I really like Pierson Workholding gasket cord material, it easily allows for vacuum to develop under sheet by being easy to compress. Has a open cell internal structure with a durable skin.
i found with my vacuum table those pneumatic fittings tend to leak on a micro level and your system loses around 35% of the available vacuum, vacuum fittings usually dont fit around the tube but rather they push into the tube and locked with a sealing nut, check it out, your results will be drastically improved..
@@JBWorx yea under vacuum those tubes shrink slightly in the pneumatic fittings, i guess they are great when the lines are under positive pressure and expand into the fittings.
The fittings do leak a little, but not that bad. I use these for epoxy vacuum infusion (where the pressure is in the ballpark of 1-5 mBar Absolute, or -0.995Bar and below) and I get away with that. So even though they sometimes leak, it's not that bad. And a hint to the oiling rotary vane pumps: they only produce oil vapor if they have to move a lot of air, below -0.9Bar and you can run them endlessly.
You have nicely showed that for a vacuum clamp you need negative pressure more than air flow! I was a little concerned with the calculation when you take the entire area as the active clamping area because the plate is painted and not porous. This would imply that only the grooves are the active clamping areas. I did then realize that, when working, the areas that are not the slots will leak air into the slots and become the same negative pressure. So the question arises about those vacuum clamps that use just MDF as a porous material, no slots on the top surface, just below. Do they have any advantages or cases where it may be a better way to clamp? I have made high friction surfaces on wood by adding very fine sand (sand blasting grit) to the last layer of varnish. You may be able to find something fine enough to be more effective in holding you workpiece from lateral movement if you used a similar material in the sealing paint. I would not suggest sandblasting grit since it’s abrasive but something like talcum powder or chalk which is softer than the cutting tools and won’t damage them when you cut into the plate.
Sucking the vacuum through the MDF can be an advantage if you cut all the way through our part. The air flow will be slowed down going through the MDF instead of the channel. Excellent idea to add something to the paint itself to increase the friction, thanks for the Tipp
My first prototype vacuum pad was made with MDF. The vacuum pressure was adequate for a test. My second prototype was made from HDPE plastic. The vacuum pressure gauge shot up significantly. MDF is porous, your 8mm pneumatic hose fitting is pulling a vacuum through the entire thickness of your plate. Make a new plate from HDPE, because it's not porous at all.
Painting it with an acrylic-latex paint worked fine. HDPE is ok but warped too much in my opinion. Delrin / POM is a much better choice in case you make another one.
venturi pumps are good for 2 scenarios only: 1. you need a vacuum pump with no moving parts to vacuum out corrosive gasses or abrasive dust. 2. you have an endless supply of compressed air and this is all you have ) for any other scenario this type of pump is ridiculously ineffective. i personally use a generic rotary vane pump (70L/min) and it is great for workholding. initially i have a same problem with oil mist coming out of the pump but i fixed it by installing an oil mist separator from the same manufacturer (Value). it is basically a filter can which is screwed on the exhaust hole. it reduced amount of mist by roughly 85-90% you can find many variants of such filters. efficiency of rotary vane pump is worth it )
I think I would add 3. The cost of $15 makes it worth for a test to see if vacuum work holding is the right tool in your shop. Yes all large routers use rotary vane pumps. I think “Gast” would be a good brand but there are many others. Also air filtration becomes a must for these types of pumps as small particles will usually damage the veins (that can be re-build however). Thanks for your input.
@@JBWorx actually, if the vacuum is quite stable, eg metal working, then you can use a solenoid on the Venturi. The flow reacts near instantly and a vacuum is a vacuum, doesn't always matter that it takes a while to get there Similarly you could attach a pressure valve to the feed hold so that the machine will pause if pressure is lost Clearly this isn't relevant to many woodworking situations with permeable materials
Yes having the vacuum monitored by the machine is a really good way to prevent scrap and a bit breakage. Interesting enough my controller can selectively control valves based on its position in x and y. Pretty interesting.
Very interesting, having a larger pump on mine small parts are a problem, I had thought re-jigging the vac-bed zones might help, clearly not. Interestingly my current bed is expanded foam PVC, I've used it since I installed the pump, being in an area close to a lot of wet, salty sea air, I wanted something that wasn't affected by the atmosphere, but personally think it's a bit soft and spongy. an engineering plastic such as HDPE is better.
