You can use non-pilot arc systems but you may need to tweak your pierce
cycle to nearly touch the work before you turn the torch on. I assume
your torch uses HF start. In that case pay very close attention to good
grounding and screening. HF start can play havoc with your electronics.
I would recommend building as big as practical. It generally doesn't
cost a lot more time or money to build a bigger machine. You can do
small jobs on a big machine but it is a real pain to try to do big jobs
on a small machine.
Ball screws aren't that great for plasma. They don't tolerate the
abrasive dust all that well and you need pretty decent speeds if you are
cutting thinner materials. Rotating nuts help with the whip problems at
higher speeds but they can be a pain to engineer and you need to be
careful you don't exceed the rated maximum rotational speed fro the nut.
I also like the 'servobelt' idea. I built a 8' x 4' plasma many years
ago using plain 30mm wide HTD belts (i.e not the doubled up servobelt'
idea) and that was reasonably accurate but it did suffer from the belts
flapping a bit.
Les
On 22/08/2018 03:09, Greg Bentzinger via Emc-users wrote:
So I want to build a combo table with dual Z slides - Plasma and Mill/Router.
I have a 50A 60% duty cycle scratch start machine now. I know that if I use it
I will have trouble with fine screen and expanded metal will be hopeless.
On raw stock it works great, but one of the key reasons I bought it was to tear
down units for recycling. Baked enamel used on washer dryers requires me to
grind a clean spot for ground clamp and a spot for each cut start.
Knowing that now I would have paid the extra coin to have the pilot arc
feature. Am I going to have to get a pilot arc system to be viable for CNC use?
I want to use a magnetic break away mount for the Plasma slide as I also may
mount a Laser on that slide.
The Mill / Router side will also have quick changeable mounts (quick being a
relative term) to hold a Router or on the other mount a SEIG X2 mill head I found on
Craig's list. The X2 head will allow use of all types of R8 tooling and the OEM DC
motor is a fair match for the rigidity of a 52" wide gantry.
I am thinking of using dual 16mm ball screws fixed with rotating nut drive on
the gantry legs - This will allow the speed I want without screw whip issues. I
actually think this might be cheaper than rack/pinion drive, but with dirt
issues.
Since plasma is not currently part of my business, this project has no real
budget, but I have collected all kinds of motion control parts, bits and pieces
that I can use.
Also what is the simplest THC to use with LCNC?
Since the budget also does not provide for enhanced compressed air sources I
will be adding air pressure switches with logic Pressure low, pause between
cuts, and pressure good, to resume or start a program.
I may do a 26"x 26" as a preparation build - but that small I might just use
belt drive.
Ideas?
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