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Jay Kempf

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Anyone have a good supplier or some knowledge of very high density polyurethane boards used for creating composite one off tooling. Been looking around and can't find a good source or much usable info.

Have been doing CNC to one off tooling experiments lately. As the tools get large the material costs add up in a hurry or the labor. Current method is to use 2 lb blue foam from lumber yard attached to MDF for stability. Then cut mold cavity directly with CNC with one pass to within a few thousandths. Then sand out the ridges and coat with bar top epoxy. That is working really well but the epoxy part is hard to control properly. We wet sand at the end to get a reasonable tool. I paint them and spot putty and fix up what wasn't happy. Would like to up the quality and streamline the process.

Some of the tooling board products look nice but look gawd awful expensive for what they are. With my router I can get 48" x 48" x 6" deep in one pass. Those panels can be combined into any larger structure. Currently working on a large wingspan UAV and developing guerrilla methods. Going well but could go better. Learning a ton about using Fusion360, MACH3 for CNC OML direct carving for aero structures. You have to be really clever with CAD before you can even start this sort of process. That is where the magic happens.
 

geraldmorrissey

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Have lots of cutoff 1/4" high temp graphite tooling board press cured at 350 degrees F. Many small pieces plus one big piece. PM me if I can help.
Gerry
 

ScaleBirdsScott

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I found some construction supply places will sell higher density 40/60/100psi capable blue/pink foam intended for going under concrete pads. I was able to get a bunch of remnant/return sheets of the 60psi that were 80-90% good, basically a whole sheet but with corners busted or a bit of surface shmoo, all at half cost so it comes out to about the cost of the regular 2lb stuff, but you may not get a full 4x8 sheet out of it, may have some corners you have to strategically locate the material you do have. Buying new, it isn't stupid cheap, but I gotta imagine its cheaper than tooling board based on the numbers I found.

Cuts much nicer than the regular 2lb stuff, that's for sure. Chips come off as tiny grains almost like sand, or mini-rice grains, or a coarse but soft powder; as opposed to the than dust and strands one gets with the 2lb, so it doesn't get into the air that much. And the resulting part is denser, heavier, holds detail better, and is much nicer to sand out.

Might be worth a shot in any case.

I got my panels from Whitecap:

https://www.whitecap.com/-Owens-Corning-Foamular-600-8-x-4-x-3-60-psi-Extruded-Polystyrene-Rigid-Foam-Insulation-252947/#59Y-59559Y/
 

1Bad88

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I used to do a lot with Renshape boards. The way that I kept cost down was to build semi hollow structures for Male tools and bowl structures for female tools. Super glue worked very well to assemble the rough shapes.
 

Jay Kempf

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Used to do the same in the pattern shop when the parts were smaller. But with larger parts the stuff is very expensive. Like $1300 for one board 6" deep by 24 x 48 I think. Won't make much of a structure out of that.
 

Jay Kempf

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I am using the concrete underlayment now. Not impressed with it. I am trying to come up with a spray and rotate method to coat evenly. Not there yet.
 

Hephaestus

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3D print the mold, epoxy the mold pieces into MDF frame.

Haven't tried it but hackaday was talking about using SLA resin painted over prints to prep for mold pulling (rather than sanding)

Big honkin 1.2mm nozzle .1200 layerheight, single perimeter 25% infill. A CR10S5 does 500mm sq prints...
 

GeeBee3

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The construction industry uses large blocks of EPS foam for foundations and earthworks. This foam is available in various densities according to the compressive strength required. Many sources listed at this site; https://epsindustry.org/other-applications/geofoam

Typical physical properties for various densities here: https://www.plastifab.com/products/geofoam-sol/geofoam.html Note that they are listing densities up to nearly 3 lbs per cubic foot with compressive strengths exceeding 100 psi.

My local supplier (Beaver Plastics) is able produce billets up to 4' x 4' x 16' in size in any density you want, then hot-wire cut slabs to your dimensions. I have used some of the lighter weight material for my own hot-wire foam cutting, but I do not have experience with the higher densities. Your local supplier may have a remnant of high density EPS that you could use for experimenting.

