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

Thanks for the info.

My pinball-machine approach is now pretty well directed toward a Prusa MK3 printer. I had lengthy conversations today with two very experienced filament printers who advised me that Prusa printers set the standard for filament printers. One guy is printing up a set of nameplates for me on a Prusa printer. They advised that PETG may be a more durable filament than PLA and that Prusa makes the best filament in the world and is well worth the 20% to 40% or so premium
that it commands over generic filaments. They also report excellent long-term product support from Prusa as compared to miserable support from the knockoffs not to mention firmaware issues often seen with knockoffs.

Anyway, that is the current state of affairs. I think I will wait until I actually get the trial prints in hand before actually ordering a Prusa. My biggest anticipated learning curve will be in CAD file generation though both guys I talked to today affered assistance as needed. I've done some work with Fusion in the past. So, I have some idea what I'm "up against."

Denis

 

Thanks. Probably going to get a Prusa MK3 kit. Made in Czech Republic and has a splendid reputation for quality and product support including upgrades.

Denis

 

I am also happy with my Ender, walked into MicroCenter a year and a half ago and walked out with it and a spool of PLA+. No warranty or support issues and I enjoyed putting it together. Ran a nine-hour print yesterday. I would get some samples from both a resin and filament printer before committing either way.

 

I went and measured those photo etched aluminium letter moulds I made a while back: they are a hair over 3/16" in size. Font style is pretty much "what you see is what you get" due to the tendency of the etching to round all the corners. So 3/16" is do-able with the process. I bet you could cast zinc words with a bit of a preheat to the mould.

 

Nice Mark. How thick would the zinc have to be as a backer to carry the type face? Machine a recess, cut the artwork to fit in the recess, and then coat-expose-develop-etch-strip? What did you use to etch? My day job deals with some of these chemicals and processes, I can see a home project coming...

Jeff, sorry your Ender experience is not positive. Our experience here is the opposite: the resin printers fouled up and the filament printer keeps trucking along with occasional bed leveling, wiping the bed with isopropyl (rubbing) alcohol, and checking belt tension. I did have a couple false starts yesterday, small features lifting on the first layer, until I wiped down the bed and checked the outside of the nozzle for goobers. My first roll of PLA+ from the store was better than the current one bought 'online', the former printed better at lower temps and was less 'goobery' on the nozzle.

 

I'd expect the zinc to be a few mm thick at a minimum, maybe set the aluminium sheet mould over a low gas flame to slow the cooling down. I used Cuprous chloride solution to etch aluminium as it's easy to recharge and etches almost anything.

https://forums.thehomefoundry.org/i...to-make-etched-data-plates-for-equipment.226/

Edit; Actually I HAVE poured molten zinc into sheet aluminium ingot moulds: the residual heat softened the aluminium and caused them to fail . Zinc's 420 deg C vs aluminium's 660 meant that I must have had the zinc too hot.

 

Getting off topic but:

Bed level is important. Adjust with a piece of standard paper until you can just hear the servo start to protest.
I have a glass bed and no problems. My brother has the magnetic bed and does. Got to be flat............!!
Offset the Z in software and/or lower the bed temp/first layer extrusion % to get rid of the 'elephant feet".

Good old fashion cheap hairspray for sticky on the glass. I use Aqua net. Actually sticks too much with PETG. Clean with isopropyl when the build up gets too thick.

There can be a steep learning curve as you tune your software to match the printer and filament. I've yet to solve the bowden tube working loose problem but that really only effects cosmetic blemishes at layer change. I do have a direct drive extruder that I may install someday. For now I just trim the bowden tube when it gets a 1/2mm of slop.

 

Here are the drawings of tiles with letters that a guy drew up in Onshape

And here is one of his test prints of a file prepared prior to the drawing shown above. He used a Prusa MK3 with a .25 nozzle. I think this quality level will work well in my system.

I'll use the tiles on a master pattern from which I will make a urethane working pattern.

Denis

 

Here's the lettering I printed on my Mars2 Pro. Printed with a thin backplate and glued to the pattern.
The pattern is FDM printed on my Ender3 and I used a technique seen on some cosplay 3d printing circles to smooth out the print lines. The technique uses acetone-diluted Bondo Spot Putty applied with a HF airbrush, like an ultra-high build primer. Very quick compared to normal sanding. If interested I will post the link or start a new thread on it

This is just the master pattern, I am going to pull molds of the cope & drag with Freeman Repro and duplicate several sets of these for a matchplate

 

Looks very nice.
A thread with a title indicating how to use diluted Bondo airbrushed for high build might be a good idea. If you bury it here in this thread how will anyone find it in the future?

Denis

 

Sounds like DIY Feather fill? Interesting idea!

Edit:

Looked up the process. Was expecting a hand sand free process. Back in my kit car build days I did a lot of touch up with airbrush sprayed gel coat. With low vapor pressure solvent you can get pretty good shine with no sand/buff.

