S03 XXL - aligning custom fixture plate?

Assembly questions and answers for the Shapeoko 3 CNC Mill
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ururk
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Joined: Sat Jul 16, 2016 4:25 pm

S03 XXL - aligning custom fixture plate?

Post by ururk » Sun Jul 23, 2017 11:47 pm

I'm considering having an aluminum fixture plate made up. I know if I were to make my own out of MDF the screws will be in "perfect" alignment with the Y-axis. But, if I have an aluminum plate made, how will I ensure the holes track along with the bit as the gantry moves along the Y-axis? I'd like to be able to insert screws all the way and use them as alignment pins.

I priced out a piece of aluminum - a .5" x 36" x 36" plate of 6061 (64lbs) is around $160 - less with correct dimensions - but I'm not too sure how much the machining will cost. I've looked at t-slot, not interested.

Thanks,

John

WillAdams
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Re: S03 XXL - aligning custom fixture plate?

Post by WillAdams » Mon Jul 24, 2017 11:46 am

Have the holes all drilled in a square grid, then when it's installed start w/ that squareness and adjust the balance of the machine to maintain it.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

Dan_the_Chemist
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Joined: Thu Nov 10, 2016 2:52 am

Re: S03 XXL - aligning custom fixture plate?

Post by Dan_the_Chemist » Mon Jul 24, 2017 6:05 pm

Do you know how to tram your vice on a milling machine? You can use the same techniques for tramming a fixture plate on a Shapeoko.

However, before we get into a long discussion on tramming, let me ask what you are doing... You say "I'd like to be able to insert screws all the way and use them as alignment pins." Standard hardware store screws are generally class 2 tolerance, but they can even be class 1... which means they rattle around a bit in the hole - perhaps plus/minus 0.002". If you add on the tolerances on head diameter, you might find that you aren't getting great alignment from screws. Dowel pins are often used instead because they can be sized much more accurately. Fixture plates often have reamed holes for dowel pins, and threaded holes for clamping.

So, tell us what you want to do and we'll brainstorm this for you.

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