Thank you for your comment in aspect of using a better plastic I would suggest Delrin (Acetal, POM) HDPE is just not stable enough unless you place a lot of hold downs on it. Yes small parts just don’t have enough clamping force as it is in direct relation to the area within the seal. Just watched your HDPE video nicely done ✅
@@JBWorx Yes, your probably right on the HDPE. I may though have to consider a second small vac board I can pop onto the bed as and when needed, with a vane pump, for small parts.
Also you can try to place one layer of fine sandpaper (I.e. 600 grit) between the part and the vac plate. This will increase the friction and avoid the side to side movement. Make sure the part is in contact with the plate once vacuum is applied and not propped up by the seal. I am looking for a vane pump that does not spit oil out the exhaust. Good luck with your project and channel
Yes same function as the Datron vacucard it’s permeablere and can take small bumps and increase the vacuum as it slows down any leaks. The sandpaper will work great between 2 metal surfaces.
Having only used Vacuum in large epoxy lay ups and having to get the air out quickly, I’ve tended to have everything set up for the vac pump but to quickly suck down the bag using a shop vac. The shop vac has to have air through to cool the workings so it’s only for that initial period.
I would love to see a test of a water vacuum pump that is common with Chinese CNC routers such as they one in this video: ruclips.net/video/LmMC6F3c5wQ/видео.html
If this is a liquid ring vacuum pump then it generates a humongous amount of airflow but usually a rarer little vacuum something in the neighborhood of -60mbar. Probably not suitable for a cnc.
Here's how you solve the oil vwcuum pump issue in the video linked below...cheap and simple. Would the harbor freight pump work for your vacuum holding jig (assuming the mist problem is solved)? ruclips.net/video/HppwlWg1XH4/видео.html
One thing to watch out for is the size of the internal orifice of the Venturi pump. On this model my California air tools 4610 can not keep up (only 1hp). But I use it for vacuum bagging not on the plate. However even with the pressure dropping I get enough vacuum to keep it very secure to the plate and this type compressor has a max cont. run time of 1h. Otherwise duty rating is 70/30. I like it because it’s really quiet.
Dang I forgot to link that … it’s from Amazon … please look at the description of the prior video (vacuum plate) the link is in there. Somehow I cannot paste the link right here. ruclips.net/video/20zH9ie-rIU/видео.html&si=Qsx5zjTyRsMke19E
Fascinating as always - Is it possible to chain two of the refrigerator type compressors/use two for two inlets to the vacuum plate? Or will they be so starved that there isn't a significant/meaningful benefit to be found?
Thank you! The unit in the video is rather small as it came from an air dryer, a refrigerator has typically a bit more air flow. To combine 2 units I would build a small vacuum reservoir from PVC tubing and place a check valve to each pump.
I have never used a vacuum plate but I have to ask the obvious, how do use insure that you don't cut deeper than your stock? And is the piece still level with the table? All in all at some point I would like to build my own based on this series of videos since I know there is probably occasions where a vacuum table is quite handy. One other thing about your videos that I like is the fact that you have used the hardware mentioned in the videos and give your opinion on how well it works.... Thanks
Thank you Peter! So the plate I made is for my MFT table but I can also use it in my CNC. So the plate is surfaced and that makes it parallel to the table. What you have to accomplish is that the part gets “sucked down” all the way to the plate. If the seal sticks too far out over the plate or the vacuum is too low the part rests on top of the seal and will most likely not be parallel to your table. Machining through is always a problem. You can use some paper (newspaper works well) or some vacuum table matt to place the part on. This will prevent that you cut into the plate and also assist in keeping a greater amount of vacuum once the part gets holes machined into it. Thanks for reaching out !!
