John, the switchbox is screwed to the underside of my table (MDF painted blue).
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John, the switchbox is screwed to the underside of my table (MDF painted blue).
I finally got the box cut out, flip op and all, tomorrow I will begin the assembly. I am going to assume that the joints are glued and brad nailed, and possibly some silicone to prevent leakage?
David
I hooked my new vac box to my table last weekend and ran it briefly to make sure it worked, and thought I liked the sound level.
Today, I finally got around to cutting with the vacuum on, and it has a very annoying variable vibration, with a frequency around .7-.9 hertz. I can feel the vibration when touching the box, and the pulsing sound gets annoying fast. This is with 2 of the 4 motors running.
Has anyone had this, and corrected it? I may disconnect all but 1 motor and see if that makes a difference. Any other ideas?
thanks,
John
It sounds like harmonic beats. This is what happens when you have tones that are very slightly out of tune. If you run two vacs at the same time, this will frequently happen. When tuning a musical instrument, you listen to the beats and adjust your tuning to make them go away. You are getting these beats because of minute differences in the two systems. It could be a slightly different shape to one vac impeller or one zone is not sealed quite the same as the other. If you wish to learn more about this, you can look up constructive and destructive interference.Quote:
Originally Posted by JDGJr
Thanks Sean.
I will do some experimentation with different pairs of motors.
Is it likely this is directly caused by the motors, or could it largely be the cabinet reacting to them? Dunno exactly how to word the question, and sure don't know how to prove the cabinet is the main cause.
You can easily confirm it. Below are a couple of images.Quote:
Originally Posted by JDGJr
http://static.ddmcdn.com/gif/butterf...terference.gif
http://upload.wikimedia.org/wikipedi...terference.gif
http://emfsafetynetwork.org/wp-conte...terference.jpg
You'll that there are regions of darkness in the third image as well as the second. Just like these images indicate, you'll find zones where you can not hear the beats and others where you can. It is not likely do to your enclosure. We do not use an enclosure on our vacs and can frequently hear beats. Usually when we have 2 vacs of similar age or use. As one is used more and more, it's tone becomes so out of tune with the others that they are no longer close to the same tone.
thanks again.
related to phase: should both of my 240V motors be wired the same, or should one have the 2 hot wires reversed? Currently they are wired the same.
I just purchased a 5 x 10 machine. Gary, can you suggest the number of motors I should use for it?
Thanks!
Joshua...
Depending on how efficient your system is and what size your parts are, 4 should do the job. With that said, my usual rule of thumb is to use 1 motor for each 2 by 4 zone (8sqft). That rule would require 6.
The old system, with many variations shown on this thread, may require 6 to deliver the same performance that the new design does.
New design here: http://www.usroutertools.com/black-b...tems-s/339.htm
Has anyone bought a black box vac from the website?
Does someone have a wiring diagram on how to connect the relays to the vacuum switch and motors?
I have the relays and motors on order but what adjustable vacuum switch regulator is recommended for the 4 lighthouse motors. I plan on running 2 motors and regulate the other 2 to turn on like the original design by Gary.
Thanks
Awesome post! Any new success stories to share? Looking like I will be building one of these guys in the near future once my bot has arrived home. Huge thanks to Gary, Brady, and Daren! DXF files look great and very helpful. :)
Thomas...
If you look at Thread page #2, Post #53, I posted that in the long run, and mostly due to weather and spoilboard condition, the "automatic" switching of the second set of vac motors was determined as being very unreliable. I suppose with a digital vac switch and a small processor, you could make a system that followed the moving target of initial vacuum setting. As stated there, the vast majority have either built with, or switched over to manual second stage vac switches.
Good luck & post pics when done.
Andrew..
You are welcome, but I had the easy part. Those before me laid all the groundwork.
All,Quote:
Originally Posted by sbd1
I know this thread has been going on for awhile. I have Dl'd the DXF file on several diff machines Mac and Windows. it claims to Dl okay. but opening it says its not an Acad file. help?
