Vacuum Hold Down

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neilgill
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Vacuum Hold Down

Post by neilgill »

Hello all,

I have been researching vacuum hold down options for my AR8 Axiom CNC. There are commercial tables, tablets and pods all of which can be costly. I thought I could make my own. This is what I found. I bought a "2- Stage 50L/m Oil Free Lab Vacuum Pump" $140. What ever you do you will need this or some form of vacuum source. FYI, I also have a 3D printer.

1. Started with PODS as Axiom and Rockler sell pods. Downloaded some STL files and 3D printed. (See Green square in picture 1). Not too successful as there is additional work required to drill and tap for the inlet vacuum plump.

2. Designed my own POD (using OpenScad, happy to share code). I design it with a load of variables such as diameter, height and 1 or two ports for single use or multiple pods. Printed Black ones and they are incredible. They hold like a vice. Printed White ones, and strangely not so good. I tested the White ones with an incense stick (for smoke) to see where the vacuum was being lost and found that the whole pod is porous. I coated it with Polyurethane and it improved. Short story, I changed the 3D printer settings and they work well too now. I think my White filament is a lower quality. Pods are great for small work or several pods for medium pieces.

3. Board, High Density Polypropylene (HDPP). I bought a white plastic cutting board. 18x12x1. Designed four channels for some 1/4" rubber gasket (also used on PODS). I drilled a small hole (1/8") half way into the board (1/2" deep) about 2" from the vacuum inlet the edge. Drilled the vacuum inlet with 1/8" from edge to meet the other small hole. I then drilled a 1/4" hole to fit the blue vacuum air tube that goes to the pump (about 1/2" deep) to make it easy to push the vacuum tube in. The four square areas are different areas that I can use depending on the size of my work piece. I simply move the gasket to match my work. The channels for the 1/4" rubber gasket are 1/5" deep and 1/4" wide. The rubber gasket fits perfectly and leaves enough proud to make a great seal. I also drilled out hold down holes to bolt to my cutting board with or without the spoiler boards.

I was stunned with how successful I was. All of these solutions hold my work. I can not get them off. The vacuum is as it highest pressure meaning it is pulling virtually no air in leaks.

The reason I share this is because these are affordable (apart from the pump but you could use a venturi valve and a pressure pump if you have one). Oh yes, also need a 3D printer, but I do so I did but I am sure you have a friend with one. The white board was $20, the pump was $140 (but you need this even if you buy someone else's pods). Gasket $13, Vacuum Tube $10. So for $43 you can create a custom vacuum that works perfectly.

Hope you find this useful.

Regards,
Neil
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TomWS
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Re: Vacuum Hold Down

Post by TomWS »

Can you provide a link for the gasket you used? That, to me, is the real secret to suck-sessful clamps :wink:

neilgill
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Re: Vacuum Hold Down

Post by neilgill »

Hi TomWS, the link is https://a.co/d/hl0wCML

wilkigr
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Re: Vacuum Hold Down

Post by wilkigr »

Great information. I do not have a 3D printer, so I made 2 @ 5" square pods and 2 @ 6" square pods out of MDF, that I sealed. They work very well. I already had a Gast pump for my lathe vacuum pump, for the cost was minimal. I really like your printed pods.

neilgill
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Re: Vacuum Hold Down

Post by neilgill »

wilkigr wrote:
Mon Sep 26, 2022 6:12 pm
Great information. I do not have a 3D printer, so I made 2 @ 5" square pods and 2 @ 6" square pods out of MDF, that I sealed. They work very well. I already had a Gast pump for my lathe vacuum pump, for the cost was minimal. I really like your printed pods.
Thanks wilkigr, I was considering cutting the PODS from the HDPP. Fairly easy task using Aspire. This way I do not need to be concerned with sealing and I can make them in any size, mostly I would use them for small pieces like boxes and 3D carving.

Neil

neilgill
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Re: Vacuum Hold Down

Post by neilgill »

If anyone is interested I have attached the STL file for the 100mm diameter with 1 port. Just change the extension back to STL.

Neil
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VacPod2_100mm_1port_20mmHeight.txt
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Bobtail Farm
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Re: Vacuum Hold Down

Post by Bobtail Farm »

thanks

neilgill
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Re: Vacuum Hold Down

Post by neilgill »

I quick update and some lessons learned.

