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Will Off-center Press Press More on One Side?

12/06/2018 3:55 PM

On my resistance welder, the top and bottom electrodes are not aligned. They are parallel, but centerlines are off by about 3/8". The top electrode presses down with 9000 lbs. psi. Given the heavy force load, and the fact that the projection (ring) around the bottom edge of the welded piece collapses as it gets heated and welded... might this weld crookedly, because of more pressure in one side? Or is the pressure equally distributed in the welded piece (the adapter), despite the misalignment of the two electrodes (as shown ind drawing)?

I feel like I'm thinking too hard on this one, and confusing myself.

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#1

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/06/2018 5:07 PM

I'm not an expert, but I'm thinking that if the upper electrode and lower electrode faces are parallel that the loading on the adapter should be uniform. If you hold something in a vice, it doesn't have to be in the center of the vice if the vice faces are parallel.

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#5
In reply to #1

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/06/2018 6:17 PM

True 'nuff. But a vice doesn't apply 9000 psi. So.....

I still can't really be sure by using that logic.

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#14
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 6:50 AM

" it doesn't have to be in the center of the vice if the vice faces are parallel"...... but, if there is play in the vice slide, the jaws will tilt & grip harder on one side.

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#18
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 8:54 AM

Yes, that's my thought, as well. I can't tell if there is play... but there may be. And if the mis-alignment was corrected in both x and y, that possibly would be eliminated or at least greatly reduced.

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#2

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/06/2018 5:40 PM

Depends on if there is any give in the assembly...how rigid is the upper and lower electrode assembly? will there be any give at 9000 psi force? It is aesthetically disturbing, but that might have no significance here...The other thing to consider is the electrical field characteristics, is this causing uneven amperage discharge? ...this should be apparent in the weld characteristics and uniformity...

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#6
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/06/2018 6:25 PM

AS I replied to lyn... Not sure how the rigidity of the welder applies to this particular weld at 9000 psi. 9000 psi is on the high side for this welder. Also, as I said below... this welder is a mess that I'm untangling one issue at a time. Currently, it's the misalignment.

As far as the electrical field... yes, that could also be an issue. But there are many issues going on at once in combination, so it's difficult to blame any one alone for the various inconsistencies. At least until I go through the list and eliminate or address a bunch of them.

I don't know enough about the what you mentioned regarding electrical field. Could you elaborate in dummy language. Electrical is not my field.

And yes, it is visually disturbing.

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#3

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/06/2018 5:42 PM

If the electrode and the base are RIGIDLY mounted and parallel and able to resist any flex when the 9,000 pounds of force is applied, it's not a big deal. (I don't think it's 9,000 PSI unless the total contact area of the two surfaces being welded = 1 sq. in.) It's probably more at the weld.

There is the issue of unequal thermal transfer into the workpiece if the electrode is offset. Probably not that important in this application.

If the joint isn't failing and the adapter is still parallel after welding, I'd fix it when it's time for PM. (or just ignore it)

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#4
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/06/2018 6:15 PM

This is at least my 2nd or 3rd question related to this particular resistance welder, whose trouble-shooting appears to have become a career. It never had a lick of PM over more than a decade. Our welds are not consistent quality welds. I'm trying to root out the problems one by one. They are undoubtedly caused by many separate things. There are so many, it's like doing an experiment with a dozen variables. So, this is where I'm at now. The misalignment. The way the weld is designed at the contact point makes it particularly susceptible to an uneven loading, if in fact an uneven load exists. Actually, I didn't draw it correctly, as there is an additional inner ring, along the ID of the adapter, that fits down into the hole in the sheet metal. It is supposed to be flush with the inside surface of the sheet metal after the welding. I'm getting inconsistency in that regard. The problem is... there are other things it could be, as well. So I'm trying to eliminate this issue if possible. I don't know how rigid the set-up is. I mean... it's a resistance welder, as shown in photo. I don't know how the 9000 psi relates to a resistance welder's rigidity.

After this, I have to try to figure out why there has been a "force creep" over the last 7 years. The set-up started with a force setting of 6000 psi. Over the years, they have had to incrementally increase the force in order to get the same weld result. Now it's 9000. Clearly the actual cause for the creep is elsewhere, and upping the force is the way they dealt with it... but I don't believe it was the proper way because they never figured out why it was happening in the first place. They dealt with symptoms rather than the cause.

