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I found this:
http://www.woodweb.com/knowledge_bas...Effective.html The expert in the discussion says the key is volume. I wonder if the best application would be to use the car engine to drive a big centrifugal fan that evacuates the air from a chamber. Somebody on here spoke of using something like that for dust collection. They blew air out of a small sealed room in their shop, connected the dust hoses to it and then once a month shoveled the chips out. |
Roger,
Thank for the link, it is very informative. The word "onion skinning" keep poping up, I did some google n the results turn out to be method to skin onion... Could anyone explain that to me please. Thanks in advance. Ciao |
Quote:
once the cut file is done you slide the whole sheet off the cnc load new sheet start cutting, while cutting you punch your parts out of the sheet and if required clean up the edges of the cut with a small router with a flush cutter bit, this can be free hand or in a router table. |
Thanks Gareth.
So that is onion-skinning, I've been doing that for a while. It happened unexpectedly. It started when I accidently has 0.1~0.2mm left on the cut. Eventually I gave up. cleaning it is a lot of work & time consuming... I recon for the vacuum table, this technique will only work on solid wood & other non-porous workpiece. Will it be effective with MDF? |
I'm speaking from the viewpoint of total ignorance, but: My impression is that a vacuum system pulls vacuum through the entire spoilboard. When the sheet to be cut out covers the spoil board there is minimal flow of air needed to maintain vacuum. Once you cut through the top sheet, it would be like poking a big hole in your seal and your vacuum pump would have to pull enough volume to maintain negative pressure on the remainder of the sheet even with this leak.
Whats needed is a miracle glue that you can turn on off somehow! |
something like gecko feet...
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Or a vac mat. http://www.youtube.com/watch?v=xr3lf...eature=related
When I was laid up for a month with broken toes I looked into a lot of vacuum discussions. There is no cure for everyone's needs (at least I didn't find it) I did learn though if you plan to use a spoil board you will need a large vacuum with lots of displacement and cost go up. If you use vacuum pods you can get by with a lot less. I had a perfect video showing a vacuum pod system using a venturi and pods. He used Melamine as the table and positioned the pods all around where the cutter wouldnt go through. In the end of the video the waste had dropped down and the all keepers were elevated. I will try and find it again. |
I have another puzzle, if we do wave carving on both side, can vacuum holdown work?
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I think the vacuum seal would not work on the waves. Not enough contact area unless you left an undisturbed border and maybe used a foam backing to keep the waves from jumping around while you cut the second side. Maybe use the first side twice to make a mold then inject poly urethane foam to make the two sided wavy board.
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Hmm... make matching seal with inject PU foam that is a brilliant idea!
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lol, if all you want is a seal, you could use plaster of paris. I figured make a two sided wavy board mold so that you could mold two sided wavy boards!
Back to the vacuum: Would it work if you were pulling a vacuum through a 1/4" mdf board, then put a laminate sheet down for the vacuum to pull against, then use wax to attach the actual object sheet to the laminate sheet. Once the pieces are cut, a hair dryer lets you detach the cut parts. The engraving people use pitch or rosin as a heat activated adhesive, but with higher temps and higher adhesion. Actually I wonder why bother with the vacuum at all if wax on a reusable platen would work. |
Hi Ken how thick you need it to be ,maybe you can do 2 and glue them together?
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Lately I receive small but steady stream of waveboard carving on solid tropical hardwoos timber panels of about 20~25mm thick. Some times there are requests to carve the whole panel. when this happens, I'll have to run 2 g-code file with different clamping position. It I don't do something in the future, the vacuum holddown will be useless for such requests.
I am in progress of a vacuum pump conversion now, have not started the table, so I hope I can get as much info & incorporate as much useful features as possible. |
[QUOTE=KenC;47854]Lately I receive small but steady stream of waveboard carving on solid tropical hardwoos timber panelsQUOTE]
any photo's sounds nice work |
Ken posted a link to a picture in post 408 above. Nice work!
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1 Attachment(s)
As per request.
Attachment 10879 |
good work Ken!
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Poor Man's Vacuum Hold Down
5 Attachment(s)
Ditched the initial auto-mobile engine conversion as vacuum pump idea as Boyles' law told me it will be hot & I will have to have the radiator installed... That I don't like...
