ideas about CNC for making Vacuum forming molds

[Mike S-H]

Can anyone suggest what kind of CNC device is the best to make molds for vacuum forming. Forms max size is 600 mm х 600mm х 100mm. We do really dislike to waste shop space/ money for large size machines. Is it possible to treat wood on steel CNC vertical machining centers and vice versa.

[tenaja]

The biggest challenge to mixing wood & metal machining is the metal requires coolant, and wood is cut dry. The wood sawdust hits the oil, and won't go away. You can do it, but you should put a vacuum cleaner at the cutter to pull all of the sawdust out so it won't gum up the slides and bearing surfaces.

[coonhunter]

Mike:
We cut all our own patterns with cnc bed mils(milltronics) Just have to clean machine off after milling is done.

[jetski]

I know of some high speed graphite machines that are for sale and run 25,000 to 30,000 rpm spindles, and 1600, to 2000 ipm. This would be perfect to cut wood patterns. I have made several blister tools in the past. These machines will even cut hard steel easily up to 60 rock well C scale. They are extreamly accurate when new .002 um. tir. used you could buy them for pennys on the dollar and they would be way more accurate then your blister tool would ever have to be. They do not use coolant and come standard with 2 large 6" dia. vacume hook ups. This was to pull off the graphite dust. They also have constant air blow hooked up to the M control on the machine. They run 160i, 160mc, or 150i Fanuc controls on them. Let me know if you are interested in them and I will hook you up. gsilberberg@progressive-plastics.net

[Boots]

Most CNC Milling machines cannot machine wood because wood requires high RPM (18,000 to 24,000) and very high feed rates from (200 ipm to 800 ipm). Most metal cutting machines are not equipped to do this. Plus wood requires different Tooling altogether. Like down cutting bits so your wood will not chip out. Most Up cutting bits do not work well with wood. They do, but not well. Plus like the others stated, you will have a big ole mess to clean up what with the wood chips and dust every where.

[low_48]

I agree with Boots on the rpm issue, but wood doesn't make the highest quality vacuum forming molds anyway. You will get grain telegraphing on some of the work. Renshape is the material to use and it will cut very nicely with lower tool speeds.

[coonhunter]

We rough out our pattern using 1 inch carbides,4 flute,.600 deep@600 ipm,6000 rpms.The finish cuts use solid carbides,4 flute anywhere between 350 to 800 ipm 2500 to6000 rpm's.When we take our pine patterns off the mill the're as smooth as glass, but when sampling they will leave grain bleed thru. mdf,renboard also do well without the grain bleed thru. We run anywhere between 20 to 50 sample parts off these before sending them out to be cast. If you're not sending pattern out to be cast and your going to run a big order use renboard.

[jetski]

You can get a better and cheaper material than ren wood. It is the same formula as renwood (ceba), but much better quality, with out voids (air pockets). It is a place call BCC products in Franklin Indiana. Ask for Roger Jr. We have used this material several times and the cost is lower than Ciba the last time I bought it.
Boots many of the new high speed graphite and steel cutting machines run past the rpms and feed rates you were talking about earlier. for example Roku Roku, Okada, Makino, Roters, even Hurco has a 20,000 rpm machine. I am sure Haas has one alson.

[Boots]

yes yer right there jetski the last Mori CNC vertical mill we purchased had the option to purchase the High Speed Spindle. But we didn't see the need for the extra cost. But the way they are designing Tooling for these machines these days is radical. The speeds and feeds are going up.

[coonhunter]

jetski
How does this other material you mention hold up to heat? We form a lot of .350 and .4oo gauge material so you're looking at 6 to 8 minute cycles.
I know the ren 550 gets a little soft after a few parts and we have to let mold cool off.
There is one thing I don't like about the ren is vacuum drilling, you pull out the drill and it seems to fill back in, you have to run drill in and out a few times to make sure you got a clean hole.
What is the max.size pattern that can be milled on a Hurco?

[drcrash]

Does anybody out there use small cheap CNC machines to make large vacuum forming tools in pieces, maybe from MDF, and then fit the pieces together to make the tools?

This seems to be a good way to leverage some of the relatively small CNC routers out there, letting you vacuum form bigger stuff than you can cut directly. (You could even make pieces deeper than the CNC machine can cut, by stacking.)

Any problems with this approach? (It's something I'm tentatively planning to do, but not soon---I don't have the CNC machine yet.)

I can imagine that you'd wear a little machine out if you did much of this, and it wouldn't be cost-effective in the long run, but for just a few big items, it seems like a good way to go.

[Geof]

..... letting you vacuum form bigger stuff than you can cut directly. (You could even make pieces deeper than the CNC machine can cut, by stacking.)....

And if you were really creative you could make collapsible moulds; separate components around the periphery with a tapered plug inside. Then you could vacuum form shapes with deep undercuts and remove the mould from the part in separate pieces.