Question, is there still tooling for Phototherm tanks? Jobo, thank goodness, had the resources to preserve the tooling. As all the old equipment dies there's going to be significant demand for equipment.
To the OP, design what you want. As long as you aren't using hard tooling changes are easy.
Andrew is probably trying to test the prototype about now. Since we haven't heard back, just thought I'd point out some design oversights that may prevent some headaches;
You mentioned you light trap design perhaps it is too bulky? It is like for good reason, the input is below the tank to allow even filling and prevent uneven development. Having the input in-line with the reels in your model may create surge marks or uneven dev phenomena across all the rolls as the tank slowly fills to capacity.
The Phototherm tanks aren't exactly as simple as you may make them out to be. They aren't perfect cylinders there is a slight draft along the length of the tank to assist with drainage but also again to assist with even filling and development. In this case the furthest rolls from the input are closest to the bottom to account for in inlet being on the opposite end. There are ribs on the bottom to keep any leftover chems put until the next full to prevent too much cross contamination.
There are a few other little things that are not immediately obvious unless you have operated the machines or have a tank in the hand. Again, you will probably find this out as you actually start to test your prototype for development with film and chemicals (not just fluid dynamics) .
Bests,
C
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Calebarchie, yeah sorry I've been very busy with my day job (https://www.rocketlabusa.com/) and trying to get a friend to assist with the control electronics side. Also trying to get some quote and hopefully some prototype sheet metal parts ordered soon so I can start building up the frame of the machine a bit. Yes I am concerned about surge marks to do with the way the fluid is entering, I originally had a bit of a baffle inside of the tank to divert fluid around but I'm going to try without as it would probably end up foaming the chemicals up. The fluid enters the tank through an oblong hole/slot which should be under the level of the film in the tank and so there shouldn't be any direct impingement onto the film but as you say I'll find out once I start testing and using silicone moulds initially mean that changes are not really expensive to make if I need to.
I know it's been a while since my last blog post but I haven't spent all of the time sitting on my hands, new post is up:
http://midtonemachines.com/news/shee...-valves-oh-my/
Sheet metal parts are on the way and I've started life-cycle testing of the pinch valve design I intend to use, to make sure that it's going to be suitable for heavy commercial use (and therefore bulletproof for home use). I also included some of the photos I've been taking recently instead of working on the machine :P all on my Chamonix 4x5 with Ektar and developed at home.
I see you are looking at thermoforming. I worked for Whirlpool and Maytag in refrigerator engineering, we would run in line and rotary vacuum thermoforming machines that would form in a "double bubble " the fresh food and refrigerator interior cavity liner in one stroke, these units were typically 22 to 25 cubic foot interior volume, about 70 inches tall 33 to 36 inches wide. I started in Amana Iowa in 1994, I still think that and co-extrusion were the most fun part of the operation. I can't remember the cycle time but it seems like we formed a set of liners every 90 to 120 seconds. The biggest co-ex line would extrude ABS sheet around 6 foot wide probably 20 feet / min.
Maytag built a plant in Reynosa Mexico, Whirlpool bought Maytag/Amana we sold the plant to Fisher Paykel. Small world.
I can only imagine how large and heavy the molds were for that! The vacuum forming production tooling I'm looking at is machined aluminium and I believe they also include heating and cooling in the mold to assist cycle times (not that I believe that will be an issue for my small volumes).
I've also just done a test of the pump filling and draining the developing tank, I can fill the 4-reel tank in 12 seconds which I think is well fast enough to avoid uneven development. I will have to look at improving the drainage however as it isn't very efficient at getting the dregs of the chemicals back out again.
Also pinch valve is now up to 7000 cycles and still going strong.
Position and slope!
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Yes there's temperature control in the molds, it's been many years back since I was directly involved. The foam insulation between the inner and outer walls required massive tooling cores and outer support structure, you can lift a truck off the ground with polyurethane foam. As I recall most of our aluminum molds and foam cores were made in Italy. Amazing craftsmanship. Today, as with injection molding tooling, I suspect China is a major player.
12 seconds sounds great to me, it takes me that long to pour solutions into my Jobo with the lift.
We used "Thermolators" to maintain foam core temperature, would heat at beginning, then chilling (heat pumps) would come on to take the enormous amounts of heat out of the foam tooling from the exotherm. Every 3 1/2 minutes one fixture produced a foamed cabinet. With 40-50 fixtures you could make a lot of big refrigerators.
Looking forward to seeing further progress.
Best Regards Mike
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