But... that's another story. I'll gt to that after I either eliminate or confirm this misalignment as being cause for inconsistent welds. Far too many scrap pieces.

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#7
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/06/2018 7:15 PM

I don't know how much actual force you have. 9000 psi is pressure, you have to multiply by the area in contact to get the force.

If the faces of the upper and lower electrodes are not exactly parallel, you would have more current and more pressure on the side where they are closer. More current on one side could also be due to the condition of the upper or lower electrode.

I don't know if this will help.

http://www.amadamiyachi.com/educationalresources/rwtroubleshooting

Or maybe here.

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#8
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/06/2018 8:29 PM

An experiment with a dozen variables can't be solved with one solution.

First question is, how many variables have you identified. We don't know that.

Let's address the flushness problem. If you mark 20 pieces, tank and adapter on each side and place them in the welder is the defect consistent. Can you identify the defect relative to the electrode offset?

What happens if you go back to 6K pounds of force?

Do you have any way to measure the force exerted on both sides of the electrode to see if it is even when seated?

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#50
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/10/2018 8:06 AM

well if you are eliminating variables then align the electrodes. now you have one less variable.

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#9

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/06/2018 11:54 PM

Maybe there is an adjustment for this. Or maybe a judicious hit with a hammer....

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#10

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 12:15 AM

Clearly the misalignment can't be good! So why haven't you corrected the misalignment? If the welder has had no PM for a decade, it's probable that some part has gradually shifted. There are three ways I can think of for shifting: bending, wear, or slipping. Since you say the electrodes are parallel, then it's not likely bending.

One of the electrodes is normally fixed, and the other one (usually the upper one) moves. That motion requires either a linear slide of some form or an arm rotating about an axis. Either the slide or the axis can wear, but 3/8 of an inch is a lot of wear. Check the moving parts for wear!

Somewhere, there are bolts that mount the electrode assemblies to the machine base. Some of those bolts may pass through slots or oversize holes, to permit correct alignment. If so, loosen, align, then retighten.

Of course one of the electrodes must be insulated from the machine base. Many insulating materials degrade over time; perhaps an insulator has worn or decomposed. Check them out!

Get the alignment corrected, then you can start thinking about other things. As Richter indicated, you said "9000 lbs. psi". It could be 9000 lbs of force, or 9000 psi pressure, but it can't be both, unless the contact area happens to be 1.0 square inch. 9000 psi is a fairly dangerous pressure, so I suspect you really mean 9000 lbs of force. Either way, that sounds high!

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#12
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 5:55 AM

Thank you. But I'm not asking how to fix the misalignment. I'm asking if the misalignment is causing more force on one side than the other. It isn't an easy fix, for reasons too many to list here. What I'm battling here is other people's opinions at my job that don't believe it matters, claiming it's the same force anywhere on the electrode, as long as they are parallel. I came here to find reasoning that I can use to explain it to them and justify ordering the fix to be made.

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#21
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 9:57 AM

Perhaps it will be easier to argue that the offset is creating a torque on the workpiece originating at the place being welded.

If people are not understanding the problem, you might ask if they think there would be a problem if the misalignment was 6"?...5"? ...4"?...

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#23
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 10:07 AM

You are correct. They are not understanding. They feel that the torque is not sufficient because the machine is rigid.

That may or may not be true. But the best way of dealing with that would be to eliminate the possibility, by making the alignment. Convincing them of that is difficult, because to accomplish the alignment is somewhat complex and it will also put the machine down for unspecified amount of time. My reasoning needs to be stronger than their concerns. Yes, I think I will use your suggestion of asking them at which point they think that there is actual torque. They won't know that answer, of course... so yes, I may use that as part of my logic to them.

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#35
In reply to #23

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 6:20 PM

As to the argument...

What is the reject rate caused by unacceptable welds?

What is the all in cost in the rejected part up to that point, materials, labor, storage, etc?

Are the rejects reworked or scrapped? How much does rework cost or how much is recovered by scrapping?

How long will correction of alignment take? How far behind will that put everything? How long will it take to recover without undue expense?

How much will the correction cost, all in?

