4'x8' vacuum table build questions

[Gary-Wiant]

I'm building a vacuum table with T-Slots for my CNCRP PRO 4896 but I have a few questions and any help is greatly appreciated.

I purchased 4 of these motors https://www.centralvacuummotor.com/P.../122178-18.pdf I'm going to wire wire each motor individually and have 4 - 2'x4' zones each with a vacuum gate. I'm using XCEL IF PVC for my plenum because I won't have to worry about sealing it like I would with MDF

Do I need to surface the bottom (original) spoil board before I glue the piece of PVC I'm going to use as the plenum?

I'm going to use the v groved trial will that work?
My plan is after I glue the plenum piece down I plan to surface the top, then route in the T-slot groves then route out the plenum grid with a 3/8" round over bit about 3/8" deep.

But how far from the edge should I keep the plenum groves? I was think .5" - .75"

Then after I have the plenum routed I will use the v grove trial to apply the glue to the LDF.

When I make the 1'x4' box that holds the vacuum motors is there anything I need to know about mounting the motors? I haven't even opened the motors yet but is there a certain size or shape of hole I need to put in the box?

I purchased rubber Fernco sleeves to place between the vacuum box & the rest of the plumbing like we talked about but when I was talking to Wade at the vacuum motor company he said not to use them but didn't elaborate.

Thanks for the help
Gary

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[Smeltvedt]

Gary, I didn’t really follow your plenum plans, but yes the original spoilboard should be flat and true. As far as the box and mounting, I used the foam gaskets sourced from Wade under the motors. Mine is setup so each motor chamber has a set of homemade check valves that allow me to use any combination of the motors. The check valves lead to a common vacuum chamber that is valved out to three sections on the table. I did use a vacuum relief valve to ensure there is enough flow to cool the vacuum motors. I did not make plans to build this system, just put it together on the fly. So far I am very pleased.
Ymmv
Cheers. Sean



Homemade check valve under the motor mount



Motor mount plate



Side view of system, the exhaust is just forced to turn 180 degrees corners a couple of times to reduce the noise

[nlancaster]

How loud is that vacuum table?

[Gary-Wiant]

Sean, can you explain more about the vacuum relief valve & the home made check valve?

This is the first I've even thought about the exhaust. I was just going to let it blow. Did you just build a common area for the exhaust and like you said force it into several 90° turns and just exhaust through the open hole at the bottom of the box?

Is your table s 4'x8'? Do you feel that 3 motors are enough? Is there any materials or sizes of material that you have an issue holding down? Do you cover the areas of the active zone(s) with anything to help with suction / vacuum?

How do you do double sided projects with a vacuum table? I don't want to drill holes into my LDF spoil board.

Thanks for the help I truely appreciate it
Gary

[Smeltvedt]

Gary, The relief valve is adjusted to keep from “deadheading” the motors. I don’t remember the curves, but I did set the relief valve to open soon enough to allow the motors to maintain minimum airflow. It was somewhere in the neighborhood of 80-100 inches of water.
The check valves allow the motors to be connected to a common chamber without the running motor causing back flow through a non-running motor.
The box was sized for 4 motors, but I rarely use more than 2 depending on the conditions of the spoil board. (How much is exposed by cutting)

(Gary and nlancaster)
All the exhausts are also common and exit the hole. You’d be surprised at how warm the exhaust air is. Then noisiest part is the motor fans, but it is just about on par with the cnc spindle noise. (I do wear hearing protection)

The table is 4x8, cordoned off in three zones. When cutting sheet goods for cabinet boxes, only one motor is needed-and overkill. When cutting smaller parts like drawer boxes, I use two motors.

I’ll be interested to hear how you and others do double sided work. My first thought would be to make a negative of the first machined side, and use this as a holder for the second side. Hopefully there are other much smarter folks who can enlighten us both
Enjoy making dust!
Cheers
Sean

[Smeltvedt]

Ps, here is a closeup of the relief valve, and of the pressure this is with one motor running, spoilboard uncovered, one zone open.

[Gary-Wiant]

Sean - Thank you I will have a vacuum gate between each of the motors & the common area. So I can run 1 motor or all 4 without the non running motors drawing air back through, so I don't think I'll need the check valves or am I wrong? Also I thought Wade from Central Vacuum said these motors did not need holes drilled for air flow & they have thermal protection.

Also each motor will have it's own power switch so it will not be turned on unless it is being used to draw vacuum. So am I correct that I won't need a relief valve also or is this something different?

As for the pressure gauge I assume it will go to the common area. What are you checking vacuum on or what is the advantage of it?

I'm going to place T-Slot around my Zones to help with holding down rough cut pieces I seem to be doing more and more of. How far away from the edge do you recommend me keeping the plenum groves? I was thinking 1/2" to 3/4". As I said I'll be routing the groves with a 3/8" round nose bit 3/8" deep. Unless you or someone else thinks I need to go with a wider bit or need a deeper grove?

Thanks
Gary

[ger21]

As I said I'll be routing the groves with a 3/8" round nose bit 3/8" deep.

If the grooves are for a gasket, go with 1/4". With PVC, you should be able to get very close to the edge, at least within 1/4"

[Gary-Wiant]

Gerry - I'm not using a gasket I'm having the LDF cover the entire plenum & draw through it. I will be sealing the edges of the LDF so it will not draw through the edges.

Are there any wrong ways to design the plenum "vacuum dead zones"?

