS[#101 + 0.1 - #2000]]]
 
M98 P[101 + #3 ]  (now either finish probing part or move on to next)

#100 = [#100 + 1]  (increment the primary loop index variable)

M99 (end of O100 subroutine)

(**************************************************************************)

O101  ( part not present - record results and move on )
#[#301 + 0] = 0   (flag part not present in table)
M99   (end of O101 subroutine)

(**************************************************************************)

O102  ( part is present - probe and record exact location)
#[#301 + 0] = 1   (flag part is present in table)
#[#301 + 1] = #2000 (store part x origin)
g00 y [#102 - 0.2]
g00 x [#101 + 0.25]
g31 y [#102 + 0.1] f 5
#[#301 + 2] = #2001 (store part y origin)
g00 y [#102 - 0.2]
g00 z [#103 + 0.3]
g00 y [#102 + 0.25]
g31 z [#103 - 0.2]  f 2
#[#301 + 3] = #2002 (store part z top of stock)
g00 z [#103 + 0.2 ]
g10 L2 P[#100+10] X #[#301 + 1] Y #[#301 + 2] Z 0 (store fixture offsets for x&y)

M99  (end of O102 subroutine)

(**************************************************************************)
( this code is used to cut the top portion of the EPM1 prismatic shoe part)
(raw stock is presumed to be 1.9"x1"x1", inside a holder .7" deep)


(**************************************************************************)

(Main loop of the individual part rough cutting with 1/4" tool, top half)
O400

(first face off the top in two passes)
#84 = 0.0375      (z cut increment)
#87 = [1.9 - #84] (starting z cut depth)

g00 z 2.2
M98 P406 L2   (call the top facing routine to remove 0.075")

(now for the prism rough cutting)
(use depth interval of 0.025", each depth pass is .025" further away from center )
(prism extends from 1.825" down to 1.575")

(for the first pass, we leave 0.5" top square + 0.050" perimeter for chamfering)
(leave x,y=0.200-0.800 for pass 1 at z=1.800"; path is  0.100-0.900)
(leave x,y=0.050-0.950 for pass 9 at z=1.600"; path is -0.075-1.075)

#81 = 0.100  (first pass low side)
#82 = 0.900  (first pass high side)
#84 = 0.025  (axial cut depth increment)
#87 = 1.800  (current z depth)

M98 P407 L9  (call the prism rough cut subroutine)

g00 x 0.2 y -0.2 g00 z 1.85

#84 = 0.050  (axial cut depth increment)
#86 = 0.15625 (radius of corner relief)
#87 = 1.55  (current z cut depth)

g00 x #86 y -0.135 z #87
M98 P410 L5  (call the bottom left cornering routine to z=1.175)
g00 x -0.15

#87 = 1.55  
g00 x -0.15 y [1.0 - #86] z #87
M98 P411 L5  (call the top left cornering routine to z=1.175)
g00 x -0.15
g00 y 1.15

#87 = 1.55  
g00 x [1.0 - #86] y 1.15 z #87
M98 P412 L5  (call the top right cornering routine to z=1.175)
g00 x 1.15

#87 = 1.55 
g00 x 1.2 y #86 z #87
M98 P413 L5  (call the bottom right cornering routine to z=1.175)
g00 y -0.15

g00 x -0.15 y -0.15 z 2

m5 m9
g0 z 4


m99

(********Th-Th-Th-That's all, folks*******)

(subroutine to face off the top of stock)
O406

g00 x 0.1 y -0.15
g00 z #87
g01 y 0.9
g01 x 0.9
g01 y 0.1
g01 x 0.3
g01 y 0.7
g01 x 0.7
g01 y 0.3
g01 x 0.45
g01 y 0.45
g01 x 0.55
g01 y 0.55
g00 z [#87 + 0.010]
g00 x 0.15 y -0.15
#87 = [#87 - #84]

M99

(subroutine to rough cut the prismatic tops in expanding squares)

O407
g00 z #87
g00 x  #81  y -0.15
g01 y  #82
g01 x  #82
g01 y  #81
g01 x  #81  
g00 y -0.15

#81 = [#81 - #84]
#82 = [#82 + #84]
#87 = [#87 - #84]

M99

(subroutine to make bottom left corner cuts)
O410

g01 x #86 y -0.125
g02 x -0.125 y #86 i 0 j #86
g00 x -0.15
#87 = [#87 - #84]
g00 z #87
g01 x -0.125
g03 x #86 y -0.125 i #86 j 0
g00 y -0.15
#87 = [#87 - #84]
g00 z #87

M99


(subroutine to make top left corner cuts)
O411

g00 x -0.125 y [1.0 - #86] z #87
g02 x #86    y  1.125      i #86 j 0
g00 y  1.15
#87 = [#87 - #84]
g00 z #87
g00 y 1.125 
g03 x -0.125 y [1.0 - #86] i 0 j [0 - #86]
g00 x -0.15
#87 = [#87 - #84]
g00 z #87

M99

(subroutine to make top right corner cuts)
O412

g00 x [1.0 - #86] y   1.125       z #87
g02 x 1.125       y  [1.0 - #86]    i 0 j [0-#86]
g00 x  1.15
#87 = [#87 - #84]
g00 z #87
g00 x 1.125
g03 x [1.0 - #86] y 1.125 i [0-#86] j 0
g00 y 1.15
#87 = [#87 - #84]
g00 z #87

M99

(subroutine to make bottom right corner cuts)
O413

g00 x 1.125  y #86 z #87
g02 x [1.0 - #86] y -0.125   i [0-#86] j 0
g00 y -0.15
#87 = [#87 - #84]
g00 z #87
g00 y -0.125
g03 x 1.125  y #86 i 0 j #86
g00 x 1.15
#87 = [#87 - #84]
g00 z #87

M99

(subroutine to setup part fixture and call chamfer cut path sub)
O440

#77 = [0.375 + 0.008] (chamfer tool radius at bottom, 0.625 at wide point)
#87 = [1.575 - 0.005] (cut from the bottom of chamfer)
G59 P[#100 + 10]
M98 P450 L1

M99


(subroutine to run chamfer tool once around the block)
O450

g00 z #87
g01 x [0 - #77 - 0.05] y [0 - #77]
g01 x [1 + #77]
g01 y [1 + #77]
g01 x [0 - #77]
g01 y [0 - #77 - 0.05]
g00 x [0 - #77 - 0.05]
g00 z 2

M99
O949
g00 x-0.5 y0 z0
g02 x-0.5 y0 z0 i0.5 j0
g00 x0 y0 z0
m99

[gjvander]

Awesome! Thanks for posting.

Geo