Trouble Finding Small Letters---~3/16" High Have them CNC'd?

Discussion in 'Pattern making' started by Melterskelter, Jun 9, 2022.

  1. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Now that you have that 3D printer heading your way, you need to design yourself a catchy little (feather?) logo.......

    Best,
    Kelly
     
  2. Melterskelter

    Melterskelter Gold Banner Member

    The reason I think it must be in the formulation of Repro is that I was testing the paint on the non-mold side of the casting and I also not the fisheye was actually worse on that surface if I had first sanded the surface. I also applied no silicone to the pattern when I made the silicone mold nor when molding
     
  3. Melterskelter

    Melterskelter Gold Banner Member

    I tried to include this in the above post, but, oddly, could not seem to paste it in in the edit mode. :confused:

    I'll ask Freeman if they have solutions for finisihing as well.

    And, yes, I am sure I will draw up a feather and FDM print it. All my other patterns have an included feather which I simply whittled out of piece of wood. There did not seem to be a particularly logical place for the Feather on this one. Still thinkin about it.

    And I did try prepainting the letters as you suggested with Repro and found that it did, indeed, eliminate the bubbles. Dang, could have saved myself some trouble. I think that is actually a commonly known idea that I should have thought of.

    Denis
     
  4. Melterskelter

    Melterskelter Gold Banner Member

    Here is an Onshape sketch of a logo reflecting my newbie status as a user of Onshape: Logo.JPG

    Hey, it's a start!

    Denis
     
  5. Melterskelter

    Melterskelter Gold Banner Member

    I have a question concerning next steps in this resin casting journey. Though Repro does not require degassing, many other brands do. I am thinking a degassing chamber is a looming investment. It turns out I already have a functioning 300W vacuum pump. So, is it a mistake to buy a 1.5 gal chamber fo around 70 dollars vs a 5 gal for around 125 dollars? I think it is very unlikely that I will need to degas more than 1 qt at a time ever and usually much less. But then, this is new territory. Thus the inquiry.

    Denis
     
  6. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I may have commented before but just because it doesn't require it doesn't mean it cant benefit from doing so.

    I'd say get one that can easily accommodate a 1-gal paint can. Most anything you degas will initially boil, and grow significantly in volume (maybe 2x depending) until the majority of the gas evolves and then it will settle. If you don't have a large enough container it will boil right out and be laying on the bottom of your chamber. This can be controlled by ramping the vacuum.

    Best,
    Kelly
     
  7. Melterskelter

    Melterskelter Gold Banner Member

    Thanks, for your comments.

    There is also talk of first degassing, then pouring and then letting the polyurethane setup under pressure. Have you tried this? Are the results that much different?

    Denis
     
  8. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Never tried that. I have pressure fed the resin into the mold via hose and having the resin in a paint pressure pot. Invest at low point vent at high point. Works well for closed cavity molding. Small hose and plastic fittings are expendables. I think I showed that in my golf tee marker match plate thread.

    Best,
    Kelly
     
  9. Melterskelter

    Melterskelter Gold Banner Member

    Freeman did get back to me and suggested silicone contamination from the silicone mold might be the problem. Their suggestion was to lightly abrade the surface and then wipe it down with acetone. I did that and got a good finish without fisheyes. Conclusion: silicone from the mold was causing surface contamination.

    As further confirmation, I dipped some Repro out of the cans using stainless measuring spoons, mixed it up and applied it to a clean board without any molding or manipulation of the surface. Then, witghout any cleaning or abrasion, I sprayed it with lacquer. I got nice finish.


    Denis
     
    Tobho Mott likes this.
  10. Melterskelter

    Melterskelter Gold Banner Member

    Matchplate progress:

    I did cut a piece of MDO ("Signboard" or "Kraft-faced plywood") and glued the four halves of the pattern to it. I did not use registration pins as the peice was cut very square. I just used a Starrett 12" combination square and was careful to make sure the toip and bottom sides lined up and checked multiple times to be sure I was not inadvertantly flipping one of the halves in relationship to its "brother." Making that kind of error would be so easy and so utterly frustrating.

    I think the halves are located to within a 64th or so of ideal location and that should be close enough.

    I also worked for the first time with "Sculpey" polymer clay to fashion a pattern for the runners and gates. I wanted to be sure to have the last area to freeze a cm or better from the casting itself and into the gate/riser so as to avoid vacuum defects and shrinks. I found the clay to be easy to form and, after baking at the recommended 275 for an hour, pretty rigid. Not quite as stiff as wood, but stiff and hard enough for the purpose, I think. It was also good to find that it was wasy to add clay to the original baked piece in areas I wanted to build out. It seemed to adhere very well. The material is easy to sand or machine. I used my belt grinder, disc grinder, and die grinder fitted with a sharp carbide cylindrical burr. The burr was my favorite forming method as feathers of cured clay shaved off nicely with good control. And, AND, it painted without a hitch. Lacquer flowed out smoothly wtih no bubbles or fisheyes. So, is it the ideal material? Maybe having it bake out to be a bit harder almost like a ceramic would be nice. But its general easy hand molding, machining and painting make it a very good option. I meant to try saturating it with thin cyano glue, but forgot. Duh!

    Here the runner/gate is laid onto the plate. This will be the drag side.
    Plate2.JPG

    The other side of the plate.
    Plate3.JPG

    The underside of the runner/gate showing the smashed-together clay and general crudeness. Plate1.JPG

    Closer vies of the top of the gate/runner. I jsut formed it well enough to carry the metal and to, hopefully, draw well. It may require modification. Modifications should be pretty easy. Not shown are a couple of risers that will be placed on the cope side of the mold and will be located overlying the bulbs in the runner/gate.
    Plate.JPG

    It may be a week before iron is poured as we have guests arriving for a few days. The last remaining step is to make flasks. [I will be using very shallow pins on one side of the flasks and plate as this system works well for me even though a certain very experienced caster doesn't appreciate that method. ;-)]

    Denis
     
  11. Melterskelter

    Melterskelter Gold Banner Member

    Not shown above are the blind risers that will be placed in the cope. I think I’ll use a pair of well-used lacquered fir patterns about 1.25” diameter and equal in height with flat tops.

    In another thread someone mentioned difficulty removing blind risers from a mold. I use blind risers with rare exception and have a drawer containing about ten pairs of various pattern sizes plus an equal number of individually-sized blind riser patterns. Almost all are squatty slightly-tapered cylinders turned from fir and a very few made of Delrin or aluminum depending what was at hand at the time. But the universal feature present in every one is a 1/8” or so hole in the center of the bottom (wide end) of the pattern. That makes removal a simple matter of screwing in a little draw spike, giving the spike a couple light raps side-to-side, and then just tapping it out. No muss, no fuss and no trying to push it out with a spike with resulting sand breakage. Draws very cleanly and easily every time.

    I do not like it when risers fall out on their own as they can damage sand if they let go after the cope is off the drag an inch or two. But, they will almost never fall out if they have reasonably shallow taper on the order of 2 to 3 degrees. Making from low density materials also helps prevent fall out.

    It’s a system that seems to work well for me anyway. Should be doing some work on flasks today. Right now we have house guests. So foundry work is taking a back seat.

    Denis
     

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