Attached is my new and improved 8.5 x 5 x 1 pod. This one is amazing.

Through experience I have realized the following:

1. A single circular pod allows slight rotational movement. Using two circular pod eliminates that, or some other form of block on each side, although I wanted a design that would stand alone, just vacuum.
2. Leveling the HDPP is critical as they are made for cutting food and do not have the tolerance required for a CNC work. I leveled one side, removing 5/1000 each surface cut until it has leveled the whole area. Then turning over and do the same. I was stunned when I cut through the original block. The profile shocked me.
3. Creating a center cavity of 0.14" really helps to raise the vacuum pressure, so much so that when I turn the pump off ,the pressure does not go down for about 2 minutes. I have to release the pressure manually if I want to remove the work sooner.
4. I made sure in all pods that the hold down bolts were out of the vacuum space, because air can escape past the bolt heads.
5. The width and depth of the gasket pocket is critical. I am using 1/4" rubber. I create a track that is 0.2 wide and 0.14 deep. This seems to work best for me. Also, because I leveled the whole surface the gasket height is consistent around the perimeter thereby giving the maximum seal.
6. Cutting HDPP plastic requires a two flute up-cut bit and slower feed and speed so as not to melt it.

I have also noticed that many YouTube videos do not show many actual applications using their designs and I suspect that many suffer from some of the above complications.

I have had fun doing and sharing this project. It is now time to get on with the real work of creating real stuff and I need to us the thousands of vacuum pods I have created. LOL.

Regards,
Neil
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Rcnewcomb
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Re: Vacuum Hold Down

Post by Rcnewcomb »

There is good information, and good gasket material, at Allstar CNC

Brady Watson has written helpful articles about affordable vacuum hold downs: The BradyVac II – A Production Vacuum Fixture on a Shoestring Budget

Gary Campbell wrote about The K.I.S.S. Vacuum Manifold
- Randall Newcomb
10 fingers in, 10 fingers out, another good day in the shop

neilgill
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Re: Vacuum Hold Down

Post by neilgill »

Hi Rcnewcomb,

Thank you, these are all very useful and interesting articles.

Regards,
Neil

Mark Jones
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Re: Vacuum Hold Down

Post by Mark Jones »

Well I spent the last 2 weeks learning vacuum pump and pods stuff. Here is my youtube video on that experience as I learned. So what you see is some of my tests and trials and learning. It was fun. Put up some great links to save money and time. Also 3d printed a mist vent camp for the HF vacuum pump to keep the mist down. Links and more. This stuff works great in the application of hold downs. I will take these pods and put them into my jigs for the CNC and for quick sanding of repetitive things. I wouldn't set this up for one or two pieces but if I was doing batch work of 6 or more this will save time and effort for sure.

Mark Jones

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Re: Vacuum Hold Down

Post by Tailmaker »

Don't forget a filter in the vacuum line. Otherwise, you will sometimes suck dust and chips into the pump and it will not like that.
Cheap fuel filters from Autozone with 3/8 hose connection work well. No hose clamps required.

I cover part of my t-slot table with aluminum flashing and use the t-slot below as vacuum conduit. Then I can tap the channel anywhere with a small hole and don't need any pods. Just a removable gasket (e.g. foam non-slip drawer liner cut to size) or weatherstrip under the board
DSC00316.JPG
.
Puzzle, Finger Joint, Maze and Guilloche freeware at https://fabrikisto.com/tailmaker-software/

wilkigr
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Re: Vacuum Hold Down

Post by wilkigr »

Tailmaker: That's freakin' brilliant!

Mark Jones
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Re: Vacuum Hold Down

Post by Mark Jones »

Do you have any video on this setup on youtube? I would like to see it in use and some more detail on it.
Mark Jones

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Re: Vacuum Hold Down

Post by Tailmaker »

Mark Jones wrote:
Sun Nov 06, 2022 2:31 am
Do you have any video on this setup on youtube? I would like to see it in use and some more detail on it.
Not video, but some more pictures. To avoid highjacking this thread, I will start a new one with explanations.
Puzzle, Finger Joint, Maze and Guilloche freeware at https://fabrikisto.com/tailmaker-software/

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