Hold Down Fixture

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Kerry Fullington
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Hold Down Fixture

Postby Kerry Fullington » Mon, Jul 11 2011, 6:57AM

I am playing with an idea for a Hold Down Fixture for parts while carving, fluting, profiling etc.

fixture.jpg
fixture.jpg (10.7 KiB) Viewed 3778 times


This fixture will be 24"X120"X5/8" melamine. I will machine grooves to accept gasket material. I will use the machine vacuum to hold the fixture in place and either drill through the fixture (and plug as needed) and the table board to get vacuum for my parts or I will use the machine vacuum to hold the fixture and use a venturi pump to vacuum the parts.

The fixture will be positioned using the pop up pins and parts can either be positioned by the pins and I will also have a 1/4" square that I can add to the fixture top to position parts and use a fixture offset.

This should work for a variety of parts.

any suggestions?

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Re: Hold Down Fixture

Postby Kerry Fullington » Mon, Jul 11 2011, 7:15AM

I noticed the jpg eCabinets produced in the Cabinet Editor did not have any detail.

Here is another picture of the fixture.

fixture.jpg

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Re: Hold Down Fixture

Postby Josh Rayburn » Mon, Jul 11 2011, 7:36AM

Hi Kerry,
Looks like you don't have any holes in the fixture to let the vacuum through - or maybe the detail is just not showing up.
I would recommend the holes or at least one hole in the middle, and maybe some edgebanding on the edges of the fixture if you plan to use it a lot. This just increases the durability of the positioning edges compared to the MDF edges, with say a 1mm PVC banding maybe...?
In most cases, we just double-stick tape the blank to the wasteboard, since we have a large variety of parts and sizes that don't always have the quantity to warrant making a fixture. But when the quantity gets to a certain level, or if the parts being machined are difficult to hold down, it is worth the investment.
jnr
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Kerry Fullington
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Re: Hold Down Fixture

Postby Kerry Fullington » Mon, Jul 11 2011, 9:22AM

Thanks Josh,

I haven't put holes in the fixture yet as I haven't decided on exact locations.

I will probably try to go the Venturi route because I don't own the machine and Keith might not like me drilling holes through his table board and I know the venturi/s will give excellent hold down.

I haven't finished the fixture in the picture because all the part editor cuts have slowed eCabinets to a crawl. It takes about five minutes for the part editor to profile each groove now. Gets very boring as I am only about half way done.

I want this fixture for cutting multiple parts (mostly fluting and panel cuts of long pieces) The double stick is just too time consuming for multiples.

Would you put this fixture over the 1/4" wasteboard or remove the wasteboard and place it on the table board?

If I drill through the table board for fixture vacuum I was planing to cut a 1/4" melamine to cover the rest of the table for better suction.

I was just thinking one benefit of drilling through the table board is that if you have an odd shaped piece you could just drill another hole to accommodate that piece and plug it later.

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Re: Hold Down Fixture

Postby Josh Rayburn » Mon, Jul 11 2011, 12:24PM

Hi Kerry,
No, I would not drill through the spoilboard. I would drill through the fixture though, somewhere towards the middle of what you think will be the most central location, depending of course on what types / sizes of parts you'll be machining. I would run it without a wasteboard.

I don't know what kind or size of vacuum you're working with, ours is an 18hp rotary vane. We pull lots of vacuum and have scraps of shower board (white one side hardboard, about 1/8" thick) that we piece together to cover up the rest of the spoilboard or wasteboard when machining smaller parts.

We haven't had much trouble, we've pretty much got it down to a science.
Feel free to give me a call and I can give you more info if you like.
jnr
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jerry johnson
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Re: Hold Down Fixture

Postby jerry johnson » Mon, Jul 11 2011, 6:01PM

New jamb part hold down board.pdf
(49.87 KiB) Downloaded 269 times
New jamb part hold down board.pdf
(49.87 KiB) Downloaded 269 times

Hi, Kerry. Unfortunately I no longer have my shop or my Thermwood router. However, I am working on another router and have had the opportunity to design and use gasketed boards for a multitude of applications especially in solid lumber machining. The attached pdf's show a small sample of the stuff we have been machining. The arches were parts for a large grape arbour and were cut out of 4x6 and 4x8 solid fir lumber. The gaskets held with no problems. I have also attached a pdf of the board I use for miscellaneous machining. I know you will need to make some specialized router table boards but it doesn't take that long and you will be amazed at how well they hold your parts. We have a fixture that is quite complicated for machining entry door parts. The parts are on elevated, gasketed pods so we can drill the edges for dowels and run a cope and stick detail. I have also designed some angled pods that have the gasket material on the side for holding the entry door stiles for routing the hinge recesses on a 3degree bevel. Take a chance and make some of these for small parts and you will expand your universe of machining options with a simple 3 axis machine. Another note is that most of the items are designed using a cad/cam softaware which is much more flexible that the part editor in Ecabinets. Have fun! 8)
Attachments
ARCHES 4--IT AND 1--IT.pdf
(32.13 KiB) Downloaded 188 times

Will Williamson
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Re: Hold Down Fixture

