Etch Press Build

[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...



Wal.

[Wal]

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



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.