Milling Plastazote LD33 closed cell Foam - Any milling advice?

[Zeeflyboy]

Hey guys,

I've got some nice Plastazote LD33 closed cell foam https://www.efoam.co.uk/zotefoam-plastazote.php


My intention is to make some nice tool drawer inserts for the CNC (e.g. here is the model so far for one drawer - haven't placed all tools yet:

http://i.imgur.com/1L3Oafn.png


So far my experimentation has led me to conclude that it likes very fast feed rates and relatively low RPM, but i still haven't got super clean results out of it yet.

I'm currently just playing with an 8mm 2 flute helical carbide end mill that's designed for aluminium as that's the only tool I have that's long enough. I have ordered some long foam specific straight 2 flute cutters - one 3x32mm and one 4x42mm, but those will take a little while to get here as they are coming from aliexpress.


So with the 8mm 2 flute, the best I have tried so far is 6000mm/min and 10,000rpm, and for whatever reason it much prefers conventional milling to climb milling... all of which gave me this on my little test block (ignore left corner, that's where the top layer of foam didn't heat weld very well to the bottom layer):


http://i.imgur.com/YI0wJRc.jpg



Has anyone played with this stuff before? Any advice as to feeds/speeds/cutter types?

I'm guessing that the smaller diameter end mills might be quite useful in bringing the effective speed down without having to drop rpm below what the chinese spindle is happy with.

Cheers for any input!

[Boyan Silyavski]

Nice one! Is it a kind of elastic a bit? Or its like dense insulation foam? the fact that is Bicolor is amazing.

The latter i cut using finishing speeds for wood, hence 16k rpm and 1800mm/min. I have never played much adjusting speeds, as this worked from the beginning with nice finish. Then i am adjusting depth.

[Zeeflyboy]

It's got good structure but somewhat soft and giving if you squeeze it... Nothing like a rigid insulation foam, and it bounces back rather than crushes. I believe that it's a type of polyethylene foam which is available in various densities - this one is 30kg/m3

It's actually two sheets - one 30mm yellow and one 5mm black. The plastazote stuff is available in black, white, red, blue yellow or they have some cheaper similar foam in black and white only. You can then heat weld them together (carefully!) using a hot air gun to create the bi-colour piece.

I've managed to find some clean looking machining of similar looking foam where they were using single flute down cutter, so i've ordered two of those (a 3mm and a 6mm) to have a try with.


https://www.youtube.com/watch?v=UQiK28fOwEU

[Zeeflyboy]

Right, nailed it I'd say!

The below is using a 6mm single flute down cut bit (belin). Conventional rather than climb, 16,000rpm, 3000mm/min feed rate and 15mm step down (except the test collet cut out was done with a ramping helix to get the wall angle smooth).

Came out nice and clean - now I'm happy to move on to actually making the proper inserts.

http://i.imgur.com/iDYRHpZ.jpg

http://i.imgur.com/eeBH5pp.jpg

[Zeeflyboy]

Well, milled really nicely but It was stuck down too firmly and i couldn't pull it off the bed without ruining the foam :miserable:


At least I have some spare material.... sigh

http://i.imgur.com/UXV32Q1.jpg

[Zeeflyboy]

Quick video of milling this stuff:



https://www.youtube.com/watch?v=EmsdlI6nCVQ


What I learned in case anyone is interested in having a go:

- When making multi layer stuff, it's much easier to use 3M super77 spray glue to stick the layers together... that is the glue that my research turned up and you can get it in this country for a fair enough price from farnell. While heat welding works, I found it quite tricky to get the right balance between hot enough to get a good weld and not too hot to deform or damage the foam.

- Down cut router bits are definitely the way forward, gives a much cleaner edge.

- Never climb! Conventional milling all the way.... climb gives a truly awful edge finish.

- If you ever get any foam stuck on the bit, hit feed hold immediately and clear it off... it can very quickly give you a fuzzy edge cut.

- Fast feeds are good, but single flute cutter is quite happy whizzing through at around 3,000mm/min or even less which is well within the reach of most machines.

