Etch Press Build

[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..?



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..?



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...)



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...

[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.



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.



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! 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 , or b. deepen the pockets that hold the springs on the underside of the pressure plates.



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:



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