Adding the Gauge on the line that's used to draw the vacuum does not necessarily give you the actual pressure in the plate. If the flow is high enough to be restricted by the tubing this might shows a pressure that's lower than the pressure in the plate body itself. Might work out for the type of table & Pump combination that you used in your example, but be careful if you use it on something that needs a higher flowrate. rotary vane pumps with oil will always produce a fine oil mist that can stay in the air seemingly forever. There are special filter units available (that might cost as much as the pump itself). The amount of "generated" fog is directly linked to the air throughput on the pump. If you plate seals well you will get nearly nothing, as soon as you need some air throughput your workshop turns into a cloud chamber wihtin a few minutes. You can route the exhaust air to the outside with some tubing if you want to go though the effort and avoid the filter system (with all the environmental drawbags and increased oil consumption) Alternatively there are oil free systems available. They have a slightly higher wear on the rotary vane system but that's acceptable for a hobby use.
Thank you for your comment, appreciate it ! Yes, certainly as I mentioned the regenerative blower is wrong for the plate and so is the used hose. I included it to demonstrate that these types are generally not generating a high vacuum. I like the oilless vane pumps the vanes are typically made from carbon and last a long time if properly protected by a filter. And they can be bought as a spare part from good manufacturers like Gast or Busch ($$$). Because my workshop is in my house I don’t like the idea of having oil mist in the air and filters always fail. Again thx for taking the time to reach out !
There is a design i saw on RUclips where the fellow puts a "notch" in the straight edges (think of the endmill doing a wobble while cutting the straight lines. So you get a sharpish point one side and a smoother arc the other) It looked like it would hold the cord better, by creating a little pinch point.
@@JBWorx as far as I know he cut the path with a single end mill the width of the slot. So we can infer the design. We want a relatively sharp triangular point on one side. The endmill will have to eat out the other side while machining this, however it will draw a different shape, a softer curve, on the opposite side
So after using the plate for a while I found that holding the seal in is not an issue. However the overall dimensions of the slot in comparison to the seal diameter is important.
There may be better performance if the venturi pump is attached directly to the suction plate without the blue tube in between. The reason is that at low air pressures there is not much driving force coaxing the air molecules to go toward the pump. The gauge could still be on the blue tube, but teed off the minimal length connection between plate and pump.
I think the flow of that model was actually pretty decent. The refrigerator pump had less flow. Yes eliminating any length of hose for low air flow situations is a good measure. Thank you for your comment !
@@JBWorx I agree the flow of the pump is good when there is still a lot of air pressure to pull on. But as the pressure drops the pump flow becomes less. Not the fault of the pump, its just an inevitable outcome of pulling vacuum. Pressure comes from air molecules bouncing off of each other and off the walls of their enclosure. As air pressure drops, molecules are less energetic at finding the exit so to speak.
I have a 12CFM vac pump for composite work that is also the oil mist variety. I knew going into it that mist would be expelled, but the first time you do it indoors, there's going to be a film on Everything. That was a one-time mistake. I've since added a DIY mist recovery valve and accumulator system that will eventually get a scavenge pump, filter, etc., just to try to turn it into a recirc system. I've pondered going with a sort of vac table for the CNC, but assuming the workpiece will fit, I have an old setup for a vacuum chamber that I will reassemble as a top cover, block off the access to whatever is open on my table, and let the pump run on the workpiece. Only problem that would require a fairly elaborate routing would be an air-cooling loop for the cnc motor, at which point I would consider moving to a liquid-chilled system. Sounds like a lot of work when I normally just run toe vise clamps or sacrificial adhesives on thin stock that I'm having a hard time getting past for justification other than Cool factor.
Adding a vac plate is nice - BUT ! It has its limitations. The main advantage is to hold down thin larger stock that, for example, could not be held down with toe clamps. Instead of going through all that trouble I like to suggest you make a prototype vac plate for the parts you normally make and use your shop vac as a pump. This can give you an idea if you like working with an vac setup or prefer the regular clamping. Hope this helps.
Another design I've seen involves using many tiny holes (0.3-0.5mm). The logic is that a vacuum is a vacuum, it doesn't need huge holes. By using many small holes it doesn't matter (so much) if some become uncovered because you machine through the piece. Broadly as long as the flow through the uncovered holes is a small part of total flow you will still be holding your vacuum. Hence using small holes. The idea is that you don't need a gasket. Have you tried this?
