Honest Opinions

[ThePudds]

I see a lot of people using manual alignments. In the quality lab i work in, I was taught to use a read point, align, while all in dcc and go from there. No manual alignment necessary. Is there a benefit of doing a manual alignment? Or do both have the same outcome?

[louisd]

I feel if you have an engineering-controlled means of fixturing your parts, readpoints are a great time saver.
Otherwise, if your part setups are "load part facing up" wherever you want on the granite (open to vast operator/setup variation) manual align is best.
But yes ultimately they get you to the same outcome.

Readpoints will save time, simplify effort, and make operation easier; however they come at a cost of developing a custom fixture, or robust setup work instruction.
If you have high part variability in your product line or receipts, maybe readpoints aren't the best approach (as the setup time will be a higher cost than they are worth).

[ThePudds]

For fixturing, we normally use standoffs. However, every part is set up exactly the same as the last. So..... we should be fine doing it this way then?

[DAN_M]

Both do the same thing. You're locating a part for the software. Whether you find the part with a read point & make the machine do it...or make a human probe out a manual alignment...you'll get the same result. The only was you'll get in trouble with manual alignments is if you have your operators taking their points too fast or not "cleanly" (giving the machine bad vector readings).

In my experience, the less I have people doing manual stuff, the longer my probes will last. Less human interaction = less stuff breaking.

I prefer read points, they're easier for everybody to use. My operators love putting the probe in a hole..or over a corner..and then pressing the green button. Opposed to measuring a 3point plane...4 hit circle...etc..

[NinjaBadger]

The answer is 'it depends'.

If you do a readpoint, then a rough alignment (so like a manual alignment in terms of features used and minimal hits) and then follow it with a full accurate DCC alignment then it's fine.

If you do a readpoint and then go straight into a main DCC alignment but use 2d features you will get a bit of cosine error and probably less repeatability.

If you do a readpoint then pick up 3d features for a main DCC alignment then you might not get as good repeatability.


This game isn't exactly 'THIS IS THE BEST METHOD AND ANYTHING ELSE IS WRONG!!!!' type thing.

You've really got to keep in mind what your equipment is capable of, what tolerances you're working to, what the part is made of and how it was produced, and what its end use is, then make a judgement call about just how careful you need to be and assess what shortcuts are acceptable.

[DAN_M]

When I use read points, I do it a certain way to negate any error I may accumulate.

My RP only roughly locates center for me...I work in and find the rest using autofeatures and manipulating my move/touch parameters.

            MOVESPEED/ 300*0.9
            TOUCHSPEED/ 10
            PREHIT/0.2
            RETRACT/0.2
            CHECK/0.2,1
READPNT1   =FEAT/POINT,CARTESIAN
            THEO/<0,0,3.68>,<0,0,1>
            ACTL/<0,0,3.68>,<0,0,1>
            READPOINT/
A1         =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
              ALIGNMENT/TRANS,XAXIS,READPNT1
              ALIGNMENT/TRANS,YAXIS,READPNT1
              ALIGNMENT/TRANS,ZAXIS,READPNT1
            ALIGNMENT/END
            MODE/DCC
CIR1       =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
            THEO/<0,0,0>,<0,0,1>,0.465
            ACTL/<0,0,0>,<0,0,1>,0.465
            TARG/<0,0,0>,<0,0,1>
            START ANG=0,END ANG=360
            ANGLE VEC=<1,0,0>
            DIRECTION=CCW
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
A2         =ALIGNMENT/START,RECALL:A1,LIST=YES
              ALIGNMENT/TRANS,XAXIS,CIR1
              ALIGNMENT/TRANS,YAXIS,CIR1
            ALIGNMENT/END
            MOVESPEED/ 300*0.9
            TOUCHSPEED/ 5
            PREHIT/0.1
            RETRACT/0.1
            CHECK/0.1,1
CIR2       =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
            THEO/<0,0,0>,<0,0,1>,0.465
            ACTL/<0,0,0>,<0,0,1>,0.465
            TARG/<0,0,0>,<0,0,1>
            START ANG=-120,END ANG=240
            ANGLE VEC=<1,0,0>
            DIRECTION=CCW
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
A3         =ALIGNMENT/START,RECALL:A2,LIST=YES
              ALIGNMENT/TRANS,XAXIS,CIR2
              ALIGNMENT/TRANS,YAXIS,CIR2
            ALIGNMENT/END
            MOVE/INCREMENT,<0,0,1>
            MOVESPEED/ 300*0.9
            TOUCHSPEED/ 5
            PREHIT/0.25
            RETRACT/0.25
            CHECK/0.25,1
PNTZ       =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.4646,0.0988,0.163>,<0,0,1>
            ACTL/<-0.4646,0.0988,0.163>,<0,0,1>
            TARG/<-0.4646,0.0988,0.163>,<0,0,1>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
A4         =ALIGNMENT/START,RECALL:A3,LIST=YES
              ALIGNMENT/TRANS,ZAXIS,PNTZ
            ALIGNMENT/END
            MOVESPEED/ 300*0.9
            TOUCHSPEED/ 5
            PREHIT/0.075
            RETRACT/0.075
            CHECK/0.020,1
PLN1       =FEAT/CONTACT/PLANE/DEFAULT,CARTESIAN,TRIANGLE,LEAST_SQR
            THEO/<0,0,0>,<0,0,1>
            ACTL/<0,0,0>,<0,0,1>
            TARG/<0,0,0>,<0,0,1>
            ANGLE VEC=<-0.9786535,0.2055172,0>,RADIAL
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
A5         =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
              ALIGNMENT/LEVEL,ZPLUS,PLN1
              ALIGNMENT/TRANS,XAXIS,CIR2
              ALIGNMENT/TRANS,YAXIS,CIR2
              ALIGNMENT/TRANS,ZAXIS,PLN1
            ALIGNMENT/END
            WORKPLANE/YPLUS
LIN1       =FEAT/LINE,CARTESIAN,UNBOUNDED,NO
            THEO/<0,-0.5,0>,<0,1,0>
            ACTL/<0,-0.5,0>,<0,1,0>
            CONSTR/LINE,ALIGN,1,WORKPLANE
            WORKPLANE/ZPLUS
A6         =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
              ALIGNMENT/LEVEL,ZPLUS,PLN1
              ALIGNMENT/ROTATE,YPLUS,TO,LIN1,ABOUT,ZPLUS
              ALIGNMENT/TRANS,XAXIS,CIR2
              ALIGNMENT/TRANS,YAXIS,CIR2
              ALIGNMENT/TRANS,ZAXIS,PLN1
            ALIGNMENT/END

