Zeroing the router

[alien_X]

Hello

I am nearing completion of my first build, and am having trouble working out how one would zero the router to the centre, or corner of their workpiece??

Say I had a 200 X 200mm block, already cut out, and I needed to CNC three pockets into it. Now lets say I tell the CAM processor that the origin is in the centre of the block.
How do I get the router to the referenced centre of this block?
Do I find the centre manually with a ruler, pencil, engineers square etc. And then put a small (0.2mm or so) drill bit in the router chuck, and line that up with the centre. Then I swap out the drill bit with lets say a 6mm endmill and run the code?

How is this meant to be done?

I also have the same question for zeroing to corner, which I can't think of any possible way to do accurately. Please could someone explain their method?

Thanks alot!

[TOTALLYRC]

Originally Posted by alien_X Hello I am nearing completion of my first build, and am having trouble working out how one would zero the router to the centre, or corner of their workpiece?? Say I had a 200 X 200mm block, already cut out, and I needed to CNC three pockets into it. Now lets say I tell the CAM processor that the origin is in the centre of the block. How do I get the router to the referenced centre of this block? Do I find the centre manually with a ruler, pencil, engineers square etc. And then put a small (0.2mm or so) drill bit in the router chuck, and line that up with the centre. Then I swap out the drill bit with lets say a 6mm endmill and run the code? How is this meant to be done? I also have the same question for zeroing to corner, which I can't think of any possible way to do accurately. Please could someone explain their method? Thanks alot!

Thsi is normally done with an edge finder. If you are using mach3 there is even a page to help you do it. Put the part on the table. use the edge finder to do the x side when you have located the zero point, click the zero x botton.
do the same for the y, you now have found the corner to the accuracy of the edge finder which is +-.002 or so depending on the device. If you can't get the edge finder that fits in the spindle, there are ways to do it with a dial indicator.

Depending on how close you need to pickup the edge, you can just use a small web cam and the video window inside mach3. The video cam gets mounted in the collet and on the sceen are cross hairs and when they are on the edge, so is the center of the cutter if you do it right.
Don't forget to compensate for the diameter of the edge finder. If you get real fancy you can go with an electronic edge finder linked into mach and have it do it automatically. I saw a video on you tube and it was real cool. I will be getting to it this year if at all possible.

to find the center of the part, you just do and MDI move from the corner to the center like this. if you have the center of the cutter over the corner and you have the 200mm x 200mm block inplace, just go to the mdi page and input g00 x100 y100 and you will be sitting at the exact center.

If you do a lot of locating, and especially in a production enviroment then home switches and locating pins are a good idea. You first do a reference all so the machine validates home by using the home switches. then your part can go right in to the locatin pins and the cutter is either at 0,0 or at some distance that you chose. This method can locate to less than .001" if you do it right and possibly closer but I haven't done it yet. Theoreticly it should be perfect, but in reality I usually accept something less. It all depends on how good you home switches are.

My new disclaimer, I haven't had my coffe yet and most of my brain is still asleep, but I tried.

Mike

[ger21]

http://cnczone.com/forums/showpost.p...&postcount=885

http://cnczone.com/forums/showthread.php?t=56079

http://cnczone.com/forums/showthread.php?t=36099

[TOTALLYRC]

Thanks ger21 for the great information. This time I book marked them on my computer so I can find them again.

These should be included in the new series called the Hitchhikers guide to CNC, coming out on DVD and Blue-ray this fall, which could be a sticky and a blinking banner on the cnczone web page. It unfortunatly could be a lifes work for one person. It is also a shame that there is not a big budget studio behind it as they would make you an executive producer in a heart beat.

It could star Robert Dinero as the aging yet still very young machinst looking to give something back to the maching comunity that he worked in all his life and Jessica Beal as his daughter getting reaquainted with her father by learning how to be a cnc machinist.

I want 2% of the box office revenue for my idea.

Now back to your regularly scheduled forum.

Mike

[alien_X]

Hi

Thanks for all of the links and useful information! Lots of things to think about!
Regarding the electronic versions, I was hoping of being able to find an accurate manual technique before I upgrade to an automatic version.

Thanks again

[ger21]

Install home switches on your machine and some type of fence or locating pins. Then, you just need to home the machine and place the part against the fence.

[TOTALLYRC]

It all depends on how close you need to be, I do it by eye on my router most of the time as I always do sheets of material and set the z travel a liitle extra deep as I always do thru holes.

If you are trying to recenter or align a piece to a close tolerance, then a mechanical edge finder would work, assuming you can get it into the chuck.
A quick and dirty way is to put a gauge pin or piece of drill rod in the collet of your router, and the using the jog commands bring it up to the side of the part using a feeler gauge of known thickness or a piece of paper and move in slow untill there is drag on the gauge. Now is a good time to learn how to use the tab button to bring up the jog controls.

A gamepad ( I use a logitech) or pendandt is also a great thing to have. I will jog in fast using the jog overide button/shift key, go to about 20% jog and get in close as I dare, then shift to incremental jog such as .010" then even .001" until I feel drag on the feeler gauge. you are now sitting half the diameter of the pin plus the thickness of the gauge from having the tool centered over the edge of the part. Same for the Y. I dont do the z like I said but I am sure somebody else will have better ways to do it all.

I am learning how to use the tool offsets and it is like everything else, once you think you know a lot about something, that is when you realize how little you really know.

Mike

P.S. If you need help on seting up a pendant or joystick, feel free to ask, and remember, I might have been correct already today and according to my wife, that is all that I am allowed.

[alien_X]

Originally Posted by ger21 Install home switches on your machine and some type of fence or locating pins. Then, you just need to home the machine and place the part against the fence.

Hi

There must be something I am missing with home switches. I can understand how they could be installed in the same place as limits, but how can you have a home switch which isn't at the maximum travel range for the axis without detracting from it's travel?

Surely when the axis tries to travel to its limit, it would hit the homeswitch and presumably snap it?

Also, how would a fence or locating pins be mounted so that they were located relative to the home switch origin?

Thanks for the info as well totallyrc, very useful

[ger21]

You can have a ramp actuate the home switch so that it can safely pass by it. But most people use one switch that is used as both a home and limit switch.

You're zero position (fence location) can be set in the software relative to the switch position. A few quick test cuts, measure, and your good to go.

[alien_X]

Hi, Okay, but how would I know where to position the fence?

If the home switch is the same as the limit, then would the zero be at the corner of my table (My cnc is a 12 X 12 inch routing area Fixed gantry design)

[ger21]

The zero can be anywhere you want it. The home switch position does not have to be zero. You can have the switch be at -2, for instance, and have the fence be at zero.

[TOTALLYRC]

Originally Posted by alien_X Hi, Okay, but how would I know where to position the fence? If the home switch is the same as the limit, then would the zero be at the corner of my table (My cnc is a 12 X 12 inch routing area Fixed gantry design)

If you use the same switch as both home and limit, and set it up on the config page that way, then the 0,0 point will be where the machine stops when you do a ref all.

You can then put the fence werever you want it and do a G54????? work offset, or possibly tell mach what to put into the dros after a home move. SO if the corner of the fence is at .5 and .5 you would put this number into mach on the home/limits page under the config tab page and then once you do a ref all, the dros should read x-.5 and y-.5 I haven't done this yet, but I am pretty sure it can be done.

Then all you do is do your drawing with 0,0 in the correct place and all is well in router land.

as ger51 said, cut measure and then you are good to go.

Mike