There is a well known brand of self adhesive neoprene sheet that has lots of holes in it, that relies on this. The holes don't need to be as small as you mentiong but smaller holes increase airflow, though I don't fully understand the mechanics of it. That was a tip I got from an engineer who specialised in it. I have a grid of 6mm holes over my spoil board for this reason. Though it has it's downsides too.
I don’t like these plates at leased I don’t like to make them. Drilling the holes is a nightmare the concept is good though. There is a company in England that provides a plastic mat that looks like it has suction cups on it and these have a tiny hole in the center. You just have to lay that in a flat surface nothing to drill. They are available in the US as well … I think Whitt or white is the distributer … that’s from top of my head though. I would prefer that set up.
@@TheCNCDen aah. The 6mm hole mat is designed to be laid over a more traditional vacuum plate. It will still fail catastrophically if you cut through the part.
@@JBWorx there is also a thick rubber Matt (not sure the exact material). It's a good few mm thick and the idea is you can perforate it around the underside of the part. It's designed to be mildly reusable, but expendable. I'm most interested in the small hole table though. I agree it's going to be a pain to make....
I really like Pierson Workholding gasket cord material, it easily allows for vacuum to develop under sheet by being easy to compress. Has a open cell internal structure with a durable skin.
Agreed, all his products are top notch !
i found with my vacuum table those pneumatic fittings tend to leak on a micro level and your system loses around 35% of the available vacuum, vacuum fittings usually dont fit around the tube but rather they push into the tube and locked with a sealing nut, check it out, your results will be drastically improved..
Thank you that is a very good tip and makes perfect sense to me.
@@JBWorx yea under vacuum those tubes shrink slightly in the pneumatic fittings, i guess they are great when the lines are under positive pressure and expand into the fittings.
Yes I thought so too once you mentioned it barbed fittings might be better
The fittings do leak a little, but not that bad. I use these for epoxy vacuum infusion (where the pressure is in the ballpark of 1-5 mBar Absolute, or -0.995Bar and below) and I get away with that. So even though they sometimes leak, it's not that bad.
And a hint to the oiling rotary vane pumps: they only produce oil vapor if they have to move a lot of air, below -0.9Bar and you can run them endlessly.
I think it was also the Harbour Freight version. A better pump is probably not having that oil vapor issue.
Love your channel man, keep up the good work
Thank you !! Hope to grow my audience … no easy task, it seems others with less contend have more “luck”.
You have nicely showed that for a vacuum clamp you need negative pressure more than air flow! I was a little concerned with the calculation when you take the entire area as the active clamping area because the plate is painted and not porous. This would imply that only the grooves are the active clamping areas. I did then realize that, when working, the areas that are not the slots will leak air into the slots and become the same negative pressure.
So the question arises about those vacuum clamps that use just MDF as a porous material, no slots on the top surface, just below. Do they have any advantages or cases where it may be a better way to clamp?
I have made high friction surfaces on wood by adding very fine sand (sand blasting grit) to the last layer of varnish. You may be able to find something fine enough to be more effective in holding you workpiece from lateral movement if you used a similar material in the sealing paint. I would not suggest sandblasting grit since it’s abrasive but something like talcum powder or chalk which is softer than the cutting tools and won’t damage them when you cut into the plate.
Sucking the vacuum through the MDF can be an advantage if you cut all the way through our part. The air flow will be slowed down going through the MDF instead of the channel. Excellent idea to add something to the paint itself to increase the friction, thanks for the Tipp
My first prototype vacuum pad was made with MDF. The vacuum pressure was adequate for a test.
My second prototype was made from HDPE plastic. The vacuum pressure gauge shot up significantly.
MDF is porous, your 8mm pneumatic hose fitting is pulling a vacuum through the entire thickness of your plate.
Make a new plate from HDPE, because it's not porous at all.
Painting it with an acrylic-latex paint worked fine. HDPE is ok but warped too much in my opinion. Delrin / POM is a much better choice in case you make another one.
venturi pumps are good for 2 scenarios only:
1. you need a vacuum pump with no moving parts to vacuum out corrosive gasses or abrasive dust.