What kind of return on investment is deemed acceptable?

...just read the replies and see that your problem appears to be enroute to being resolved. Congrats.

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#37
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 8:49 PM

All those costs are high. But there are rejects along literally every step of the process. There are a lot of steps. So I may have job security if I keep solving the issues at every station. Once I wrap this one up, I may go to the girth seam welders that keep having tracking problems. That's one of the biggest reject points. Sometimes 15-20 a day. That one seems relatively simple, but if I hit a wall, I'm sure I'll pop in here again. All resources are valuable, including this one.

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#39
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/08/2018 12:21 AM

Tackling one problem at a time is a logical approach, but downtime might be significantly reduced if several problems are fixed at the same time.

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#31
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 12:40 PM

Oops - never mind, I read the OP again.

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#27
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 11:31 AM

By the way... I believe that the reason for the aforementioned shifting is that the linear actuators are failing or have shifted themselves. The welder has three positions. These three positions are attained by two actuators in line... end to end. For the first position, both actuators are un-extended, and the first lower electrode is under the upper electrode. For the second position, one actuator extends, moving the middle electrode into place. And for the third, far right electrode, the second actuator also extends.

This should have been obvious to our maintenance guys. And they should have fixed it long ago. But as I said, they didn't think the misalignment (in this case, the x axis) mattered.

In any case... if you read my last reply to lyn, you'll see that I've managed to get the manufacturer to agree to come in and fix every single thing and make the whole welder as close to like-new, as possible! Our crappy maintenance contractors won't have to lift a finger. Not that they would, anyway.

It'll cost us a bit to have this kind of complete overhaul (stuff we should have done ourselves through regular PM)... but it will be well worth it to finally have this poor welder attended to. I believe it will be an offer we can't refuse.

After that, all I'll have to do is to enforce a strict daily, weekly, monthly PM Schedule. Easier said than done, but I think management here will help me with that enforcement, as they know they have egg on their face by being manipulated by our maintenance guys for so long, and letting it get to this stage.

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#32
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 2:21 PM

" linear actuators are failing"

I thought it was hydraulic. Electric explains a lot.

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#33
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 3:14 PM

They may be pneumatic. Didn't get a good look at them. Just on a small rather confusing drawing.

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#11

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 5:21 AM

Most people think that solving multiple problems on a machine is like pealing an onion. Getting rid of one layer/problem reveals the next one. You don't have one large problem, a machine that is unreliable, but a series of smaller problems most of which can be solved easily. The trick is to list all the symptoms and then guess if solving one problem will eliminate or mitigate some of the others. The fix that has an effect on the largest number of these small problems, even if the effect is very small, is the one to tackle first. Often one fix eliminates the need for further fixes or exposes a way of making other fixes much simpler.

Solve the misalignment first. Even if it is not obviously causing electrical problems, it will one day or already has caused problems with the hydraulic cylinder or whatever other mechanism is employed to apply 9000 lbs force. The press was not made offset which means that someone has assembled it incorrectly, probably putting washers or a packer on the wrong side or missing one out. That should be a relatively easy fix.

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#13
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 6:02 AM

I need justification to order the misalignment fixed. It's misaligned in both x and y directions. The fix isn't easy and I'm going up against some people who are saying it isn't necessary since anywhere on the face will be the same as long as the two faces are parallel.

I don't need a how, I need a why, so that I can make my case and stop the pushback.

The machine runs practically 24/7 and scheduling downtime is like passing a bill thru congress. I need a valid reason other than "because I say so".

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#15
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 6:53 AM

If I recall correctly, you have not been in your position with this company for very long. It takes time to build up a 'because I said so' respect. I agree with all the others on the misalignment. You have clamping pressure that is offset, which is not good. Even the most rigid set-up will want to flex. You say this is near the top of the machine's clamping force, near the maximum allowable. Presses (stamping, brake) shouldn't run production day in and day out at over 80% capacity. It's just too much stress on the working components and moving parts. You don't run your car at over 80% of it's maximum RPM (red line) all day long. There is a working margin for a reason.

I won't dwell much on the electrical. Path of least resistance and all. :) Everyone here has given the same reasons for alignment. You will have more amperage passing through in a direct line and drops off the further you get from that line. A perfect circle in direct alignment will have your current flow evenly around the diameter. If it is out of alignment, the current will flow more on the shortest route and less on the indirect route.

