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Author Topic: better to ask first than pay later  (Read 2784 times)

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better to ask first than pay later
« on: June 03, 2009, 08:28:46 PM »
im a newbie with enoght exsperiance to be dangerous. 10 years ago i was a sheet metal engineer i worked with autocad and programed lasers and turret presses as well as many other cnc machines. im now a industrial e&i so thats the dangerous part

i want to build a plasma/oxy cutting table. i dont need 0.001 accrucy i just need it to look like it was machine cut rather than hacked out with a chalk mark and gas axe

now for the free advice.
i would like the table to be able to cut a 8x4 full sheet up to 12g stainless steel or up to 1" with oxy i know this will present problems as plasma requires high speed and oxy cuts alot slower so i might have to forgo the oxy and one day invest in a larger plasma that can handle 1" neatly. the table will need a water tray as my wife will get upset if i set fire to the workshop again.

so questions.
1/ i would like to make the gantry over the 8' side of the table this allows me to load material easier with out having to drag it over a slide rail. if the gantry was made from alluminum and kept light weight is this possible (2 steppers on this axis)
2/ using slides and linear bearing what should i use for the drive (cheap is nice as long as it works) chain-tooth belt-gear rail-ball screw i would be happy with +/- 0.3mm
3/ as the manual points out the best place to work out the size of the steper motors required for a gantry is to ask the forum as its a grey art of acceleration and over run as the axis is not having to work on the material but it does have to move fast
4/ anyone ever worked on a flooded plasma table? does it require a special torch to cut with its tip in the water? does it affect the ampage required to cut dry material.

any advise would be welcome as i would rather start right then end up with a bunch of parts that carnt do the job.

Offline Tweakie.CNC

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Re: better to ask first than pay later
« Reply #1 on: June 07, 2009, 12:25:39 PM »
Before you go buying anything and for what it is worth, I would suggest that steppers will be far too slow for a table that size and you will be disappointed with the time it takes for the rapid positioning moves and that servo motors are the way to go.