[peteeng]

Evening All - I have ordered a diamond coated bit to trial. I picked up another bucket of CF last week and realised I have several buckets of the stuff to use. So may use it on Frankenrouter parts. The supplier recommends 2000rpm and wet. But my spindle is 6000rpm min so we'll start there fast and light. Anybody experienced with diamond grit tooling? It will be 40-50 mesh and 6mm diameter... Peter

[peteeng]

Hi All- I have been waxing and polishing the glass and now at 6 coats I can plan the cast.... Peter

[peteeng]

Hi All - Australia has been rebranded. Image wise we are now a kangaroo consisting of three types of boomerangs. Spose its better then the shrimps thing.... Peter

https://www.brandaustralia.com/

[peteeng]

Morning All - The material test program has started again, that's the good news. The not so good news is that I can't get the target fibre volume I want Vf=50%. The Random carbon fibre billet stack gets about 25% and the short fibre CF gets around 13% which is too low to be helpful. The short CF is really fluffy and has small balls of fluff in it which stops it from debunking. I'll still make the billets to check it out. This is pushing me back to aluminium powder in which I achieved better then 60% Vf... I'll cast these to see how that goes... Low Vf means it will vac cast very easily.... The CF is mainly woven which mean the fibres have crimp and its compressed thickness is twice as thick as a flat fibre stack.... Hence the low Vf. The cavity should accept 400g of CF at 50% Vf but I only got 230g stuffed in... Peter

[peteeng]

Evening All and Sundry - A couple of things today:
1) I cast the CF samples. The short fibre surface was a bit bumpy as expected. The fill didn't go as expected and I had to use a syringe to get the middle to fill.
The resin raced around the edge of the mould and closed it out. But I did fill it. Release it tomorrow
2) I did a test cut with the diamond burr. Went quite well dry cutting.... so maybe that's a way forward with some of the parts. Odd looking at it it glitters and doesn't look like its turning...
3) I cut the hole for the washroom sink. Now can finalise the plumbing....

Been a good day. Peter

[luke peter]

This is an amazing thread Peter. It would have spared me many hours if I had stumbled across it a year ago

[peteeng]

Ta Luke - bit of a tome. Useful to look back on. Peter

[peteeng]

Morning all you lot - Released the coupons today. Very happy with the fill but the short CF cast is too thin in spots to block for the test I think. I'll block the Random CF block to see how that goes. I've sent a note the CF fibre supplier to see if they have 3mm fibers vs the 12mm fibres. The steel fibres are closer to what I want at the moment. So next cast is AL powder. Had a little trouble getting the part off the glass. 6 double coats of wax not quite enough. Had to warm the glass to get it and the excess resin off. Clean it up and 12 coats next time! But as it gets used it gets better... Peter

[peteeng]

Evening all and sundry - This evenings job was to level the random CF billet. This prepares it for blocking. I'm not sure if this will be a test piece yet. After blocking I'll decide. I may level the short CF cast but there won't be much left of it if I bring it right down. I'll guage it tomorrow.

levelling billet - using 18mm bit to level
billet CF - adding 5g of resin to the surface to make it shiny and smooth.... Peter

[peteeng]

Evening all - Todays job was to cut the blocks out of their frame and true the edges. I didn't get to the truing as a friend dropped in and wanted a fret board cut for a slide guitar his making. I decided to do it on the spot to get it done. He'll fill the engraving with black epoxy. I'll set up my vacuum table to do the CF truing... The CF short fibre coupon I decided to keep and not test, it doesn't have enough CF in it and its really lumpy and no way to get rid of the lumps in a real part I think, so that fibres out.... I think I'll cast an aluminium and steel one next. Peter

[peteeng]

Evening all - Today I blocked the CF billet on Brevis and weighed it and measured it up. Its approx density is 1273kg/m3 which means its fibre volume ratio is 30%. This is better then I expected. Its approx half the usual if I'd used multiaxial cloth vs woven cloth. I usually get 58-60% fibre volume at 1450kg.m3 I used the diamond bit for this profiling & it cut well. I may slice this up and send it for modulus test but I'd like to also send the aluminium grit sample as well. Peter

That's brevis1 last job for me. It gets picked up tomorrow by its new owner and goes north to make bread boards and signs.... need to get Brevis2 rebuilt now...