[charliejoe]

OK cool, I'm going to try that, i just upgraded to windows 10 and 2019 R2 and all of a suddenly the Global 7-10-7 woke right up and is almost scary fast at 300 mm/sec . Thanks and Merry Christmas!

[DAN_M]

@charliejoe

-Open up any program. Hit "F5" to open "Setup Options" menu. Click to "Part/Machine" tab.
-Look where it says "Display Absolute Speeds". There is a checkbox there. THIS CHECKBOX IS A GLOBAL COMMAND THAT EFFECTS ALL OF YOUR PROGRAMS.
-IF THAT BOX IS CHECKED....PC DMIS will read MOVESPEED commands in your programs and make your machine drive at that exact speed.
-IF THAT BOX IS NOT CHECKED...PC DMIS will read MOVESPEED commands in your programs and make your machine drive AT A PERCENTAGE OF IT'S MAX MOVESPEED. For example, if you leave the box unchecked, and then wrote a program where you put "MOVESPEED/50", your machine would travel at 50% of its max speed (whatever that number may be) INSTEAD of 50mm/sec.

Your update most likely switched that setting on you, causing the noticeable change in speed.

Sidenote....
I'm hoping you guys beat the Ravens this week! That would put the Pats in good standing! Merry Xmas to you too!

[louisd]

DAN_M absolute speeds toggle is routine/program specific, NOT a global parameter.

[bherrin]

I don't mean to piggy back, but this is somewhat related;
There's been a push here to remove manual features and alignments from all of our programs, and use fixtures to place parts consistently enough to execute the first few features at least in DCC on machine coords. Is this a viable method? If not what are the arguing points against, and if so what pitfalls do i need to watch out for?

Readpoint alignments would probably make a good compromise point.

[louisd]

yes, we use fixtures, and a mag-base with posts on a rayco fixture grid. We load parts on fixtures, and put fixtures on the mag base, pushing fixture base against 2 posts in X and 1 post in Y. We hit go and DCC measures without any readpoint or manual hits. We still embed a yes/no operator input option for a manual alignment at the beginning of the routine to maintain routine functionality and interchangeability of measurement routines between 4 difference CMM's..

[DAN_M]

bherrin
Fixture alignments are awesome! Everybody loves them.

Create an alignment program for the fixture, save that to an external alignment file, then recall that external alignment AT THE TOP of your new programs. You’ll have to put an alignment in between the external and the original first alignment you had to relate them to one another to make everything work.

This is how you make your programs “jogbox free”. Once your people get used to never having to touch the jogbox they’ll never want to go back. 80% of my programs are like this and the rest use read points. I have NO manual alignment programs out of the few hundred in my library (except for one really funky part that needs an iterative).

