Vacuum Jig with 5 areas of vacuum

[Mark Jones]

I am making some CNC Vacuum jigs. 5 different pods on one pvc board. Grin! Forget to accept the z change and the bit runs right through the brand new jig..... a "great scott" moment for sure. I am on my 4th revision on this vacuum jig that is 7.5" wide by 24" long. I have as much fun making these jigs as I have making these gift puzzle boxes. Vectric works great. I just learned associating Layers with toolpaths and automatic layers using toolpath option is really nice.

Here is a link to my experience with making this jig. Video of the process. I don't have revision 4 on there yet but I am learning as I go.


My first jig worked great as long as I was using onion skin on my boards by not cutting all the way through it..but after feeding it through the sander for 15 times I wanted a faster way and that is cutting all the way through the hardwood on top of the vacuum clamp. (I am still learning so this may be a futile attempt. I will say Vcarve makes this fun and the 3d view is really handy for spotting my layout mistakes.

I plan on making at least 50 of these boxes as gifts for years of service. So the vacuum jig will be better and make the work even fun. I have already made about 15 of these using screws and wood to hold them down.

[Tex_Lawrence]

I am making some CNC Vacuum jigs.

Mark, I didn't read what you're using for a vacuum source, but I've often wondered why folks with vacuum jigs don't add a vacuum "reservoir" to the output.

It should work just like a tank on an air compressor. One could easily be made from an old 20 pound propane tank, too.

[neilgill]

FYI I originally bought a small 1.5 CFM pump which has on constantly, but I realized when I had a good seal on the pods even with the pump off it held vacuum for a while. So I purchased a pump 5.5 CFM with a tank. I have altered it a little by adding a one way valve where the air is taken from the tank, thus preventing any minor leaks from the solenoid shut off that can be set to shut off at a set vacuum and turned on when the vacuum drops below a set pressure. This means the pump is on for a few minutes every 10 minutes or more if the seals on the work piece are good.

[Mark Jones]

I am just a hobby guy so no commercial stuff needed here as of yet. I am using a 3.5 cfm vacuum pump from Harbor Freight. I bought cheap to explore the possibilities. Will buy better if the need arises.

I did get the vacuum jig with 5 areas of vacuum made and working. It did fine on a white oak board. I did have to put a piece of tape to cover a small crack to get the inches of mercury to 15 or so. It milled out good. I milled the 2nd half of the Ranger Puzzle Box out of white oak, and it did great. I was set ....... so I thought.

Put a piece of walnut on it. My stock is 3/8" thick 6.5" wide by 23" long. Couldn't get it to seal and hold a vacuum. Hum... tried some tape. Put some Walmart self-adhesive shelf liner on the suction side of the walnut. It sucked down but the shelf liner started delaminating from the walnut and at best it was problematic.

Then tried some cedar same size. lots of cracks and knots and it wouldn't hold on the vacuum. Grumbled. Fiddled more.

I put two screws and fender washers in the middle of the vac jig to hold the outside center of the walnut board down and then milled the Ranger Puzzle boxes. Inches of mercury vacuum was 3 or 4. So the vacuum was doing nothing except making a fancy pinned hold down jig with location line up holes in it. GRIN! The oak worked fine. I installed 6 valves to test with so I could shut the various vacuum sections off. I was hungry and it was 5 pm so I put it off until today.

Note:
My plastic vacuum jig board has a slight warp in it. I am going to add some more screws to hold it down and see if I can get better results. It's a work in progress. I will say that vacuum clamping is problematic. When it works its sweet. When it isn't working screws and clamps do the job as always. I am having fun though.

If I get to the point this is a must have in the shop I will most likely add a vacuum reserve tank. I put a vapor mist filter I made on the HF vacuum pump and it works great for a hour or so but then I can start smelling the vapor mist...so I am going to vent that exhaust from the top of the filter outside so I can't smell it.

I will say that Vcarve makes making these jigs a snap and fun. I am thinking of making another jig with a deeper gasket grove to accept the front king foam like I just added to my bench sides to accommodate rougher material. I am videoing my learning curves so will post it back here later today.

Thanks for the tips and suggestions. Learning here so I don't know anything yet.

[martin54]

Many different ways to create a vacuum & which direction you go depends to some extent on what sort of work you are doing, it may be that vacuum pods are not the best option for the sort of work you are doing but as you say it's fun experimenting
The problem with vacuum pods is that the style of pump they use will produce a high vacuum pressure but they have a low flow rate which means you need to get a fairly good seal for them to work. When working with wood not only do you have to deal with cracks & splits but different types of wood vary in how porous they are so air can also be drawn in through the wood itself as well as any defects in the board. Add the fact that boards are not always perfectly flat & can cup & bow & there are more potential areas for air to leak in & when more air leaks in than the pump can remove it leads to failure
Make sure there are no leaks in your system first, check all the joints are 100% leak free. Not sure what sort of board you are using for your jig but some plastics have a degree of porosity which won't help.

I did look at your video but it was hard to tell how big your vacuum pockets are in relation to the parts that they were holding down. Increasing the size of each of the 5 zones so they are almost as large as the 5 bits of the box they are holding will give you better hold-down providing it doesn't allow more air to leak in

[Mark Jones]

Thanks for the tips. It finally occurred to me. Is my vacuum pump oil getting to old to create the vacuum? I bought it 3 weeks ago and have had it running for 50 hours ish.

Will find out today if that is the case. I have read on line that these things need oil changed after every use. After every 10 hours of use. After 50 hours of use. All the way up to 500 hours or so.

