Etch Press Build

[Wal]

Hi all,

Just wondering if anyone has any experience with building an etch press - something along the lines of this:


https://www.youtube.com/watch?v=N-UKQVtnF2o

I've started to design one and have begun collecting odds and sods that I'll be using along the way (take-up bearings, flange bearings etc.)

One thing that's got me a bit stumped, though, is how to get my hands on a pair of live shaft stainless rollers. I'm attaching a .pdf of what it is I'm after. Dimensions are approximate at the moment, but won't be far off that. The long 60mm shaft will need a flat on it for the hand-wheel grub-screw to bite on.

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Ok, there's the obvious way, pay someone to turn 'em - I imagine this will be pretty pricey, given the chunkiness of what I'm after, but if you know any different then let me know..!

Or I could fabricate 'em from a steel pipe with a steel shaft passing through it held central by a couple of alu caps made on the mini-mill. (All probably glued up with the strongest epoxy I can find...)

Any other ideas..?

Wal.

[Doddy]

Even with a lathe I'd be temped to centre drill stock 50mm stainless bar pre-cut to length, bore out (or drill) then ream to 15mm dia and maybe 40mm depth, then tap some 15mm dowel into the reamed holes with some loctite.

I wouldn't bother trying to turn down the 50mm bar. At least with my ML7 (small spindle bore) I'd have to turn between centres.

I guess there's a reason it has to be stainless?

[Wal]

Having just read a bit more on the topic, the drive roller would be fine in 7075T6 with the idler in mild steel - had stainless in mind as it's what (little) I remember from the college art room... The crucial bit is that the rollers run absolutely parallel to each other (this can be tweaked via the take-up bearings) and that the running gear can withstand high pressures.

I may well have to consider increasing the shaft diameter to a more substantial 20mm and have a closer look at using self-aligning bearings to accommodate said tweakage... This could get a bit pricey... :whistle:

Wal.

[cropwell]

Hi Wal,

This build uses tube for the rollers

https://www.youtube.com/watch?v=UhlSZU63S7g

and these for the pressure adjustment

http://www.arceurotrade.co.uk/Catalogue/Bearings/Take-up-Units

Interesting project, but not for me (too many projects stalled on the bench :butterfly:)

Cheers, Rob

[Wal]

Cheers Rob - that clip makes it look too easy..!

Wal.

[cropwell]

Cheers Rob - that clip makes it look too easy..!

Wal.

If you made a cock-up, would you edit it out of the video - Just asking :hopelessness:

[magicniner]

If you could find an old number plate machine you'd have no work to do, they're effectively a heavy duty mangle with geared steel rollers.

[Wal]

Or indeed a (somewhat modified) beeswax foundation roller:

https://www.amazon.com/Beeswax-Foundation-Machine-Printing-Optional/dp/B01LZE05HU

(Chances are my grandad had one of these - long gone now..)

Unfortunately none of this hardware's cheap - hence the DIY approach. Still won't be cheap, but it'll keep me occupied..!


If you made a cock-up, would you edit it out of the video - Just asking

True that, Rob. It's why my vids tend to be short and finish abruptly...

Wal.

[phill05]

Hi all,


I've started to design one and have begun collecting odds and sods that I'll be using along the way (take-up bearings, flange bearings etc.)

One thing that's got me a bit stumped, though, is how to get my hands on a pair of live shaft stainless rollers.

Or I could fabricate 'em from a steel pipe with a steel shaft passing through it held central by a couple of alu caps made on the mini-mill. (All probably glued up with the strongest epoxy I can find...)

Any other ideas..?

Wal.

Hi Wal,

Don't know if this could be what you need but I have a 610mm x 50mm dia with a 30mm bore through it Stainless steel rod, I also have a piece of 465mm x 32mm dia solid stainless bar which would turn down for the ends.

All you would need then is someone with a large enough lathe to turn down the ends to fit into the tube then skim off true the tube and away you go, easy!

Phill

[Wal]

Hiya Phil,

Thanks very much for the heads-up on those materials.

