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View Full Version : Cnc hotwire build from kit - couple questions! Pic Comming!



blake374
01-24-2010, 09:55 PM
Hi I am new here so take it easy on me :)

I ordered a hot cnc hotwire kit from 8linx. The setup is going to to have a 55" x and a 55" y axis and an 8' hotwire. I still need to find my own driver board and power supply for the hot wire. Also I need some eye bolts and motor couplors but I am going to tackle those later.

I ordered my own driver board:http://cgi.ebay.com/4-AXIS-CNC-ROUTER-OR-MILL-STEPPER-MOTOR-DRIVER-BOARD_W0QQitemZ330398367986QQcategoryZ78197QQcmdZViewItemQQ_trksidZp4340.m263QQ_trkparmsZalgo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D10%26ps%3D63 (http://cgi.ebay.com/4-AXIS-CNC-ROUTER-OR-MILL-STEPPER-MOTOR-DRIVER-BOARD_W0QQitemZ330398367986QQcategoryZ78197QQcmdZViewItemQQ_trksidZp4340.m263QQ_trkparmsZalgo%3DSIC%26its%3DI%252BC%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D10%26ps%3D63)

I havn't got the powersupply for the hotwire yet. I was thingking of getting this to controll temp :http://webtronics.stores.yahoo.net/ensavat.html

I belive I still need to get a "high current power supply" to go from the variable power supply to the hot wire. Does anyone have a recomondation?

How do I get the temp and speed right? Play with the machine and experiment?

How do I get the tension on the hot wire correct?

I think I have an idea on how to hook up the wire to the machine. Is there any special tricks to hooking it up like this:
http://s252.photobucket.com/albums/hh7/blake374/?action=view&current=rcfoamcutter_hot_wire_cnc_foam_cutt.jpg&newest=1

I should be getting my parts soon and I am going to have some fun putting this together. Stay tunned for some tons of pics!

blake374
01-25-2010, 11:25 PM
No one? Really?

blake374
02-16-2010, 12:10 AM
There has got to be someone out there that has some comments!!!!!

Pandinus
02-16-2010, 03:36 AM
re the variac- It is a variable transformer with 5amp an .5KVA output max Ie. 100 volts at 5 amps = 500 VA ...125 volts at 4 amps =500va 10 volts at 5 amps =50 VA but your 5amps max, you can only put a high current supply after this if its low voltage, you have to stay under the 500 VA, So Id assume your talking about a chopper circuit for current control which IMO makes the variac a useless front end.

Now on its own, Nichrome wire 22 Ga gets to 1000F at 5.6 amps so about 900F at 5 amps, at 1.055ohms a foot * 8 foot = 8.44 ohms * 5 amps = 42.2 volts so as long as you meter the voltage or current / maybe put a stop on the variac at 40 volts you could just use it as your control.... maybe even mark temperature graduations on the dial... It seems to me that people just use High power dimmer switches / Fan speed controllers for hot wire cutting ... no??? Maybe add a 3:1 step down xformer before it to cap you at about 60 volts peak. I believe the triac will still work??? Don't quote me on any of this as I have never done any hot wire cutting, but I did learn enough about electronics to get me in trouble :P

I actually got my arm caught in an industrial heat sealing machine once, it had a 10 foot and two 4 foot 16 GA nichromes, running off of 3phase power ( mostly for the motors on the conveyor belt.... that crap gets hot in a hurry lol, not to mention that 60Hz buzz you feel LOL


re the wire mount --- Just had a quick look and to me it looks like the slides are a plastic of some sort as well as the nut... so the whole Z-Plate is isolated from the rest of the machine... Id avoid this as the whole plate could be at a hich enough voltage to kill you.... if the eyebolt is threaded through an insulator then just the wire is at potential, and I think your less likely to touch a smoking hot wire than lean against a machine to grab a piece of foam before it gets ruined.
That's how I got my arm caught... trying to save a piece of mirror...... Just a trip to the hospital for some ointment... it never actually hurt thanks to the electricity confusing the heck out of my nerves :P