2. you have an endless supply of compressed air and this is all you have )
for any other scenario this type of pump is ridiculously ineffective.
i personally use a generic rotary vane pump (70L/min) and it is great for workholding.
initially i have a same problem with oil mist coming out of the pump but i fixed it by installing an oil mist separator from the same manufacturer (Value).
it is basically a filter can which is screwed on the exhaust hole. it reduced amount of mist by roughly 85-90%
you can find many variants of such filters. efficiency of rotary vane pump is worth it )
I think I would add 3. The cost of $15 makes it worth for a test to see if vacuum work holding is the right tool in your shop.
Yes all large routers use rotary vane pumps. I think “Gast” would be a good brand but there are many others. Also air filtration becomes a must for these types of pumps as small particles will usually damage the veins (that can be re-build however). Thanks for your input.
@@JBWorx actually, if the vacuum is quite stable, eg metal working, then you can use a solenoid on the Venturi. The flow reacts near instantly and a vacuum is a vacuum, doesn't always matter that it takes a while to get there
Similarly you could attach a pressure valve to the feed hold so that the machine will pause if pressure is lost
Clearly this isn't relevant to many woodworking situations with permeable materials
@@JBWorx Gast makes/made carbon vane pumps, they have no oil present at all. We used them for vacuum and pressure on some Univac tape drives.
Yes having the vacuum monitored by the machine is a really good way to prevent scrap and a bit breakage. Interesting enough my controller can selectively control valves based on its position in x and y. Pretty interesting.
Yes I think also Busch has these oilless vane pumps. But for hobby use quite expensive.
Very interesting, having a larger pump on mine small parts are a problem, I had thought re-jigging the vac-bed zones might help, clearly not.
Interestingly my current bed is expanded foam PVC, I've used it since I installed the pump, being in an area close to a lot of wet, salty sea air, I wanted something that wasn't affected by the atmosphere, but personally think it's a bit soft and spongy. an engineering plastic such as HDPE is better.
Thank you for your comment in aspect of using a better plastic I would suggest Delrin (Acetal, POM) HDPE is just not stable enough unless you place a lot of hold downs on it. Yes small parts just don’t have enough clamping force as it is in direct relation to the area within the seal.
Just watched your HDPE video nicely done ✅
@@JBWorx Yes, your probably right on the HDPE.
I may though have to consider a second small vac board I can pop onto the bed as and when needed, with a vane pump, for small parts.
Also you can try to place one layer of fine sandpaper (I.e. 600 grit) between the part and the vac plate. This will increase the friction and avoid the side to side movement. Make sure the part is in contact with the plate once vacuum is applied and not propped up by the seal. I am looking for a vane pump that does not spit oil out the exhaust. Good luck with your project and channel
@@JBWorx Funny enough newspaper does the same, which I use occasionally, as we buy it for packaging (unprinted) so it's to hand.
Yes same function as the Datron vacucard it’s permeablere and can take small bumps and increase the vacuum as it slows down any leaks. The sandpaper will work great between 2 metal surfaces.
Having only used Vacuum in large epoxy lay ups and having to get the air out quickly, I’ve tended to have everything set up for the vac pump but to quickly suck down the bag using a shop vac.
The shop vac has to have air through to cool the workings so it’s only for that initial period.
Some shop vac’s have a separate fan that cooles the motor. Festool, Fein and Dewalt do make several models. No worries about them getting too hot
Great
Thx!
I would love to see a test of a water vacuum pump that is common with Chinese CNC routers such as they one in this video:
ruclips.net/video/LmMC6F3c5wQ/видео.html
If this is a liquid ring vacuum pump then it generates a humongous amount of airflow but usually a rarer little vacuum something in the neighborhood of -60mbar. Probably not suitable for a cnc.
Here's how you solve the oil vwcuum pump issue in the video linked below...cheap and simple.
Would the harbor freight pump work for your vacuum holding jig (assuming the mist problem is solved)?
ruclips.net/video/HppwlWg1XH4/видео.html
Thank you for sharing this, very interesting idea. Yes the larger pump from HF would do the job no problem.
What size compressor are you using with that venturi pump? and usually, how much time of use do you get with it?