I think I'm leaning more towards the 'one-piece' solution as it'll probably end up easier communicating what it is I need doing to a shop (and will result in fewer steps for them to take to get it made). From a strength point of view: these rollers need to take around 40Kpsi - I'm guessing that by sliding the shaft through the middle like that you'd be talking about a fairly substantial non-slip interference fit along the length of the roller - not sure what kind of stresses that would introduce and how they'd interact with additional stresses that the printing process will put 'em through...

Wal.

[Wal]

Still doing my research on this (materials, why some have a spring under the take up bearing etc.) but this is how the design is shaping up so far...


https://youtu.be/0dPmMILkLe0

Wal.

[Wal]

Okay, I've been thinking a bit more with regards to the springs under the take-up bearings - an example:

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I take it that the primary job of these springs is to pre-load the top roller to remove any slack and prevent it from flopping about when not under a printing load, with a secondary purpose of perhaps aiding the raising of the roller? Or am I missing something? Will I be making a grave error by omitting these springs from my design? I've seen other presses without 'em - but I want to be sure on their purpose and the pros and cons of having them incorporated.

I posed this exact question to a press manufacturer over in the States - he got back to me (and I'm grateful for that) but his answer to the spring question was a rather vague 'yes'. Hmm... yes as in the springs do that job, or yes as in you're making a big mistake by omitting them from your design..? And with regards to getting some general advice on material specs - well - here's what I managed to extract from him:


You have to pick the right material with the proper thickness in the right places.

Hehe. Blood from a stone...

Anyway - back to the question - am I missing something with this spring..? Any mechanical engineers here have any thoughts on the matter..?

Wal.

[m_c]

Going by that photo, the springs only serve to raise the roller up when tension is removed.

If you design so just the screws lift the roller, you're likely to get a bit free movement while going from under tension to lifting the rollers. It just means you need to turn the tension screws a bit further to lift the roller.
By adding suitable springs, it could simplify the screw design, as the spring would hold the end of the screw engaged with the bearing block/carrier.
You could implement it so both the screw and spring do the lifting.

Any method will work, it's just you need something to lift the roller, otherwise it could be a bit of a faff getting everything loaded between the rollers.

[Wal]

Cheers m_c.

Yeah, it would be nice to have a bit of pre-load on the roller to eliminate any rattle when not under load. I may have to go for a spring pushing down, though (also seen in the wild) - the take up bearing I'm using has a curved underside which complicates getting a spring under there - it'll mean a bit more elbow grease when lifting the roller, but if it's too problematic I can always remove it. Thanks again.

Wal.

Sent from my HTC One M9 using Tapatalk

[Wal]

I'm almost definitely over-thinking this - but there's no harm in knowing the correct way of doing something...

I spent yesterday making the knobs for the pressure adjustment spindles. They're out of what I believe to be 2014 (the larger plate from which it was cut sat in a shed for 30-40-years, so it's nice to see something getting made from it..!)

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https://youtu.be/0plU0V1b8Kw

I was assuming I'd be using a standard 1.75 coarse pitch tap, but when I double checked my M12 tap, I found it to have a pitch of 1.5. This got me thinking about which thread-form would actually be most suitable for the application...

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The diagram should make things reasonably clear - but basically the knobs attach to a threaded rod which connects to the take-up bearing uniand allows for adjustment of the roller height and the resulting pressure that this puts on the plate/paper which is being printed.

As you can imagine - there will be a fair bit of shear force acting on the threads which are engaged in the aluminium pressure plate and this is where I'd like to know a bit more about which thread-form would do a better job a withstanding this force. I've done a bit of (non-technical) reading on the matter, and Wikipedia says:


Coarse threads are more resistant to stripping and cross threading because they have greater flank engagement. Coarse threads install much faster as they require fewer turns per unit length. Finer threads are stronger as they have a larger stress area for the same diameter thread. Fine threads are less likely to vibrate loose as they have a smaller helix angle and allow finer adjustment. Finer threads develop greater preload with less tightening torque.

Which leaves me a bit confused - Yep - I want something that's more resistant to stripping so 1.75, then? Oh hold on, finer threads are stronger (?!), allow for finer adjustment and develop greater preload with less effort - excellent - so a finer pitch, then..? But wait - I've also read that a finer pitch is more susceptible to stripping and galling in 'softer' materials, like aluminium. Bugger, so back to the coarse pitch of 1.75, then?

