www.TK560.com

[Mattax]

I made a design for the plastic frame holder but need some FAST input on clamping it together.

The frame is made from 3/4 inch tall by 1/2 wide aluminum angle welded into a square (four sides). A smaller frame 1/2 inch tall by 1/2 wide is placed inside and on top of the larger square. There is 1/32 of an inch play so that it fits ok. The entire frame will go inside the bottom edge of the oven for heating the plastic.

The only areas I have to play with are 3 inch sections that will be open into the table frame on the inside of the four corners.

I am thinking of cutting the upright section of the 3/4 inch and welding a solid piece to the inner frame 1/2 upright. This will extend it out to the outer frame. From here, run a bolt down through the outer frame and tighten with a nut.

I understand without a drawing this is not helping you.

Are there better fasteners other than using nuts and bolts?
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Mattax
TK487
Garrison Tyranus

[Mattax]

Here is another way to look at the fastner I need.

The top frame needs to be held down tight into the bottom frame. The holding mechanism needs to be mounted under the bottom frame. A hole can run up to the top frame.

From a side view both of the frames look like an "L".

Basically, a pin can be welded to the top frame going down through the bottom frame. Then a fastener can grab hold of the pin (or some a catch device)and tighten it down thus securing the top frame to the bottom frame and keeping the plastic held in tight. I am not having any luck finding this type of fastener.

www.mcmaster.com look up "latch"

HELP???
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Mattax
TK487
Garrison Tyranus

[crashmann]

Hi Mattax,

I am also interested in finding a better plastic clamping mechanism. Ideally some type of cam lock that can be operated by one hand. If you add a pin to the top frame that passes through the bottom, make sure it doesn't need a notch or hole cut in the plastic. Making the notch for every sheet can be a pain in the butt

My eye bolt and wingnut method requires using a wrench to lock down and release the plastic sheet. Also, the threads on the eye bolts get stripped after a while, and I end up replacing them on a regular basis.

Is there any way you can provide close up pictures of your frame?

Charlie
TI-386

[Mattax]

Not yet. I am having it made.

I am looking at using Work-Load Rated Draw Latches with Slide Bolt on page 2826 mcmaster carr. I will have to weld on flat bar of aluminum going 90 degrees down under the bottom of the frame at the 4 corners in order to use this clamping device.

The nice thing about my table is the holes in the frame design for the four corners. Although limited it will allow for the underside add ons to go below the table surface.

I will need to talk to the local fabricator to ensure this can happen.
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Mattax
TK487
Garrison Tyranus

[jegner]

I have heard about using some sort of luggage buckle too.

[Mattax]

Lugage buckles will not tighten down the metal.

By using the draw latches, the logistics in frame design may be pushed a bit and it may not work at all due to the distance the latch needs to open. Right now I have 1.312 inch of opening distance. I may be able to open this up if I make the latch at least 6 inches below the table surface. The other problem being I may not be able to get the inner frame out of the outer frame due to the latch catch.

I think I am over engineering these draw latches into the design. I want to keep it simple but I am running out of ideas.

Fresh perspective anyone?
_________________
Mattax
TK487
Garrison Tyranus

[jegner]

If you have any pics of your problem post them. Maybe someone here might have an idea.

I use a #8 bolt about 3 inches long. I bend it in a 90 Degree angle, towards the head, and then fold over a piece of flat metal. This attaches it to the bottom frame. I then took a second piece of flat metal, and made a 'U' shape on the end, and mounted that to the top frame. A solid brass #8 wingnut is all I needed to hold the frames tightly to the plastic.

Jim



This shows the config. I have since moved to the solid brass wingnuts, as the cheap ones kept stripping out. Oh, and please don't laugh at my pathetic welding skills. It's been 20 plus years since I had done any. LOL.

[Mattax]

Thanks for the info. No laughing here. My welding skills are only a little better.

I just want to stay away from wing nuts and threaded rods/bolts. What about a quick connect? Perhaps a single 90 or 180 degree twist to take off a connector. One could place a spring underneath the twist off connector on the pin shaft.

There are compression cam latches that would do this, but the swing area is too wide.

I will continue to ponder this. I have a couple of weeks before the vac tank is in and a couple more after that to get all the valves.
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Mattax
TK487
Garrison Tyranus

[Mattax]

I have figured out that Toggle clamps will work. I just need to figure out which one will fit in the alloted space. These clamps will hold down a minimum of 100 workforce pounds. And a bolt can be screwed into the end which makes it perfect for designing around corners.

Once I actually figure out the exact mounting and distances, I will post my design.
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Mattax
TK487
Garrison Tyranus

[Mattax]

BTW, I like your rolled edge to the table top. I would have to remake my table top in order to do this.

How did you roll the edge? Will my cut edge be a problem in cutting into the hot plastic sheet?

I suppose I could grind the edge off. My drop is only 1/8 of an inch and even that is adjustable by raising the 24 by 24 table height. I could even have the table be flush with the bottom of the frame holder.

Thoughts?
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Mattax
TK487
Garrison Tyranus

[crashmann]

You'll definitely want to roll the edge of the forming platen. Otherwise there's a danger of it tearing the plastic sheet, and you will lose vacuum seal. Also, I think the platen works better if it is raised higher than where the sheet is mounted in the frame. This will lead to a better seal between the plastic sheet and the platen. With my design, the top of the platen is 1/2" above the clamping frame. I think with Jim's, it is 3/4"

Definitely let us know what you find for a clamping solution!

Charlie
TI-386

[Mattax]

Will grinding the edge work?

If not, I will have the local fabricators add a lip and grind the surface flat.
_________________
Mattax
TK487
Garrison Tyranus

[crashmann]

I would think that grinding the edge would be fine. I was concerned about the corners of my platen tearing the plastic, but that hasn't happened yet. The main thing is to avoid something really sharp, because wasting a sheet is just disheartening

Charlie
TI-386

[jegner]

The edge of my plastic when it is held in the frame and is lowered onto the forming platen, the platen pushes up into the soft plastic leaving about a 1/4 to 3/8 inch indent. This gives a great seal.

The corners are the areas I would be most concerned about. I used a hammer and tapped the corners of the platen to get a good soft corner.

Jim

[Mattax]

I talked with the fabricators and they can add edges then roll them down.

At this point I will have to alter the lower chamber to meet the new rolled edges unless I can simply grind them down.

I am allowing 1/32" between the frame and the table top. If this gets pushed down 1/8 of an inch, It should suffice with the rolled edge for spacing.
_________________
Mattax
TK487
Garrison Tyranus