As far as my app is concerned my error is
"dxf is not valid DXF file
Invalid or incomplete DXF input -- drawing discarded."
-S
All,Quote:
Originally Posted by TheSniper
After many attempts to open the file. seems like renaming it from a DXF file to a DWG file did the trick.. odd but it worked. So cry for help averted!
-S
A few questions for the experts - ;)
-For the sake of simplicity, if one already has a shopbot with a 4 zoned 4x8 table, would it be easiest just to plumb one lighthouse motor directly to each zone? I realize that more holding power would be realized combining motors, but would this be needed for each 2x4 section? I'd likely not be cutting anything smaller than 12x24", and even then I could use masking panels to minimize leakage, correct?
-I've read through this thread a few times but I'm new to all of this and I'm a bit dense. :p In the original blackbox design, do all of the motors run in parallel?
Many thanks,
Andrew
Ugh, a few more since I can no longer edit - :)
-In the original design, my understanding is the check valve is used to keep the pairs of motors from fighting each other. Are these implemented at each zone right before hooking to the table? Brady's pictures in page 3 appear that is the case, but I wasn't totally clear.
-Does anyone have a good, clear picture of how the motors can be hooked together in series? I'm an electronics guy and the definition of series/parallel is clear to me, just want to visualize how the same is done in terms of the plumbing.
I'm pretty sure serial setups are frowned upon by Lighthouse/Ward at this point. Parallel is the way to go if you want them to last. Just throw all the motors in one box to maximize airflow - then plumb from the box to your zones.
-B
Thanks Brady. If all four are always running is the check valve still needed? Anyone here using any type of a filter to prevent debris from entering the motors?Quote:
Originally Posted by bradywatson
If you use a spoil board there is nothing that will get sucked in
You don't need a check valve on any motor for it to be an ideal setup. My 'Ova da hump' valve concept is for high Hg" vacs to be used in conjunction with high CFM/Low Hg" to get over the hump & start building negative pressure with the little pump. It is mostly for guys with pucks, vacuum bagging or vacuum forming.
You should most definitely run filtration on those motors. An automotive air filter or cylindrical shopvac filter (Rigid brand ones work well) to keep anything the bleeder misses or chunks/debris when you first fire up your system. Also, put a little filter/breather on your bleeder holes for the vac cooling holes so that junk doesn't get into the pump that way. Cheap insurance...Few even think about the little PVC chips that are stuck to the inside of pipes when you cut them while plumbing the system the first time...
-B
Thanks Brady. I think I've got a good grasp and was probably over thinking the setup before. Let me get my machine and dust collection set up and I'll be on to building this.
If anyone has ideas for an inline filter that would work with a ~3" inlet/outlet, feel free to post them up. :)
Guys, I am new to this, but am trying to configure my vacuum table. I have a 1 mand cabinet shop and the size of my table is 2m x 3m. I just orderd 4 lighthouse pumps from Ward and he recomended I talk to you guys. I really liked the black box as was and the QUAD setup. My question is simple. I need to be able to get the max suction, and also do not even know the best way to connect the 4 pumps. Can you provide me some diagrams to help me with this - Will really appreciate this!
I usually cut 12mm MDF with a single cut, but then from time to time also have smaller peaces I cut such as 3mm MDF. The MDF sheet size is 1.7m x 2.8m
I'm about to wire up my (4) LH7123 motors and was wondering if someone could double check my wiring diagram that I plan on using? I'm going to add this indicator light (https://www.carltonbates.com/Indicat.../78966098732-1) for a couple of reasons. One is to make sure a fuse hasn't blown and the other reason is that it will give me a visual indication when the vacuum is running. Please let me know if you think this setup will work. Thanks.
Attachment 20408
I'm putting together a vac box following the work outlined in this thread. I was discussing it with an electrician friend and he asked about thermal overload protection. I assume with these "replacement" motors this is handled with the rest of the electronics and housing the motors go into. In the application outlined here I'm curious what are others doing to add thermal protection to the individual motors.