We can't know why your machine is out of alignment. It may be an easy fix, it may be and expensive fix. I would want to know if the machine is working toward catastrophic failure of a major component or if you need to replace a bushing or tighten a couple bolts.

My personal pet peeve is "that's the way we've always done it". I got fed up with one operator and replied back, "Then you've been doing it wrong all this time." Though I had experience and knowledge backing me up.

Look at the answers given here. All I did was repeat them. Everyone is saying the same basic things. Present it to your superiors in a way that they can understand. An analogy may help, or a demonstration. I've used paper to help demonstrate forming concepts for steel sheet. Water flow (water falls) could represent current flow. Good Luck!

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#19
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 9:12 AM

Thanx, Torqued. Yes, I agree 100%. Especially on your pet peeve. Ditto. As a trouble-shooter, that is what I come up against all the time. But in this case, it's simply people who don't know enough about the machine, and have long ago convinced themselves that these issues I point out are not the causes of the poor results and many scrap parts. And you're right... I've only been here a few months, therefor I need solid reasoning to make a case for each corrective action that I recommend to them. "I say so" isn't enough.

You know, I'm going to copy an email I'm writing right now, and post it. Just so you guys can get the whole picture, and you might even find my situation interesting, if only for curiosity's sake.

I am, this morning, writing to the manufacturer of this welder... the ones that sold it to us many years ago. My company has been wanting them to fix this welder for a long time. But every time they come out, they tell us we need to fix the obvious shit first, that has been caused by NO PM ever having been done. Then they will come back and fine-tune the more technical aspects. But after they leave, it's just forgotten. So, this time I'm here, to follow through and make it happen. I'm sending my contact a list of what I've found and want them to email my supervisor to tell him they agree with my list, and that they will come and fine-tune the settings after all these things are done. That should validate my recommendations.

I WILL get this damn machine fixed, and get a PM program going, if it kills me. Just have to play a bit of politics and psychology to make it happen.

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#28
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 11:56 AM

Oh, and by the way... thank you for the explanation regarding the electrical aspect to misalignment. That will certainly help. And it is relevant, as we are pushing the envelope not only mechanically... with the force setting of 9000 lbs, but also electrically... in fact they have been running beyond the recommended amperage for the thickness of metal we are welding to, and are still falling short. It shows on the welds... significant number of scrap due to this as well. Also... I'm getting occasional arcing and sparks on the TOP of the welded part, where it is being pressed by the upper electrode. What you are describing may have something to do with that. Although, it's more likely that it is due to a deformed lower base where the bottom electrode sits... making the faces not perfectly parallel.

Anyway, that's good to know and understand.

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#17
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 8:37 AM

Work out and present in writing the cost in parts and labor and in lost production, or with the option of completing the work as part of part of a planned shutdown, of stripping the machine, slotting holes to correct one misalignment and packers to correct the other misalignment. Then work out the cost (plus loss of knock on production and down time to all other departments) of a major failure to the structure and or the hydraulics, and point out that such a failure will happen during production with no planned shutdown option. It might be worth while to add the cost option for a replacement machine, but to do this you might have to show an increase in productivity to justify the capital spend. If this machine is critical and the whole factory grinds to a halt without it then it is a no brainer that failure will cost several (often up to 50x) times a fix. Then point out that a failure will happen but that you don't know when. The dissenting managers then have two options. Fix the misalignment or gamble on waiting for the failure and live with the extra costs that brings and the loss of face for failing to listen.

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#29
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Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 12:03 PM

Yes, all very good advice. In fact, I've done some of that, and your comment was about to make me do all of it, in detail. But... since I first asked this question last night, I have already gotten a response (below, in my discussion with lyn) from the manufacturer, after having sent them a detailed explanation of every single deficiency... and they have agreed to do ALL the work, instead of relying on our crappy Maintenance Dept, which is only good for excuses.

They will make it like new! Or as close as possible. It will be worth every penny. And I don't believe management will have any choice, when they are given an opportunity to get a complete overhaul.