Postby Will Williamson » Tue, Jul 12 2011, 9:09AM

I don't hesitate to drill through my spoil board . just use a hot glue gun to fill the hole. I want maximum holding power. I usually make a new fixture for every new part and throw them away when I am done. Make sure that when you pull a part down that you grab it and try to pull it off . If you can pull it loose by hand you are taking a chance on the part coming loose and flying across the shop. Believe me if you do a lot of machining of thick solid lumber you will soon learn to check the part every time. and don't stand in front of the part you are working on. the best place to watch from is sitting at the control panel so you can slam the E Stop, This machine is no different than a shaper or jointer or table saw if it grabs that part just right it will go half way through your gut.
I put my machine right to its limit on a regular basis
I use DXF files to dowel my fixtures to the spoil board of the machine and then use the profile modeler to run the part . be careful because the profile modeler does not take into consideration the wasteboard or fixture thickness. So you have to write it in every time you write a file to CNC

Hey Jerry good to see you on here again,
Same here, we do a lot of machining of thick solid lumber for Architectural Millwork Big doors in particular. I have been using simular fixtures could you send me an email will@willmade.com about the software you are using? what brand of aggregate are you using?
Thanks Will Williamson
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Re: Hold Down Fixture

Postby Kerry Fullington » Fri, Jul 15 2011, 6:17AM

Thanks All,

Some good Ideas here. I am looking for a way to hold different size and shape parts with a fixture that is easy to set up and remove.
I forgot to mention that this fixture is just for parts that have no through cuts, just profiling and carving.

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Re: Hold Down Fixture

Postby Brad McIntosh » Fri, Jul 15 2011, 8:41AM

Kerry,

Take a look at this YouTube video. Thermwood Sizing Solid 5 Piece Doors On A Flat Table (Be patient with the intro... and note that at around 1:47 there is an example of machining the exterior of just a frame with NO CENTER PANEL.)

The material use on the table is "FSE0135 - Thermwood - Spoilboard Cover Vacuum Seal" and is sold in rolls 48" wide x 120" long. (We sometimes refer to it as "rubber matting".) It is available on Thermwood's On-Line Store FSE0135. (CNC Automation's Canadian clients can get it here-SBC-CE0648)

Image

The material is applied to a pre-surfaced MDF fixture board/sheet. In the video linked above we then drilled an array or grid of shallow/blind holes across the surface. These holes act as little vacuum chambers. The video should speak for itself. (Of course it is a good idea to use down shear tooling.)

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Re: Hold Down Fixture

Postby Kerry Fullington » Sat, Jul 16 2011, 7:40AM

Brad,

Thank you very much. That looks like it might be the best solution.

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Re: Hold Down Fixture

Postby Daniel Odom » Thu, Jun 21 2012, 4:40PM

Brad McIntosh wrote:Kerry,

Take a look at this YouTube video. Thermwood Sizing Solid 5 Piece Doors On A Flat Table (Be patient with the intro... and note that at around 1:47 there is an example of machining the exterior of just a frame with NO CENTER PANEL.)

The material use on the table is "FSE0135 - Thermwood - Spoilboard Cover Vacuum Seal" and is sold in rolls 48" wide x 120" long. (We sometimes refer to it as "rubber matting".) It is available on Thermwood's On-Line Store FSE0135. (CNC Automation's Canadian clients can get it here-SBC-CE0648)

Image

The material is applied to a pre-surfaced MDF fixture board/sheet. In the video linked above we then drilled an array or grid of shallow/blind holes across the surface. These holes act as little vacuum chambers. The video should speak for itself. (Of course it is a good idea to use down shear tooling.)


We may be doing a job soon where we'll have to cut out thousands of 3x11 inch rectangles out of 1/4 mdf melamine 4x8 sheets; would this rubber matting be a good way to cut these parts without using support tabs? Or is there no good/easy way to do this? My past experience tells me no way no how, I've been asked to quote it anyhow.

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Re: Hold Down Fixture

Postby Will Williamson » Thu, Jun 21 2012, 7:41PM

Try 1/8 single flute down spiral set to Z0p1875 followed by 1/8 single flute up spiral set at Z0p25
no tabs, turn off dust collector let sawdust hold everything in place
Will

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Re: Hold Down Fixture

Postby Daniel Odom » Fri, Jun 22 2012, 9:13AM

Thanks, I'll certainly try the dust packing method, still just curious if you can machine an entire sheet with this mat though, I run into small parts all the time and it would be nice if there was an easy way to machine them and save time. I guess there's only one way to find out, just wondering if anyone had experience with this rubber mat technique.

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Re: Hold Down Fixture

Postby Brad McIntosh » Fri, Jun 22 2012, 10:02AM

Daniel,

As demonstrated in the video, the matting with the "general purpose" hole grid will not work for small parts. The intention with our hole grid was to hold 5 piece doors in place and it is working well at a recent installation. The ability to hold various sized doors without specific fixtures sized for each door was crucial.

Solid Wood Door System installation in Saskatoon

For your "small parts" you would go back to the original intended application of this material - You would machine/pocket areas of the membrane under each part location and within the boundary of each part (say 1/8" to 1/4" in from the part perimeter). The machining should removes the membrane completely in those areas (and maybe just a little ~0.010"-0.020"~ into the underlying fixture board). What you are left with is custom conventional vacuum cups or pods under each of the small nested components.

Hope this makes sense....

Daniel Odom
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Re: Hold Down Fixture

Postby Daniel Odom » Fri, Jun 22 2012, 10:05AM

Cool, that would still save me a lot of time/ frustration, thanks.


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