The only mention I have found was in another thread where someone used Lighthouse motors and mentioned "having their electrician install thermal protection" before the thread died out.
Thanks in advance for any help with this question.
Best,
Mike
My two motors are on the way from TN. Going to depot tommorrow for pvc and plywood. I have read so much on this forum about vacuum hold down, and I just got to give it a try.Quote:
Originally Posted by bradywatson
Nice! Make sure you add a filter...:)
-B
David,
My 2 motors were shipped Thursday or Friday from TN also so should be here today or tomorrow. Also called Ward to say I forgot to mention the gaskets and he had them added before shipping. I will be getting my plywood and pvc by this weekend, just too much going on to get it sooner. I have pulled down everything from this thread w/pics too to try to put it all together prior to heading the HomeDepot. Will take pics and post as I get going.
One question, to clear up the confusion, what is the actual recommendation of cutting the zones, I'm assuming the 1"x1" grid? How are they gluing the bleeder board down, by that I mean if you are using the grid, what part is being glued. I hope this part doesn't sound too stupid but I always was under the impression that you just layed the bleeder on top of the grid, is the bleeder board also the spoilboard? I will be sealing the edges.
Thanks for any help with this.
Joe
Joe,
I am doing the 1"x1" squares. But I have seen some that have done slightly different patterens or grooves throughout the plenum. I think it is all about air moving, could be circles I guess? As far as the bleeder board, it looks like you skim a little off side number one, then glue it down to the plenum. From what I have read here on the forum I think the best way would be to glue all around perimeter and in between the zones. (That is the way I understand it.) Then skim a little off the top side and ready to go.
My plan is this:
I have just redone my table base last week. I took it back to the stringers and started with a 3/4" MDO bolted to frame. Then added Rockler ttrack and screwed it down. Then glued down 3/4" MDF in between the tracks and skimmed .005 off the surface until flat.
Now, for my vaccum. I plan to build a box, cut one hole in the far end of my table for the PVC, and make a BradyVac one piece drop on board. I am keeping it small for my first try with vaccum hold down, After I work out the kinks, I will then probably make a 4'x4' Plenum and bleeder board for the far end of my table that will stay on the table most of the time.
I rarely cut things over 4'x4' so I figure most of the time I will have all the options available. Working on setting up Jigs, gonna start zeroing off my limit switches with custom c3 comands. I am trying to stop running my Bot like a cave man.....LOL
Dave
My new table base finished last week.
Hi Joe,Quote:
Originally Posted by barrowj
I cut mine at 2" squares but you can cut 1" - the bleeder is the spoil board - I took someone else's advice from this forum and used silicone to glue the bleeder down around the outside edge and between partitions - Hope this helps
Tim
Here are some pictures of when we setup ours
http://www.talkshopbot.com/forum/showthread.php?t=19117
post #2
We just used the stock files from Shopbot.
Thanks Tim, think I will do that, just silicone the edges and between the zones. I will also seal the edges too.
Kyle, thanks for the info.
Everyone has been more than helpful and I really appreciate it.
Joe
Quote:
Originally Posted by Kyle Stapleton
Great re post Kyle. I have read over your setup pics a few times at least. Wish CNC training training was offered when I was in school. You are doing an awesome job.
Dave
OK, I know this was in 2010, but someone help me out...Quote:
Originally Posted by islaww
The performance of that motor is listed on the XLS here:
http://www.centralvacuummotor.com/lighthouse.htm
7" static is 95" H2O and that motor is rated to move 35 CFM (per motor).
9" is 122" H2O and that motor moves about 13 CFM.
But the 110 CFM free-air rating shouldn't be relevant. Whether or not there's plywood stock covering the bleeder board, the bleeder board is going to make a lot of static pressure drop.
What's the size of the "less that the zones" that this measurement was taken under?
