Edgefinder question

[BrandanS]

Hey again SBotters,

I have successfully run 2x 4.5" bores through 1" aluminum plate with a nice interference fit for receivers that I am setting a jig into. So far so good!

I am now looking to pick up the edges of 8 aluminum parts on my jig and I will need to do them all separately with accuracy. I would like to use an edge finder to accomplish this feat for now (I will be looking into writing a routine similar to Z-zero w/ a circuit and Dowel Pin).

I've read posts about laser finders and the like, but really need to accomplish this with an 'old school' edgefinder for now.

I need help with the controls on the ShopBot to get it to move small distances efficiently. For those who have run CNC's, this would typically be done with an incremental dial.

Could someone who has experience with edgefinding on a ShopBot give me a hand?

Thanks in advance,

Brandan

[gundog]

Hi Brandan,
I have a laser edge finder and also a wiggler. The laser is quick but not supper accurate I use it when I am looking to find the edge of a sheet that I am going to machine and the parts are not laid right to that edge. I use the wiggler on my CNC bed mill all the time it is more accurate and repeats to about .003" or better.

If I were to use the wiggler on the Shopbot I would bring up the SK screen and change the default setting to move .001" I think default is .100" or .010" I am not at my shop right now to check. Then a tap will move the machine .001" and should work fine for your edge finder.

If I remember right there might be a button to click to put it in incremental mode so that it moves you specified increment.
Mike

[srwtlc]

There are two files in your SBParts folder that you could use to find the centers of the holes using an input connection just like your Z zero plate does. Those are sample_Center_inHole.sbp and sample_Center_inHole_wZtest.sbp

[Brady Watson]

There are two files in your SBParts folder that you could use to find the centers of the holes using an input connection just like your Z zero plate does. Those are sample_Center_inHole.sbp and sample_Center_inHole_wZtest.sbp

X2 to that.

PLEASE err on the side of caution with a conventional edge finder. They are probably not rated for the lowest spindle RPM possible on a ShopBot (5,000) and unless you have a Super PID, a Porter Cable won't go lower than around 9,000. They are meant to be used at low RPM on a mill...I imagine it would not take much to make one of those fly apart in a router - so be cautious! (Safety glasses, flak jacket etc)

-B

[gundog]

Brady has a good point. When I use the wiggler on the mill I do it at 1000 RPM it would fly in pieces @ 5000 RPM I suspect.

I have never used my wiggler on my SB but I put my spindle on as an after market item and with my VFD I can run mine down to 100 RPM and often drill plastic at 2500 RPM. The spindle is rated for 24000 RPM max.

[donek]

There is a very simple way to find the edge of a part, or locate the edge of a part. We install a 1/4in dowel pin (or the broken shank from a bit) in the collet and then move the router to the correct position on the table and clamp a part stop to the table. You can then locate the part very accurately repeatedly. The code below is the program I wrote to accomplish this. It locates part stops at the center of the part along the short side and two additional stops on the long side on the side farthest from the operator. This could be altered to your needs and machine setup very easily.

MSGBOX ( Have you installed a 1/4in pin and zeroed it to the table?, YesNo, Ready?)
if &msganswer = No then end

BEGINENTRY:
INPUT "Enter X value for origin offset:" &_x_offset
INPUT "Enter Y value for origin offset:" &_y_offset

INPUT "Enter X length of rectangle:" &_x_length
INPUT "Enter Y length of rectangle:" &_y_length

JZ,1
J2,&_x_offset,&_y_offset
MSGBOX ( Is the machine over the corner of your desired origin?, YesNo, Ready?)
if &msganswer = No then goto BEGINENTRY

J2,&_x_offset+0.125,&_y_offset+(&_y_length/2)
MZ,0.1

'Position end stop!
PAUSE
JZ,1

J2,&_x_offset+(&_x_length/5),&_y_offset+&_y_length-0.125
MZ,0.1

'Position edge stop!
PAUSE
JZ,1

J2,&_x_offset+4*(&_x_length/5),&_y_offset+&_y_length-0.125
MZ,0.1

'Position edge stop!
PAUSE
JZ,1

JH
END

[gundog]

Another method used by machinst is to use a piece of paper or tape bewteen the bit and the work piece. Move up slow with the spindle turning until it tears the paper or tape. Measure tape or paper with a mic and that will get you as close as an edge finder and better than a laser edge finder. I like blue painters tape best.

[shoeshine]

yup, old school is to use paper (thermal paper i.e. receipt is almost universally ~ 2 thou) set your increment to a thou and edge up till the shank of the bit (not spinning) compresses the paper, z out, and the set your zero for x or y at +/- radius of the bit +/- a thou and you are pretty dead nuts on.

[Burkhardt]

I have used paper for this purpose but lately I bought some 3/1000" spring steel shim stock (McMaster 9503K13). It is thin enough to be cut with scissors and a piece (I use a 1.5x3" strip) lasts very long. I hold it with a magnet on the gantry to have at hand when needed.

I use it for edge finding but mostly for z-zero setting. I do have a zero-plate but I can do it just as fast with the steel strip by hand without a cable device.