I am new to this stuff so I don't know any thing and am learning.

When I first started using this clamping method 2 weeks ago. It would hold 6 pods running and you could lift the work work table cart up with out loosing suction on these.

I could pull 29 inches of mercury with the gauge just on the pump and a 1' long hose. I would amagine if I went out and fired it up I would only be pulling 23 inches of mercury under the same conditions.

I plan on shooting a video on the test between 3 week old vacuum oil and fresh oil. Today.

Between last night and this morning I was wondering if the PVC board was passing air through it. I even put nylon tape on the threads again on the fittings that went into the new pvc board. Will find out in a bit.

[martin54]

If you have a half-decent pump then the manufacturer's owner's manual should give you what maintenance is required & how frequently this should be carried out, I would be inclined to go with that As you have found out there is so much info available online & it can be difficult to know what is right & what is completely wrong

There are also a lot of factors to take into account, oils like a lot of other things are not all created equal so how well they perform & how long they last will vary quite a bit.
The most likely cause of the drop in vacuum pressure will be leaks, finding them & eliminating them can be time-consuming if you have a lot of joints in a system, don't be fooled by thinking that a leak is only very slight & won't make a big difference because they will all affect the sort of vacuum you will be able to achieve & maintain with this sort of system,

[Mark Jones]

I found the culprit. I am still using mineral oil in the pump. I did change it but it didn't need it this soon even at 50 plus hours. I did need to add more to the pump. By using the gauge and drawing a 29 inches of mercury from the pump stopping at each point shuting down the pump with a valve right where it comes out of the pump and then watching for vacuum. By process of elimination using this method the filter that was the next thing in the line up that was part of the valve and gauge setup. I took them all apart and tested each section for vacuum loss. The filter was full of plastic and sawdust. Cleaned that out and tested again. It improved but wouldn't hold the vacuum. I removed it and bought a inline gas fuel line filter and put that next to the pump. Now it's holding 29 inches of mercury up to the 5 port pod jig that is made out of pvc. It holds that board pretty tight with 12 inches of mercury.

Modified my gauge and ball value cut off so it will still work on my clamping table and my cnc.

It was a fun day!

Now to get back to making those Ranger Puzzle boxes. Christmas party is next 15 days away and I need about 4 carved and finished for that!

[martin54]

Progress is always satisfying
If you have some small pieces of something like acrylic you could test the jig by covering the 5 pocket areas, I would cover them individually so you can easily check if you have any leaks around whatever you use as a cover. If the PVC is not porous then you should be able to pull the same vacuum as you have up to the jig. If you can't then you might want to look at some way to seal the PVC jig

If your 5 ported areas are big enough then 12 inches should be more than enough to hold it, the larger the surface area of those are the better hold down you will have even at a reduced vacuum

[Mark Jones]

My trouble shooting process on this vacuum jig.

[neilgill]

One more note. I was using a 10"x10"x1" oak. It has a few open cracks, very small, but was loosing vacuum too fast.. So I covered the back with painters tape (masking tape) and it held perfectly, as though it was holding glass. Almost no loss over time.

Neil

[Mark Jones]

Thanks Neil. I had covered one crack in my first white oak board and it made the difference for sure.

While I was in my vacuum leak "lost as a duck out of water" from my air filter that is for compressed air it had a slight leak in it and was plugging up with pvc and sawdust. I even went to walmart and got some self adhesive shelf liner and it held for a few minutes until it started letting loose on the board it was sealing.

After I replaced the leaking air filter and put a inline gas filter the suction was back up to like it was in my "this is going to work great faze"

It holds real well when the stuff is all tight!

It's funny how this stuff will sneak up on one and make one go down a few rabbit paths until one trouble shoots it back around to the issue at hand.

I took some of these carved up 2' long boards of pvc and made 2 feather boards and one shaving cream and foot spray holders out of them. Vcarve is so much fun and each time I use it I get better at it.

I am learning on this vacuum jig stuff. I am better off to leave the tabs in place to hold down the whole board while it's being carved out in most cases.

[neilgill]

This is the 10x10 3d model that took 4 hours and my vacuum pump never even got warm as I have tracked down any possible leaks. I was really please with the result and how easy a vacuum system is once all set up.

By the way, this was straight off the machine without any sanding.

Neil

[Mark Jones]

Nice carve. I like how those two images make 3 faces.

Really nice carve. These things are fun.

I have only done 2.5 vcarving with the exception of a heart that I carved out but it was all already setup all I had to do was load the stock and the bit and run the tool paths. This stuff is truly amazing and fun to do.

Vectric is really good software. I upgraded once from desktop to pro. If I get into 3d carving it maybe -will be time for another upgrade!

Ha. I told my wife I was going to give Leonardo DaVinci a run for his money with my plotter drawing my clip -artwork now...Ha! I couldn't draw something to save my life but I can tell Vcarve to get er done!

[Mark Jones]

Made a 24" by 24" Vcarve file for a Vacuum Jig with just one gasket that will handle something flat 24 by 24. My plan is to carve this out this week in some PVC trim board from the local box store. I will glue up 4 pieces of this pvc siding trim to get a 24" wide piece. Then carve it out using the pod file that has all of my vacuum pods in the one file. This includes the toolpaths using layers and sheets.

Here is the vcarve desktop pro file. Feel free to look it over, carve it and if ok give it out.
https://drive.google.com/file/d/1e8F6nU ... share_link

Learning to use the template toolpaths and layers makes creating these things fast and easy.

Vcarve is so much fun and so logical. Learning new stuff each week as I try new things or make more things with it.