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#51
In reply to #13

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/10/2018 8:19 AM

reasons your welds are not consistant:

parts are not uniformly in contact with each other.

parts are not clean of oxide and dirt (such as oils)

charge is not optimized for power and time and force (including duel pulse)

these are the only variables i can think of, what are the other dozen variables?

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#53
In reply to #13

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/11/2018 1:19 AM

Maybe you could make a coffee mug holder to go on the naysayers desk with an offset support, such that when their full coffee mug is put on the coffee mug holder it will spill coffee all over their desk.

You can explain to them that the desk pushing up and the gravity pushing down forces are parallel and so that by their logic there should be no spilled coffee on their desk.

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#16

Re: WILL OFF-CENTER PRESS PRESS MORE ON ONE SIDE?

12/07/2018 7:58 AM

Fix what you know is wrong and sometimes other problems that you do not think are related magically go away.

Fix the alignment problem.

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#20

Re: Will Off-center Press Press More on One Side?

12/07/2018 9:44 AM

Okay, so here is the WHOLE STORY, for your amusement. I am sending the letter below, to my contact at the manufacturer of our welder. They have been trying to help for years, but there are certain elements at my company that sabotage their efforts, simply out of ignorance, laziness... or who knows what. Bottom line... the welder still acts up and is all out of whack... mechanically, electrically and electronically. So, I'm gathering all the info that I can, and between me and the manufacturer, plan to finally make this happen. Below is the letter. Feel free to make any practical suggestions on what I've written, or... just take solace that you are not facing this same challenge!

******************************************************

The favor I’d like to ask of you is that you contact my supervisor, and tell him that you would be glad to come here or send someone here to help train us and to diagnose the numerous settings… but that it would essentially be a waste of our time and money, if we here don’t first address all these mechanical issues first.

Does that sound reasonable? If so, that will give me the back up in authority and believability that I need, for them to stop blowing off my recommendations. THEN… you guys can come down and help assess the less obvious issues that may be revealed and to go over the settings and whatever other non-mechanical issues we can then find.

Here are the irregularities that I have found:

  1. The upper and lower electrodes do not line up in the x direction. Something about the two linear actuators has slipped, and when changing position between the three lower electrode positions, the entire lower table does not stop in the correct place. They believe it doesn’t matter. I believe the reason for this should be sussed out and corrected by examining the actuators, since the original set-up was obviously not mis-aligned.
  2. The upper and lower electrodes do not line up in the y direction. When the upper electrode comes down to initiate the weld, the upper electrode is set farther back, toward the machine, than the lower electrode. There are T-slots in the upper electrode mount that allow y re-positioning of the upper assembly. It needs to be moved forward. They believe it doesn’t matter. I believe the reason for this should be sussed out and corrected by examining the T-slot bolts, since the original set-up was obviously not mis-aligned.

3. There is a jumble of folded and refolded shim stock between the upper electrode mount , and the block that it attaches to (the block with the T-slots). I understand the original reason for these shims. But… this mass of shims is positioned along the right side edge of the two blocks, and it’s rather thick. This results in a wedge-shaped air gap between the blocks. I can only assume that there is potentially arcing and voltage/amperage leak between these two blocks, as only the left edge is in physical contact between these two blocks, and the right edge where the shims are. There is no full contact between these two faces. Furthermore, they have added to these shims and moved them around over the years, and there is no telling how much the material of the shims has mashed or been deformed after millions of strikes, of 9000 lbs of force on each hit. This haphazard way of trying to make the face of the upper electrode and lower electrode parallel to each other, is just a mess, and completely unreliable and amateurish. When I bring this up, they tell me that you… or someone from your company… set it up that way. I find that difficult to believe. It’s my belief that one way to address this is to face off the two faces by machining. There’s no telling what kind of condition the surfaces of those two faces are in by now. Given that there has been that wedge shaped gap between them for many years, I suspect that there may be some corrosion or other non-desirable surface effects, due to possible arcing and or just exposure to the air. I've been told that some type of carbon paper procedure was used to determine where pressure was highest and lowest. But it may be that an angular misalignment is cause by other issues (see #1, #2, #5, and #8). I feel it would be best if these two faces had 100% contact… or at least just a shim or two… not a big thick messy wad, which they have moved from the front to either side over the years, and undoubtedly continued to add to, and make thicker to compensate for other misalignments. So first, I’d like to ask your opinion on whether these faces should be re-machined? Because they really are balking at doing that.