Saw what Buzz did here and the rest is history... A few months of research, a few days work, and A pair of vacuum cleaner motors & 5' of 2" PVC pipes, 2 Y-fittings, 2 elbows, 1.5m of flexible hose, 2 hose fitting, 2 PVC union coupling, a 49"x97" 1/2 in MDF board, 2 liters or lacquer, some thinner, 2 tubes of Epoxy glue & the fat lady sings. A single zone 49"x97" plenum with a impossibly simple bleeder valve. Bench Test figure 8"Hg vacuum continuous operation, capable of 10"Hg but the exhaust is near 100C within 5 minutes of running seriously too hot for my mental health, at 9"Hg it runs 80~90C still too hot for my comfort, so I operate it at 8~8.5"Hg where the eahaust is at 60-~70C at 38C ambient temp all day long. Commissioning Continuously operating for 10hours, 3 days at 38~40C ambient temperature. Motor temp consistently between 65~75C. Very noisy but no smoke :D with just enough seal to get 8~8.5"Hg, cutting Merbao & Nyatoh of 2 sizes 1800mm x 600mm & 1900 x 650mm. max cutting depth 6mm @ 6000mm/minutes. Dia 50mm ball nose. I apologise for the not so good quality pix from my cell phone camera but I hope some of you may enjoy it. The Vacuum cleamer motor, with not so good packaging for shipping Attachment 11741 Attachment 11742 Plenum Attachment 11743 Plenum close up Attachment 11744 All completed. Attachment 11745 |
what is the blue pneumatic tube for - in the last pic
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Be cautious of that noise
If you can put those noisy vacuum motors in a box without cooking them, that would be good. According to present theory, the sins you commit against your hearing now, may show up in 30 or 40 years as deafness: ehhh?? What???? CAN'T YOU SPEAK MORE CLEARLY???
Personally I think it is genetic, but the concerts, the trap shooting and driving at 95 mph with the windows down may not have helped. |
EAR PLUGS.....
Without them I would not only be deaf by now, I'll be a pretty agitated all day long too... I don't think it is possible for me to box em up without cooking them... Noise reduction will be another never ending work in progress. I bought the matching silencer but they are useless. I also has a Mini Minor exhaust silencer in my free junk pile. will get there eventually. For now, I will climb the steep curve of vacuum hold down with me ear plugs on... Irfan, That pneumatic pipe is connected to my vacuum gauge at the Y=0 end of the table. The are perfect for this purpose, won't collapse even when I step on it accidental. |
Irfan, I reckon the blue tube is the high-tech "pressure and temperature ajusting bleed air inlet"
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Ken, do those motors have a small fan on the back end of the motor shaft? If so, you can box them and let that small fan draw cooling air into the box.
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My primary goal is to have a functional vacuum system soonest... with minimum outlay... :p
The motor cooling fan does pull some serious air around, I reckon if we can figure out a good flow path, coolling effect may just improove. There was a Ver. 1.0 vacuum reservoir box out of 18mm thk MDF with all the bells & whistles. The instant I block off the inlet (with the motors running) All the wall panels deflected by more the 20mm inwards... The current set up is the 2nd attempt & it works without a fuss... The "table board" is what left from the Ver 1.0... The moral of the story... K.I.S.S. Other stuff I'll add on eventually 1) Exhaust silencers 2) a check valves for each of the motor inlet so that I can run a motor at a time. 3) a 3rd motor 4) a microprocessor to a)turn on & off the 3 motors with respect to the pressure. b) over heat shut down c) cycle between the 3 motors in hope of extending their useful life... About the noise, my last resort is to stuff the pair of motors in the toilet & brick it up along with the dust collector fan...:mad: I do have 2 toilet in the shop... |
Mix the dust with some water and flush it down the toilet..... :D
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Gerald D.
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Ken,
I would be interested in seeing you microprocessor ideas. I am looking at adding vacuum table. |
Ken,
As far as the approach to the Microprocessor to turn on & off the 3 motors in pressure flux, how would you approch this? Is there a board out there one could use for this or do you have to design one? I'm very curious to see how this would work as well. |
Maybe I am missing it but why not use 3 (or how many vacuum motors) Adjustable Vacuum Switches. Set them up as a tear so all three come on and once the vacuum builds each will shut off as the vacuum builds.
