Pin Installation Machine

Lancie1,

I respectfully disagre with you on the drum issue. With ADs drum you can skip/jump positions on condition, and step the same drum by event or time or a combination of events. "Rolling your own" drum us pretty simple also, just a matter of indexing a pointer though a data table.

I would suggest if this topic were about Paula using the durm, it would have been long done by now...Not to say all you need is a drum, but a drum would be the heart of it.

elevmike said:

Lancie1,

I respectfully disagre with you on the drum issue. With ADs drum you can skip/jump positions on condition, and step the same drum by event or time or a combination of events. "Rolling your own" drum us pretty simple also, just a matter of indexing a pointer though a data table.

I would suggest if this topic were about Paula using the durm, it would have been long done by now...Not to say all you need is a drum, but a drum would be the heart of it.

Click to expand...

OK provide the drum since it is so simple and would be done by now. I would like to see it and add it to my collection.

Its kinda funny, according to this thread ANY machine that has a start here and go there should be a drum...I do not see the rationale.

I just tried to assist Paula but as usual what I am doing is wrong BUT of ALL that speak of using a DRUM, NOONE has provided one as an example.

Paula, my apologies, I hope what I have offered has assisted you in developing your program. I will not be able to provide further assistance.

rsdoran said:

NOTE: Your home compressor may just be 3-4 SCFM which can cause issues with maintaining system pressure on demand. A factory system should be capable of 50 SCFM or so on demand, maybe more. I would not worry too much about the pressure switch dropping out until tested on site...

Click to expand...

You are definitely right about that. Still, in messing around with adjusting the pressure switch to obtain a consistent signal, I'm beginning to regret setting it up that way. Leaving the issue of the drill's pressure bleed aside for a moment, the pressure switch seems to be only marginally capable of distinguishing between the static pressure in the cylinder (fully extended), and the dynamic pressure during extension, when flow-controlled down to a reasonable speed. This could be a problem I'll have to deal with down the road.

I am not sure a sub-routine is needed. You have a "dwell" time for the pin seat so those conditions may be possible for pin loading in a ladder routine...as I addressed in my latest version.

Click to expand...

Studying your program in more detail, I'm inclined to agree. I think I may be stuck on the idea of a subroutine purely for the novelty of it. In watching the bowl feeder system operate at the vendor's yesterday, I was struck by how little time the feed sequence takes, and the way you have it set up should work well without noticeably lengthening the cycle time.

What would be nice, since I do not have the machine, is you using my program and telling me what happens. I know you do not have alot of time for experimenting but if you do I would appreciate it.

Click to expand...

Unfortunately, I had to tear down my temporary setup yesterday morning so that I could drop off the components at the fabricator's. So, the next opportunity I will have to run any program will be when the machine is assembled and wired, probably on Thursday. I'm in complete agreement with you on the benefits of having access to the actual machine (or a good simulator) while developing a program.

One question on your program: There's a NC contact in the first rung labled "Whole Cycle" (C1). Since C1 doesn't show up anywhere else in the program, I'm wondering if this is supposed to be a "Stop Cycle" (C0) contact.

Paula

Ron & Paula,

I did not mean to interfere with your assisting Paula. I was only responding to Lancie1, and maybe it was inapproprate for me to do so in the manner I did. There's a dozen ways to skin a cat, and your way is fine. No sense in changing horses now.

My appologies.

C1 should show on rung 13, rung 12 is a stop cycle and 13 whole cycle i.e. cycle complete.

Attached is the pdf printed version, let me know if it is different from the code files I posted.

Dang Dang Dang

Paula forgive me, the pdf was not complete, this is the correct version.

The whole program is in a zip file in a thread on page 3.

About the pressure problem...

In cases like that, I have found that a pressure switch is a very reliable indicator of position as long as it's a good quality (diaphragms tend to break in sytems with a lot of "pneumatic shock") and the supply is good. We've have situations where an array of valves on a manifold "scavenge" pressure from each other and the quick and dirty fix was to use a separate valve and a big piece of hose as an accumulator. With an Air drill, you may need a lot of 3" hose!

This may get you past testing, but your control program still needs to deal with an intermittent signal in a predictable way. Once the part is clamped, ignore the pressure switch. It already WAS, now all you care about is drilling.

Or, and more likely, in the final application, I would think that you may want to abort the process if the clamp pressure fails. How do we know the cyclinder port supply line didn't break off?

Add a step "8 Fault" and while you are at a step "9 Cycle Timeout".

If you are in step "4 DRILL", and the pressure switch drops out, what should happen? It may be that you need a switch with two adjustable thresholds, like hysteresis. It will engage at say 40 psi, and stay on until it drops below 20, or something like that.

And add a cycle timeout so your program does not hit a dead end waiting on a step that can't complete. Set the timer liberally higher than the longest expected cycle rate, and if it times out, bail into the step "9 Cycle Timeout".

Now you can control what is required to resume the process, and you can inhibit the appropriate devices.

Hope this gives you some ideas...
Paul

Terry Woods said:

Now... there are other considerations...
- what if the drill bit is broken?
- what if the Table Extender fails?
- what if the Pin Driver somehow ends up mis-aligned? And doesn't complete the function?

