Zero-able Jig!

[twelchPTM]

So it took some doing but I figured out how to re-write the xy zero routine to use the contact switch instead of prox sensors. This enables me to build a jig that I can place anywhere on my table and as long as I make sure the jig sits parrelel to the y-car I can recut sa privously cut pice with out risking being off.
For the first use I built a jig for drilling holes in the bottom of a part for my toy rockets, the xy routine asks for input for the distance to zero from the contact plates for both axis and then the bit diameter and calculates the offset from the plate to the zero before running its routine. Now whenever I need to make parts I can be certain my hole will fall dead center everytime...
http://i1282.photobucket.com/albums/a533/twelch82tw/IMG_20121205_210732.jpg

Also here is the zeroing program if anyone want to check it out....

[dana_swift]

Well done-

Good thinking!

I do a similar thing with a copper sweat fitting end cap. Pocket a hole in a project just big enough to make a press fit. Then one cheap part and a repeatable known point on the project. With two or more known points it is possible to completely reproduce a setup after removing a workpeice from the table. It will locate the center of each sweat fitting to the accuracy of the machine. Usually 0.001 or 0.002.

For some projects I use 1/2" end caps, for others 3/4" end caps. Mostly determined by whether I am using a 1/4" or smaller bit or a 1/2" bit.

The "center in hole" routine is provided in the SbParts directory I did a little modification of that for my purposes. But its already there and comes with the shopbot..

D

[twelchPTM]

I had posted a few days ago asking about using the contact switch to zero since i remember seeing it on here before but didn't get a response until i started this. i didn't know it was included in the bot software nor did i even think about pocketing the cap into the jig. I would of had to beef up the jig on this project in order to do it but it also gave me the push i needed to dive into learning the programming end of the bot.
One question though, if your cap is pressed down into the jig how do you connect it the the input for the conact switch?

[adrianm]

I use a similar system to Dana. The pictures show how it works.

The bit that sticks out on the bottom lines up with the t-track on my table so it's always square to the work. The other end of the wire is a crocodile clamp that connects to the z-zero plate.

I did use to zero all three axis using one of these but I have a fixed z-zero point on the table now that is used to automatically set the z-zero.

There have been lots of variations of this type of jig posted on the forum along with the code to make them work. This one for instance - http://www.talkshopbot.com/forum/showthread.php?t=5495

[steve_g]

"crocodile clamp" is that any thing like an Alligator clip?...

England and America are two countries separated by a common language. (George Bernard Shaw)

SG

[dana_swift]

Thomas- I use a peice of wire with two alligator clips on it to connect the cap to the ZZero plate just like you show in your photos.

On one end I have a car battery clip for a battery charger big enough to clamp around the cap. On the other end I use a smaller electronic general-purpose alligator clip like you show in your photos. The alligator clip on the cap has to be clipped on such that it cant touch the bit and make a false contact.

Welcome to programming the SB3 version of the BASIC language. Its a fascinating and rewarding journey. The bot is extremely flexible using nothing but the Vectric design tools, but when you add the SB3 language its just unbelievable.

Things like my bolt threading applications take full advantage of the SB3 coding capabilities. Adding my upper Z limit prox switch etc..


D

[twelchPTM]

I think a crocodile clamp has a shorter snout....

[adrianm]

"crocodile clamp" is that any thing like an Alligator clip?...

England and America are two countries separated by a common language. (George Bernard Shaw)
Some people call them alligator clips over here and some call them crocodile clamps. Same thing with jubilee clips and hose clips. It always seems that whatever I call something the person I'm speaking to at the time calls them by the other name!

[twelchPTM]

its funny , I went looking for these posts befor I started and couldn't find them...


The ideas for where I can can go from here with this set up are starting to snowball. The more I think about the copper cap idea the more I like it, The motivation behing the way I did my set up was to have the contact plates permanetly attached to the jig so that once I record the offsets I need for my zero point they will always be the same I am now thinking If I embed a copper cap permanently in the jig I can do the same thing but for all 3 axis instead of just the x and y

Dana - I would love to here more about the z upper limit sensor, situations like the jig picture have me extremely close to my upper limit and if it hits the physical stop I lose my zero, is the switch setup insuch a way that the motor won't drive past that point at all even when just using the sb3 keypad controls?

[adrianm]

Explanations, pictures and code in this thread - http://www.talkshopbot.com/forum/showthread.php?t=15436

[jkaras2000]

Hi Dana: I built the copper sweat cap jig today. I just dont know where to find the routine to center a bit in copper cap? Ca you please help. Thanks Joe Karas

[Greencarvings]

For those of you who do not want a shop made jig, these are awesome. I use it as a corner finder, and then flip it over and use it to zero to the top of the table!

Solid piece of aluminum using banana clips.

http://www.themakersguide.com/home/products/triple-edge-finder-2