Proofing Press Bed Twist


Has anyone ever come across this before? Our new(ish) FAG proofing press has a twisted bed.

We had an aluminium base plate made up for the photopolymer plates and could never get it to sit flat on the bed.

I tested the base plate and it was flat, so then looked at the press.

Here’s the set up I used to test it:

The two vertical strips of tape in the overview image mark the measuring locations and the engineers level is placed in the middle of the bed at these locations. Obviously they should read the same, but the images below show the actual readings.

I jacked up the feet of the low corners (front left and back right from this image) in the hope that the bed would naturally untwist itself, but after a week there has been no movement.

The deviation is about It’s about 7 or 8 thou / 0.2mm over length of the usable part of the bed.

Has anyone else ever come accross this and if so any advice on how to cure? It bent out of shape, so presumably could bend back in?



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I’d test with a precise straight edge. Bed AND base.
That the base does not sit flat is very worrisome, but level and flat are two different things. On a production press, I could see low areas worn into the bed, but not on a proofing press unless seriously abused. But I have never seen a warped bed either.
If the base sat flat I’d be checking bed-to-bearer distances.

Hi parallel_imp,

Thanks for your message. The bed to bearer distances seem fine - I checked them with a dial test indicator on a stand and there was no deviation.

Sadly it does genuinely seem like the press has twisted, maybe from not being set flat over a long period?


That’s the thing. I could see the frame twisting over time on uneven footing, but the bed should be absolutely the strongest and most rigid part of the press, even more than the cylinder. It is hard to imagine what conditions would cause it to warp.

I know on a lathe you adjust the four feet until the bed runs true, so I do know they can move more than we might image (or certainly a lathe can) - but of course on a lathe they are bolted to the floor so you can do that.

A lathe bed has two parallel ways that can be skewed easily if not true level, and then three sections to be aligned to them. The slab of a press bed should be more rigid, and less prone to error than a lathe.

It may not have been right from the factory, though that would be a bad case of quality control. If it’s cast iron there can be residual stresses in it that show up. I’d consult a good machinist and see what they think about how to correct it.

I’ll bet the way it happened was that it was unevenly supported during transport and some heavy bouncing of the transport truck did it.

If you had access to a strong platform (like a reinforced cement floor), and you could put anchor bolts in the floor to bolt the press down, and then you experimented with putting sheet metal plates under different corners, to raise some corners and keep others lower, you might be able to straighten it. Or at least, if you could leave the press bolted to a strong floor with the plates under certain corners, you might be able to keep it straight even though it might spring back if it was unbolted. (We don’t always do it, but in industry, most machines are bolted to the floor anyway).

Thanks so much for your messages.

To discount the level I used an almost new Starrett 24” straight edge to check it. I had to get my head around where to check, so I did the drawing attached - although initially I took a piece of paper and twisted it. The red line represents the cylinder end of the press bed and the black line the opposite end (of course this is exaggerated!). The blue line represents the straight edge going from high corner to high corner, leaving a gap under the middle (which is what I found). Doing it across the other two corners would mean the middle is high, which is again what I found.

I need some feeler gauges to check what the deviation is, but as I say if the engineered photopolymer plate base is right (and I suspect it broadly is) the deviation seems to be 7 or 8 thou or 0.2 mm. And I have seen that in the printing I have done on it.

Sadly it looks like the problem is genuine. I suppose I wonder in my head if other presses are the same and just never checked? I also suspect that with type there would be a certainly amount of rolling with the bed, it’s only that the photopolymer plate base is rigid and so shows up the issue.

The only solution seems to be to bolt it to the floor, but the feet don’t have holes and the floor isn’t ours. Jacking it up enough to get under and drill holes would be a fair task.

All and any thoughts very welcome.

Kind regards,


image: Press testing.jpg

Press testing.jpg

Hi all,

Just thought I would update this, in part in case anyone in the future has the same issue.

It was suggested to me that the bed may have been poorly ground down at some point and that this had created the distortion.

I have checked the bearer in the past, but roughly, so I did it again using a metric 0.01mm Dial Test Indicator. As per the diagram below I was checking the bed against the bearer. Remarkably this showed almost no (less than 0.01mm) deviation over both the bearers. I checked the bed the other side of the bearer & gear rack and that was similarly consistent. So I think I can rule that out.

What was curious is that the bed height measured 23.60mm, which seems to be 0.04mm higher than you would expect for a German press. A DTI perhaps isn’t the best way to measure this, but it’s all I had to hand at the time. I did do it a few times and more or less got the same result.

The other positive news is that I didn’t do a very good job of checking for mounting holes on the base of the press. It does actually have one right in the corner of each of the legs. So with some floor bolts I should be able to slowly and gently ease the bed back into flat.

That’s my plan and I will make a note here of how I get on.

Thanks for all your help, really appreciated.


image: Press testing 2-02.jpg

Press testing 2-02.jpg

I had three printing visitors for an afternoons printing chat yesterday. Combined printing experience trade and amateur
maybe towards a couple of hundred years (we are old folks now) Two point arise: nobody had ever heard of a twisted bed before, save some wavy ones on Albions, and also
that FAG was seen as the best make of proofing press around, by some way..

Dear harrildplaten,

Thank you so much for your message. I’m not quite sure how to respond.

I’m sure you are right on both points, but sadly I also have a good straight edge that rocks on the diagonals. I guess I’m just unlucky?

I have had the floor bolts arrive today, so I am hoping to have time to work on it again later this week.

Kind regards,