I'm having new molds built, mainly cuz i need a rocker mold, and i also want more length options, etc.
Anyway, one cnc guy recommended we just make a giant block out of smaller hardwood pieces, or whatever we decide to use, and router out the whole thing 3d, as opposed to trying to line up 20 strips while bolting/glueing them together. Anyone done it this way? After seeing some of the samples of the 3d work I think it can come out real solid. And it might actually end up cheaper. We're gonna try to do some small mockups first before going for it.
new molds questions
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knightsofnii
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new molds questions
Doug
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doughboyshredder
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I hadn't thought of that. Definitely sounds like the correct way to do it. Does this make it a lot harder to do the cad drawing though? I would assume there would be more work involved and more cost, but I still haven't got my cad guy out here yet.
I think I am going to look in to having my tip and tail blocks redone this way.
I think I am going to look in to having my tip and tail blocks redone this way.
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Head Monkey
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I’ve done it… once. I cut an entire mold, including nose/tail blocks out of one big glued up block of MDF. I still build my molds by cutting 21 pieces and bolting them together 
It’s faster, and has acceptable accuracy.
It’s a time/accuracy tradeoff, or a money/accuracy tradeoff if you’re contracting out.
The machine time to make a mold like that is significantly longer than doing it the 21 piece way. You use a cylinder to shape a 3D surface, and that leaves “cusps” (like little waves) of greater height the further away from horizontal the surface gets. You have to make more passes to lower the cusp height until you don’t care about it anymore. More passes = more machine time.
Couldn’t quickly find a good example of this online, but this page from Haas has something that will give you the idea about half way down: http://www.haascnc.com/solutions_3D.asp#3D. I can’t imagine how long it’s taken that machine to make the bowl in the picture doughboyshredder included above with that tiny bit… hours and hours, I’m sure…
Our mold surfaces are blazingly simple. It’s a whole extra 30 seconds of work to turn the outline into a surface in a reasonable CAD package once you know how. The extra software time will be in the CAM package, and it’s probably longer for the 21 piece way actually. To layout the toolpaths for the 21 piece way, you need decent nesting software ($$$), or take the time manually. Not too hard to do, and even a cheap CAM package enables the manual way easily. For the 3D way you need a CAM package that supports 3D and that does a good job of converting a surface to a tool path that meets the cusp tolerance you’re willing to accept. For a surface this simple, again, a relatively cheap CAM package should do it. If you’re contracting out, you should find programming cost a wash in terms of cost, since any decent place will have good CAM software that supports nesting and 3D surfaces easily.
It’s faster, and has acceptable accuracy.It’s a time/accuracy tradeoff, or a money/accuracy tradeoff if you’re contracting out.
The machine time to make a mold like that is significantly longer than doing it the 21 piece way. You use a cylinder to shape a 3D surface, and that leaves “cusps” (like little waves) of greater height the further away from horizontal the surface gets. You have to make more passes to lower the cusp height until you don’t care about it anymore. More passes = more machine time.
Couldn’t quickly find a good example of this online, but this page from Haas has something that will give you the idea about half way down: http://www.haascnc.com/solutions_3D.asp#3D. I can’t imagine how long it’s taken that machine to make the bowl in the picture doughboyshredder included above with that tiny bit… hours and hours, I’m sure…
Our mold surfaces are blazingly simple. It’s a whole extra 30 seconds of work to turn the outline into a surface in a reasonable CAD package once you know how. The extra software time will be in the CAM package, and it’s probably longer for the 21 piece way actually. To layout the toolpaths for the 21 piece way, you need decent nesting software ($$$), or take the time manually. Not too hard to do, and even a cheap CAM package enables the manual way easily. For the 3D way you need a CAM package that supports 3D and that does a good job of converting a surface to a tool path that meets the cusp tolerance you’re willing to accept. For a surface this simple, again, a relatively cheap CAM package should do it. If you’re contracting out, you should find programming cost a wash in terms of cost, since any decent place will have good CAM software that supports nesting and 3D surfaces easily.
Everything I know about snowboard building, almost: MonkeyWiki, a guide to snowboard construction
Free open source ski and snowboard CADCAM: MonkeyCAM, snoCAD-X
Free open source ski and snowboard CADCAM: MonkeyCAM, snoCAD-X
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knightsofnii
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Yea this guy does all kinds of 3d artwork and relief and stuff like that.
I'm almost thinking it may be cheaper this way, we can make the top molds ourselves using the strip method and 2x4's really.
I'm thinking its going to run me about 200-350 per mold for the first one,
then for the rest it's just making different center sections, so probably less.
I'm almost thinking it may be cheaper this way, we can make the top molds ourselves using the strip method and 2x4's really.
I'm thinking its going to run me about 200-350 per mold for the first one,
then for the rest it's just making different center sections, so probably less.
Doug
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knightsofnii
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yea i'm thinkin stacking the normal strip way is better though, dont know how those lego layers will hold up to shear stresses.
we can possibly bandsaw the strips close, then let the cnc take care of the rest.
he's gonna do a mockup for me with some leftover material, then we'll take it from there.
we can possibly bandsaw the strips close, then let the cnc take care of the rest.
he's gonna do a mockup for me with some leftover material, then we'll take it from there.
Doug
I get what you're saying now. I'm used to seeing the CNC process used to make molds where the composite is just layed up and either vacuum formed or just allowed to cure without pressure.
If MDF were glued up lego fashion like in that picture it would shear off. Like you say, get the pieces close with a bandsaw then glue them all up and let the CNC smooth the final surface.
Man, I need to find a CNC operator out here...
If MDF were glued up lego fashion like in that picture it would shear off. Like you say, get the pieces close with a bandsaw then glue them all up and let the CNC smooth the final surface.
Man, I need to find a CNC operator out here...