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jdougn
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Joined: 18 Mar 2009
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Location: Louisville KY area

PostPosted: Wed Oct 21, 2009 7:48 am    Post subject: two stage Reply with quote

I'd suggest a two-stage system. The vac pump can be isolated from the tank/s which provides better vacuum at the latter stages of the pull. Try doing a search on two-stage, especially stuff by Dr Crash.
dn
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felixx
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Location: San Diego, CA

PostPosted: Wed Oct 21, 2009 9:48 am    Post subject: Re: two stage Reply with quote

jdougn wrote:
I'd suggest a two-stage system. The vac pump can be isolated from the tank/s which provides better vacuum at the latter stages of the pull. Try doing a search on two-stage, especially stuff by Dr Crash.
dn


wow, THIS is a ton of info! I am wondering if I should use the two ball valve. still reading it all. thanks Doug
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spektr
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PostPosted: Wed Oct 21, 2009 11:06 am    Post subject: no need for 2 stage system. Reply with quote

Gentlemen must agree to disagree agreeably, so even though I disagree with my friends here on this subject, you need to remember that I find them to be very sharp dudes and either way you do things will ultimately work.. Pick your poison........

If you want to go to pump only vacuum, which I do not use,(hint hint) plumb it this way. platen to a (t) t to pump and tank. The pump will pull air from the platen and tank together. This is fine in my mind and is the way I have things hooked up. I also have the line going to the tank from the t ball valved to run pump only if i need it (never do). This gets you around the issue of 2 vac sources that I've never understood the need to use. I do see it if you dont buy a decent pump tank combo, and it will work with a shop vac/pump setup, but why bother.....

You have built a good machine, finish it right and dont mickey mouse the process. Theres a reason you dont see shop vacs powering "real" vac formers in a production environment........ Not that these machines arent "real".


I advocate a foot operated valve so you can time things well, and a bypass around the foot valve so you can take your foot off. I have a tank isolation valve, but It isnt necessary. The only added thing i have is a check valve between the pump and vac system so I can cycle the pump with vac switches and not have the oil sucked out of my wet pump or backflow thru my vane pump depending on which nachine you look at.

Scott.
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jdougn
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Joined: 18 Mar 2009
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Location: Louisville KY area

PostPosted: Wed Oct 21, 2009 11:39 am    Post subject: two-stage Reply with quote

Hey, you found it at CNC. That's the thread I was remembering. DrCrash loves delving into various theories about ways to improve performance for vac formers. In my book, simple is good!

My setup is like this diagram that he shows using two shut-off valves. Closing off the tank after the initial pull is especially useful if you don't have a high volume vac pump. That way the pump is not trying to recover vacuum at the planten (critical) and a big tank (not critical) while the plastic is still forming.....

Code:

Code:
+ - - - - - - - - - - +       
|        platen       |       
+--------+  +---------+       
         |  |               
         |  |                                       +-------------+
         |  |        +-------+       +-------+      |             |
         |  +--------+  ball +-------+  ball +------+   vacuum    |
         +-----------+ valve1+--+ +--+ valve2+------+    tank     |
                     +-------+  | |  +-------+      |             |
                                | |                 |             |
                                | |                 |             |
                                | |                 |             |
                                | |                 |             |
                                | |                 |             |
                             +--+ +--+              |             |
                             |  high |              |             |
                             |  vac  |              |             |
                             | pump  |              |             |
                             +--+ +--+              +-------------+
                                | |
                              exhaust


The location of the planten and pump could be switched like in this diagram and may work better that way. I've not seen any hard data to know.
Code:

        exhaust
         |  |
   +-----+  +-----+       
   | hi vac pump  |       
   +-----+  +-----+       
         |  |               
         |  |                                       +-------------+
         |  |        +-------+       +-------+      |             |
         |  +--------+  ball +-------+  ball +------+   vacuum    |
         +-----------+ valve +--+ +--+ valve +------+    tank     |
                     +-------+  | |  +-------+      |             |
                                | |                 |             |
                                | |                 |             |
                                | |                 |             |
                                | |                 |             |
                                | |                 |             |
                             +--+ +---+             |             |
                             |        |             |             |
                             |planten |             |             |
                             |        |             |             |
                             +--------+             +-------------+
         



Do I remember that you're using a Gast 1023 pump? If so, it should do really well on a system similar to this.
YRMV, dn
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jdougn
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Joined: 18 Mar 2009
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Location: Louisville KY area

PostPosted: Wed Oct 21, 2009 11:51 am    Post subject: Re: no need for 2 stage system. Reply with quote

spektr wrote:
Gentlemen must agree to disagree agreeably, so even though I disagree with my friends here on this subject, you need to remember that I find them to be very sharp dudes and either way you do things will ultimately work.. Pick your poison........

Scott.