[bherrin]

How consistent are your part setups? I've been tracking mine on a spreadsheet and am seeing up to a 0.04" deviance from part to part in some cases. I'm thinking that will be okay with careful point selection and opening up prehit, check, etc. for the beginning.

[DAN_M]

My fixture is just a grid plate with a bunch of tapped holes.

I tell my operators (with instructions) where to screw in threaded risers. Then on to the top of the riser, they screw in a magnet. Then they stick the parts to the magnets.

This only locates parts within ± an inch or so of where they're supposed to be and I play with my move/touch parameters to find the parts with a rough dcc then i do a more clean dcc then i measure the datums.

[JEFMAN]

I made some tests of repeatability (same part, same location on the cmm or not), and saw that performing the dcc alignment directly after the manual was less accurate than performing a "light" dcc alignment between both others...
Running this "light dcc alignment" allows giving a better repeatabilty than running directly the classical alignment.
I don't use read point, but I don't program serial parts !

[JGRIFFIN]

By "light" do you mean progressive alignment?

[JEFMAN]

JGRIFFIN : no, just few dcc hits per feature (3 or 4 /plane - circles, 2 /lines, sometimes auto center points for little holes...)

[JGRIFFIN]

I will test that. Thanks JEFMAN

[dwade]

Many of our older programs (written BMT) use a readpoint then go directly into DCC mode and use only one alignment. We have been going through some of these programs and looping the alignments to improve repeatability of the alignment and measurement results. As a quick way of determining whether or not your alignments are good recall some of the features that were used to create the alignment and the IJK should be perfect or very very close to being perfect and your XYZ origin should be zero.

[Don Meredith]

Our three CMMs are fitted with the same size Rayco plates, 1/4-20 tapped holes on 1/2 in centers. There is a 1/2 x 1/2 standoff in D-3 on each plate, which is re-measured at the end of the Probe Qual program that is run at the beginning of each shift. The location of the standoff is stored as an External Alignment and is recalled at the start of all programs. This allows us to store the programs on the server and run them on any of the three machines without doing a manual alignment. All programs include detailed setup instructions, with pictures, as to standoff location and part loading.

[A-machine-insp]

For me the answer depends of the part I am checking. Most of the time I use readpoint alignments. Sometimes we get a part where the datum a points are on moldline (aircraft parts) so I run a manual alignment on those. I know I can use a readpoint but the setup on the CMM becomes more critical and some of our inspectors seem to throw the parts on there almost randomly so I use manual alignments for those parts. The vast majority of my parts are readpoints though. Much faster to get running.

[R2ah1ze1l]

Do to repeat setups and traditional use of readpoint, there are some programs that when the operator finishes inputing some required part information, the machine can DCC to the readpoint and then on from there.

Essentially, it has now been programmed based on the home position of the machine.

Readpoints make setups better IMO. If something goes wrong from the readpoint, you don't have to get any farther to figure out the setup is incorrect.

[Paperback Rocker]

Mount in the same spot with setup instructions and run 100% DCC with no manual.

[louisd]

and stock up on spare parts if you don't have a rock-solid set of instructions! :-D

[Schrocknroll]

I chuckle when I see some who feel readpoints are all you ever need, not saying that it was said here. I do use them for small parts. Try locating a part with a 20" I.D. and a .125 timing hole with just a readpoint.

As has been said above, it's good know all the different methods and choose what works best for that case. If it's a high production part, use a fixture for repeatability. I have parts that are held in repeatable fixturing that I have done a manual alignment on in years. I have a question at the beginning that asks if the alignment has been done, then skips to DCC mode if Yes. The default is Yes. Just hit the done button and start beeping.

[DAN_M]

No problem! I do this all of the time.

1) Read point in the timing hole. Make that your XY origin. Measure circle (cir1) AT X0Y0.
2) Do a plane around cir1.
3) Move increment up..move increment over to above the big hole hole
4) With a wide open prehit/retract/check/and a fast touchspeed (so its not painfully slow), probe a 3 point diameter (cir2) (just to find it).
5) Probe another diameter (cir3)(3-5pnts) at the XY nominal of cir2 with prehit/retract/check/and a fast touchspeed parameters all set back to normal numbers.
6) Construct a line between cir1 and cir3.
7) Make a new alignment recalling startup...Level to plane, rotate to line, offset line back to nominal angle (if applicable), cir3=XY origin, pln=z origin

This will locate the part and give you a sound enough alignment to go and start finding part datums.

[VinniUSMC]

I have a manual alignment in most of my programs. We switch between parts a lot, and only run most of them 1 time a year. They are nearly universally in car body, and rarely square to machine or car body coordinates. RP alignment just isn't very conducive to that. But, 1 manual alignment (iterative, followed by iterative DCC) is hardly much of a time waster.