Alignment holes for a two sides part.

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zimmer62
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Alignment holes for a two sides part.

Post by zimmer62 » Tue Aug 14, 2012 3:52 pm

I'm still trying to build the dust shoe, and I've run into something that might cause issues.

Here is what I'm thinking of doing for flipping the part over and milling the other side.

1) CNC drill 2 or more 1/8" holes in the acrylic and into the waste board with exact measurements from the part, outside where the profile would be.
2) CNC the slot for the brush.
3) flip the acrylic over and push 1/8" bits into the holes from step one until they align with the holes in the waste board, and clamp down the acrylic.
4) mill the holes for the dust shoe
5) mill the profile for the dust shoe.

q1) Does anyone see or know of an easier way to align the part after flipping it?
q2) What kind of bits do you use to drill through acrylic and wood at the same time? (end-mills don't plunge so well into acrylic and I ran into problem when trying this.)
q3) how are people clamping things to their board, something like 3/8" acrylic I've been drilling a couple holes in it and screwing it to my waste board.

bubblehead
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Re: Alignment holes for a two sides part.

Post by bubblehead » Tue Aug 14, 2012 5:24 pm

Mill a shallow recess with the outside dimensions of the dust shoe into your waste board. Mill the outside of the dust shoe. Then put in in the recess to mill one side. Flip the shoe over and mill the other side. If the dust shoe isn't symetrical, you may need to mill two recesses.

For other ideas look in the June/July issue of American Woodworker there is an article about CNC-routing wood chain links (http://americanwoodworker.com/blogs/ran ... oject.aspx).

Tom Smith
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Re: Alignment holes for a two sides part.

Post by Tom Smith » Tue Aug 14, 2012 6:02 pm

Haven't tried this, but how does this sound?

0. Set up your CAD/GCode so that the origin (x=0, y=0) is in the same place, somewhere in the MIDDLE of the object, vs lower-left or lower right.
1. Plunge a hole that will represent x=0, y=0 in the material, and cut one side.
2. Flip material, and zero the spindle on the hole.
3. Cut second side.

This would probably be even easier if you did the interior cuts first on both sides, then did the exterior cuts, so that you have a regular piece of material to clamp down.

I hope I have described this clearly, though the images in my head are no doubt clearer :roll:

Tom
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cvoinescu
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Re: Alignment holes for a two sides part.

Post by cvoinescu » Tue Aug 14, 2012 6:59 pm

I think Tom Smith is right in saying that it would be easier if you could first do interior cuts and recesses on both sides and then do the final cut that detaches the piece from the rest of the material.

I don't particularly like Bubblehead's idea of milling a recess, because it would be a waste of waste board in this case. The recess is the right thing to do for some parts, but this one can be done more economically.

I suggest you get a few short steel pins, 4-6mm in diameter, then clamp down your plastic stock and drill four holes, outside where the part is going to be (far enough that there is no risk that the tool hits them while cutting the part). The holes should be the corners of a rectangle aligned with the axes, to keep things simple. Drill them through the plastic and well into the waste board, slightly undersized (some experimenting is needed here). Insert four pins in the holes, then proceed to mill one side, flip the part over and align it on the pins, clamp it down, and mill the other side, including the exterior cut.

The holes are less damage to the waste board than a recess, but serve the same purpose. If the part does not fit on the pins when you flip it over, it means your machine is not square (or maybe it skips steps). Fix that first. The two sides of the part would not have matched too well anyway. Two holes along the axis you want to flip the part around would work too, and they work even if the machine is not square.

I should mention that it is a good idea not to cut the part out completely. Leave a few thin bridges that can be snapped by hand. This is to protect the part, the tool and the bystanders when the part breaks free and moves around, possibly into the tool...

[Edit] I'm sorry, I've just realized that I suggested exactly the same method as zimmer62...
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Improbable Construct
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Re: Alignment holes for a two sides part.

Post by Improbable Construct » Tue Aug 14, 2012 8:31 pm

When I made mine, I aligned the acrylic with the edge of the spoil board. (which is square to the x and y axis)
I then used screws with washers, on the edges of the acrylic as a hold down. I used a center start point and cut the brush slot. I then removed the screws on one end flipped the acrylic, realigned the acrylic back to the edge of the spoil board , and screwed it back down(using the same holes) Then I cut the magnet recesses,the inner edge, and then the outer edge of the part.
Does that make any sense?
I actually cut out three of the brush plates and one of the top plates from one piece of acrylic. I divided it into four 120mm sections and then found the center of each section. So I cut out a bottom, then a top, then two more bottoms. I ended up flipping the same piece 5 or 6 times. I had to re-zero X and Y after each part was cut but that is easy enough with my setup.
Here is a picture of the leftover piece:
ShapeOko 066 (Large).jpg
ShapeOko 066 (Large).jpg (81.25 KiB) Viewed 4826 times
Sorry I don't have any pictures of actually cutting them out but it went very smoothly.
This was a scrap of acrylic that I already had and was already this size.
Shapeoko #Classified some of the bolts may be original parts.
Shapeoko 1 # ???? Stainless plates, still in the box.
Shapeoko 2 # 3926 not stock
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zimmer62
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Re: Alignment holes for a two sides part.

Post by zimmer62 » Wed Aug 15, 2012 1:17 pm

zimmer62 wrote: q2) What kind of bits do you use to drill through acrylic and wood at the same time? (end-mills don't plunge so well into acrylic and I ran into problem when trying this.)
q3) how are people clamping things to their board, something like 3/8" acrylic I've been drilling a couple holes in it and screwing it to my waste board.
I feel like I found a special drill bit is required for milling through holes in acrylic. I've been trying to find some 1/8" bits designed for plunge drilling... Anyone?

q3, The blog posting on http://blog.makezine.com/2012/08/14/too ... ore-233114
Any idea what that is or how it was made? That looks like a pretty good way to clamp things down.

edwardrford
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Re: Alignment holes for a two sides part.

Post by edwardrford » Wed Aug 15, 2012 1:33 pm

I'm trying to find a contact for the user who wrote the review. Mainly to say thanks for the great article and to ask what his hold down method is. Because I agree, it looks simple and awesome!

From the picture it appears to be 2 paint stirrers butted together, then a space, then two more paint stirrers. Could that be true?

-Edward
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zimmer62
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Re: Alignment holes for a two sides part.

Post by zimmer62 » Wed Aug 15, 2012 1:43 pm

edwardrford wrote:From the picture it appears to be 2 paint stirrers butted together, then a space, then two more paint stirrers. Could that be true?
After looking at it for a little bit, that was the conclusion I came to as well... I would like to know how they built it, and I'd be interested in trying that. A very interesting idea given the price of pain stirrers.

bobt
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Re: Alignment holes for a two sides part.

Post by bobt » Wed Aug 15, 2012 5:42 pm

The article appears to have been written by http://blog.makezine.com/author/mjnewman/

You can probably contact him thru make magazine.

Bob Teeter
"What Box???" ShapeOko #397

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