 

No, there's still hand sanding involved, but it's much quicker I think
Started a new thread, here's the link:
http://forums.thehomefoundry.org/in...d-for-finishing-fdm-3d-printed-patterns.2267/

 

Well, I finally got some letters 3-D printed in PLA by a sympathetic guy in the PNW. Today I let them into my master pattern. Since I asked for 3/16" wide backing plates with radiused ends, dropping them into corresponding mortises in the pattern was amazingly easy. I just set the pattern up on the mill and located the mortises and made appropriate-length grooves with a 3/16" end mill. Then the tiles just fell into place. In fact, pulling them back out after dry fitting them was a bit of a trick as there was only a very slight gap between the pattern and the tiles bearing the lettering.



There was very slight fettling to do after I glued them in. Then I misted on a couple coats of lacquer. From this I will make a silicone negative mold and then cast 2 Repro copies.

Once those are done I will be attaching them to a matchplate and then adding gates and runners made from a combination of wood (for straight parts) and Sculpey baked modeling clay for curved or flared portions of the gate/runner system. Then fianlly I will cast the whole works again. I will not be surprised if some tweaking of the matchplate will be nededed to get good clean draws of the plate as well as possibly needing to adjust gate/runner. But, ya gotta start somewhere, I guess.

BTW, I have a Prusa MK3 kit on order with an expected shipping date of 2-3 weeks. It is made in Czech Republic but DHL claims they can transport it in 3 days for 50+ dollars. Here's hoping there are no hang ups along the way. I had recently agreed to buy a nearly new MK3 from a guy in Seattle with delivery on Sunday. But, then he backed out unexpectedly and without explanation. Bummed about that a bit. I felt like a deal was a deal and I sure would not have backed out on my end. Oh, well...

I have been doing tutorials and practicing modeling in Onshape CAD software. Like all full-featured CAD software it has a bit of learning curve with the requisite occasional head banging. I am hoping to be able to print largish patterns in segments and glue them together to act as masters but not working patterns. We'll see how that works out in reality.

Denis

 

The next logical step was to make a negative mold of the pattern and this time I used my "Magicfly" brand silicone. In short, it worked perfectly. It poured very nicely with no degassing and no evident bubble formation. It set up in 12 hours just as advertised and was very tear resistant and medium soft around 20 or 30 durometer. I did make an uncoated wood frame around and above the pattern to ensure good support of the silicone as it is so flexible that it does need an exoskeleton to prevent bulging of its sides and being "thrifty" (a polite term) I also wanted to minimize consumption of the silicone which is universally pricey and in some cases very pricey. I used a nearly identical strategy as shown above when making the urethane rubber mold.

http://forums.thehomefoundry.org/in...trology-parallel-level.2223/page-2#post-45809

This material is provided in an equal parts mix ratio and did not seem at all friendly to bubble formation or retention. I can certainly claim no skill in pouring mold materials but I was extremely pleased with the results.

Once that mold was made, I broke out the Repro One and filled the mold with 450gm of Repro One. That material also has been engineered to not require degassing and simply does not seem to include bubbles in the pour. The casting was ready for demolding in about 1 hour. I used no wax or other release agents on the silicone mold and hoped it would release "as advertised." It did. I was able to push on the underside of the cured filled mold with my fingers vigorously and the Repro let go of the silicone very cleanly and with little hesitation. (Had this been an unsupported silicone mold, it would have peeled off extremely easily.)

Here are a couple pics to indicate the resulting Repro One casting. I did an open casting while planning to mill off the back. In my situation milling it is very simple. But I did not have easy access to a mill, casting it with a closed back would have been better and would gotten away from post-molding machining. The slight down-side would have been that I could not have as easily monitored the mold for complete filling unless I had used plexiglass as a backing.





You can see there are some tiny bubbles that evidently were included overlying the letters. I suspect that more care in pouring the Repro over these areas would reduce the likelihood of these occurring. They are indeed tiny being on the order of the size of a period on the printed page. I may go back and try to fill them in with something like Bondo. But they are so small they may not actually print in the sand. I don't know for sure. I will be making one more copy of this side and will see if I can avoid them with a bit more care. In this pour I just poured the Repro into the mold without taking any care to keep the pouring stream very thin. I think when letters like this are involved, I should slow down the pour until the letters are filled in. I guess that is what experience is all about. Learning by trial and error. As it is, I poured so casually that to have results as good as I got is a testament to the ease of use of this material.

Denis

 

Looking good Denis!

 

Looks good, must be time to get a syringe full of resin to fill the bubbles.

 

Now ya tell me!

I will definitely try that method soon over the letters only just to confirm it works for me. I expect it will.

I did repour a bit more carefully and did reduce the pinholes by 75%. But, the goal is to eliminate them.

I did make a couple "dental" tools to push Bondo into the holes. They are much too small for me to syringe any resin into them.

Here I have Bondo'd them using a dissecting microscope and my shop-made tools. Here are some filled holes.


This is a little "pusher' I used to stuff the slightly thineed bondo into the pinholes.


And here is the other end which is a sort of knife-like scraper and cutting tool made from a piece of 1/8" tig welding filler rod.


My usual pattern is to work on a pattern and then lacquer it for final finish and then wax it when I put it into service. However, when I did a couple of test sprays I found that silicone is evidently incorporated into the formula for Repro One. So, fisheyes are going to be a problem. I hope that a couple thin coats of shellac followed by several misted coats of lacquer and then a final wetting coat of lacquer will get around the fisheyes. Open to ideas.

Next I plan to attach the patterns to my match plate.

Denis