4. Sometimes, during the weld, there is arcing and major sparks on the TOP of the adapter that we are welding to the tank. This leaves a scorched mark on one side of the top of the adapter, where it comes into contact with the upper electrode. I suspect this might be because the contact between upper electrode and adapter is not even and parallel. I don’t know, but it can’t just be ignored, as clearly something is not as it should be, and it is causing a certain number of scrap pieces. But it isn’t being addressed. Do you have any suggestions on what else may cause that, if it isn't what I've suggested?

5. The FORCE setting, in the control panel, has slowly been increased from 6000 lbs force, when it was first set up, all the way to 9000 lbs of force now, in order to achieve a suitable weld. Again, this can’t be ignored. Incrementally increasing the force setting over the years is only addressing a symptom, and not the root cause. I suspect the root cause is one of the other deficiencies, even if it isn’t obvious.

6. The outtake hose for the coolant is nearly doubled over because of a kink. Regardless of how much this may or may not matter… this is not how the welder was designed to run. Otherwise a smaller hose would have been used at the out take. This hose needs to be changed. Again, I’m told it doesn’t matter.

7. The ancient lower electrodes with the `15-20 radial cracks in them are still being used. This leaves a heavy pattern on the weld itself, that matches the cracks on the electrodes. This, obviously, is not a clean effective weld.

8. The base, on which the lower electrode sits, is deformed because of the constant pounding (see photo below). This, I believe, may very well be the cause of the arcing on the top of the adapter, as it causes a un-parallel condition between the faces of the upper and lower electrodes. This may what they are trying to compensate for, by that mass of shims. Also it results in uneven contact to the welded adapter, pushing harder on one side than the other.

The two yokes holding the lower electrodes in place (see photo) seem sloppy, and possibly not the right size. I don’t know if there is any deficiency caused by this, but it doesn’t seem right. Do you have any opinion on this, as I’m not sure. But I thought I’d mention it anyway.

So… that’s all I can think of at the moment.

Thank you.

****************************************

So, that's it. That's what I'm sending to my contact at the welder manufacturer. They've long been frustrated with my company and have tried to help. But they've not had an actual ally here to help make it happen.

I am determined to fix this damn machine for my company, despite themselves!

That's why I asked this question from you guys, so I can collect as much ammunition and justification as possible, before I make my big push, and start getting a bit more assertive and confronting those who are my obstacles. I just have to be well prepared.

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#25
In reply to #20

Re: Will Off-center Press Press More on One Side?

12/07/2018 10:26 AM

The letter's fine. You are most familiar with the issues.

I would take photos to try to describe each condition and label or number each photo so there is no confusion as to which issue the photo belongs.

If you haven't already, work up the cost of the failures in lost time for each station, lost time handling materials, lost time for inspection and rejection, increased inventory required due to scrap. Any cost/lost productivity caused by the rejections.

That may help sway the bean counters and the bosses once the see how this is affecting the bottom line.

Good Luck!

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#26
In reply to #25

Re: Will Off-center Press Press More on One Side?

12/07/2018 11:12 AM

Yes, all good advice. I'm ahead of you though. I already received a response from the manufacturer and it's all set up:

Good Morning Stef,

You have my confidence that this will stay between us.

I’ll get a maintenance quote prepared that addresses the issues.

It will be our official recommendation to perform the work.

I’ll emphasize this is a must have, not optional.

Thanks for the detail, it’s essential to prepare the quote.

I look forward to seeing you soon,

Stay off of the ice this weekend.

Regards,

So, they are going to do all of it. I won't have to depend on our shoddy Maintenance contractors to left a finger, or... to give me any more excuses. By the way, I just talked to Maintenance and told them I've arranged for manufacturer to do ALL the work, and that they don't need to do what they promised for this weekend... machining the two faces of those blocks that I mentioned in my letter. He told me that they weren't going to be able to do it anyways because "blah blah bla-blah-blah".

LOL... so once again... another excuse they had all ready for me. How freakin' predictable.

Anyway... yeah, the manufacturer is 100% behind me and they will communicate it in a way that we will have no choice but to make this happen. Will cost a bit, but as you said.. all the scrap wasted and all the issues we've had all these years have been very expensive, so whatever they charge will be more than worth it.