[Boyan Silyavski]

So you have mastered it it seems. I think you need now a dust shoe :joker:

[Zeeflyboy]

I do have one actually that i made a while ago - I just need to get the magnets to finish it off and actually use it!

http://i.imgur.com/JRFZiPc.jpg

http://i.imgur.com/lBflCQi.jpg

[Boyan Silyavski]

Great, is that the Chinese 70mmx3mm brush? How does it perform? I am thinking o buying from aliexpress to check it

[Zeeflyboy]

This is the one I used:

http://s.aliexpress.com/zeQvEFN7

Seems fine. On my first dust show I used some from an American place that had a neater rubber moulding around the top rather than the cloth, but they don't seem to sell it anymore. This was all I could find when doing my second one, but it seems okay.

[Foamer]

Zeeflyboy,
How did you get the caliper and knife shapes in Fusion360?

[Zeeflyboy]

Take a photo with the component you want to use, preferably with a ruler next to it for scale. Try to get things lined up as square as you can and it helps to take photo from further away with a zoom if possible to flatten the image. For best results keep the component in the centre of the image away from the border to avoid any potential issues with lens distortion.

In fusion, import the photo and scale it using either the ruler in the picture or a known distance on the component itself. Rotate and move the canvas so that it is where you want and then just draw around it using line tool and splines. I tend to hug the thing as close as possible and then do a sketch offset to achieve an acceptable tolerance.

[MPi11]

Trying to buy some of this with your initial link, but can't get through to checkout for some reason? Is this the same plastazote you used before I buy? (https://www.gbfoamdirect.co.uk/foam-cut-to-size/plastazote-foam-closed-cell-foam-sheets/)

[Zeeflyboy]

Looks to be the same stuff!

[Tigger]

Hi Zeeflyboy, your foam cutting is impressive. We have ordered a Workbee CNC machine and are waiting for delivery, as we will be using the machine to make bespoke foam inserts for the tool, UAV batteries and parts the info you have share here will be invalueble to us.

We intend to use the LD33 foam and would like to know what cutter would be best and where did you purchase them from?

Could share the cutting speed dept of cut that you have found to be the best for the LD33?

Regards

[Zeeflyboy]

As mentioned I got the best results with single flute down cut, make sure they are nice and sharp. I used Belin but there are plenty of single flute down cut bits around... Choice is probably most limited by cutter length depending on what you want to do, although there is no problem doing 2 passes with the second pass below cutter height (as long as shank is same diameter as cutter obviously), it’s just slower. I think the Belin only go up to 38mm on a 6mm cutter.

I bought those here https://www.cncroutershop.com/uk_en/top-sellers/belin-single-flute-down-spiral.html

The most important thing I found is to use conventional milling and NOT climb.

Depth of cut is fairly unimportant. The foam is soft enough that it won’t test the rigidity of any half decent machine, same goes for width of cut and it more becomes a question of having swarf that can clear easily. I had good results using 16k rpm and 3,000mm/min on the 6mm tool, and I think around 20,000 on the 3mm.... but there’s certainly plenty of room to play around there.

For hold down I would box it in if working very close to the edge, and a vacuum plate would be the easiest way to keep it stuck down.

[Tigger]

As mentioned I got the best results with single flute down cut, make sure they are nice and sharp. I used Belin but there are plenty of single flute down cut bits around... Choice is probably most limited by cutter length depending on what you want to do, although there is no problem doing 2 passes with the second pass below cutter height (as long as shank is same diameter as cutter obviously), it’s just slower. I think the Belin only go up to 38mm on a 6mm cutter.

I bought those here https://www.cncroutershop.com/uk_en/top-sellers/belin-single-flute-down-spiral.html

The most important thing I found is to use conventional milling and NOT climb.

Depth of cut is fairly unimportant. The foam is soft enough that it won’t test the rigidity of any half decent machine, same goes for width of cut and it more becomes a question of having swarf that can clear easily. I had good results using 16k rpm and 3,000mm/min on the 6mm tool, and I think around 20,000 on the 3mm.... but there’s certainly plenty of room to play around there.

For hold down I would box it in if working very close to the edge, and a vacuum plate would be the easiest way to keep it stuck down.

Cheers, I cannot wait to get started.

[tomtailford]

Zeeflyboy / Tigger

Don't suppose either of you would be able to cut some of this foam to a spec?!

I've asked around quite a few companies, some had agreed, others can't get sorted by the required date (14th April)

If this is something either of you could potentially do, would be amazing, can pay for the service!