Sorry that it has been so frustrating for you PE, but thanks for making the plans available.
I know from personal experience that the quality and cost of shop work varies widely, and they don't necessarily correspond. We needed some 1/2" copper plate with an explosively bonded stainless face bent into a very specific, but odd shape (not circular at all). We had 28 pieces that needed the exact same curvature. One company priced at $3k/piece, for a total of around $90k. We got a second quote from another company for $200/piece. They did a great job and bent it right to spec. This was for a fusion research device, by the way.
The research I participate in requires LOTS of one off designs, and almost everything is custom machined. It really does get expensive.
Not that I have the knowledge to help, but I'm sure a lot of the problems you are running into have already been solved by someone else. If you just knew who to contact...
Idea 1 - What do you think about a plate that has a well that is tapered - when looking from the end of the blade? As it you are making them now, you have the well go the entire depth of the blade and at a uniform dimension - what about cutting the well at a 45 degree angle (instead of vertical as they are now) so that the well is say 5 to 10 mm wide right in front of the doctor blade where if meets the paper, but it is wider as you get further away from the paper. Think of a funnel profile but one that is "cut in half" so that one side (the side of the blade) is striaght, and the other side (the side of the body) has the funnel shape. It doesn't need a compound curve like some funnels, a simple triangular well shape would be fine. The body would need to be taller than you currently have in order to hold the same volume, but the triangular shape of the new body would be stiffer than the currently rectangular bodies.
Second idea - only the doctor blade needs to be precisely parallel to the surface of the material being coated - the body of blade does not. So what about a blade body design that has the same U/rectangular shape you currently have, but one that uses a rubber casket/wiper to make contact with the paper along the long dimension of the blade. This way, the long dimension doesn't need to be precise since the flexible wiper contains the emulsion and keeps it from running out of the well as only the ends that the doctor blade that screw into need to be precisely parallel with each other. A slightly larger blade body could be made to reduce flexing and only the ends, which are polished and parallel to each other need precise machining and polishing. It would sure cut down on the machinging expense of these blades.
That would be me.
Originally Posted by Photo Engineer
It is extremely basic, and entirely hand built. It uses a design broadly similar to PE's blades, but I tweaked the design to make it more stable and resistant to flipping over - a problem I was warned about with lightweight blades.
I haven't had my design snag or flip over as yet, but I haven't exactly used it a lot.
However, it does get the job done after a fashion. It would greatly benefit from a more accurately made doctor blade, but even with the one I have in place, the results are better than brush coating.
I have spoken to PE via PM, and he suggested the lightweight blade might have problems coating particularly on baryta papers - I haven't tried this as yet, so I don't know.
If it did have serious problems, I have thought of several ways to add mass to the blade, but I have not actually tried them yet.
Lens caps and cable releases can become invisible at will. :D
With the many possibilities of modern 3D printers, it should be possible to print coating blade with high precision and at a price that will allow for changing when the start to corrode if made from metals. A 3D printer will allow for making plastic models, that can be tweeked to optimize performace. Some of the printers will allow for making hollow prints. They could be filled with sand or something heavier. Some printers can print with polysulfon wich is temperature and very chemical resistant. The printers also allow for making moveable parts an integral part of the design if needed. I am not affiliated to any 3D printersupplier, but I have seen some amizing things come out of these printers.
These are fascinating devices that seem to be coming into their own - I think over the next decade or so, we are going to see a revolution in manufacturing based on these 3-D printers.
Originally Posted by Falkenberg
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Both ideas sound doable, but in #1 there is more surface to polish and the larger surface area may be more subject to scratching the film or paper. As it is now, the blade can be flipped over if one side becomes scratched. Also, the higher a blade is the more tippy it becomes.
I had forgotten your name, sorry. As I wrote that my mind went blank. Good luck.
As for the rest of the suggestions, it seems that there are a lot of ideas that might work. I guess having unhappy customers at Christmas has gotten me down a bit. Those with special orders, please take heart, I am doing the best I can. I just shipped a batch of them back to the shop that were re-done and were very accurate but had minute scratches in the surface finish. This ruined their ability to coat quality material. I have one with scratches but they run perpendicular to the direction of travel. If they run parallel to the direction of travel, they show up.
BTW, Kodak used over 5 different designs including some mentioned above. I have tried all of these before settling on the one now being made. Kodak's versions all worked but probably cost $1 M each to make. If any of you are in Rochester, I would be glad to show you my drawer full of prototypes.