One thing to watch out for is the size of the internal orifice of the Venturi pump. On this model my California air tools 4610 can not keep up (only 1hp). But I use it for vacuum bagging not on the plate. However even with the pressure dropping I get enough vacuum to keep it very secure to the plate and this type compressor has a max cont. run time of 1h. Otherwise duty rating is 70/30. I like it because it’s really quiet.
Where did you get the gasket material for the grooves on the plate..????
Dang I forgot to link that … it’s from Amazon … please look at the description of the prior video (vacuum plate) the link is in there. Somehow I cannot paste the link right here. ruclips.net/video/20zH9ie-rIU/видео.html&si=Qsx5zjTyRsMke19E
Fascinating as always - Is it possible to chain two of the refrigerator type compressors/use two for two inlets to the vacuum plate? Or will they be so starved that there isn't a significant/meaningful benefit to be found?
Thank you! The unit in the video is rather small as it came from an air dryer, a refrigerator has typically a bit more air flow. To combine 2 units I would build a small vacuum reservoir from PVC tubing and place a check valve to each pump.
For a very fast calclation of "clamping forces": Approx 1 kg (10N) pr. cm2 at full vacum.
Half the vacum makes half the force and so on.
Yep that will do ! Kind of follows what they do here in the US with inches2 and pounds
I have never used a vacuum plate but I have to ask the obvious, how do use insure that you don't cut deeper than your stock? And is the piece still level with the table?
All in all at some point I would like to build my own based on this series of videos since I know there is probably occasions where a vacuum table is quite handy.
One other thing about your videos that I like is the fact that you have used the hardware mentioned in the videos and give your opinion on how well it works....
Thanks
Thank you Peter! So the plate I made is for my MFT table but I can also use it in my CNC. So the plate is surfaced and that makes it parallel to the table. What you have to accomplish is that the part gets “sucked down” all the way to the plate. If the seal sticks too far out over the plate or the vacuum is too low the part rests on top of the seal and will most likely not be parallel to your table. Machining through is always a problem. You can use some paper (newspaper works well) or some vacuum table matt to place the part on. This will prevent that you cut into the plate and also assist in keeping a greater amount of vacuum once the part gets holes machined into it. Thanks for reaching out !!
Very informative & thank you very much ... cheers Tim
Thank you Tim !
Great videos as always!
Thank you Stefan
Adding the Gauge on the line that's used to draw the vacuum does not necessarily give you the actual pressure in the plate. If the flow is high enough to be restricted by the tubing this might shows a pressure that's lower than the pressure in the plate body itself. Might work out for the type of table & Pump combination that you used in your example, but be careful if you use it on something that needs a higher flowrate.
rotary vane pumps with oil will always produce a fine oil mist that can stay in the air seemingly forever. There are special filter units available (that might cost as much as the pump itself). The amount of "generated" fog is directly linked to the air throughput on the pump. If you plate seals well you will get nearly nothing, as soon as you need some air throughput your workshop turns into a cloud chamber wihtin a few minutes. You can route the exhaust air to the outside with some tubing if you want to go though the effort and avoid the filter system (with all the environmental drawbags and increased oil consumption)
Alternatively there are oil free systems available. They have a slightly higher wear on the rotary vane system but that's acceptable for a hobby use.
Thank you for your comment, appreciate it ! Yes, certainly as I mentioned the regenerative blower is wrong for the plate and so is the used hose. I included it to demonstrate that these types are generally not generating a high vacuum. I like the oilless vane pumps the vanes are typically made from carbon and last a long time if properly protected by a filter. And they can be bought as a spare part from good manufacturers like Gast or Busch ($$$). Because my workshop is in my house I don’t like the idea of having oil mist in the air and filters always fail. Again thx for taking the time to reach out !
@@JBWorx yea the oil free version is the way to go. I only use a oil on because I already had it sitting in the basement 🤣
😀😀👍 yes I know how that goes … the regenerative blower from the video is for my pond 🤣🤣
just use difuser's..
Hmmm 🤔 not sure what you mean
There is a design i saw on RUclips where the fellow puts a "notch" in the straight edges (think of the endmill doing a wobble while cutting the straight lines. So you get a sharpish point one side and a smoother arc the other)
It looked like it would hold the cord better, by creating a little pinch point.