Hehe. What would you guys do? And this is before the suitability of materials in even considered - high tensile vs. stainless vs. aluminium... 😂

Wal.

[Doddy]

From an non mechanically-minded perspective, I'd say if the difference between a 1.5mm and a 1.75mm thread is the difference between the thread working or failing, then you're too close to the edge. I'd go with the tooling that you already have, and if you strip the thread use that newly purchased lathe that you just know that you need to turn a tapped steel insert into the newly reamed hole in the ali pressure plate. Or re-make the whole plate from steel.

Preload?, if ease of turning is an issue make a bigger hand wheel - but I doubt that it is. Finer control?, not really much of a difference to worry about.

[Wal]

>I'd go with the tooling that you already have

Heh - well, I have threaded rod in 1.75 and, yep - you've guessed it - taps in 1.5...!

Wal.

[Doddy]

Ah, one of those classic Homer moments. Doh!

[m_c]

Generally in softer materials, bigger pitch is better.

For this kind of application though, some form of square/acme thread would probably be a more suitable application, but that can get expensive.
I think I'd personally go for finer, rather than courser, as the forces aren't going to be that big in the grand scheme of things. If it does strip, either remake the top bars in steel, or put a helicoil in the aluminium.

[Wal]

Good call on the ACME - the thought had crossed my mind, but I just assumed too expensive and a bit more of a hassle to come by. My assumption regarding the expense was wrong:

https://www.ebay.co.uk/itm/1-2-10-ACME-Threaded-Rod-Lead-Ball-Screw-w-Brass-Nut-12-24-36-48-T10-2-/382095182523

- that's about half the price of 1m of 1.5 pitch high tensile threaded rod - and I only need around 12", and this tap seems like good value:

https://www.ebay.co.uk/i/352138720525?chn=ps&adgroupid=50725142863&rlsatarget=pla-413913428796&abcId=1133946&adtype=pla&merchantid=7259694&poi=&googleloc=9046436&device=c&campaignid=1057750313&crdt=0

If you dig a bit deeper, though, you'll see the rod's readily available in metric, but the taps aren't... Or if they are then they're a couple of hundred quid..!

Right, I'm faffing now. I've ordered a coarse 12mm tap (not in ignorance of your suggestion m_c - I looked at what I already had and what was going to give me the least amount of ball-ache going forward..) - I'll try it. If it's shite then I'll remake it so it's not shite. 👍

Wal.

[JohnHaine]

Wal, I've worked on 2 etching presses for my wife, and I think you are overthinking this. One is a small tabletop one, the other a beast weighing the best part of half a ton that sits on a stand on the floor.

Neither has anything very fancy in the way of bearings, just a u-shaped recess in a lump of steel or iron that a spigot on the end of the roller sits in. On the tabletop press I made a nice pair of CI blocks bored out to fit the spigots that slide on the edges of the slots in the sides, mainly so I could lift the roller using some springs to make it easier to manage, but the previous ones were just brass blocks with the u-shaped cutouts.

There needs to be a steel platen between the rollers that gets wound across supporting the plate and paper. On the smaller press this is 1/8 inch bit of mild steel plate, on the big one its 3/4 inch by 18 inches by 3 ft or so, a real brute.

You absolutely don't need any fancy thread on the pressure screws, an ordinary coarse metric thread would be fine. It doesn't get much use, the pressure isn't very great. Remember that there will be a felt blanket between the rollers and the paper that regulates the pressure and takes up any unevenness.

I'll try to take some photos for you and post them here, any questions just ask.

[JohnHaine]

By the way neither press had the springs originally. I added them to the smaller ones to make it easier for my wife to get stuff between the rollers by reducing the top weight. The big one, which has VERY heavy rollers, doesn't have them but it's still manageable. When you put the plate + paper + blanket on the platen you then have to get it between the rollers and as you can imagine it can get a bit hard to turn the handle.

[Wal]

Hi John,

Excellent stuff. Would be great to see a couple of pics of what you've built.

The bearings and blocks I've gone for are pretty cheap and easy to come by and what with readily available CAD files it makes the designing that bit more straightforward: just need a correctly sized slot and a bunch of holes drilled in the right places on each of the walls and it should be good..!

