On Jan 29, 2024, at 19:50, sgbrody <[email protected]> wrote:
That standard is ISO 15066 which is Collaborative Robots. After
measuring force and then determining the surface areas of the part
contacting whatever, you can determine the pressure.
This standard provides tables for allowable forces and pressures -
both are needed - to determine if the robot 'crash' is within
acceptable range.
For example, I have two clients using robots which are billed by
their manufacturers as collaborative, but it is the end effector
when tested for the 'crash' force and pressure, that will confirm
they are collaborative in that specific application.
In both cases they were confirmed collaborative.
However, if the flat surface of the end effector was replaced with
a needle, they would not be collaborative. They would be
dangerous and guarding would be required.
Thanks,
Sent from my T-Mobile 5G Device
-------- Original message --------
From: Douglas Powell <[email protected]>
Date: 1/29/24 7:05 PM (GMT-05:00)
To: [email protected]
Subject: Re: [PSES] Reduce Speed of Moving Part to Reduce Risk
All valid points; however, I was taking my information from the
established ISO/IEC standards for machinery, with which I am
familiar. I do recall another standrd some years ago, mentioning
contact surface area when I was looking into finger crush as well
as sharp edges. And the original question was solely about speed,
so that's how I responded.
All the best, ~ Doug
Douglas E Powell
Laporte, Colorado, USA
[email protected]
LinkedIn <https://www.linkedin.com/in/coloradocomplianceguy/>
(UTC-06:00, US-MDT)
On Mon, Jan 29, 2024 at 4:41 PM Richard Nute <[email protected]> wrote:
Hi Doug and Brian:
I thought I would offer my (radical) point of view on the issue
of “speed of moving parts.”
Consider moving aluminum foil and moving aluminum block, both
at the same speed. The aluminum foil has very little mass,
while the aluminum block has relatively high mass. The foil is
not likely to cause injury, while the block may cause injury.
Consider an aluminum needle and an aluminum block, both having
the same speed and mass. The needle is likely to cause injury,
while the block is not likely to cause injury.
Consider the time of contact with a moving part. If the time
is long, then injury is not likely. If the time is short, then
injury is likely.
So, in addition to speed, we must consider mass of the block,
contact area, and duration of the contact in predicting injury.
In other words, energy per area (mv^2 per area in this case)
whether mechanical, thermal, radiant, chemical, or electrical,
transferred to a body part for a (usually short) period of
time, causes injury. The same energy magnitude transferred
over a long period of time is not likely to cause injury.
An injury occurs only when energy per contact area of
sufficient magnitude and duration is imparted to a body part.
Both the safety science article and the IRSST paper discuss
energy of moving parts and area, but do not address the other
parameters. Both introduce (to me) the concept of “force” on
various body parts. I’m not sure of how this fits into this
safety discussion.
Consideration of speed alone is over-simplification.
Best regards,
Rich
*From:* Doug Nix <[email protected]>
*Sent:* Monday, January 22, 2024 11:16 AM
*To:* [email protected]
*Subject:* Re: [PSES] Reduce Speed of Moving Part to Reduce Risk
Hi Brian,
In the machinery sector, 250 mm/s has long been used as the
threshold for avoidability. This figure comes from the robot
standards and has been used for about 30 years. Studies done at
the Polytechnique de Montréal [1] and IRSST [2] have shown that
a speed closer to 140 mm/s is more universally avoidable by
people working in various environments, but the long use of 250
mm/s has entrenched that higher speed. Related to that is the
IRSST’s Repoer R-956. I’ve attached copies of these documents
for you.
You can find the 250 mm/s number quoted in most machinery
safety standards where reduced speed is considered for risk
reduction. The origin is in ANSI/RIA R15.06 1992, which made
its way into CSA Z434 and then eventually to ISO 10218.
[1]Y. Chinniah, B. Aucourt, and R. Bourbonnière, “Study of
Machine Safety for Reduced-Speed or Reduced-Force Work R-956,”
IRRST - Institut de recherche Robert-Sauvé en santé et en
sécurité du travail, Montreal, 2017.
[2]Y. Chinniah, B. Aucourt, and R. Bourbonnière, “Safety of
industrial machinery in reduced risk conditions,” Safety
Science, vol. 93, pp. 152–161, Mar. 2017, doi:
10.1016/j.ssci.2016.12.002.
Best regards,
Doug Nix
[email protected]
+1 (519) 729-5704
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