BTW, the check valve thing sounds like an issue. A check value by nature requires an actuation pressure differential. And that pressure differential doesn't go away once it opens- the ongoing pressure difference is what makes the force that keeps it open. The thing is, of course, that pressure differentials are the entire product here, and difficult to achieve in the magnitude we want. So... it's eating up some of the performance.
You would need some pretty sophisticated instrumentation and time/testing to fully answer all of your questions. Vacuum is not always easy to quantify in terms of what is actually going on, especially since in the practical world of CNC routing, things are not always linear.
One possibility regarding less than 4-zones, could be that there is enough leakage (and there should be SOME for cooling of these motors) to move the working vacuum characteristics into a different area of the compressor trim map. This is akin to a turbocharger compressor map - and while ideal is linear, actual is not. Plus, unless you are running a completely sealed setup with gasketing, there is going to be some leakage, such as around the table perimeter, or if you didn't do such a hot job with the plumbing.
Static CFM is very much relevant during the initial suck down when the pump is beginning to build negative pressure - aka getting over the hump. For example - you may have one of these motors capable of 100 CFM static and an air conditioning pump that only pulls 5 CFM, but maxes out at 27 Hg". That pump will NEVER build vacuum without properly sealed and gasketed fixturing. It just doesn't have enough CFM to seal things off. This is where a check valve makes sense in conjunction with a high CFM vac - especially if you are doing something like vacuum bagging. Big CFM vac to remove most of the air; small high suction vac to pick up where the big CFM pump left off. Neg pressure pulls the valve shut & big vac can be turned off.
The thing to remember with these vacuum systems is that they are designed to be a shoestring solution to more expensive vacuum pumps. The original idea was to employ these bargain setups and make some money until you can afford a proper commercial/industrial grade setup. Some users don't have 3 phase or simply can't afford (or don't need) a pro setup - so certain provisions and allowances have to be made...as in, 'you get what you pay for' & 'everything has a price'. So...some questions probably cannot be answered without either paying someone to do the research/study or you have to do this sort of thing yourself.
-B
Hmm I think it may boil down to this-
With a well-designed bleeder board, how many inches of vacuum is required to get a useful holding force on a small object, and how many CFM per sq ft will occur at that pressure?
Now the CFM situation drops when you throw a whole sheet on it and vacuum increases its hold. But once you're talking about a whole intact sheet the holding force is absolutely tremendous and holding is not a problem if you could hold a small object. The ability to hold a small object drives the specification for the job.
I don't know what the most practical spec to set up for a small-object is. Like I could ask "can I cut out a 3" circle from a 5" square of plywood and have it stay in place?" But then again if I didn't have vacuum table I probably would never try to use Raptor plastic nails to secure a little 3" circle, I expect a person would leave it tabbed together and break it out later.
The inches of vac needed to hold a small part should be the same whether the rest of the zone were covered or not. The question becomes whether that inches-of-vac spec can be met under the CFM flowrate of a mostly uncovered bleeder board zone. Which can readily be predicted by blower spec sheets if there's a spec for what CFM-per-sq-ft should be through a bleeder board at the minimum static pressure spec for holding small objects.
An interesting study Mechanoman. Please keep up the study and post your results. I used to run a plant with komo routers with 40 horse becker vacuum pumps and we would never have dreamed of trying to run a 5" square with a mostly uncovered spoilboard. Becker pump could pull nearly 27" of mercury. I don't remember how many cfm but it was substantial. Bob
I would also like to hear what you've discovered about this. BTW, welcome to the SB Forum. Most of us go by a first and last name basis. Feel free to introduce yourself. I know a few SBers down in your neck of the woods.Quote:
Originally Posted by bobmoore
You have to run some calculations. There isn't a hard and steadfast yardstick because many variables are at play; such as: tooling geometry - is the cutter defeating hold down with upward helix/lift? What is the chipload and in turn, the amount of force being exerted upon the workpiece? Does the bleeder board have shallow kerf marks in it coincidental with the current toolpath (you cut a sheet of circles with freshly flattened bleeder...now parts don't hold on your 2nd sheet) ? There are other things too.Quote:
Originally Posted by MechanoMan
In an ideal world, CFM would equal 0 or very close to zero when holding down a given part. However...this is hard to quantify since the first part that is completely cut out of a piece of material has full vacuum force holding it down - as the kerf starts to bleed out (or in), suction is reduced and airflow increases. This is with a bleeder board...not a gasketed setup.