Yep - after the initial faff, I'm going with a standard coarse M12 for the pressure adjustment spindles - I finished up the knobs for these earlier (pics below) - they're also threaded and I'll likely use a strong epoxy to hold 'em captive - or a grub-screw - or a nut... will decide when I get there..!

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The biggest issue I've come across are the rollers themselves. I've looked at conveyor belt spares (not much in the way of live axle, no Ø80mm options and they all seem a bit flimsy), replacement parts for commercial presses (well expensive), fabricating them myself out of tube stock / steel bar etc. (too ramshackle). I'm pretty much committed to having 'em turned, which will cost, but I'm keen to get it right..! Right now I'm thinking of 7075-T6 for the bottom roller (suggested as it minimises the effects of cold-working/distorting the steel plate over time - yes, yes - a RIDICULOUS consideration for the use this will get, but have a read about it here (http://www.bureauprintresearchdesign.com/2006/11/so-you-wanna-know-about-etching-press.html)) - and a mild steel top roller - but what grade of mild steel..?

Yep - I'm aware of the plate - it's in my 3D model, just rendered with a bit of transparency. I'll use a steel plate (again, any suggestions on a suitable grade?) - 8mm thick, ideally stress-relieved and ground parallel. Yes, yes - RIDICULOUS...

As you can see, I'm probably over-doing this - but you know, why not..?!

Wal.

[JohnHaine]

Our small press uses BMS for both rollers - much cheaper. Some increase in weight I guess. I'd have concerns about the lower roller bending if it's ali. The main constraint on BMS type is probably machineability - a FC type would turn better.

Regarding bearings - beware using roller bearings unless you can rely on the rollers remaining aligned. The crude open cradle type are very tolerant. You can get self-aligning ball bearings.

Plate - really it doesn't matter! Since the part that does all the work is under compression from top and bottom rollers, which will also tend to straighten out any lateral bend, you could use aluminium sheet or BMS plate. If you use the latter, probably any of the laser cutting suppliers that for example supply laser cut loco frames would cut you a piece which would have clean edges and not be buckled. 1/8" would be plenty think enough. The main thing is to make sure it's smooth with no nicks or dings.
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[JohnHaine]

First and second pics show bearing blocks on smaller press with lift springs. Third shows to and bottom roller - actually on this press the bottom roller is slightly ribbed with circumferential grooves. It's the bottom roller that is driven so it presumably increases the friction. Also the bottom roller is smaller, about 1.5" dia to give better mechanical advantage - another reason to use BMS, you don't want it to bend under the pressure. Top roller is about 3 " dia. I've mounted it on my S7 once to get the rust off and repolish it. 3rd pic shows the platen, the 4th is the side plate of the big Haddon press which dates from late 19th / early 20th century, showing the very crude bearings. It has rollers that are 5 - 6" dia, they are heavy! Both presses have ordinary thread forms, on the smaller press I think it's 1/2" BSW. The handles have roll pins to lock them. You could try Loctite 638, I wouldn't trust Araldite.

I have seen press making threads on the net where they describe making the rollers from a central shaft, say 1" BMS, and an outer drum which could be steel or ali tube; with the spave between filled with for example epoxy / granite chips. If you made accurate end caps to hold the core I think that would be quite successful, though you would need probably to skim the outer surface for exact concentricity.

When you think about this, remember that one of the greatest ever etchers was Rembrandt and I'm sure they didn't have the sorts of machine tools, materials and processes we have in his age!

[JohnHaine]

By the way when you are not using the press you take the pressure off the rollers...if the springs allow.

[Wal]

Hi John,

Thank you kindly for taking the time to photograph and post detailed descriptions of your presses..! Very helpful and much appreciated.

Ok, so bright mild steel looks like it could be a decent way to go in terms of the rollers - certainly expense wise. I'm really surprised to see that EN3B has an elastic modulus over two and a half times greater than 7075-T6. I'd still be surprised if the press managed to bend a 7075 roller - although I probably won't take the chance now that I've seen the numbers..!

