Cutting insulation foam

[performancenut]

I'm planning on using Dow Highload 60 (http://building.dow.com/na/en/products/insulation/highload60.htm) to make some vacuum molds. I'm fairly new to ShopBot, so I'm unsure what settings to use (feed rate, plunge rate, and spindle speed). Current default for the 2mm ball nose is 12k RPM, 20 mm/sec feed rate, and 10 mm/sec plunge rate. I don't need to make this in 60 seconds or less but I also don't want this to run all day. My initial test molds are small, so it won't make much difference (maybe save a minute or two). However, the larger molds are taking upwards of 2 hours each or more (software estimate) so this could save a significant amount of time tweaking these.

Second question getting improved details. The piece I have has a combination of curves (horizontal and vertical), flat angles, and flat verticals. The ball nose is doing a great job on 90% of it but isn't squaring off the 90* angles like I'd like. Is there a way to add another finishing pass with an end mill bit or would I have to restart the job again but this time using a different bit for the finishing tool path? If the answer is the latter, since it is only cutting a minute amount of material, would I change any of the feed and speed settings?

[steve_g]

Denis
Check out this thread... especially page 2 and Steve Knights testing. See if this answers any of your questions!

SG

http://www.talkshopbot.com/forum/showthread.php?t=15076&highlight=foam+cutting+speed (http://www.talkshopbot.com/forum/showthread.php?t=15076&highlight=foam+cutting+speed)

[myxpykalix]

I'm sorry i can't give you specific feeds and speeds however i can tell you that if you go too fast you risk creating too much heat that re melts the foam shards onto your bit...(ask me how i know:rolleyes:)

[knight_toolworks]

you can't really get away with a shaft of a tool rubbing the foam. so you need flutes as long as your depth of cut.

[myxpykalix]

now you tell me....:rolleyes::D

[performancenut]

you can't really get away with a shaft of a tool rubbing the foam. so you need flutes as long as your depth of cut.

Any idea where to find bits that have long flutes? The ones I have found are pretty short. Sorry for the newb questions but this is new to me.

[bobmoore]

You can sometimes use bits that have the cutter larger diameter than the shank.
Bob

[performancenut]

Well, I finally made my first piece today. I was rather impressed with the results. As feared, the corners are weak but someone recommended using epoxy to reinforce it before molding.

[Billions]

Denis - looks great! I know it's been about 6 months since you posted this stuff but I've been cutting foam and looking for more tips online myself. As for holding down the piece, I use 3M Super77 spray on the bottom surface and stick it to my spoil board. Foam is very light and shifting or moving hasn't been a problem. It's actually proven to be a little difficult to get parts off the table again in some cases.

I found some info here at Streamline, with their "Frog" line, specifically about long bits and coating solutions after the cut to protect and strengthen the final piece.

Seems that these bits might require a custom collet system (lame) but at least it's a start -

http://www.3dcutting.com/solutions/frogtools.html

Their FrogCoat looks interesting for coating the final pieces.

A friend told me about a product called AquaResin that also coats foam and seals it, allowing you to use paint that might normally attack and dissolve the foam.

http://www.aquaresin.com

[steve_g]

** ATTENTION ** FROGTools™ should not exceed 6000 RPMs. Please contact Streamline Automation for more details before use.

SG