Oh and it wasn't so much the bean counters, as it was our maintenance guys being too lazy and ignorant... and convincing the top people that all this stuff isn't necessary and didn't need doing.

It's a good day! I'll get this monkey off my back and move to the next monkey. There is a whole zoo to keep me busy here.

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#22

Re: Will Off-center Press Press More on One Side?

12/07/2018 10:04 AM

The people opposing you are desperately incompetent, and their asses should be fired, preferably with a blowtorch.

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#24
In reply to #22

Re: Will Off-center Press Press More on One Side?

12/07/2018 10:18 AM

Tell me about it.

Nevertheless... I need to use tact, and just make it happen, despite them. It's challenging, but I'm sure I'll find a way.

Part of the problem is that the people who are responsible for machine maintenance, in fact plant maintenance, are a subcontractor department of 5 guys who work through a service. They are are used in all our branches all over the country. So that adds an additional level of complexity to the whole thing. I'm just going to have to find a way around their ineptitude. yet I still need to maintain good relations with everyone here. I need to work here with these people every day and will need their continued cooperation, as minimal as it is.

It's just another challenge, which is how I make my living. Although, i will say... I'm mighty glad I have this resource of CR4 people to give me a hand every now and then. Quite invaluable, really.

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#52
In reply to #24

Re: Will Off-center Press Press More on One Side?

12/10/2018 8:34 AM

usually one of the reasons to contract work is that it is easy to fire the inept. not sure why this isn't happening?

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#30

Re: Will Off-center Press Press More on One Side?

12/07/2018 12:05 PM

The result depends largely on the upper electrode guidance and support structure. If the guidance or structure is flexible or there is slop in the guides, then misalignment could be an issue. A good way to find out is to attach a long rod horizontally to the uppeer electrode and run it to the down position. Then put in reference marks behind the rod on the machine frame. Then weld a part and see if the long rod is in alignment with the reference marks. If they line up reasonably well, then no issue. If not, realign the electrodes to be in line and see if the results are better. After that, get to work on the guides and structure to get what you want.

Perhaps, though, precise alignment is not a specification criteria.

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#34

Re: Will Off-center Press Press More on One Side?

12/07/2018 5:43 PM

Out of Box- Having read the thread from top to bottom I can scarcely express my admiration for your dedication to doing the right thing.

My father had a saying for situations like this. I don't know if I can get the Latin right but "Illigitmi non carborundum", or Don't let the bastards grind you down.

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#36
In reply to #34

Re: Will Off-center Press Press More on One Side?

12/07/2018 8:40 PM

Thank you Mfmatusky. I appreciate that. But really, I bring it on myself. I seek out jobs like this. Been mostly contracting all over the world for 30 years. And what others have failed at, I love to have a shot at. So far... it seems to be working.

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#38
In reply to #36

Re: Will Off-center Press Press More on One Side?

12/07/2018 9:43 PM

Based on your thread I had pictured you as less experienced than your years. One of the most important things I have learned in my (similar) years is that I can't succeed without my engineering smarts, but I won't succeed if I don't muster my political smarts. And the political smarts can be much harder to muster.

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#40

Re: Will Off-center Press Press More on One Side?

12/08/2018 10:12 AM

" I'm asking if the misalignment is causing more force on one side than the other."
Yes.
Next!
Del
PD...I think we all knew this really,'cos there is no such thing as"rigid"

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#42
In reply to #40

Re: Will Off-center Press Press More on One Side?

12/08/2018 4:50 PM

Not so fast!

Look at the photo in #20.

The amount of force required to cause unequal pressure on the work piece/electrodes is unknown. The force applied may not be enough to deform the weld.

There is much more to be learned.

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#43
In reply to #42

Re: Will Off-center Press Press More on One Side?

12/09/2018 4:01 AM

"The amount of force required to cause unequal pressure on the work piece/electrodes is unknown"
Exactly, that why it makes sense to get everything lined up correctly before trying to fault find anything else.
c'mon guys this is the fundamental of any fault finding!
Get all the basics right first...if that doesn't fix it, then and only then start looking for the weird and subtle.