Click to expand...

Since this project was to be done "on-the-cheap" (so what else is new?), I'm limited to a single Fault lamp, connected to Y10. My plan is to add logic where appropriate to determine when a particular event doesn't happen within a reasonable time, and turn on the Fault lamp (and halt the cycle) when the time expires. The operator will have to shut down the system (cycle the E-stop), which will clear the fault conditional, when the cause of the problem has been determined and fixed.

And by the way, thanks for your very informative post!

Paula

Paula,

Regarding fault lamps; we use 1 lamp with a flashing code to indicate maybe 5 faults. There's a 4 second pause between the flash faults. There's a vinyl label adjacent to the lamp. If there is more then one fault, they all play in succession.

For example:

1 flash = Overload
2 flashes = Time out
3 flashes = Out of stock
4 flashes = Machine Jamb
etc...

elevmike said:

Paula,

Regarding fault lamps; we use 1 lamp with a flashing code to indicate maybe 5 faults. There's a 4 second pause between the flash faults. There's a vinyl label adjacent to the lamp. If there is more then one fault, they all play in succession.

For example:

1 flash = Overload
2 flashes = Time out
3 flashes = Out of stock
4 flashes = Machine Jamb
etc...

Click to expand...

Don't forget:
0 flash = Burned out fault light

Seriously, Elevmike's idea is a method that I've used before.

Another good and cheap fault display idea I use all the time (although too complicated for Paula's simple application) is to drive two seven-segment displays with eight outputs in BCD to give a fault number from 00-99. One hundred possible fault codes for eight digital outputs is cheap.

Then, tack a printed and laminated fault list to the machine with what the poor techie or operator has to do (based on the number displayed) to resolve the problem and you're done!

In an effort to avoid the "0 flash" issue we use led lamps.

Paula,

I also have used the single light in the past...but in addition to Mike's post

Light on solid = All ok
Light out = Light burnt out

Also use a LED...More cycles

rsdoran said:

Its kinda funny, according to this thread ANY machine that has a start here and go there should be a drum...I do not see the rationale. I just tried to assist Paula, but as usual what I am doing is wrong, BUT of ALL that speak of using a DRUM, NO ONE has provided one as an example.

Click to expand...

I saw it coming... As soon as a few individuals started beating the drum for Stage Programming, the stage was set for the Drum advocates to speak up. But seriously, I don't see anyone pushing a particular agenda with this thread, at least not to the point of minimizing anyone else's efforts.

I'm happy to hear from all quarters, and will listen to any sincerely offered advice. My problem is that I'm trying to do eleventeen things right now, and having a hard time staying focussed. It's just not a good time to start trying to wrap my brain around a different type of programming. The last project (the wire feed & cut) was different in that I had lots of time to let the program evolve, plus I had access to the actual machine (or at least it's main components) for an extended period of debugging. Unfortunately, that's not the case here. I'm just trying to get this project completed on time so I can get caught up on three other jobs I've either started, or have waiting in the wings. For that reason, I'm very glad that Ron and Lancie have offered the most immediate and direct help. Other's opinions and suggestions are valuable too, and will be kept "on file" for future use.

Paula

For that reason, I'm very glad that Ron and Lancie have offered the most immediate and direct help. Other's opinions and suggestions are valuable too, and will be kept on file for future use.

Click to expand...

Message understood and duly noted...

Originally Posted by Terry Woods

Now... there are other considerations...
- what if the drill bit is broken?
- what if the Table Extender fails?
- what if the Pin Driver somehow ends up mis-aligned? And doesn't complete the function?

The point I was trying to raise was...
How are these conditions handled? It's one thing to have an idiot-light blinking at you. But... what happens when you respond to the idiot-light? Simply pressing an E-Stop, thus turning off all driven devices, might create a worse situation.

A drill-problem is not so bad because the drilling operation occurs while the Table is at Home. But, if the bit gets stuck in the part and then the E-Stop is pressed, the Part Clamp will release at the same time that the Drill retracts - the part will be retracted, with the drill-bit (maybe), away from the clamp. Will this produce a problem?

And by the way, you can count on the bits going dull! In order to prevent a dull-bit issue, you might want to intall a cycle-counter that will let you know (a flashing light?) when it is time to change the bit. The bit-change could be scheduled at an opportune time... before it results in down-time.

Now, what if the Pin Driver fails to complete the stroke, and the E-Stop is pressed while the Driver is in mid-stroke... what happens?

At this point, the Table is extended and the pin, held by the pusher, is partially inserted into the hole. When the E-Stop is pressed, both the Table and the Pin Driver will try to retract at the same time. Is this going to produce a more costly problem? Will the Pin Driver, or Pin Holder, get bent?

You need to consider everything when the E-Stop is pressed. In some cases, you need to develop a "controlled stop routine" as opposed to an absolute "hard crash-stop". As usual... it depends!

It's always those damned "what-ifs" that get you!

Always design your process for the normal, expected activity. But then, always consider and incorporate what is necessary for the "exceptions". That includes E-Stops.

Just a heads-up.