So...Surface area is going to be the yardstick here. If you have a vac capable of delivering a solid 9 Hg", then you'd be a little more than 1/3 atmospheric pressure, 14.7 psi, so we'll say 5 psi. Can your surface @ 5 psi total resist the force of a cutter going XY,Z speed at fC (ChipLoad)?
It's not the pump that is the most important...It's how you use what you've got. I've seen plenty of shopvac setups trump industrial pumps in their usefulness because the operator knew how to use the vacuum he had at his disposal. Universal bleeders are not the end all be all. They are meant to be a 'throw a lot of vacuum and airfow and see what sticks' solution. They waste so much energy compared to a puck system with gasketing and a smaller pump - provided the material isn't too porous...but they sure are convenient if you mainly do full sheets.
It would be lovely to quantify vacuum and say for sure what will and won't work. When it gets down to the nitty gritty, there's too much room for variation. So I'm afraid for now, the best we can do is guesstimate, take our own readings and do our own testing in our own shop. Something as simple as a material vendor (such as Trupan UL vs Sierra Pine) could mean a substantial difference in performance with identical hardware...so like most other things in life, YMMV.
-B
Yet one should not throw up one's hands and declare it incomprehensible because the problem has variables and variable standards.
Clearly there's a wide variation in the achieved vacuums people have worked with. It'd be good to know what people found a useful minimum. Are we saying 9"Hg as a minimum to get "basic" results?
Hmm, how does this work exactly? See a bleeder board might lose 80% of its thickness before being replaced. When "new", a high vacuum underneath doesn't mean high holding force on top. If you fail to resurface the sealed faces of the bleeder board, you develop high vacuum but no CFM.
Conversely, if you had a perforated (drilled-through) conventional vac table, but only used a fan with low vacuum, you could see some high figures for CFM, but this wouldn't equate to holding force.
I'd think "vacuum at the workpiece" would be the appropriate figure, however, there is no appreciable pressure drop at the open surface for a Trupan bleeder board. Or a perforated board, either.
I think what we're looking for is a SEALED surface pressure drop. That is, you have a cup with a rubber seal on the rim, and stick it on the table. How much pressure drop is there in the cup? That should dictate holding force. If you have a low-porosity bleeder board that you failed to surface, you would develop "impressive" vacuum underneath but the lack of vacuum on top would be apparent. Similarly, if you had a perforated bleeder board and didn't cover the unused holes, you get impressively high CFM but again the surface cup test shows the low vacuum pressure indicating poor performance.
The cup would need to be large enough that the sideways leakage- CFM- under the seal does not relieve the generated vacuum. That sort of leakage is going to happen even if the seal were "perfect" and the cup was glued to the board, because the bleeder board is porous by nature.
Yes of course cuts in the surface from prior use will mean you have greater pumping requirements until resurfacing. I do see that. But the test would lead to a proper understanding of the design requirements.
For example, I'd like to be able to know that "for a standard 1/2" Trupan board, properly faced, you need X inches of static underneath, which loads down the pump with Y CFM per sq ft. This will allow you to cut a 1 ft diameter circle of plywood with a 1/4" bit of a certain type at a certain depth-of-cut and IPM".
From there a person could say "I have an impressive 5HP spindle and want to cut faster" or "but I need to cut smaller parts at the same speed" and be able to calculate what the vac pump requirements are to achieve a solid hold under different side forces.
Just, not this guesswork thing. So far I've seen anecdotal accounts going all over the place.