Underpinner Problem

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rsm5574
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Underpinner Problem

Post by rsm5574 »

Hope someone can help me with this problem. I have a old Euro underpinner (I think) that my father used for years without any issue. He recently passed away and I have kind of taken up the reins of the business.
The problem is that when the pin is fired up into the moulding the frame lifts slightly causing a bad join. I took the underpinner apart complelely and cleaned all the gunk etc. out and this seemed to solve the problem.
Next day the problem was back so don't really know what to do. Over the next few days the problem came and went. Pressure seems alright and I can't detect any air leaks.

Anyone any ideas.
Attached photo is underpinner model if that helps. Will try and upload a video later

Thanks
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David McCormack
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Re: Underpinner Problem

Post by David McCormack »

Hi Richard,

I only use a foot underpinner but I think this is a common problem... that is the top pressure pad maybe too high? Adjust the height so that it is closer to the top of the moulding. I can't say how close but just experiment and see if it makes a difference. I'm sure uses of air powered underpinners will chip in with ideas soon.
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Re: Underpinner Problem

Post by poliopete »

This occasionally happens with my cs 89. if the moulding profile is particularly curvaceous :wink: It never happens with flat or reversed mouldings.

I do as David suggested and lower the pressure pad as well as having a few triangles of mdf and thinnish ply to place over the mitre on order to spread the weight. But my golden rule is always to make a chevron with any new moulding in order to ascertain how it cuts and joins. A little time spent doing this often saves a lot of time and materials later :wink:

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Re: Underpinner Problem

Post by rsm5574 »

Thanks for the replies. This happens with all mouldings and comes and goes on a daily basis. Here is a video showing what I mean. Compressor just happens to kick in on the clip, sorry about that.

[youtube]https://www.youtube.com/watch?v=HJf_D_1xRIk[/youtube]
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Re: Underpinner Problem

Post by David McCormack »

"You know, there's a right and wrong way to do everything!"
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Re: Underpinner Problem

Post by prospero »

The Euro top pad is not particularly sophisticated. :roll: I have a Euro manual machine and never use the pad in
direct contact. It's too hard and has 'sharp' edges for a start. The (useless) felt covering fell off many moons ago. I made
a wooden triangle which is covered with 1/8" cork sheet (floor tile). This spreads the pressure and doesn't crush any
high points. OK, you have to insert it manually, but I don't find that a prob. Cover the triangle with handywrap to stop the
cork getting gunged up with glue. Replace as and when.

Another thing to watch for is having the pad bearing on a point that is too far offset from the nail insertion point. Such as
on a scoop moulding - you pin toward the back - OK - and then pin the front. The pressure is still on the back though and the
moulding will lift and separate. With a bit of ingenuity you can make various packing pieces to make sure the pressure is
applied in the right place.
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Re: Underpinner Problem

Post by Steve N »

Don't know anything about Euro underpinners, but from the video, the pin is going in before the top pad has come down, so I would lower the top pad right down and see it it's still happening,
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Re: Underpinner Problem

Post by rsm5574 »

I completely agree that the pad is rubbish. Any chance of a photo of the widget your talking about prospero?

If I move the pad down to pretty much touch the moulding it still lifts slightly. I have discovered that when it is working correctly and I double pin, the next pin starts causing the lifting to happen again (like its not powerful enough after doing two). Could it be the piston not exerting enough force?

I have been trouble shooting this for weeks and don't seem to be getting anywhere fast. Maybe need to get a new one. Any suggestions for around £500?
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Re: Underpinner Problem

Post by vintage frames »

From what I can see on your video, the top pressure pad is out of sync. with the nail driver - the pressure pad should be holding down the moulding just before the nail is inserted underneath. I'm afraid I have no easy solution to cure that but it maybe that the air pressure is too low. Try increasing it to see if that helps. Otherwise seek out a framing engineer.
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Re: Underpinner Problem

Post by prospero »

I will grab a pic of the widgets later, but if it is a question of the action being out of sync then you need to get that sorted first.

