Re: [CAD_CAM_EDM_DRO] Re: Build CNC Plasma cutting Table

Chris,

We have some small parts to make out of galvanized
sheets. On a given day they can ask us to make 1000 -
1500 pieces.
I calculated it would take me around 4 weeks to make
1000 of these things manually.
Because I have to cut the sheet in 5cm strips, then
cut the strips again in 11cm pieces, then drill 4x
1/2" holes, then 2x 3/16" holes, then bend it to make
a U form.

Lucky for us we have an Ironworker, but stil the
manual labor is alot.

Naturally I want to build a machine that I could use
for other purpuses later on

Deborah

--- Chris L <datac@...> wrote:

> indy123456 wrote:
>
> >I used heavy steel floor grating (24"x24" sections)
> in the cutting
> >area (bought one to check it out, found it was very
> flat, so I got
> >more) and got them all leveled to the carriage
> axii, and was able to
> >bolt risers in fixed locations where the cut path
> wouldn't hit them,
> >since I would always be cutting the same parts.
> >
> Same here. I picked mine up from a "Raising company"
> who tears down old
> buildings. Far cheaper than new stuff. The only
> thing I did maybe
> different is put that on a completely seperate
> table, that rolls between
> the frame of the plasma cutter. This way I can load
> stuff away from the
> machine and roll it into place. I too have adjusters
> to level if necessary.
>
> If I had time to do it again though, I would use the
> typical zigzag cut
> points to set stuff on. This way things "fall thru"
> after cutting and
> you have a lesser chance of the torch tip getting
> caught when you are
> not looking.
>
> >The problem I ran into was gap control... no
> problem making the torch
> >travel in a flat plane of course, and no problem
> establishing a flat
> >table plane. The steel being cut is the problem.
> Even assuming it
> >is flat to start with (I got a lot that wasn't, and
> was useless), it
> >doesn't stay that way long when you start
> cutting... edges of cut
> >sections pop up, catching on the torch tip, moving
> the part or
> >stopping progress.
> >
> This is true.... But it does depend on the thickness
> of material, and
> how fast and even you can transverse the steel.
>
> > I know some costly systems use sensors that
> >manipulate torch height with a servo... I tried to
> come up with a
> >mechanical version that rode the surface. I know
> people have plasma
> >tables that work, so I'm not discouraging you from
> your project...
> >just warning that, with HEAT involved, things don't
> always go the way
> >you envision.
> >
> I see Torch Height Control discussions in the MACH1
> newsgroup now and
> then. It could be that there are fellows who have
> this working under
> Mach1, but I am not sure. I do know it requires a
> Plasma cutter that can
> deliver a signal that indicates current amperage
> draw as that changes
> continuously as the tip gets closer or farther from
> the material. Not
> everyone needs torch height control though.......
>
> > To avoid headaches and heartbreak, investigate
> the
> >marketed systems thouroughly and ask lots of
> questions first and talk
> >to people who use them; see how they handle the
> heat warp problems.
> >The feed control that CNC allows vs. my manual path
> tracing (hard to
> >maintain a steady path following a pattern,
> fighting carriage
> >inertia, etc.) may go a ways toward reducing the
> heat induced into
> >the sheet.
> >
> The ability to control feeds under CNC control is
> the key to keeping
> heat minimzed. You must have a controller capable of
> very smooth motion
> thru mixed geometry to avoid excessive heat and also
> to avoid any
> jittery cuts. Good adjustable Acceleration is also
> important because you
> need as little ramp up and down time in the corners
> as well.
>
> > (snip)I thought plasma cutting was a neat,
> "little-guy-enabling"
> >technology until my experience with it... now I'm
> not a fan.
> >
> There is no doubt that it depends on your needs. If
> you are really in
> need of a "production" machine in the immediate
> sense, you likely do not
> have the time to fiddle with building a CNC Plasma
> cutter. However, if
> you cut things occasionally, or if you would like to
> be able to cut any
> "one off" item now and then without the hassles of
> getting another
> company to do a "onesey twosey" for you, you will
> very much appreciate
> the time and energy you spent getting your own
> machine.
>
> The one I built could *never* run as a production
> machine. It was built
> so I could create "prototypes" rapidly to make sure
> they work. In my
> case, I made 50 or so prototype designs for one
> application before
> concluding how it really should be. I would have
> went crazy and lost
> lots of time waiting for someone else to "fit in"
> those 50 samples on
> the way to the final item. I do send all the final
> work to someone else
> and like mentioned, I don;t think I could do it for
> what they charge.
> But I'm not giving up the ability to make what I
> want when I want
> anytime soon. Even though it could never be a
> production machine, It
> takes little time to slam out a few hundred things
> now and then.
>
> I do not have Torch Height control either. I do have
> a "machine torch"
> style head with holder, which allows me to simply
> rotate a knob to raise
> or lower the torch. On any challenging cut, I can
> just stand there and
> move it up and down if necessary, but with what I
> cut, it is seldom a
> problem.
>
> I could envision a half dozen cheap alternatives
> for my Torch height
> control needs..... A cable operated hand held device
> to "Squeeze and
> Release"- Raise Lower.... while standing at a
> distance, A motor Driven Z
> axis using my Kids servos and Radio from his Rc
> Car...... Or even a
> "full pull" electric selenoid lift just for
> emergencies.
>
> I guess really, If all it takes is a motor driven Z
> axis, an easy to
> build circuit, and a control software with some THC
> functions built in
> like Mach1 (you'd have to research how that is
> coming along), you may as
> well "design for the future" and at least make sure
> you could ADD the Z
> axis if necessary. You can start with just a to
> axis.
>
> So, My advise would be to consider your needs. Then
> determine just how
> "in depth" the machine to fit your needs must be. If
> you plan on turning
> out thousands of parts with no-one standing there,
> you should consider a
> proven OEM machine. However, if you need to computer
> generate a hundred
> parts now and then, it is amazing how little of
> machine you really need
> to accomplish that goal.
>
> Chris L
>
>
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