I think I'll stick to a thicker platen - the reason being that the bearing blocks are sizeable things - part of the reason I've had to go so big with the rollers (ie. to get them to meet..!) - if I used a thinner plate I'd be operating the press with the top roller near to bottoming out, as it were - a thicker platen will give me a bit of grace in that respect. Sure, I could do that with a bit of wood, plate or what-not - but I like chunky stuff with mass...

...Talking of which - my bearings arrived today. Yep - they're self aligning (old-school, not the dual race sort) - the outer ring has a spherical profile which allows it to rotate into position within the housing:

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Right, call me sad - I'm off to read up on Loctite 638..!

Thanks again for your advice and help..!

Wal.

EDIT: Holy Moly - Loctite 276 has a breakaway torque of 60Nm (M10 thread)..! The 270's 33Nm should do me, though...

[Wal]

Hey John (if you're still reading..!)

With regards to the platen - would you size it so that it's full width passed through the rollers, or so that it was slightly wider that the rollers as in the image below..?

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Would there be any advantage of milling a couple of shallow grooves on the underside of the platen to enable it to be guided by the support bearings, or does it tend to ride perpendicular to the rollers with the plate/art/blanket in position..?

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Wal.

[JohnHaine]

Hil Wal, on the small press the plate slides snugly between the side plates which guide it. On the big one there are stepped rollers rather like the ones you show in your second shot but the platen rests on the shoulder of the step. Trying to machine a groove in a large steel plate is probably best avoided. I don't see any reason why you wouldn't go for the first approach TBH, quick and easy. Most of the plate support comes from the bottom roller, it rests on one of the side plate spacers, which one depends on where it is.

[Wal]

Hello all,

Bit of an update on this (I'll likely post something a bit more comprehensive in the metalwork showcase once properly finished...)


https://youtu.be/CZI5FTijU_w

Had the rollers made in EN8 at a local machine shop. Sterling job. Not cheap at £450, but top quality, perfect slide fits into the bearings, great finish etc.

Also had the platen flame-cut and Lumsden ground at a local fabricators. Mild steel, £40 all in. Not sure what to make of it. It's definitely bowed (see pic below) but I haven't been able to get a silver Rizla through the gap (they're around .02mm) - gaps look bigger than they are, I backlit the press with some strong light. I imagine this is something to do with the stock not having been stress relieved prior to grinding... The underside of the plate is working the shoulders of the drive roller a bit, so I might just fit a sheet of 1mm thick vulcanised fibreboard to the underside of the platen. As a material, it's very hard to compress, but should squeeze into that couple of hundredths, I reckon...

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[JohnHaine]

Good progress there. The bowing is almost certainly due to the stress relief when the first side was ground. To be frank, I don't know why you bothered to get it ground, since in use you have to put packing under the plate and a felt "blanket" on top, which will take up any small unevenness in the platen. I think the springs are in the wrong place - really you want them to take the weight of the top roller to make it easier to get the plate/blanket sandwich under the roller, then use the screws to apply compression. You have allowed enough space for the plate/blanket?

[Wal]

Hi John,


I think the springs are in the wrong place - really you want them to take the weight of the top roller to make it easier to get the plate/blanket sandwich under the roller, then use the screws to apply compression.

Hmm - that's an odd thing to throw in at this stage - it was fairly obvious from my earlier posts that I was going for a 'sprung above' approach. There are a lot of vagaries on putting together one of these presses - so as well as taking advice from good folk such as yourself, I've had to (for better or for worse) go my own way a bit here...

Anyway - allow me to explain my approach... Instead of a collar, I made a couple of threaded flanges and used a thrust bearing in the take up unit (flange stud-locked and captive to the threaded rod) - this means that there is very little friction turning the pressure adjustment knobs to raise or lower the roller, it's literally as easy as turning a tap.

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As I understand it, the springs have two purposes:


sprung under they can aid with lifting the roller
sprung over or under they apply a bit of pre-load to the roller to stop it flapping about when not under pressure


So, the thrust bearing negates the need for the spring to help lift the roller, but that downwards pre-load is still very useful. If you look at the side-on view of the take-up bearing you'll notice a gap between the threaded rod and where it would normally contact the take-up unit.

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This effectively means that the press has a bit of suspension - the roller can still be positioned to kiss the plate or print at lower/softer spring pressure when printing from lino or wood - of course, these gaps can also be shimmed for a hard stop when printing etched plates.


