Milli a new composite mill kit

[peteeng]

Hi All- Here's the calcs for Plank2. Will weigh and tamp the Alox as it goes in so I will know the weight ratio and volume ratio once dry filled. Then close up, tamp a little further add some thru a top hole if needed and then bag up... Peter

[mactec54]

G-penny, I did not know about them, sadly though, some of their shipping prices are kind of artificial, meaning way overpriced for the shipped weight, the cheaper ones makes sense but the better ones shipping almost as high as the spindles, add customs on top of that and you can get something from Teknomotor instead for the same price. Plus you get torque curves from Teknomotor.

Anyway I found this obscure paper on a 'budget' 2-axis milling head. Like those adjustable angle heads but on steroids. I made mockups using 23x10.2x1.7(1mm thick) bellevilles from schnorr and I was able to shorten a bt30 shaft and still get about +3500N on the toolholder while also freeing enough space at the end to put 2 bearings and squeeze a small hydraulic cylinder at the very end. The whole cartridge ended up being approx. 240mm. For the side gears I used mod1 72 teeth helical spur gears. and everything fit just nicely. So space wise it's doable.

The question is who's gonna make it...

Who would want to have this hanging on the end of a spindle, it would not be very stable for doing normal cutting and the index accuracy would be poor as well

[mactec54]

Hi All - Re G-Penny 4 pole. They have responded over a couple of messages until I get the message right with my "Friend". They only have the 4 pole 24000rpm available so shall look at tecknomotor they have 12k rpm in their list... Peter

They make a good spindle, Ok if you like the air cooled spindle and the noise from the fan 12000 RPM at 200Hz check the Pole count this normally indicates that it is only a 2 Pole motor

[peteeng]

Hi All - I looked up the notes from Plank 1 and it was filled at 60% Vf that was until the mould separated! . This means the Alox/Ep mix is nearly the same density as aluminium. See calc attached. So when I do the side by side cantilever test this will tell us if the alox is stiffer then the aluminium using gravity alone...Aluminium is a tad over 2700 depending on the alloy and my estimate for this mix is 2775kg/m3. I do not know the correct density for the alox I have but I think the 3920 is close... Peter

[peteeng]

Hi All - Heres a small carbon fibre mill - Peter

https://roboticsandautomationnews.co...obotics/17994/

[peteeng]

Evening All & others - Started waxing Plank2 today and thinking about the best way to fill it. I decided to get rid of the steps in the sides of the moulds as they could become "races" for the resin if it decides to go under the al strips to the outside of the mould. So I planed them off. Once assembled I'll put masking tape down the edges and this will stop any resin race from happening. Resin will take the easiest route (like electricity or water) from start to finish. Woke up to a surprise in the loo this morning... Looked at my tubes and fittings and need to buy some T's for this fill so will get those tomorrow. I think I'll try this fill vertically to make sure it fills well. Its cold here at the moment so resin is a bit thick will have to wait for a warm afternoon. So two more waxes and I'll assemble and load the mould... Peter

Re: Milli itself - I have been back through the thread looking for gems and clues to how to go fwd when I start designing again. Putting the search for E70 casting material aside the base seems to be a bit of a hurdle. So I may do some parametric studies of the base to see how to resolve that component then ramp up the search for the Grail again...

[peteeng]

Hi All - I've decided to get some MTI tube for this fill. When the mould has no flange it is difficult to control the internal pressure once filled due to various technical effects. The mould tends to decompress once filled due to reduced internal pressure from the resin port and outgassing from the resin... MTI allows the outgassing to escape without letting the resin out which keeps the bag under negative pressure. I pick this up next monday so you will have to wait a wee while for Plank2. I want to make Plank2 a really good plank.

https://german-advanced-composites.c...n-suction-hose

will keep uz in the loop... Peter

[peteeng]

Hi All -------- Started to think through the infusion set up. Decided to do a middle resin port vs at an end. Its quite cold here (for Oz) and in summer 1200mm is no problem for resin to flow. The middle port means it only has to flow 600mm, so much more reliable this time of year. Plus using the MTI tube means I don't have to worry about a long "wet time" which is the time from part fill to the time of resin gelling. This is when things go wrong with bags as they may decompress or start to leak for various reasons.

The cloth wrap provides a vacuum path, the system has to "communicate" with the vac pump until the resin gels. Maybe 1hr this time of year... I got a new Droid yesterday, my old Droid was held together with masking tape and elastic bands, was time for an upgrade. The salesman had a hood and was covered in sand... ... Peter

[peteeng]

Hi All - I have been asked a couple of Q's about vibration lately here's a good video... Peter

[peteeng]

Morning all - a small article on carbon fibre tooling ... Peter
https://www.mmsonline.com/articles/c...osite-infusion

[peteeng]

Hi All - Plank2 set up keeps peering at me on my bench. I will try to forward it this week. Peter

[--JawZ--]

Loving the content in here so far Peter, very informative for my own "mini" machine build

// Ander

[peteeng]

Evening All - Spent some time on Plank2 setup today. Been too cold to do a nice infusion but maybe tomorrow. So I mustered all the gear and roughly set it out. Tested the vacuum system as it hasn't been used in a while and I'm happy with its ultimate pressure. I'm using a plastic vac tube for this one. Silly me has put the clamp screws on the bottom of the mould (or mold) so once filled I'll have to clamp it and roll it over then screw it together... I put the mid port in so it only has to flow 600mm. The bottom pressure was 169Pa and 101000Pa (14.69psi) is 1atm. So its 99.83% vacuum. So if the mould volume was 1000ml it would still have 2ml of air in there. So will have a new Plank soon... Peter

