Official Luthiers Forum!

Rather than posting in the Fret Slotting thread I figured I'd show off a new vacuum table I made to hopefully speed up working with sheet goods.

The interesting things about this table are that I'm using 1/4" round foam cord for the seal in square cornered slots per Bob's recommendation. Additionally, I added a 41.5 degree chamfer on the slots which completely eliminates the chance of pinching the cord between the table and the part. I ended up cutting the slots .175 deep because at .150, on small parts the foam was pushing the ends up a little bit.

The material is the 40 lb/ft^3 tooling board from General Plastics suggested by Stuart and this stuff is a dream to work with. No warping, cuts like butter and is at least as strong as MDF.

To use this table, I originally bought a 7cfm rotary vein pump but that ended up being completely unacceptable because it's an oiled pump and the mist from the exhaust completely filled my basement with a fog. I've got a 5.5cfm oilless pump on the way.

With the 7cfm pump it sucked down even very porous materials like 1/2" mdf with no problem what so ever. I'm hoping the 5.5cfm pump will provide similar clamping action.

The square pockets on the table are there to accept needle plates which will prevent the parts from squirming. On bigger parts that's probably not even necessary as there's enough surface area to get good clamping pressure without them but for small parts it will be invaluable.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Do tell more Andy! How do you have it divided up? What kind of valves for the zones etc? Looks Awesome!

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

At the moment, it's only one big zone with one vacuum inlet hole near the origin (lower left corner). The 1/4" cord is used to cordon off whatever shape is required for the part. I may run a line to the center of the table for parts or instruments or whatever that won't be conveniently rectangular in shape. Basically, I'll worry about that when I need to.

The idea would be to use this for flat types of projects (obviously I guess). I made some guitar molds a while back (using regular clamps, not vacuum) and I found that a good work flow for me was to leave an 1/8" onion skin at the bottom of the part and then freeing the parts on my router table using a flush trim bit.

With a 1/8" onion skin I shouldn't loose too much vacuum when cutting out parts. I've got a couple of moulds to do next week and I can report back on how it went.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

That's awesome. Can you show a picture of the chord you're using to section it off?

Needle plates?

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Andy that looks awesome! You continue to amaze with the great things you are doing with your CNC, since you acquired it!

Did you first surface the top and bottom of the tooling board, since the aluminum table might not be exactly flat?

Do you have a link for the tooling board and the cord?

I am currently in the process of building a vacuum table(s) for my CNC machine, fixtures etc....I have a 4cfm oil less pump on order....and yes, I almost made the mistake of getting an oil pump from Harbor Freight, but luckily I stumbled upon a post that talked about the mist, so I quickly dumped that idea! Your needle plates look interesting as well, and will have to try them out soon!

Great work!

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-CyborgCNC
http://www.cncguitar.com
https://www.facebook.com/CncGuitar

Taking a picture would involve that long trip downstairs and unfortunately, I seem to have gotten the flu and just typing is wearing me out

This is the stuff I'm using: http://www.mcmaster.com/#catalog/119/3540/=l3anfi it's P/N 8605K42 - just a round section smooth cord. When I gain enough strength (poor me) I'll take a couple of pictures that show how it works.

The needle plates are something that I discovered through a friend and am now actually the U.S. distributor for. You can see them here: http://www.birkonium.com/product-catego ... omponents/

It's basically a thin plate with a bunch of steel needles embedded in it that dig into the part under vacuum. I've done some informal testing and they work very well. Not entirely necessary for large parts where you can develop a lot of clamping pressure but for small parts or pod systems I think they'll be fantastic.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Oh, and here's the link to the tooling board: https://www.generalplastics.com/product ... ms/fr-4500

The board comes very flat and consistent but I did surface .010 off of the top before cutting.

Yea, unfortunately I'm out $40 in shipping on the oiled pump as I had no idea about the oil misting. When I googled vacuum pump oil misting I got a million hits but who knows what they don't know?