I don't know why you bothered to get it ground

Ah yes, my mistake - a chunk covered in mill-scale that's been sat in the garden for a few years would have done the job! :highly_amused: Joking aside - I totally get your point, but for the price there was no harm in at least attempting to get it as parallel as possible, job worth doing and all that...

Regarding blankets, yep - there's a fair amount of gap available - not loads, but should be enough. If I run into any problems I have the option to either a. get myself one of those thin rusty plates you've been advocating :wink:, or b. deepen the pockets that hold the springs on the underside of the pressure plates.

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This is probably all moot anyway - I'm shite at art...

[JohnHaine]

Aha! Sorry I didn't appreciate that you had designed the screws to lift as well - that's a refinement that I don't think many presses have!

Once the press is finished you'll be able to get lots of practice. Ii's probably well worth while finding a printmaking course to learn the basics of grounds, the actual etching process, printing and so on. The studio will have all the materials, acids and so on. It is possible to use aluminium for plates, and etch them with a solution of sodium carbonate (washing soda) - a bit kinder than copper/nitric acid or ferric chloride.

[Wal]

It is possible to use aluminium for plates, and etch them with a solution of sodium carbonate (washing soda)

Cool tip - cheers John, will look into that.

I've been reading up a bit on various techniques - I'm quite interested in having a go at generating the line-work digitally and using my CNC gear to do the etching - I put this together in Illustrator a while back:

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So it'll be a combination of old/new techniques - and seeing what happens..!

[JohnHaine]

Yes, nice. Technically that's engraving - printmakers get hot under the collar about the confusion! You can get a nice variation in the line width by varying the cut depth, not so easy in etching I believe. Or you could use a sprung scribing point on the chuck (non rotating) and scratch through a ground and subsequently etch the plate.

[Wal]

Or you could use a sprung scribing point on the chuck (non rotating) and scratch through a ground and subsequently etch the plate.

Heh - way ahead of me skipper - that's exactly what I'm trying to design at the moment... I have a whole heap of broken small diameter carbide end-mills that I'm thinking of grinding to a point...

[Wal]

Right, it's pretty much done, until I figure out any tweaks that may need doing whilst I get to grips with using it - the only obvious one would be the deeper spring pocket to allow for a bigger gap between the top roller and the platen - so far I haven't needed it, but it would afford me some flexibility, so why not..?

Anyway - here's an animated turnaround:


https://www.youtube.com/watch?v=HDsZsAkQvx8

And here's a woodcut print I gone and done - normally the shapes are cut into the wood by hand - I do all of the artwork digitally using Photoshop and Illustrator and then CNC cut the wood before inking and printing. Eventually I'll probably combine both methods - just have to see what works for me!

The digital design:

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The inked wood:

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The print:

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Wal.

[mekanik]

Very nice Wal :thumsup:

[magicniner]

I don't know about it's output, the machine itself is a work of art!

[Wal]

Heh, cheers guys!

Sent from my HTC One M9 using Tapatalk

[JohnHaine]

Wal, a thing of beauty!

You probably know this, but woodcuts are usually done on end-grain blocks, typically maple or boxwood, which can take a fine line. There are also quasi-synthetic versions such as Resingrave. I believe that you can also use MDF at least for test cuts to get the image right, and probably use something like PVA or dry-rot cure resin to stabilise the surface. Lawrence (https://www.lawrence.co.uk/category/printmaking/relief-printing-wood-engraving-and-lino-cutting/engraving-blocks?currentPage=1&resultsPerPage=18) seems to be the preferred supplier.

[Wal]

Hi John,

Thanks for that additional info - I'm vaguely aware of the end-grain blocks, although that's a slightly different approach to what I'm currently up to. The end-grain blocks are more suited to the more detailed style of wood engraving as opposed to woodcutting - I'm not at that level just yet - just exploring the more accessible woodcut process - probably a good thing too - the prices of those blocks over on the Lawrence site..!

There's a bit more info on the differences between the two techniques here: http://www.chrisdaunt.com/endgrain-wood-engraving-blocks/

Some beautiful wood engraving work out there!

Wal.