Re: safety

--- In CAD_CAM_EDM_DRO@y..., "ballendo" <ballendo@y...> wrote:

> Thank you for starting this thread. Safety is unfortunately often
> overlooked in "homemade" projects. Whether it is due to lack of
> imformation, cost-cutting, or thoughts of saving time, or it-won't-
> ever-be-a-problem thinking; the result will be the same if these
> choices/assumptions are incorrect...

Hi Ballendo,

Thanks for picking up this thread. Although mundane and definately
doesn't get our hormone levels up (until situation demands it),
attention I believe should be given to it, not just personal safety,
but safefy to equipment as well. Aspects like this probably had been
discussed, but if it is all bought into a single thread, it will be
so much more convenient and help focus our sometimes forgetful mind
on it.

>Besides this, specific questions are most easily answered. What
>besides power supply inside a control box, did you wish information
>on?

Some on the list (me included) are not professional engineers so some
questions may be .......... hope the professionals will be
patient/educate us ignorants.

i. FUSES: Hope I don't get flamed on this, how about how to
size/chose fuses - how many amps, slow blow/fast blow, etc.

example: for a bipolar chopper 2A vs. unipolar 2A do we use
same/different types (slow/fast) should the fuse be exactly 2A, 2.5A,
3A? What are the considerations?

My conjecture - slow blow for unipolar and fast blow (controlled
current) for chopper?

ii. E-stop. How does one wire up an e-stop? A simple large-button
flame colored switch/relay to cut off all power to the machine
(driver plus mill/lathe), or just a switch/relay to the driver? etc.
What are the considerations, advantages/disadvantages to the various
possiblilities? How does one use the disable terminal on the Gecko,
etc? Is this meant to be used as an E-stop?

iii. bridge rectifier. Does one have to ground the metal casing of
the bridge rectifier or does it have to be insulated from contact
with the box, etc? Currently, I have a bridge rectifier on a heat
sink which is mounted on an acrylic plate (for insulation) which is
then mounted on top of the transformer casing. If ever the heat sink
gets overheated (actually bridge is way over requirement, something
like +20A when only 6A expected) and the acrylic plate sags, what may
happen? Will it be better to mount the heatsink directly onto the
driver box (which would then be connected to the ground?

iv. Should PCB be mounted on metal/plastic legs? I see that the
camtronics 2A board has the hole where the legs are to be fixed
connected to the common ground. Is this meant to be grounded (to the
driver box) via metal PCB legs or is it safet to mount them on
plastic legs for insulation? (sorry for this question)

v. How many home machines have safety enclosures? Were there any
incidents where a safety enclosure would have earned its keep?

vi. If one is stubborn enough to want a safety enclosure, what
material and thickenes should the enclosure be? relatively thin
polycarbonate or very thick acrylic, etc.?

Ballendo, would these micro-contributions attract a discount for your
up-coming book or flamethrowers?

Lee

PS. can you give one or two/more publication/link preferably closely
related to CNC/driver boxes or nearest to kick-start my idiotic
search for safety standards?