Thank you
Gary
Thank you

[ger21]

You'll need a rubber gasket around the perimeter, or the vacuum will leak between the PVC and LDF.

[Smeltvedt]

Sean - Thank you I will have a vacuum gate between each of the motors & the common area. So I can run 1 motor or all 4 without the non running motors drawing air back through, so I don't think I'll need the check valves or am I wrong? Also I thought Wade from Central Vacuum said these motors did not need holes drilled for air flow & they have thermal protection.

Also each motor will have it's own power switch so it will not be turned on unless it is being used to draw vacuum. So am I correct that I won't need a relief valve also or is this something different?

As for the pressure gauge I assume it will go to the common area. What are you checking vacuum on or what is the advantage of it?

I'm going to place T-Slot around my Zones to help with holding down rough cut pieces I seem to be doing more and more of. How far away from the edge do you recommend me keeping the plenum groves? I was thinking 1/2" to 3/4". As I said I'll be routing the groves with a 3/8" round nose bit 3/8" deep. Unless you or someone else thinks I need to go with a wider bit or need a deeper grove?

Thanks
Gary

Gary I’ll try to reply from my phone, so please overlook spelling and grammatical errors.
What you are referring to as vacuum gate-I believe is the same thing I am calling a check valve.

As far as holes and thermal protection-I do not want to rely on a single safety switch to prevent a potentially catastrophic meltdown. So the relief valve effectively gives the motor the same protection as the hole, without having a continuous hole always wasting vacuum.
The gauge just allows me to see the supplied vacuum pressure, and I use it to decide whether to turn on or off another motor.

I didn’t use t slots, but I did run the plenum carving to within about 0.75” from the edge.

Also another thought-don’t forget to bring sufficient power supply for the motors, and fuse or breaker each motor as required. In my case, I have a single feed powering individual switches each with its own double pole circuit breaker.

Hopefully this helps
Cheers
Sean

[Gary-Wiant]

Sean this is what I am calling the vacuum gate.
Attachment 409424

The electrical is way way over my head. I have a buddy that is an electrical engineer figure it out & wire it up for me.

Thank you
Gary


Is the relief valve plumbed into your common area or do you have 1 on each motor?

I'm assuming the pressure valve is also plumbed into the common area. And I think we are setting up our tables differently It looks to me like you are using you motor box as your common area mine will look similar to this rough sketch I did freehand on my phone but I think it shows what I'm doing.

[Smeltvedt]

Sean this is what I am calling the vacuum gate.


The electrical is way way over my head. I have a buddy that is an electrical engineer figure it out & wire it up for me.

Thank you
Gary


Is the relief valve plumbed into your common area or do you have 1 on each motor?

I'm assuming the pressure valve is also plumbed into the common area. And I think we are setting up our tables differently It looks to me like you are using you motor box as your common area mine will look similar to this rough sketch I did freehand on my phone but I think it shows what I'm doing.

Gary you are correct, the relief valve and gauge are both plugged into the common area between your valve sets. My homemade check valves are just automatic versions of your manual valves on each motor. I tend to get a bit OCD on control systems, and tend to make them as idiot proof as possible (including the primary idiot-myself). It is a carryover from my profession, that is I’m also a EE specializing in control systems. So if I can make it foolproof enough for myself, it ought to be good enough for anybody that comes to my shop??
Enjoy your machine, and post pictures of it in action when you get it completed
Cheers
Sean

[Gary-Wiant]

Well I've officially started on the vacuum table build. I sanded both the top of the 3/4" MDF base and the bottom of the Excel IF 1" PVC and applied heavy duty liquid nail with a v grove trowel then laid the PVC directly down onto the MDF and used so home made caul clamps to clamp them together.

I have included a photo of what I've gotten done today

[Gary-Wiant]

I was able to get my plenum routed and Saturday I'm going to build the T-Slot track installed, vacuum motor box & hopefully plumb the zone & get the edges of the LDF sealed.

My question is for anyone using the motors from central vacuum
8.4" 240V p/n 122178-18), What filter are you using to filter the cooling intake air? Warren from central vacuum said to make sure the cooling air is filtered.

Than you.
Gary

[Gary-Wiant]

Today I didn't get as much done as I wanted but I got a bit done. I was able to get the t-slot tracking installed, the vacuum motor box built & 2 coats of triple thick polyethylene on the edges of my LDF.

Today's question is does my vacuum motor box need painted? Instead of gluing and screwing it together I used silicone to help seal the joints, so I'm not sure if I'll be able to get paint to stick to the areas were I wiped off the squeeze out.

Thanks

[Smeltvedt]

Gary- Looking good! Curiosity question, is each motor going to be connected to a common plenum, or is each motor going to be dedicated to a section of the table?
Cheers
Sean

[Gary-Wiant]

Sean, Thanks there is a divider between each motor inside the box, and each box will have it's own power switch. The output of each motor comes out to a 90° up into a gate valve that that keeps air from coming back into the motor(s) that are not turned on. Then each of the 4 gates T into a common area that in turn, T's out into 4 more gates. (The 8 T's & stubs between them create the common area) these last 4 gates direct the vacuum into each of the 4 zones. This way I can run either 1 motor for all 4 zones or 4 motors on one zone or any other combination.

What about needing to paint the vacuum box? I wouldn't think air would be able to leak through 3/4" plywood.

Thanks
Gary

[ger21]

I'd brush a coat of polyurethane on it. It won't hurt. You'd be surprised how vacuum can go through wood products.

[Gary-Wiant]

Thanks Gerry I'll do that today