[ardenum]

Hey Peter

I came across a paper about a honeycomb carbon fiber worktable. Something for your collection maybe...

https://www.mdpi.com/1996-1944/14/1/74/htm

[peteeng]

Hi Ard - Thks for that. Got to be careful with hollow bases on machines. They will slowly fill up with lub or moisture if not vented correctly. Been involved with honeycomb constructed yachts over many years and some slowly fill up with moisture. So I'd prefer a high density foam sandwich with CF skins. Even then I'm worried that lub will slowly degrade the sandwich. I hope to get an aluminium powder sample built then I can get the CF, steel and al coupons tested for modulus....Peter

[ardenum]

Hi Ard - Thks for that. Got to be careful with hollow bases on machines. They will slowly fill up with lub or moisture if not vented correctly. Been involved with honeycomb constructed yachts over many years and some slowly fill up with moisture. So I'd prefer a high density foam sandwich with CF skins. Even then I'm worried that lub will slowly degrade the sandwich. I hope to get an aluminium powder sample built then I can get the CF, steel and al coupons tested for modulus....Peter

huh, that's interesting, are we talking about a completely closed off structure or half closed like in the paper?

[peteeng]

Hi Ard - If the structure is completely closed off. Plastics (epoxy) are semipermeable. If you have a high humidity outside then the moisture will travel through the plastic to the inside then condense. Only small but over a long time can fill the voids. Peter

[peteeng]

Hi All - Been a while since I've been on my machines so today I did a couple of little jobs to catch up. I have been epoxy coating benches and with the left over I added some pigment I picked up and mixed in some aluminium powder. Today I used my "corn cutter" tool on it for the first time. Went well. Plunge needs to be slow or use a ramp to engage. This will be the machined areas of the next design. Cast in CSA-UHP concrete. Cast in pockets so second cast will be the aluminium epoxy then machine that to finish.... I also did a plaque for a friend.. Peter

[peteeng]

Evening All - Milli has bubbled up in my consciousness again. I'm thinking along the lines of an octohedral-hexapod frame around the machine. Here's some info on stiffness. The article also quotes an ASME standard for machine acceptance that outlines a std approach to stiffness testing. So anyone doing FE on their design it would be good to follow this approach. Just found a copy so haven't read it fully yet. Peter

[ardenum]

Starrag ecospeed is somewhat similar, the structure seems much stiffer than the ingersoll hexapod, I think.

https://www.youtube.com/watch?v=qD9koFY9EKE

Thanks for the ASME, undoubtably will help with some aspects that require real maths to work well.

[peteeng]

Hi Ard - The ecospeed has a hexopod head supported via a massive column structure. It has to be open to allow automated part and billet access. Very large aero parts. The ingersoll machine would be hard to get parts into and out of. Milli has struggled to achieve bed stiffness at the target weight. Since Milli is a benchtop machine I think the exoskeloton idea may work. Complex but that's what it may take to achieve the brief Linuxcnc has a hexapod driver I think....Peter

[ardenum]

Hi Ard - The ecospeed has a hexopod head supported via a massive column structure. It has to be open to allow automated part and billet access. Very large aero parts. The ingersoll machine would be hard to get parts into and out of. Milli has struggled to achieve bed stiffness at the target weight. Since Milli is a benchtop machine I think the exoskeloton idea may work. Complex but that's what it may take to achieve the brief Linuxcnc has a hexapod driver I think....Peter

I'm not sure but delta 3d printers use this setup and there are open source drivers and software on github but its known in the 3d printer community that stiffness ain't the best with these printers. Are you still deciding whether milli gets a steel undertable or it goes directly on someone's desk?

Bed stiffness is a problem to get right at low weight, I know it very well. the holy grail with this problem is to make the bed as stiff as possible within reason and then figure out how it could be transported to lets say 8th floor apt that has no elevator...