Seeking help cutting aluminum Vacuum Plenum

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Seeking help cutting aluminum Vacuum Plenum

Postby ccm » Sat Aug 31, 2019 1:54 am

Hello All,


My CNC project has been shelved for quite some time due to work and other projects. So I actually got back going on it a few days ago and the large part of cutting the vac table is close at hand. I have most of the design done but still need a few tweaks like coming up with a manual clamping facility as well (threaded holes???). In my Aspire file I have included my under table supports, angle iron mounts and screws for them. The overall table size (the aluminum) is 48.625" X 112" so a full size sheet fits on it. I'm putting (2) 2" holes in each section for vacuum and had to offset them on the left side just so the pipes clear each other to the rear manifold and so that I have clearance to get under there and tap them without the table supports being in the way.

Bit I have to cut this is a Niagara N66102 which is a 2 flute TiNC coated carbide bit. What I have calculated for speeds and feeds is 67 inches per minute speed rate at 16,800 rpm. I was planning to just take .1 inches per pass while using my little blower with some mist of cooling fluid (water and Kool Mist).

So some questions I have are...

- I am having trouble getting the vectors closed on my grids...

- One of my corners won't radius

- Is there a better way to do manual hold downs for long 3D work, etc. so the 10HP vac pump doesn't have to run?

- Does this table layout look worth a darn?

- How do those feeds and speeds look with that bit?

- Do I do a climb or conventional cut?

Thanks for any advice you all can give me on this. I'm going to try and get some of it cut sometime tomorrow.

Chris...






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Re: Seeking help cutting aluminum Vacuum Plenum

Postby Adrian » Sat Aug 31, 2019 9:55 am

You won't be able to close those vectors. You can't join a vector to the mid-point of another vector. They can only be joined at end points. Generally you would use the profile toolpath set to be On the vector with vectors like that but I don't know what the overall result is supposed to look like.

The corner won't radius as you have overlapping vectors at that point. If you drag the node away you can see the extra line and it's visible by looking at the dashed vector line as well.
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Re: Seeking help cutting aluminum Vacuum Plenum

Postby ccm » Sat Aug 31, 2019 12:34 pm

Adrian,

Thank You.. I got the corner fixed... those sure seem hard to find and get a hold of to remove. I want my table to just look similar to the 3rd pic here https://nemi.com/vacuumgridtable-2.aspx but I'm using a ball nose so I want rounded bottoms for the sealing cord to lay in. I was getting an error of open vectors when trying to create a tool path and it told me to join them. So what I'll have to do to them is use the profile for the outer perimeter and then the fluting tool path for all the individual lines, correct?

Thanks again,

Chris...
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Re: Seeking help cutting aluminum Vacuum Plenum

Postby ccm » Sat Aug 31, 2019 12:42 pm

It seems to be doing what I want that way... Now I'm rethinking those offset vac holes. I was trying to minimize the use of fittings but now it just looks dumb and I should probably just insert a tee where I want them offset??

Chris...
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Re: Seeking help cutting aluminum Vacuum Plenum

Postby ger21 » Sat Aug 31, 2019 12:54 pm

I'd use the profile toolpath for all of the slots.

I'd remove as much material as possible with a straight bit, and a final cleanup pass with a ballnose. I've never done it, but I think cutting slots in aluminum with a ballnose bit is going to be problematic. Imo, you don't need round bottom slots. Our Morbidelli has square slots, and uses round gasket. And I've used a pod and rail machine where the pods had square grooves and used square gasket from All Star Adhesives.
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Re: Seeking help cutting aluminum Vacuum Plenum

Postby ccm » Sat Aug 31, 2019 2:21 pm

So this is with some modifications. I just thought rounded bottoms was the way to go for the round sealing cord. I no see there's even "d" shaped sealing cord that can be used on the flat bottoms and having the round cord against a flat is the same as it'll be against the mdf spoilboard. duh!

So in looking at this thing what else am I missing or should I do? I was trying to embed some t track at one point but all the tracks I could find then were too tall to embed for the 3/4" thick plenum. I'm really wanting some useful manual hold down solution so I don't have to run the pump except for when it's needed. This 10 HP Becker along with 4 HP dust collection, the spindle, etc. is going to spin my meter like crazy!

I'm also wondering if there's enough metal left at the vac holes to thread and attach my 2" PVC nipples...


The Aspire file is now too large too attach.

Chris...
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Re: Seeking help cutting aluminum Vacuum Plenum

Postby ger21 » Sat Aug 31, 2019 3:37 pm

With a 10HP Becker, I'd use vacuum for everything, if possible. We use vacuum exclusively on our Morbidelli. It has two 10HP Beckers on a 5x12 table. For small parts that may move, I block them in with scrap melamine.

You could always drill and tap the aluminum in between the gasket slots.
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Re: Seeking help cutting aluminum Vacuum Plenum

Postby ccm » Sat Aug 31, 2019 4:27 pm

ger21 wrote:With a 10HP Becker, I'd use vacuum for everything, if possible. We use vacuum exclusively on our Morbidelli. It has two 10HP Beckers on a 5x12 table. For small parts that may move, I block them in with scrap melamine.

You could always drill and tap the aluminum in between the gasket slots.



Hey Ger21,

I'm in Cali... do you know how high our electricity rates are? We are punished here just for breathing now days... I think going the route of drilling and tapping some holes on the square flats is a good idea. I can then make a spoilboard with t-tracks, etc. on 1" mdf to clamp small stuff to. The reason is when doing 3D carvings and such they can take 12+ hours working in a small area so the vacuum would be a waste. I like those rockler hold down clamps that are made for t track... quick, easy, cheap and effective.

Chris...
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