It's a bit like saying saying there's this vibration in a drive train... you know the prop shaft is bent, but you're not going to fix that, you're going to take off the brake rotors and have them skimmed and dynamically balance!
Occam's razor!
Del

In practical terms I'd get it all lined up and actually get the surfaces to be clean and parallel, even if it was just by putting wet & dry paper between 'em with v light pressure applied and drawing it back and forth to check for high spots, or use some engineers blue.
BTW I'm quite happy to be wrong, but getting the basics right is rarely a waste of time.

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#44
In reply to #43

Re: Will Off-center Press Press More on One Side?

12/09/2018 9:59 AM

We are in agreement, See #8.

Still, your statement about rigidity is likely incorrect in this case and just conjecture.

We don't know how much pressure is actually being applied anyway. Is the force actually being measured or is this just a dial setting of the current being applied of the, admittedly, failing linear actuator? I mistakenly thought this was a hydraulic system where the pressure could be read on a gauge, but it's not.

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#45
In reply to #44

Re: Will Off-center Press Press More on One Side?

12/09/2018 12:56 PM

You make a good point. Yes, it is the setting (the 9000 lbs.). Perhaps that is not the actual pressure. As I said, over several years, the setting has been continuously raised from 6000 to 9000 lbs., as has the voltage. The voltage setting is nearly at max, and well above the suggested setting for the thickness of material. It's maxed out (or nearly so). My thinking is that there are current leaks in several places, where there is arcing in the various gaps between metal surfaces (radial cracks in lower electrode, wedge shaped gap because of the pile of shims on one edge above upper electrode, etc.). I'm working at eliminating the causes of these leaks.

Oh, hold on... I just noticed that there is a misunderstanding about the linear actuators. This is a hydraulic system, as far as the upper electrode pressing down on the lower (the 9000 lbs). The actuators are only used to move the lower electrodes horizontally, between the three different size lower electrodes. This is where the horizontal positioning is causing a misalignment in the x direction, because when the three lower electrodes move, they don't line up directly below the upper electrode.

There is one upper electrode that moves up and down.

There are three lower electrodes, which move horizontally, because there are three sizes. It's just that they don't stop in the exactly right position. That causes one of the misalignments that I'm talking about. In the x direction. Left to right.

The y direction misalignment (forward & back) is caused by the upper electrode assembly being too far back (in the T-slots).

My maintenance guys don't want to correct these because they say it doesn't matter. Hence, the reason I posted this question, because I believe it does in fact matter. And correcting these misalignments should be the first step in rooting out the cause of all the problems this welder is having, regarding weld quality and scrap rate.

Sorry for not being clear on this.

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#46
In reply to #45

Re: Will Off-center Press Press More on One Side?

12/09/2018 2:07 PM

Question. Is the x error consistent in the three positions? If I was designing this type of machine I would stop the x actuators on limits rather than bottoming them against their end stops. Much easier to set up. I would also use non contact inductive proximity switches triggered by a moving flag or plate as these are much less prone to wear. Inductive switches will trigger at a different position when the plate is nearer or further from the face of the switch. It may be that your y error is causing the plate to be nearer the switches and this is creating your x error. Without seeing the machine this is a stab in the dark but the telltale symptom would be a consistent error because the moving target plate is nearer at all three positions. If the plate is nearer the inductive sensor the actuators will stop short, if further away the actuators will overrun.

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#47
In reply to #46

Re: Will Off-center Press Press More on One Side?

12/09/2018 2:16 PM

Yeah, the first thing I ordered was an adjustment of the limits. But was told that both bottom out. No limit switches or sensors. The 3 electrode assemblies move as one. Yes, poor design.

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#41

Re: Will Off-center Press Press More on One Side?

12/08/2018 4:45 PM

As long as the machine doesn't deform, the pressure will be uniform.

If the machine deforms when used, I submit it is probably mis-designed.

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#48
In reply to #41

Re: Will Off-center Press Press More on One Side?

12/10/2018 4:39 AM

If the machine doesn't deform, I submit it isn't being used.

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#49

Re: Will Off-center Press Press More on One Side?

12/10/2018 8:02 AM

will not matter. doesn't matter if the head that applies the force is off center. the force is down and as long as nothing moves, that force will still be down.

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