Apparently you can make a filter from an oil filter but I didn't want to bother with that. The 5.5cfm pump was just over double the price but it's a U.S. made Gast pump that I'm sure will provide service for a long time. I got it from Joe Woodworker - his stuff isn't the cheapest but it's pretty dang good http://www.veneersupplies.com/products/ ... n-New.html . They've also got a 3cfm pump for just over $100 which is dirt cheap for a pump of that size. I went for the 5.5 because it can make up for leaky fixtures and porous woods more betterererly.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

dang!! I am in NY, and we are getting hit hard by the Flu as well, but so far, we have managed to stay flu-free (Praying...)

Hope you feel better, and my wishes for a speedy recovery!

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-CyborgCNC
http://www.cncguitar.com
https://www.facebook.com/CncGuitar

Oh and one other thing - I finally got around to making my aluminum fence blocks which are also visible in the shot. they sit along X0Y0 and are machined once they're in place. If I ever re-tram the machine or whatever that might change the position, I simply re-home the machine after re-assembly, scootch the fences in a little and re-cut my zero faces.

You can't see it but the block at the origin is "L" shaped with about 3/8" sticking out into the Y direction. Whenever I make a new fixture I just shove it in to the corner and that way I can re-place the fixture within a thou pretty much every time.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Looks good!

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Brad
Avon, OH

Nice indeed! How expensive is the tooling board?

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David Malicky

I got it for $200 for a 24x80x1" sheet but, I also have a local distributor. The manufacturer quoted me more than triple that delivered to my house.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Dear Andy,

Wow, that's a really nice vac table. I remember my first vacuum table. I was aluminum, and I was using that stupid square gasket that got pinched under parts. It sucked. I can't express the feeling of joy I have for your accomplishments, combined with envy at how quickly they're coming along, as there is no word for that yet. Maybe friendvy.

Glad to see things are moving along so quickly for you, I can only imagine the terrors you will unleash upon the world as your powers increase and you inevitably fall into madness and disillusionment with those who cannot so easily bend the robots to their will. Just remember that I've always had your back.

Seriously, that's a nice looking table. I used to build carbide pins into my fixtures (I had a LOT of snapped off 1/64" cutters around) but they were rather annoying to remove when I didn't need them. Anything increasing the amount of friction you have available to you shoots up the effectiveness of a vacuum system immensely. Having nice tooling makes every job so much more pleasant, partly due to the knowledge that you're much less likely to have a part launched at you. I tell you, I will always miss the windows on the Fadal.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Nice Andy. When you get it up and running, let me know. Might be time for a visit! I am still doing the tape routine. I set up an MDF board for cutting braces and after a test with fir, I gave it a go on red spruce. Love this machine! Within a few minutes I had a full set of nicely radiused braces. Would love to add a good vacuum table.

Nice job with the table!

Ken

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http://www.casperguitar.com

Oh, it's up and running - c'mon over! Cut out some guitar molds with it the other day and I'm loving it. With large pieces like that it's a rock solid connection and the needle plates just lock it in.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Hi Andy,

I am doing some tests with the same cord on a 1' thick HDPE slab....just cut the first slab for machining a neck. Question for you: How wide did you wind up cutting the channel for the cord? My cord is also 1/4' round, and I cut the slot a little over half the diameter of the cord at .150. I cut the depth of the channel at .180. I am still doing some tests with a 4 CFM pump, but I am finding that the part stays a bit high, and I think that would cause it to deflect with a down-cut bit, around the edges....

When you turn your vacuum on, does the part make full contact with your table, in other words, the cord deflects as such the part gets flush with the tooling table? I might need to cut my depths a bit deeper....

Just wondering what your findings are..

thanks!

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-CyborgCNC
http://www.cncguitar.com
https://www.facebook.com/CncGuitar

I cut my channels to .175" so you should be fine at .180. I'd check for leaks or something like that. How much vacuum are you pulling when get a seal? I can get 25" with mine and even with porous stock like MDF I get more than 15" and a tight seal. check the sizes of your orifices too - if they're too small they might be restricting the evacuation of air.

Couple other things: I cut a square cornered slot, not a round bottom slot so that the gasket has somewhere to go. I also chamfered the edges of all the gasket slots by 1/32" to help guide an errant gasket back in to the slot if necessary.

With this, I'm getting a full flat seal. With the needle plates, I have to give the stock a little pound with my fist to dig in the needles but one they're down, it's totally flat.