Here is a link to what I am talking about. http://www.omega.com/pptst/PSW21_PSW22.html Either way you have me really interested in your project and looking forward to your progress. |
for not so cheap solution you can find PLC with 6 analogue inputs and couple digital outs, 3 analog for temp sensors and 3 analog for pressure, digital outputs for control to shut down individual overheated or at enough pressure motors.
Other than that, you could use AVR Atmega series MCU, or Arduino as it seems popular board with these microcontrolers, They can have from 8 up to 16 or more analogue inputs and at least 16 digital outputs. PLC is reliable and ready to use but at a price, especially that ones with analogue inputs are most expensive or require addons for expanding number of inputs or outputs. It should not be a problem to program any of them. |
My tentative solution is
Arduino + FREESCALE SEMICONDUCTOR MPX2100DP Differential Pressure sensor + Temp Sensor (which I've yet to select) + 16x2 LCD display I hope the DP sensor is a correct choice & this will be my 2nd Micro Processor project after nearly 2 decades... I'm no electronic wiz kid & Arduino comes in a easy enough package where I can start programming (or copying scripts :o) & get down to work.:D I find setting up MicroP from scratch a huge challenge. There are many advantages using a MicroP, I can use it to control, read pressure & temp... basically, the limit is your imagination. AND no need to work out the physic equations to have them working... Russel, The topology is what I have in mind, start with all 3 motors, then switch off one at a time when the vacuum is achieved In my wildest dream, I wish to use a car MAF (Mass Air Flow) Sensor to measure the flow as well but I just couldn't find the data sheet for any MAF sensor. Any commercially available Air flow sensors are expensive... I also looked at Pitot tube & it requires another DP & temperature sensor, temp compensation & pressure compensation... etc... can be veryy messy stuff at the end... Until the MAF data sheet for an economy locally available MAF is available, this option will be buried in my dungeon of ideas... Its not a essential option at this moment. Nils, Don't think! Just do it. Its not difficult to get a functional vacuum table once you put your hands to work. I wasted too much time weighing too many option & all the possible "what-if???" When you have them running like mine, many things will turn crystal clear. Noise, heat, etc etc... I trust your ability to have them resolve in no time. |
You can try LM35 sensor, its cheap and easy to use, gives voltage output in respect to temperature.
http://www.national.com/mpf/LM/LM35.html#Overview how to use it http://www.ladyada.net/learn/sensors/tmp36.html |
I've finally done it!!!!
I fried the Chinese spindle windings!!! Sadly, no big bang & no smoke... just a tripped VFD... |
What happened.. no water ?... or it this the excuse your wife hears so that you can buy a new 3kW spindle ? :D
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I reckon the cause is running it too near its 10A margin (8A) for too long & it spiked over 11A one last time & burst the coil winding insulation...
This proof one thing, the advertised VFD rating is more honest then the spindle's... :p Well.... this sure is the best excuse to up size to 3kW :D Sorry wify, there goes your birthday present budget... Good thing I have a spare spindle sitting in the box... Will keep my current operation load with the coming 3kW spindle & hopefully I'll get reliable service from it for a few thousand running hours. |
More Tinkering
5 Attachment(s)
More "upgrading" were completed
What's done this time round 3kW Spindle, Solid cast aluminium Spindle holder Ball ScAttachment 11921rew Z-axis Attachment 11917 Attachment 11918 Attachment 11919 Attachment 11920 |
Where did you get that spindle holder from?
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Cut a Styrofoam mould & evaporated cast by a local foundry. That is about the biggest size they would handle. then horizontal mill the mating surface, bore the hole, dirll & tap.
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http://www.stappenmotor.nl/Steppermo...%20housing.htm
The 80mm fits perfect on my 1.5kw chinese spindle. |
Ken
Thank you for the interesting read, brought up a few things I had not thought of before maybe Im just too tired to think But I could not find any referance to the Bob I am using... I wil try reading it again tomorrow thanks to you and all your friends who shared their knowledge to make your build a reality Shane |
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