Little test - CNC Knee Mill/Router vs kaizen foam

[bkharman]

Thanks for the update Matt!  Great first run (even though it didn't turn out the way you wanted). My Dev team finished a sprint today that they had been working on for almost a year. Crazy amount of rejections before we got to a final version.

Thanks for being persistent.  Look forward to your next "sprint".

Cheers. Bryan.

 

[fritter63]

Thanks for the update Matt!  Great first run (even though it didn't turn out the way you wanted). My Dev team finished a sprint today that they had been working on for almost a year. Crazy amount of rejections before we got to a final version.

Thanks for being persistent.  Look forward to your next "sprint".

Cheers. Bryan.

Whahhhhhhhh? (Software?) sprints are supposed to be two weeks. If it lasted a year, you're not doing agile development! [emoji12]

 

[bkharman]

We are... Have been a full blown DevOps shop for 3 years or so...but... Some things handed by investors and need to show some PM status on occasion and can't "die" but are not exactly our cup of tea... Time is of the (non) essence.

It was an xx-small effort

Cheers. Bryan.

 

[rmwarren]

[member=27782]Scorpion[/member] FWIW I suspect your end mills have the wrong geometry (don't know the technical terms) i.e. a spiral that is too "short" for foam, and perhaps the mill runs too slow compared to a CNC router. Here's a photo of my brand spankin' new, unused, foam cutting bit next to a bit meant for wood/composites:

[attachimg=1]

In your video the end mills don't seem to be getting much "slicing" action, which I did notice in other YT videos of foam cutting.

I hope to give this a test myself next week something, my new cnc has a bricked controller board so am waiting for the replacement to arrive. Thanks for continuing to post your results.

BTW - was really interested in the process of heat-laminating the foam, I did not realize that was a viable method. Does this apply to many/most foams or is it specific to the type you chose?

Thanks,

RMW

 

[Scorpion]

Thanks for the update Matt!  Great first run (even though it didn't turn out the way you wanted). My Dev team finished a sprint today that they had been working on for almost a year. Crazy amount of rejections before we got to a final version.

Thanks for being persistent.  Look forward to your next "sprint".

Cheers. Bryan.

Whahhhhhhhh? (Software?) sprints are supposed to be two weeks. If it lasted a year, you're not doing agile development! [emoji12]

It's probably language.  Anything that lasted a year had to be smaller iterative cycles with demo's, (re)prioritization efforts, design activities, etc.  Hard to know unless you're inside.

Sounds like the definition of done is tightly coupled to acceptance even to a fault.

 

[Scorpion]

It was an xx-small effort

Cheers. Bryan.

Lol...it always is.  [emoji6]

 

[Scorpion]

[member=27782]Scorpion[/member] FWIW I suspect your end mills have the wrong geometry (don't know the technical terms) i.e. a spiral that is too "short" for foam, and perhaps the mill runs too slow compared to a CNC router. Here's a photo of my brand spankin' new, unused, foam cutting bit next to a bit meant for wood/composites:

[attachimg=1]

In your video the end mills don't seem to be getting much "slicing" action, which I did notice in other YT videos of foam cutting.

Thanks,

RMW

I'm going to split my response in two to simplify it.

I completely agree with your observation.  The tool geometry isn't correct I suspect.  First I'll cover what I used, then what I think I need. 

Left to right - 3/8-inch ball and 3/16-inch mill which I use for aluminum and plastics, and the right is the up-cutting 1/4-inch bit for wood. 

I have a lot of end mills but not a lot of different profiles within.  I selected these three for my test for specific reasons.  The up-cut has a specific end-cutting angle that draws the chips up.  See how the opposing cutting edges on the tip make a slight V?

A regular profile tip is flat

I believe that portion of the tool grind is called the edge concavity angle in the pic below.

In hind sight, I don't think we want the foam to be pulled up as its being cut because the material removal would draw up and maybe push the  surface foam out of the way causing what I experienced.  However I notice yours is up-cutting so that theory is out.

The smallest end mill I wanted to try because it had normal chip removing properties and a slightly less helix angle more similar to your foam cutting bit.  Not down cutting per-se, but not up-cutting.

My theory being the ball was that the radius of the ball would naturally lay the foam down as it was cutting because of the radius end.  Seemed to work that way and worked the best.