GB3
 

Jay Kempf

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Thanks for all that. I already have 3+lb density stuff for underlayment. Investigating higher stuff that won't dent with a finger. That is the expensive stuff like Renboard that is expensive. I have also looked at two part foam pour in for making large volumes. Also looked at spray in insulation.

One thing to note is that I am in the middle of nowhere. So the concept of a local supplier is just non existent. Everything has to be shipped in. I can glue thinner blocks together and I can make plywood frames to attach panels to to make larger molds but that means the surface has to be able to hold vacuum across those panels. Right now I am working within my router dimensions which is about 48 x 48 x 12max (more like 6" total mold cavity depth)

3D printing is so slow it isn't practical and you still have to seal and smooth out the surface.

These are all one off so time through the mold making process is a key consideration. I have the router cycle time optimized I think.

MDF molds are VERY heavy. We are using MDF as backer right now and it makes a 4' square heavy to move around.
 

Jay Kempf

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Yes, that was the first tack I took. But it doubles and triples the run time.

Current thought is to build a rotisserie to coat the molds so you aren't dealing with sag. Then come up with some sort of thick spray coating that I can control the thickness of. I can do a pass with a ball end mill and get to within .003 and do an entire panel in about 4-5 hours. Light sanding to take off the ridges and I have a really nice surface. If I could find a coating that would more soak in than run on the surface I would have it pretty much optimized. Stuff that won't eat foam limits you. Took a lot of time and experimenting to get the cavities to machine properly.

Lots of stuff to try yet. Was just hoping to not make all the mistakes that have been made before.
 

TFF

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Sounds like you need to glass the form, then build up to a smooth surface to do the layups on.

Might be expensive but what about coating foam with foam safe CA glue.
 

Jay Kempf

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Heph,

If you haven't gotten into 3D printing you can't imagine how long it takes to do anything simple and I am working at scales that are way beyond what most of the guys you mention are doing. YouTube videos lie because they can fast forward and they can leave out all the times the thing just blows it. Can be done takes forever compared to what I am doing for large scale stuff. I am trying to ramp up to a modular tooling strategy that fits 4x4' x 6" deep in my router. Try 3D printing 4x4' by any real depth useful for making an aero surface of anything measured in feet of wingspan. That's a lot of volume.
 

Hephaestus

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9th printer just arrived... One of the e3d toolchanger prototypes.

I think you've got some preconceived notions... I was working with a local company on their printer - they're doing kayak hulls in 8 sections.

They're now dialed in enough that it's printer to assembly table - with .1600 layer height only prep is 3 airbrush coats of lacquer. Then straight to mold release.

 

Jay Kempf

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I went to a demo of the machines of which you sent the video before they were in production because we were looking at them for wing molds. It is not as you are alluding. The machine was a very large Thermwood gantry mill and it had an entire injection molding machine bolted for a head for 3D printing. For the price of one of those machines or the output of one at the scale I need I could just buy a nice private jet. VERY long run times for that machine. And gawd awful expensive to acquire operate. For production tooling for a boat factory it might be competitive. For one off for prototyping GA parts not so much.

Parts I have run off my router are in the 4-6 hour to get a cavity (4' x and 4' y including facing) to withing sanding .003-.005 inch. The way we are processing we leave the tip of the ball endmill cusps in the material with about a 1/16" stepover and that means the cusps are in the main .003 above the target geometry and the troughs are on the target. With non friable material that means you can sand to very close tolerances just by watching the cusps disappear while you sand. It has proven to be very accurate. I couldn't 3D print anything of this type in a single spool of filament or in a week of run time.

I am trying to get a single 4' x 4' mold cavity down to 2-3 hours to ready to vacuum bag. Not there yet but I haven't been pushing the milling speeds to the edge.
 

Hephaestus

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Oh no question that particular machine is huge and expensive. Last I checked you were talking a much smaller scale.

The printer for the kayak molds is fairly standard 2000x500x500 - 2040 extrusions, old school 2.85 filament, 5kg spools. Usually running 1.2mm nozzle. Yeah probably 2 days to fully print molds of the 6 pieces.

Partly why I grabbed the toolchange printer, run .1000 layers on a .4 nozzle then swap to a 2mm nozzle and fill at .5mm tall and a single perimeter.
 
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