Something to be mindful of as well - in my experience, HDPE warps pretty badly after machining but, it can be pulled flat. Just keep an eye out. If you surfaced one side, it will tend to go concave on that side.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Yeah, HDPE is warpy stuff. PVC, ABS, paper filled phenolic, or tooling boards and even MDF are more stable for tooling if you can't use metal.

It sounds like you're using way too thin a channel, it should be cord diameter. So far as parameters for the cord go, always use a flat bottomed channel at full gasket diameter and cut ~60-70% of diameter for depth and you won't have any issues with the gasket sinking in perfectly. I use 3/16" gasket and cut channels at 0.110", and no problems have ever been the gasket's fault. Chamfers on the channel are nice, but not necessary.

With the gasket installed correctly, the usual culprits are leakage or warpy stock (causing leakage). The pressure reading at the pump can be very different from the pressure reading at the part interface, especially if there isn't much air space underneath the part. You should have as much hollow space as possible under the part while keeping enough solid material to stop it warping into the void.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

So Andy and I have been talking on and off for a while, picking each other's brains on various things. I just wanted to post my version of Andy's fence blocks. Many thanks to Andy for all the wonderful ideas and advice he's given me.

Anyhow, here's my version. I think I made a couple of worthwhile improvements and maybe someone might like to incorporate some of these features in their own fences. The differences are:

1) my blocks insure that you can only ever contact at 3 points. If you don't do this, and there is any error in the squareness of your jig, you can have an ambiguity. Since I don't have a table saw in my shop anymore, I needed to make sure I could deal with less than ideal boards. In case it's not clear, think about what happens when you have a board with an angle less than 90 degrees. It's impossible to contact all three, flat faces at the same time.

2) I aligned the registration points directly over the t-Slots, and I defined my axis so that (0,0) is dead center in a T-slot. Now, any debris can never interfere with the registration of the jig since any debris at the registration point simply falls into the T slot.

Disadvantage...you can't just face it off to remachine it like Andy's. I looked at it again tonight, and I think I have enough room to re-machine it exactly once, and that's it. The smaller the radius of the registration point, and the less it protrudes, the more times you can remachine it in place. Really, though, I'm just using a piece of 3/4" phenolic that I got at Woodcraft, and that will last me for quite a few fences, so I don't really care. I'll just make a new one when I damage this one or I have recalibrate the machine. No big deal.



I'm working on getting those pictures and code to you, Andy! The thaw and freeze from yesterday turned my entire property into an ice palace, and there hasn't been a bag of ice melt...or even softener salt...to be found anywhere in weeks. Even Grainger is out, and Lord knows that's the last place I go for anything. GRRRRR.....

Those look great!

I like your idea of using protrusions to enable work with imperfectly square stock.

I really like that idea too but there's one other thing I've been doing that's been useful as well. I've got some of these:



With the flat faced fence, I can use them as the "other half" of the cam clamp.

I think what I might do on the next go around is to make the short leg have a bulbous face like John's and keep the flat faces on the long edge. I also recommended to John that in the future he cuts the short leg off right after the contact point so it doesn't get in the way.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

I DID cut them shorter...and then I had to take them off again because I decided to get that last couple of thou out of the system and I needed to remake them....and they got longer again! I'll probably just slice it off with a mill in the CNC tonight so you stop making fun of me about it

I've been looking for good work holding solutions. Those look interesting.

Those are from Grizzly

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

The company below often has vacuums, vacuum parts, pieces, fittings, gauges and other items at very reasonable prices........ Just have to keep checking if they're out of the items.

http://www.surpluscenter.com/

Another thing you can do with a small pump is make a vacuum storage reservoir which also will help in immediate setting of the part....... ( PVC Utility Water Line works great and you can often find small pieces..... 8" to 24" diameter and various lengths from local utilities or contractors the pipe usually has wall thickness's of 3/8" or thicker.... the utility people often have to saw off ends to make something fit ...... purchase caps at a local supplier of utility supplies/materials...... )

Blessings,

Kevin

Thanks for that cam clamp photo Andy.

So many great ideas on this forum!