Your end mills are so small it may be difficult to see but here's what I'm guessing the grind/profile is.  The edge in the flute most likely has a more positive (simplified difference in pic below)

Radial rake and a more extreme radial cutting edge. 

Both of which should effectively sheer, or pull the foam as it cuts, instead of push it out of the way.  Your thought on RPM may have something to do with it.  There's no way I could ever generate the equivalent surface speed as a router on my mill.  Did the end mill you got come with recommended surface speed settings?

 

[Scorpion]

[member=27782]Scorpion[/member]

BTW - was really interested in the process of heat-laminating the foam, I did not realize that was a viable method. Does this apply to many/most foams or is it specific to the type you chose?

The site that sent me the foam had a how-to section on lamination.  All three types and both densities of the closed cell foam laminated perfectly.  Of i didn't mention it above, over heating caused the foam to collapse actually which I believe is really just the internal cells laminating as well. 

This told me that the ability to laminate had nothing to do with the surface treating of the foam and it was actually the foam itself.

An interesting test would be to attempt to laminate some kaizen foam and see if it does as well.  If it also does I may speculate that maybe closed cell foams do.

I know not all foams laminate.  Some I've heated in the past, both by mistake and intentionally, have done weird things. 

 

[rmwarren]

[member=27782]Scorpion[/member] FWIW I suspect your end mills have the wrong geometry (don't know the technical terms) i.e. a spiral that is too "short" for foam, and perhaps the mill runs too slow compared to a CNC router. Here's a photo of my brand spankin' new, unused, foam cutting bit next to a bit meant for wood/composites:

[attachimg=1]

In your video the end mills don't seem to be getting much "slicing" action, which I did notice in other YT videos of foam cutting.

Thanks,

RMW

I'm going to split my response in two to simplify it.

I completely agree with your observation.  The tool geometry isn't correct I suspect.  First I'll cover what I used, then what I think I need. 

Left to right - 3/8-inch ball and 3/16-inch mill which I use for aluminum and plastics, and the right is the up-cutting 1/4-inch bit for wood. 

I have a lot of end mills but not a lot of different profiles within.  I selected these three for my test for specific reasons.  The up-cut has a specific end-cutting angle that draws the chips up.  See how the opposing cutting edges on the tip make a slight V?

A regular profile tip is flat

I believe that portion of the tool grind is called the edge concavity angle in the pic below.

In hind sight, I don't think we want the foam to be pulled up as its being cut because the material removal would draw up and maybe push the  surface foam out of the way causing what I experienced.  However I notice yours is up-cutting so that theory is out.

The smallest end mill I wanted to try because it had normal chip removing properties and a slightly less helix angle more similar to your foam cutting bit.  Not down cutting per-se, but not up-cutting.

My theory being the ball was that the radius of the ball would naturally lay the foam down as it was cutting because of the radius end.  Seemed to work that way and worked the best.

Your end mills are so small it may be difficult to see but here's what I'm guessing the grind/profile is.  The edge in the flute most likely has a more positive (simplified difference in pic below)

Radial rake and a more extreme radial cutting edge. 

Both of which should effectively sheer, or pull the foam as it cuts, instead of push it out of the way.  Your thought on RPM may have something to do with it.  There's no way I could ever generate the equivalent surface speed as a router on my mill.  Did the end mill you got come with recommended surface speed settings?

[member=27782]Scorpion[/member] - full disclosure, I know absolutely nothing about what I am talking about when it comes to feeds/speeds/bit geometry, total seat-of-the-pants effort for me. Once I get my shop in good order I hope to really spend some time experimenting and learning about the equipment I have.

The bit I purchased is an Amana 46274 - feeds/speeds are listed here in detail but looks like they recommend 18K RPM and .004-.006" chips.

[attachimg=1]

This is the video I referred to, lots of HP & speed, appears there is little to no up-cutting action and the bit seems to shear the foam off.


From the poster's comments:

Milling PE30 Polyethylene foam on a CNC mill.
7200 rpm, 4 flute 12mm HSS cutter.
Feeding at 2000 or 3000 mm a min, from memory.

So if I understand any of this correctly 4-flutes @ 7,200 RPM is equal to 2 flutes @ ~14K RPM? does this mean more flutes would be better on your mill?

If I get to run a test next week I will post a video to have a comparison.

RMW

 

[rmwarren]

[member=27782]Scorpion[/member]

BTW - was really interested in the process of heat-laminating the foam, I did not realize that was a viable method. Does this apply to many/most foams or is it specific to the type you chose?