Interesting thank you for sharing I will have a look if I can figure this out.
@@JBWorx as far as I know he cut the path with a single end mill the width of the slot. So we can infer the design. We want a relatively sharp triangular point on one side. The endmill will have to eat out the other side while machining this, however it will draw a different shape, a softer curve, on the opposite side
So after using the plate for a while I found that holding the seal in is not an issue. However the overall dimensions of the slot in comparison to the seal diameter is important.
There may be better performance if the venturi pump is attached directly to the suction plate without the blue tube in between. The reason is that at low air pressures there is not much driving force coaxing the air molecules to go toward the pump. The gauge could still be on the blue tube, but teed off the minimal length connection between plate and pump.
I think the flow of that model was actually pretty decent. The refrigerator pump had less flow. Yes eliminating any length of hose for low air flow situations is a good measure. Thank you for your comment !
@@JBWorx I agree the flow of the pump is good when there is still a lot of air pressure to pull on. But as the pressure drops the pump flow becomes less. Not the fault of the pump, its just an inevitable outcome of pulling vacuum. Pressure comes from air molecules bouncing off of each other and off the walls of their enclosure. As air pressure drops, molecules are less energetic at finding the exit so to speak.
Yes that makes sense thank you for your explanation.
I have a 12CFM vac pump for composite work that is also the oil mist variety. I knew going into it that mist would be expelled, but the first time you do it indoors, there's going to be a film on Everything. That was a one-time mistake. I've since added a DIY mist recovery valve and accumulator system that will eventually get a scavenge pump, filter, etc., just to try to turn it into a recirc system.
I've pondered going with a sort of vac table for the CNC, but assuming the workpiece will fit, I have an old setup for a vacuum chamber that I will reassemble as a top cover, block off the access to whatever is open on my table, and let the pump run on the workpiece. Only problem that would require a fairly elaborate routing would be an air-cooling loop for the cnc motor, at which point I would consider moving to a liquid-chilled system. Sounds like a lot of work when I normally just run toe vise clamps or sacrificial adhesives on thin stock that I'm having a hard time getting past for justification other than Cool factor.
Adding a vac plate is nice - BUT ! It has its limitations. The main advantage is to hold down thin larger stock that, for example, could not be held down with toe clamps. Instead of going through all that trouble I like to suggest you make a prototype vac plate for the parts you normally make and use your shop vac as a pump. This can give you an idea if you like working with an vac setup or prefer the regular clamping. Hope this helps.
Another design I've seen involves using many tiny holes (0.3-0.5mm). The logic is that a vacuum is a vacuum, it doesn't need huge holes.
By using many small holes it doesn't matter (so much) if some become uncovered because you machine through the piece. Broadly as long as the flow through the uncovered holes is a small part of total flow you will still be holding your vacuum. Hence using small holes.
The idea is that you don't need a gasket.
Have you tried this?
There is a well known brand of self adhesive neoprene sheet that has lots of holes in it, that relies on this.
The holes don't need to be as small as you mentiong but smaller holes increase airflow, though I don't fully understand the mechanics of it. That was a tip I got from an engineer who specialised in it. I have a grid of 6mm holes over my spoil board for this reason. Though it has it's downsides too.
I don’t like these plates at leased I don’t like to make them. Drilling the holes is a nightmare the concept is good though. There is a company in England that provides a plastic mat that looks like it has suction cups on it and these have a tiny hole in the center. You just have to lay that in a flat surface nothing to drill. They are available in the US as well … I think Whitt or white is the distributer … that’s from top of my head though. I would prefer that set up.
@@TheCNCDen aah. The 6mm hole mat is designed to be laid over a more traditional vacuum plate. It will still fail catastrophically if you cut through the part.
@@JBWorx there is also a thick rubber Matt (not sure the exact material). It's a good few mm thick and the idea is you can perforate it around the underside of the part. It's designed to be mildly reusable, but expendable.
I'm most interested in the small hole table though. I agree it's going to be a pain to make....
@@ewildgoose It will only fail over time and you go through the material, it's designed to be a consumable, it's part of their business plan.
Would love to make one of these
I think it’s a really handy tool to have, I don’t use mine all the time but for some work it is really really good to have.