Best way to achieve proper wire tension...
Hi guys!
Our machine is being built, it´s 220x120cms in width and length in X and Y and 300cms deep in cutting length (wire length).
Can anyone help us out as to an optimal "spring-based" solution?
Maybe somebody has a hotwire cutter of these dimensions and knows how or where and which spring type to use on it...
Thanks!
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Best way to achieve proper wire tension...
I would use some form of a bow, but make sure the bow is longer than the extent of all 3 axis. You will have to ensure the 'bow string' can slide flush through the guides on the axis too and it may be an idea to somehow feed the current via the guides.
anyone wants to chat our way through the ideas? MSN Messenger way?
add me I'm boggyplanet@gmail.com
If you are hell bent on a "spring based" solution why not go down the "Tensator" route. Obviously (Granny) a bit of simple trigonometry will tell you the range of extension required for anything other the mildest wing taper for instance, a linear spring will vary in tension and once past the yield point will need resettting/replacing. We found the spring setup supplied with the Foamworks kit rather less than satisfactory.Originally Posted by boggyplanet
Punch "tensator" into your browser and you will find the extending barrier application but I am referring to the tool suspension system and I mean to replicate the virtually rateless extension principle derived from the use of a coil spring rather than a linear tension spring. Another option would be to multiply the action of a short linear spring by the use of a pulley set as found on rope hoists. (multiply spring rate required by number of pulleys in system)
Cheers
GEFR
Hello Kingpav
We supplied current via devices at the axis but suffered contact variability on account of melted foam on the wire. We reverted to clips until we find a better ssolution. (I know we shouldn't get stuff on the wire)
Personally, I found that a spring bar worked better by far for me than any spring. It just a simple piece of spring steel, 1/2 inch by .064 with a groove for a pin to wrap the wire to.
Will post a drawing of it if needed. The nice thing is that the heat does not effect it, and it never seems to loose tension no matter how long the cut or length of wire. I usually use a 38 to 64 inch length wire for the cutting. Power supply is a lightning 24 VDC 8 amp job with a heavy duty wire wound variable resistor rated to 1200 watts.
yep pictures are needed for us slow to visualize dummys!
thanks
Michael T.
"If you don't stand for something, chances are, you'll fall for anything!"
Spring tensioner for hot wire cutter
I got the idea for it from an old scroll saw I had, its just a piece of spring steel with a few bends and whort enough to make the tension fairly strong. Dont have any pics of it, but can post a autocad drawing of it for those interested.
I also have drawings for several different arangements for home built linear bearings that I can post, some of which I have used for more than ten years with no binding problems.
freejac
Spring Tensioner
OK, heres a quick and dirty version of the tensioner I use on my foam cutter.
Hope the autocad file is attached, have not uploaded an attachment on this system before.
I use pneumatic cylinders, check it out at http://www.poly-cor.com
Last edited by esawyja; 02-20-2008 at 12:13 AM.
Erm, this might be totaly off base, but surely if you tightened the wire to a specified torquer then it would vibrate at a given frequency... couldn't you use an electronic guitar tuner to hit the pitch exactly?
I love deadlines- I like the whooshing sound they make as they fly by.
I think that might be a problem as the wire is heated and changes properties as it get warmer, so it stretches all the time, hence the spring.. or in my case the pneumatics
Ah, gotcha! just a thought
I love deadlines- I like the whooshing sound they make as they fly by.
I'd sure like to see some good photos of this system? Sounds like it would be a lot cleaner operation and less affected by any outside sources.
I'll see if I can take some better photos, did you check the website? http://www.poly-cor.com/
It is basically a pneumatic cylinder, connected one side to the wire, kept at 4bar, which gives me about 4Kg of force on the wire, so as the wire stretch, the piston in the cylinder maintains the wire at 4Kg force
http://www.poly-cor.com
spring tension
Theres always someone going to build a better mouse trap, what ever works for you is what counts. Personally I have tried many devices and setups to tension the wire on my foam cutter, and the spring bar works better by far than all others Iv tried. The coil springs and other devices put to much tension, causing the wire to snap or stretch beyond use. The temperature I find is more critical than the tension, since the largest degredation of the wire is due to heat effect, and not the tension of the wire, although the heat effects the wire more while under higher tension. PWM is the secret to make it last longer and have less heat damage, along with the type wire you use. Use what works for you, my setup works fine for me, and Iv been using the same wire for two years.
The spring tensioner in NON-CAD format
One of these days I'm going to have to learn how to draw in CAD.
The main handycap of the spring system is that the tension depends lineary on the elongation of it. So, when you make a 'straigt' cut (this is, both vertical axis one in front of the other) the spring has low tension. But if you make a 'tapered' cut (this is, one vertical axe at the begining of the X axe and the other at the end of the X axe) the tension on the spring is maximum, maybe the wire or the sping itself may break.
On my oppinion, a good system should keep a constant tension on the wire, like the pneumatic cylinder of esawyja, or hanging a mass at one end of the wire, using a sheave:
Regards from Spain
Re: Best way to achieve proper wire tension...
Long time ago you talked here about pneumatic cylinder, but the website poly-cor.com does not exist anymore. Where can I find more information on this now?
