The stuff I cut this week.

[knight_toolworks]

First are these aluminum boxes for some high end ipod amping. I had to make the jig to hold them and I wanted them as close to the same height as possible, I have not had time to setup air cooling and my test holes did not cut well so I just drilled the holes on my mill. It was faster anyway as I could have the cnc doing the v carving at the same time. The boxes took about 12 minutes for three of them and the endplates. That’s two passes with a copied toolpath. As the aluminum tended to stick in the grooves. I found an engraving bit made a nicer cut then my regular 60 v bit did. But it also takes more effort to cut so things need to be held down well. The jig will have be all toggle clamps by the time I use it again. I wanted to try a set before I bought 12 of them. The only bad part is the safe z needs to be higher then normal.

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Then onto the ipod block docking stations. They are 4x4.25 and 2.7 tall These were fun to do, pretty hard to draw out. The base is hollow and it is cut with 2d toolplaths for the basic hogging and the larger ramp is done in 3d. it could all be done in 2d using a ½” 90 v but I found it hard to get the right depth on the small v cut. I zero on the table surface raise the bit to the right height and zero. Then I run a raster at 0 to level the block so they are all the sale height. The ramp worked ok. But I found it faster to do 2d and 3d. Total cutting time is about 6 minutes with a bit change to do the hollow most of the work is done with a ½” bit then a 90 V to do the v cut. Depth is critical because the connector is not very long. I hold them with a simple angle bracket screwed to my table.
Then onto the face. This was a fun one to get it all right since depth was critical and it is hard to hold this block in place. I remove the bulk of the face on the table saw. Then do a raster to face them to the exact higher and remove the bulk with a straight bit and then do the rest with a bowl router bit. I clamp them in a big v jig but it is hard to clamp them as the sides are so then. I think I have it worked out on the next ones. I am waiting for the pattern to drill the holes in the back. Here are pics to a finished one.

http://www.knight-toolworks.com/cnc/ALO-Vcap-Maple.jpg

http://www.knight-toolworks.com/cnc/ALO-Vcap-Maple2.jpg

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[joe]

Thanks Steve for the post.

Now I realise the need to spend more time with my hold downs, and jigs. It's good to see how you approach this element of your work.

As usual your skill and attention to detail is of the highest quality. To me, the docking station is a piece of art itself.

Perhaps you could post a photo or two of your decorative boxes. They are jewels.

[knight_toolworks]

I wish I could say they are perfect but most of my jigging is not much. I have always hated setups but on the cnc it's easier to make jigs. I need something better for the ipod blocks. I had trouble cutting the top and holding it in place. when you clamp it the sides are pretty thin. but I am doing such oddball things that I have to figure these things out. my first jig for the metal boxes let things move around and scraped the finish off.
my skill level and attention to detail are not very good. I have to work hard at it. I used to be pretty sloppy now I am just ok (G) pictures don't show the mistakes always.

[Brady Watson]

Steve,
Why are you not using vacuum?

-B

[knight_toolworks]

well it did not work. I made a little puck for the ipod blocks and they just popped loose. plus there was a hight issue the blocks are 3" tall the bit has a cutting length of about 2.5" and the puck together does not leave enough z room.
I had not even though of one on the boxes. they are really small about 3.1x2.5 and they need to be really solid to get good engraving.
the ipod blocks work great getting clamped to the angle bracket. I can take them off and put them back very fast and they are always lined up.

[Brady Watson]

Steve,
You don't need much room for a vaccum fixture. It can be as thin as an 1/8" (even thinner in some cases) depending on what you have as a vac source & where the vacuum enters the jig. If you are only engraving, then vacuum is a no-brainer as there is no real side force on the workpiece. If vacuum doesn't work the 1st time out...try, try again! AllStar gasketing is a great help as well.

-B

[richards]

At first I thought that the 3.1 X 2.5 size would be too small for vacuum, but, after doing the math, it looks like it might work. After allowing a little room for gasket tape, you end up with a vacuum pocket area of about 2.75 X 2.25, or about 6.2 square inches. If you used a vacuum pump (GAST or similar) that can pull 23 inches of mercury (or more if you're at a lower altitude than I have here in Salt Lake City, which is about 4,500 ft), you would end up with about 6.2 X 23 X 0.5 = 70 lbs (aprox) pushing down on that part.

A lot would depend on how hard you're pushing the cutter, but if I think it just might work.

[knight_toolworks]

I found using an engraving bit causes a lot of movement. I had to put a fair amount of pressure on these pieces to keep them from moving. using a 60 v did not put much stress on the piece but it does not cut as nicely.
but if the vac won't hold the block it is kind of pointless. the block is tall enough I think it is a matter of leverage.
vacuum is good but it can be a pain it has it's problems too. part jiggle is one of the biggest issues I have had with small parts holdown.
but it is also the time to make vacuum pucks running lines and such. and if you need really good parts lineup you need some sort of mechanical device to use to align the part with.
so sometimes the simple method is far easier and fast. the parts are always lined up and you don't have to worry about the vacuum failing or the pice moving