Mine is foot-powered and the top clamp mechanism is different. Less to go wrong and easier to fix. :lol:
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Re: Underpinner Problem

Post by misterdiy »

Well spotted Steve. I would say that is the complete answer to the problem. It wouldn't matter bringing the top pad right down because the pin has already gone in to the moulding before clamp pressure. It looks like you are using polymer mouldings which are very soft so the problem is synchronisation.
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Re: Underpinner Problem

Post by rsm5574 »

Any idea what i should tinker with regarding synchronisation? Its pretty basic machine. Air goes into pedal and then spits in two into piston (push and pull i assume). There are no setting to alter so don't really know what to do.
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Re: Underpinner Problem

Post by vintage frames »

Have you tried increasing the air pressure? Could be that too low air pressure can cause the unbalanced operation.
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Re: Underpinner Problem

Post by Mark Thornton »

On basic pneumatic underpinners the wedge is only fired once there is sifficent clamping pressure being applied, as yours is firing before the clamp makes contact with the moulding there must be some dirt / rust etc binding the vertical shaft that connects the cylinder to the top clamp beam hence causing the wedge to fire.
I would look at lubricating / cleaning that shaft + ensure the cylinder has not moved slightly sideways out of alignment, (slacken the cylinder nut alittle to test)

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Re: Underpinner Problem

Post by Not your average framer »

I was the owner of a euro pneumatic underpinner, so I may have a few ideas to consider. mine was a desk top model, but some of the principles will be the same.

First, you said that you gunked it to clean it and then it worked fine, but the following day the problem was back. To me that suggests that the bearings dried out over night, and did not have any lubrication in the sliding mechanism. If this is so My I suggest re-assembling this part of the machine with plenty of lubrication inside the bushes before assembly and wipe of the residue after assembly.

Second, if there is wear in the bushes, the operating shaft for the top pressure pad may move out of line a little and add a little extra drag to the movement of the operating shaft. This is not ideal, but removing and re-lubricating the the bushes and the shaft with molykote may even things up a little.

Thirdly, is the wedge catching in the firing block as it comes up below the mitre, if so this may momentarily stop the upward movement of the wedge and hammer, resulting in the top clamp coming down until it touches the top of the moulding, leading to an increase in pressure to the wedge in the firing block and this wedge suddenly being released and the pressure on the top pressure pad being reduced momentarily permitting the top pad to lift momentarily and causing the problem you describe.

Forth, the hammer return springs on the pneumatic euro underpinners do have a history of breaking and at least some of these machines had to be partly disassembled to inspect the hammer return spring to make sure this is intact. Broken springs can cause all sorts of difficult to diagnose problems, which can be quite erratic also, so sometimes it seems o.k. and sometimes it doesn't. I hope this helps.

Fifth, what wedges are you using, not all machines perform at their best with all types of wedges. Some wedges are a bit tight when going through some machines, don't get me wrong when I say this, the differences are almost nothing, but I've known it make a difference myself. Just another possibility to consider, if all else fails.
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Re: Underpinner Problem

Post by rsm5574 »

Thanks for all the advice.

The only parts I cleaned where inside where the firing mechanism. I didn't touch the pneumatic piston or the connecting shafts.
Looking at 'Not your average framers' suggestions I think number three looks the most likely. A while ago the hammer got jammed and I had to take it apart to release it (spring nearly hit me in the face :shock: )

Should i lubricate the channel the hammer travels along?

Sorry for all the questions
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Re: Underpinner Problem

Post by rsm5574 »

So after two weeks of taking apart and cleaning, reassembling, rinse and repeat I have sorted the problem. Unbelievably all it took was a couple of sprays of WD40 on the shaft that is connected to the pressure pad to loosen the dried grease and it now works like a dream.

Thanks again for everyone's suggestions (kudos to the two Marks for the eventual solution :clap: ). Saved me from spending hundreds of pounds on a replacement.

Richard
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