[peteeng]

Evening all and sundry - Well I thought today may have been Plank2 day but alas I started late getting other stuff done and by the time I got the bag down the temp was dropping so I'll do it tomorrow midday when its warmest. Bag came together well. The fill is over 60% by volume. Being 40% void I'm sure if this was a closed mould I could just pour the epoxy in and it would fill neatly no need for vacuum. But here we go with vacuum for this one. The pack for 60% V solid should weigh 1.322kg and I poured in 1.333kg so close to +60% by volume. The bag came down to below 500Pa, so happy with that, a good one hour vac soak will boil off lots more water and I expect to get better then 500Pa... 500Pa absolute is a good process pressure and the resin will fill fast... So we wait for good temp tomorrow Peter

for those eagle eyed onlookers you can see that the absolute pressure guage has a saturated vapour temperature output. In this case its -2.2C so being 19deg C ambient means the water in the timber and AlOX is boiling off quite well as the ambient is >> -2.2C... one hour vac soak and I expect the water to be gone, this means the epoxy will stick to everything in the bag very very well.

[peteeng]

Good day all - Yah Plank2 is off my list. A bit cold but did it anyway. Fill was extremely slow due to thick vanilla resin took 40min to get to the first witness mark so I'm happy I did the middle port not from the end. But it did fill up and a slow fill is a good fill... less porosity due to turbulence. The bubbles at the exit hardly rose through the piping telling me its very thick. But all the weighed resin went in so its full. So tomorrow will put it in our warmer for 24hrs to get it nicely cured then I can release it. So its a couple of days away ladies and gents. Sorry to keep you in suspenders! The witness 1 is the hole I filed the cavity with by the way.... Peter

[peteeng]

Evening all and sundry - Been down to see how the Plank is doing. The pot has gone off but the part hasn't so I suppose that's tonight sometime. I need to wrap it in an electric blanket if I had one, its in our honey warmer! . But the vac line has some bubbles in it as it should, so I thought I'd chuck some bubble trivia at you. I've been involved with composites for over 30 years and its an ongoing discussion and concern (especially in aerospace) about laminate porosity. Aerospace love autoclaves because they provide a positive pressure so the bubbles get compressed into the laminate (as a saturated gas) There have been no crashes attributable to porosity or failures that I know of. Its a hangover attitude from metals which do suffer transverse fracture and fatigue from internal and external defects. Its also known that laminates do not suffer stress fatigue. So the "bubbles here" image shows the bubbles in the low vacuum zone. They are under slight vacuum. If I squish the tube and put it under pressure the bubbles disappear. This is what happens in an autoclave. Removing the saturated gasses (degassing or deairing) is done when possible to fix this issue. I did not degas Planks resin not needed in this application. These bubbles where created or initiated as they came through the last bit of AlOx in the tube. This is the same mechanism as a champagne bubble stream from a small defect in a glass or something with lots of crevices like sugar / alox... Peter

[badhabit]

.... AlOX ...

Have you considered using pure corundum instead? I'm a bit skeptic about the performance with the impurities in the alminium oxide you are using...

I'd also like to see a sample with a fuller-matched grading of this plank using alox... i know you don't agree on the whole grading stuff(lets not go there), but it would be interesting to see real-life examples anyway ;-)

/Thomas

[peteeng]

Hi Thomas - Corundum and alpha alox (see except from SDS for the material) are the same thing. If you make a fuller grading mix please test and tell me what its solid volume fraction is. This is a theoretical mix based on spheres which in practice does not work, from others work in this forum. But always open to new information. Concrete with micro fines does get higher solid ratios. Many of the high modulus values are determined from compression tests which is not a suitable test for machine parts. Need to do flexure and tensile to get the full picture. My current thoughts are to use local CSA hydraulic grout. Its half the cost of epoxy and 40GPa out of the bag, easy clean up, just add water etc...... this alox test is to check what the alox can offer as it is the highest stiffness additive I can find. By the way I calculated the density from the Plank2 constituents and I estimate its 6% denser then aluminium. So the cantilever test is nearly apples to apples. if the alox deflects less which using ROM it should, then I shall pursue further. A couple of days until I can do that. Checked the Plank and its gelled so good to get into the warmer tomorrow... thanks for participating Plus Plank2 maybe not a good shape when I release it, its still a mystery part...

I have found a cheap source of short fibre carbon fibre (china as usual) . Waiting on info if they can get me a sample lot vs buying 40kg then that will be Plank3 ! .... Plank3 maybe the CSA Peter

https://en.wikipedia.org/wiki/Aluminium_oxide

[badhabit]

..If you make a fuller grading mix please test and tell me what its solid volume fraction is. This is a theoretical mix based on spheres which in practice does not work, from others work in this forum. But always open to new information. ...

I already did: https://www.cnczone.com/forums/epoxy...ml#post2434014

Which is why i thought t be nice to see if the same could be achived with aluminium oxide....

/Thomas

[peteeng]

Hi Thomas - yes I remember that. Cement is interesting chemistry, its more complex then its solid ratio. It has ingredients that modify surface tension, particle dispersion and attraction and the binder is very very fine. Its hard to find for me, useful technical info on it as they (civil engs) are looking for other things then what we machine builders are looking for. The E90 material is silimax with alumina/alox/carborumdum etc added. Its time for me to move along to building vs research.... Peter

edit - 1) Thomas would you send me a cup of Silimax? if so PM me for my address.
2) Heres Plank2 in the honey warmer 30C and my electric blanket