Another Input 4 question

[andym]

My workplace had a visit from a Health and Safety inspector a while back, and despite our ShopBot being housed an enclosed in a room, we were asked to install a safety mechanism to stop the CNC from operating if anyone opened the door to enter the room.


I should point out that I am in the uK and there are some quite strict Health and Safety regulations, so if an inspector officially asks you to do something and you don't there can be legal implications. We have a PRS Alpha purchased in 2008-9.


So I got hold of a magnetic safety switch that has been attached the door, and a relay that I have installed in the control box and connected to input 5.


Initially I wanted to use input 4 as I read in the documentation that it acts just like pressing the space bar. I assumed that meant that when input 4 is triggered the CNC would stop and you would receive the same message has hitting the space bar.


I wanted the option of resuming the cutting file instead of having to reload it and restart it from the line it was last on. Unfortunately I can't get input 4 to work.


I connected a simple switch to the input 4 terminal and ground, but there was no response from input 4. I tried setting input 4 to Normal Open and Normal Closed but still nothing. The input 4 indicator is dark green and the number 4 is red, not sure what that indicates.


Have I misunderstood being able to use input 4 in this way?


If I can get input 4 to work would I get the same options to restart the cutting file as hitting the space bar?


Sorry about the long post.




P.S I did try to post the same question earlier but not sure what happened to it....

[Martin Reid]

Dear Andy

Let me start by saying a simple work around for the [SPACE BAR] 'stopping' would be to use a wireless keyboard and take this with you when you leave the room.

On a wider note...

The jobsworth doesn't understand CNC. Did he let on what he thought the hazard was - noise, dust, finger retention, or training? You of course know that most shops have staff milling around all the time.

Background reading for H&S

PUWER regs for cnc woodworking machines..
HSE information sheet - Routers and machining centres - Safe working practices - can be found at... http://www.hse.gov.uk/pubns/wis22.pdf

Quote
"CNC routers can be guarded by a variety of fixed guards but any safety distances should comply with BS EN 13857:2008.5"

BS EN ISO 13857:2008 Safety of machinery — Safety distances to prevent hazard zones being reached by upper and lower limbs - can be found below... (good luck with this one?)

http://coa.mesnac.com:8080/MesNac_EIP/lantai/files/upload/201012201341355781.pdf

Anyway that's my two-penn'orth
Sincerely
Martin
(Lancashire)

[srwtlc]

Not sure if you could tie it to the spacebar (imagine there's a way, just haven't delved into it), and #4 is used for E-Stop, so that will drop everything. Either way, your chances of resuming without issue can be hit and miss. If it happens often, your percentage of ruined work will be high. Just my observations on the reliability of pausing over the years.

Stopping it when someone (even the operator that may have left the room and came back) is kind of silly. You may never get anything done! Lock everyone out and the operator in. ;)

Perhaps a warning buzzer/light.

[ken_rychlik]

It's been a while for me, but pause and resume was never reliable on my shopbot.

[andym]

Thanks for the feedback,

Just to clarify...The CNC is enclosed in a room but the operator sits outside and is able to view the machine through safety glass windows in the shutter doors. So let's call it a safety enclosure. This was done to cut down on dust and noise. We machine a lot of 3D shapes in various foams and it can very messy.

The H and S inspector didn't like the dust boot that came with the shopbot because "you could put your fingers under that" (which is true if you're a complete idiot). He said that we had to either put a more substantial "guard" around the tool or shut the machine off automatically if the operator approaches the machine. So either a light barrier or a safety switch on the door.

Martin, yes you are right he doesn't understand CNC and we couldn't bother to argue the finer points of how we need to use the machine, like having to approach it to switch valves on the vacuum hold down when cutting small parts. I did actually read the H and S documentation and the switch and relay we got is manufactured specifically for that purpose and comply to BS standards.

It is a pain and when in operation does mean that you have to restart the cutting file each time but it is possible to override in the software. So input 5 works and can be seen to work if the inspector pays another visit. It is just that in the user guide it states....

"Input Switch #4. Input #4 is set up to function as a Panic Switch / Stop Button. Anytime that Switch #4 is Activated/ON, the action of your tool will stop, just as if you had hit the Spacebar, and you will receive the same 'Stopped' message. When this switch is activated it will also have the same automatic effect on Output Switch #4 as hitting the Spacebar. Your tool will not function until the Input Switch #4 is released. Note that Switch #4 always functions as a Stop Switch. It cannot be re-assigned for other use. By hooking the switches up in series, you can set up as many Stop Switches on your tool as you would like."

I have had no issues in the past with hitting the space bar and then resuming a job, unlike restarting the file from a particular line. That is why I was hoping to use Input 4, but I can't get it to function at all.

In a way it doesn't matter as what i have done works and we can override it (although we shouldn't) I was just wanting to understand if there was something wrong with the control board or if I was doing something wrong.

It is frustrating as on the same industrial estate there is another, bigger company that has three CNC machine working all day long, with no barriers or guarding, just little dust boots, and people walking around them. This can be seen if you walk past as the shutter doors are always open, yet they have had no issues.

So thanks for the help and if anyone has any idea as to why input 4 might not be working it would be nice to hear, just out of interest.

Andy

[dlcw]

It is frustrating as on the same industrial estate there is another, bigger company that has three CNC machine working all day long, with no barriers or guarding, just little dust boots, and people walking around them. This can be seen if you walk past as the shutter doors are always open, yet they have had no issues.

Andy

Looks like an instance of a government beauracRat picking on a little guy because he knows you can't fight it, whereas the bigger company has told him to get lost and there's not much he can do about it. Government beauracRats are such a pain to deal with because they think they are all powerful and there's nothing us little guys can do about it. Selective enforcement really sucks. I write a lot of letters to my state representative when having to deal with these beauracRats.