That could work, in fact a CNC engraver would probably tick all the right boxes...in this case I'm adapting existing equipment and processes that gives me 1440 dots per inch resolution. After a bit of thought I'm now thinking of making some reversed female masters and casting resin copies as needed. That sounds pretty interesting, magnesium is going to etch pretty quickly. I have electro etched stainless steel for monuments and noticed that it gave a very rounded cross section with no undercuts and a mirror smooth finish that would be ideal for casting letters.
I've made up some reversed resist masks on 316 stainless steel and I'll wire them up for electrolytic etching now. If I do a deep etch the letters should get some undercut and make them more like a fatter bold font.
Have over etched the top sample with a 60 minute etch and turned the voltage down too far for the bottom sample which gives a stippled texture. It's deep enough to pour some clear epoxy over the waxed stainless mould and see if the result will leave a legible sand impression. There's a point where the epoxy has solidified but is still bendable so I hope to peel it off at that point which would also let me wrap it round curves too.
Thanks, I think the method will work, it's cheaper than 3D printing to set up but needs a bit of technique. I have a result from the mould now, it's full of air bubbles so I gave it a coat of rattlecan primer/filler and I have another casting in the process of curing, this time without bubbles. With the right selection of font it should be possible to get a good result this way and the only requirement is an inkjet printer, some transparency film, sheet metal and some buckets with common hardware store chemicals in them.
I whipped out a set of letter moulds in aluminium: 5 minutes to film coat the sheet aluminium (let it sit for a day to dry), 10 minutes to type and print the artwork, 4 minutes to expose the mask, 3 minutes to develop the mask, 8 minutes to etch the mask, 5 minutes to strip the mask = 35 minutes all told. Aluminium has a textured etch so I hit it with a fine brass wire brush to smooth the etch. I found a nice thin skinny font this time and only used uppercase text to give it a chance. Right now the mould release wax is drying overnight ready for some epoxy resin.
And none of the gear is really expensive: all you need really is an inkjet printer and inkjet transparency film and some photo-resist film bought off the net.
A little follow up concerning my requesting a refund from Freeman on these letters: I reported my concerns about these foundry letters 5 days ago to their inside sales person whose name I won’t post here. She contacted here technical staff. 5 days later after a couple prods from me, she wrote me this morning that “ that is how they are supposed to look.” I guess I would differ with her as they are essentially useless, there is no photo on their webpage of the letters showing mounting holes, and there is no description of such. Worst of all the holes are so poorly executed that the “foundry” letters cannot be cleanly pulled from sand. I am amazed that Freeman would be so careless as to market such a poorly made product and even more disappointed they won’t make it right. I would suggest Slaters as a good source of foundry letters in a wider choice of sizes and styles. Myfordboy boy has used them and found them to work fine. http://forums.thehomefoundry.org/in...astic-foundry-letter-supplier-—-slaters.1323/ Denis
My response from them was "all our sets look like that". Even after I pointed out that one size had nibs and the other size had pin depressions (I won't call them holes), they still denied a flaw. I told them they had a bad batch and the letters were useless for pattern making. After they sat around my small shop for a couple months and I had to keep moving them, I pitched them in the trash. That was a 100+ dollar lesson.
This is one of our new projects...acid etched magnesium logo pressed to fit on our dome shaped camp lid pattern. Worked out very nicely! We already converted our old logo from plastic to this. The quality is 100x better than we got with plastic.
That looks really good!, in some ways etched logos and graphics are suited to sand casting as the radiused features, relief and smoothing are built in with the method. Imagine CNC ing the same graphic and then having to hand polish the cutter marks!. I need to get some sheet magnesium!.