The site that sent me the foam had a how-to section on lamination.  All three types and both densities of the closed cell foam laminated perfectly.  Of i didn't mention it above, over heating caused the foam to collapse actually which I believe is really just the internal cells laminating as well. 

This told me that the ability to laminate had nothing to do with the surface treating of the foam and it was actually the foam itself.

An interesting test would be to attempt to laminate some kaizen foam and see if it does as well.  If it also does I may speculate that maybe closed cell foams do.

I know not all foams laminate.  Some I've heated in the past, both by mistake and intentionally, have done weird things.

I just ordered some samples to try it out myself. This looks better that Kaizen to me, they show how you can cut the top layer first then laminate it, should works great for most toolbox needs:

[attachimg=1]

RMW

 

[Cheese]

[member=27782]Scorpion[/member]
Do you heat both layers to laminate or just 1 layer?

 

[rmwarren]

[member=27782]Scorpion[/member]
Do you heat both layers to laminate or just 1 layer?

[member=44099]Cheese[/member] - here's their link:http://www.toolfoam.com/lamination.asp

RMW

 

[Cheese]

Thanks Richard...so if i'm understanding the process correctly, both pieces of the foam will be heated at the same time...that makes sense.

That should also ensure a very strong bond between the two, probably stronger than an adhesive bond.

 

[rmwarren]

Thanks Richard...so if i'm understanding the process correctly, both pieces of the foam will be heated at the same time...that makes sense. That should also ensure a very strong bond between the two, probably stronger than an adhesive bond.

I believe that is so. They also sell a PSA foam, but from their comments it sounds like that bond is not as strong.

They have some good specials, no idea how bad shipping cost it cross country but I will probably give them a try.

RMW

 

[Scorpion]

Thanks Richard...so if i'm understanding the process correctly, both pieces of the foam will be heated at the same time...that makes sense. That should also ensure a very strong bond between the two, probably stronger than an adhesive bond.

I believe that is so. They also sell a PSA foam, but from their comments it sounds like that bond is not as strong.

They have some good specials, no idea how bad shipping cost it cross country but I will probably give them a try.

RMW

Richard is right, heat crates little bubbles on both sides.  When they touch, it works like adhesive.  Very strong bond more like its fused than glued.

The specials do seem like a good deal.  I'd recommend asking them for some samples and trying out your fooling before messing with shipping.  They sent me enough to run multiple tests, certainly enough to know what I'm dealing with before going all in.

This weekend I'll order some end mills so I can try them against my samples.

 

[Holmz]

Can the foam cut with a hot knife or hot wire?

 

[nclemmons]

I don't think you can cut as accurately with a hot knife or a wire.  I've cut styrofoam in the past with a hot wire and you get shrinkage far greater than what the video that RMW shared above.

That looks like the best alternative I have seen thus far.  Very interested in further learning on this.  Kaizen with tracing with a knife and then plucking is not that consistent.  This looks to be near perfect if it works.

Thanks for sharing your learnings, guys!

 

[Scorpion]

Milling PE30 Polyethylene foam on a CNC mill.
7200 rpm, 4 flute 12mm HSS cutter.
Feeding at 2000 or 3000 mm a min, from memory.

So if I understand any of this correctly 4-flutes @ 7,200 RPM is equal to 2 flutes @ ~14K RPM? does this mean more flutes would be better on your mill?

If I get to run a test next week I will post a video to have a comparison.

RMW

Never replied to this, sorry. 

You're correct, more flutes and larger diameter tool would increase the surface speed.  It can have other detrimental side effects as well surrounding heat and chip evacuation but that's unlikely a factor in foam.

My max speed is about 3300rpm.  I'd have to plug everything into a calculator to see if I can get there.  Even if I can't though, the cut quality may be good enough that no one could tell.  I never run at the recommended settings with other materials anyway.

Looking forward to your results.

Matt

 

[fritter63]

Can the foam cut with a hot knife or hot wire?

Yes, I've seen vids but requires spindle control so you can turn it only when needed . Also requires you to cut all the way through which isn't always desired.

 

[Cheese]

Can the foam cut with a hot knife or hot wire?

The owner of a CNC can use a drag knife, however they are usually restricted to a 1/4" cutting depth and sharp corners are hard to achieve unless you modify the CNC tool path.
http://donektools.com