[BrandanS]

You guys are the greatest and super helpful!


X2 to that.

PLEASE err on the side of caution with a conventional edge finder. They are probably not rated for the lowest spindle RPM possible on a ShopBot (5,000) and unless you have a Super PID, a Porter Cable won't go lower than around 9,000. They are meant to be used at low RPM on a mill...I imagine it would not take much to make one of those fly apart in a router - so be cautious! (Safety glasses, flak jacket etc)

-B

@Brady, I thought of this exactly; I can't get my spindle lower than 4k RPM, and was a bit of a showstopper for me for a conventional edge finder or wiggler...

So then I was thinking about an electronic edge finder or laser, but I have no experience with these:


Hi Brandan,
I have a laser edge finder and also a wiggler. The laser is quick but not supper accurate I use it when I am looking to find the edge of a sheet that I am going to machine and the parts are not laid right to that edge. I use the wiggler on my CNC bed mill all the time it is more accurate and repeats to about .003" or better.

If I were to use the wiggler on the Shopbot I would bring up the SK screen and change the default setting to move .001" I think default is .100" or .010" I am not at my shop right now to check. Then a tap will move the machine .001" and should work fine for your edge finder.

If I remember right there might be a button to click to put it in incremental mode so that it moves you specified increment.
Mike

@Michael I don't know if you need to to spin and LED edge finder. If anyone has experience with it please let me know. The laser seemed like my best option, but still dialing in the position seemed tedious with the .001" increments from the control. Would be more effective if there was a dial on ShopBot similar to CNC (from my OP).

@Sean So then I started thinking about a program similar to the z-zero plate. I would expect this to be the most simple and efficient. Using a dowel in the collet seems reasonable and could run simply. Thanks for the helpful code!


There is a very simple way to find the edge of a part, or locate the edge of a part. We install a 1/4in dowel pin (or the broken shank from a bit) in the collet and then move the router to the correct position on the table and clamp a part stop to the table. You can then locate the part very accurately repeatedly. The code below is the program I wrote to accomplish this. It locates part stops at the center of the part along the short side and two additional stops on the long side on the side farthest from the operator. This could be altered to your needs and machine setup very easily.

MSGBOX ( Have you installed a 1/4in pin and zeroed it to the table?, YesNo, Ready?)
if &msganswer = No then end

BEGINENTRY:
INPUT "Enter X value for origin offset:" &_x_offset
INPUT "Enter Y value for origin offset:" &_y_offset

INPUT "Enter X length of rectangle:" &_x_length
INPUT "Enter Y length of rectangle:" &_y_length

JZ,1
J2,&_x_offset,&_y_offset
MSGBOX ( Is the machine over the corner of your desired origin?, YesNo, Ready?)
if &msganswer = No then goto BEGINENTRY

J2,&_x_offset+0.125,&_y_offset+(&_y_length/2)
MZ,0.1

'Position end stop!
PAUSE
JZ,1

J2,&_x_offset+(&_x_length/5),&_y_offset+&_y_length-0.125
MZ,0.1

'Position edge stop!
PAUSE
JZ,1

J2,&_x_offset+4*(&_x_length/5),&_y_offset+&_y_length-0.125
MZ,0.1

'Position edge stop!
PAUSE
JZ,1

JH
END

@michael and @chris The paper/tape method is what I am using now. Problem being that I will have a lot of parts to setup in a single Operation rapidly and may eventually lead to another ShopBot. I need to find a solution better than what i am using :D.


Another method used by machinst is to use a piece of paper or tape bewteen the bit and the work piece. Move up slow with the spindle turning until it tears the paper or tape. Measure tape or paper with a mic and that will get you as close as an edge finder and better than a laser edge finder. I like blue painters tape best.


yup, old school is to use paper (thermal paper i.e. receipt is almost universally ~ 2 thou) set your increment to a thou and edge up till the shank of the bit (not spinning) compresses the paper, z out, and the set your zero for x or y at +/- radius of the bit +/- a thou and you are pretty dead nuts on.

So think for now I will continue with the paper/tape method until I require capability report for the machine. Once I do I will use the Zero-Plate method extended to X/Y edgefind.

Thanks ever so much for all your valuable input, with such a great community, it's difficult to go wrong!

Brandan Smith

[feinddj]

Check out the super zero plate as well. Its a piece of al with a hole milled in it. He has software routines to find corners and zero the bit all in one shot.

http://www.talkshopbot.com/forum/showthread.php?t=1862

[gundog]

I do not spin the spindle when using the laser edge finder. I very rarely use them any more on the mill the wiggler is more accurate and on the SB I have the 0, 0 corner setup with the prox switches and with the new control software I have points saved for the jigs I use most.

I do use the laser for setting up material I double side machine. Different materials make the dot look larger or smaller if the surface is rough the dot looks larger. I think about .010" is as accurate as the laser can be your results maybe better.

When using the laser I usually just give the machine a move command the distance I think it needs to go for example MX .050 if it looks like it is off .050 and adjust back and forth until I get it right.

Mike