Hey Scott, I don't think that I'm disagreeing with you! But, I think some of this depends upon the system setup. I know with the 4CFM pump the system on my 2'x4' vac former, 30g tank included, could not recover vacuum fast enough to get sharp pulls on big molds. The volume of the tank was just too great for the little pump to quickly evacuate. What CFM pump/s do you use or recommend? Also, what diameter piping do you suggest for a vac former 2'x3'? It seems that 3/4" pipe or smaller seems to restrict overall flow on larger systems but does that sound right to you?
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felixx
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Joined: 21 Sep 2009
Posts: 68
Location: San Diego, CA

PostPosted: Wed Oct 21, 2009 11:43 pm    Post subject: Reply with quote

This is my pump, it is a Gast 1023



I also got this with it,


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jdougn
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Joined: 18 Mar 2009
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Location: Louisville KY area

PostPosted: Thu Oct 22, 2009 7:28 am    Post subject: Gast 1023 Reply with quote

Yeah, that Gast is a nice pump and you've got a good vacuum gauge with it. You probably know this already, but plumb the gauge into part of the system that will be at full vacuum. My system actually has two gauges on it so I can judge when to shut off the tank and go to the vac pump only.
Nice setup! dn
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felixx
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Joined: 21 Sep 2009
Posts: 68
Location: San Diego, CA

PostPosted: Thu Oct 22, 2009 8:27 pm    Post subject: Reply with quote

Went to the Hanger today to bend the sheet metal using a leaf break machine.




Nice fit



here is a shot during drawing the lines for drilling. 640 holes!



mounting the sheet metal with tack nails. used a drill to countersink so i dont bend the nail, risking hammering the wood.



something isnt quite right, can you see it?



how about now?



After I nailed all four sides, turned it over, i noticed a bubble. when i press on the surface its about (but not quite) 1/4 inch gap i would say.

when I was mounting/nailing the sheetmetal, i was careful not to hammer it too hard. Once the nail was in, there was no couple more swings to make sure, i didnt want to start bending the metal.

I didnt start drilling the 1/8 inch holes until i got an opinion on what to do. The nails are in pretty good (they are ribbed) and if i try to stick a screwdriver or any other tool in there im going to start tearing things up. i thought about spraying the metal down before i secured it, but felt there was no need.

I guess what im asking is, will it make much of a difference? will it go into shape once the holes are drilled and will the pulling of plastic simply put it in place?

I got to thinking that the last table i worked on, had a couple of ripples on the surface and it worked fine.

I hope I didnt just screw up my Platen :-/
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felixx
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Joined: 21 Sep 2009
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Location: San Diego, CA

PostPosted: Sun Oct 25, 2009 12:53 am    Post subject: Reply with quote

well I have my block ready so i dont drill too far. Before I start drilling, any advice for me in regards to my metal bubble?
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spektr
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Joined: 07 Jan 2008
Posts: 425

PostPosted: Mon Oct 26, 2009 7:13 am    Post subject: Reply with quote

Slap a few drywall screws in it, and dont worry about that part leaking so DO NOT seal it, the sealant will melt anyway.... Shouldnt be too big a deal mostly asthetic. Drive on big guy....... Scott.
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felixx
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PostPosted: Mon Oct 26, 2009 3:45 pm    Post subject: Reply with quote

my arms are tired! taking a break. I cant imagine drilling holes for a 2 X 4 let alone a 4 X 8!
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felixx
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Location: San Diego, CA

PostPosted: Mon Oct 26, 2009 7:42 pm    Post subject: Reply with quote

Man, my arm is so tired, and buffed out, it looks like like Quagmires arm after he discovered internet porn!



Seriously though, I got them all done.





I have foil tape i will wrap around the edges, take my Dyson vacuum and clear all the leftover shreddings and make sure all the holes are clear.
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felixx
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PostPosted: Thu Oct 29, 2009 7:43 pm    Post subject: Reply with quote

I took a small video testing my platen today.

CLICK HERE to check it out.
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jdougn
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PostPosted: Fri Oct 30, 2009 7:12 am    Post subject: Reply with quote

felixx wrote:
I took a small video testing my platen today..........

Good work on the platen. If you use the same careful & thorough approach to the rest of your vac former it should work real well.

dn
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lobosmedic
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Joined: 30 May 2008
Posts: 15

PostPosted: Fri Oct 30, 2009 9:05 am    Post subject: Reply with quote

Eureka, success!

I'm glad it's going well for you, you could have almost formed a part out of plastic sheet and that dyson!

Is that floral foam I see, hmm, looks strikingly familiar to a TK handplate. Wouldn't be trying the Dan Laws sculpt to vac technique I linked earlier would you ... Razz Probably just made it to quick to test it, but its a great technique for making positives, you could just harden the outside, fine tune it and whala! instant mold. And i'd be happy if anyone took my vac form advise, lol.

keep up the great work


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