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  1. #841
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    Default Re: Milli a new composite mill kit

    Hi All and Sundry - I broke out Brick No5 couldn't wait till tomorrow. This is a very high ratio AlOx brick. I weighed it and realised I had missed adding 250g of alox to the list at mixing (when checking thru my notes). So its 3750g and has an alox volume ratio of 53% which is very close to the theoretical of 56%. I dressed it using 120grit alum Oxide paper I usually use on timber. It dressed the cement meniscus easily but the bottom edges where the alox grit was it skated. So its hard I suspect it will be very hard to drill. I'll try an impact masonry drill on it in a few days.... So this seems to be the path. This brings me back to the thoughts of an infused fibreglass skin with a high pack fill. The skin (E30) can be machined and the fill is the rigidity (E90+)... Still keen on aluminium inserts.... But need to do some stiffness testing to prove out the theories... Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-alox-edge-1-jpg   Milli a new composite mill kit-alox-edge-2-jpg   Milli a new composite mill kit-broken-jpg  


  2. #842
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    Default Re: Milli a new composite mill kit

    just found this on Al2O3 quite good - Peter

    Attached Files Attached Files


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    Default Re: Milli a new composite mill kit

    Morning All - Here are the 4 test bricks. I'm using them as trivets but they have four feet so I suppose they are quadvets. Next step is : 1) maybe try a water infused concrete brick 2) make a plank mould to do a bending test to check the alox stiffness. 3) maybe infuse an alox plank 4) get back to YaG its officially stalled and needs restarting....Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-trivet-collection-jpg  


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    Default Re: Milli a new composite mill kit

    Peter, thank you so much for all the sharing and teaching, a fantastic thread sharing your professional knowledge . I have been watching, lurking, learning* for many years on CNC forum as a hobbyist* as you refine your parameters and ideas for Milli. (a really burned newbie $$$$ wise and time wise 8* years ago with one of - if not the first, nonshipped SVM-0 from D).* **


    * * * One question regarding Milli.*

    When casting the top plate of the base, will you incorporate* a slight trough or depression in the top of the* base (* in between the two side rails under the traveling table) and will that change the stiffness substantially? . This would allow gravity drainage of coolant away from the rails and top* into one location for collection or a drain hole.*

    Also I tried to download
    /read your recent 1.8 mb pdf about Alox and couldn't read it with several different pdf readers - - - " corrupted file format". Didn't know if it's my phone / setting within Tapatalk or just Tapatalk acting up, seen this happening from time to time on Tapatalk.
    Chuck Menz


    Sent from my SM-N986U using Tapatalk



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    Default Re: Milli a new composite mill kit

    Hi Chuck - I downloaded the pdf on al2o3 and it worked fine for me so can't help with that question. There are several features to add to the basic design once that is decided. Troughs for drive screws and coolant are needed, Inserts or lands for rails and motors and connections. Its really early days for those features until the basic stiffness DNA is put in place. I have struggled a little in staying in the composite area and achieving the benchtop mill / 50kg per part rule. I hope the alox solves the material problem then I can move onto those details. Currently I'm thinking about making Milli smaller again. Its still a little bigger then I set out to achieve. The relationship between rigidity and machine size has been interesting. Turns out its quite hard to make a small machine as stiff as I want. Geometry wins.... so size does mater in this case... Peter

    Heres the link to the requested doc vs it in person...
    https://cris.vtt.fi/en/publications/...lumina-ceramic



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    Default Re: Milli a new composite mill kit

    Morning all - I starting setting up an infusion this morning but the vac pump didn't start. The starting capacitor has died so I'm off to find a new one. Peter



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    Default Re: Milli a new composite mill kit

    Peter, thanks for the fill in,
    * * *
    Regarding some research I've done about* CSA* based cements.* Not to hijack this fantastic design, build thread that you are doing.* *Mostly N. A.*
    *In North America, it seems the only manufacturer of pure hydraulic CSA, non Portland based cements* is CTS Cement Corporation. They seem to have quite a few large plants in the U. S. and many technical reps throughout N. A.(Canada and Mexico as well- - some presence in Asia) .* CTS* seems to mostly distribute some* retail product* (think" Rapidset") through* some bigbox DIY* chain stores (H.D, some* L..) and more* of their line through Whitecap, a distributor of professional building supplies throughout the U.S./? Canada.* * * **
    * * * *CTS has many different product lines , two of which might be of good use as an alternative to E. G. in machine building from the big box retail stores.* *2 of their many* products machine builders might use, more readily available as DIY* *would seem to be* "RapidSet Cement All" in 10, 25 and 55 # bags* and* "RapidSet Precision Grout" in 25# bags.)* The "RapidSet Cement All" is a water add only bag of a* combination of csa + fine sand and some plasticizers etc with 8000 psi compression @ 7 days and 9k psi @28 day and my guess is* E34. This has wide* use as grout,* including cement table tops, planters, etc . The more expensive RapidSet Precision Grout" is fairly attractive for building machinery.* It* is designed as* grout in machine bases of all types of equipment* with high strengths of 8, 000 to 11, 000 psi @28 day* (depending on water/mix content>>> flowabilty .)* *Again unfortunately probably only* E34,* cause of custom fine sand based aggregates used along with lots of special additives* .* *It has very low shrinkage* of 0.2% to 0.3% noted along with very rapid initial 3k 1day compression strength >>11k @28 days* and* compatible CTE for steel.* I have information requests out to CTS for* optimizations for surface prep for steel and aluminum adhesion and also any comments about inserts and adhesion pullout strengths etc. .*
    * * * *The pure CSA only hydraulic cement for mixing into custom concrete (i.e.* E80, mortars and* * * is "RapidSet purple bag cement " (a 40 kg- bag about 38$ 40$ U.S. - only seems to be readily available at* *Whitecap. You can use "RapidSet cement purple bag". to mix your custom mix* of cement plus aggregate ( think* granite or AlOx or Sil Dio etc). This seems to be* mostly* available through Whitecap in the USA, a distributor chain of professional building supplies throughout the U. S.*
    * * * The concrete kitchen/ countertop information* *on the web and yes - YouTube -* shows that these products set up really really quickly (like 5 to 15 minutes depending on temp).* * To help slow down the very rapid set reactions* use* combinations* chemical retarders and/or controlling mix temps by cool water and* ice mixtures* .* *These need* mixing* asap in 4-5 minutes and pour/set* by 12-15 MINUTES, sometimes even faster times if temp is 85 to 100 degrees. .* You don't want to retemper or vibrate the CSA mix once initially mixed, no more 4-5.minutes* as extended vibrate >>>will then* lead to aggregate and cement and water separation.* Look at the various YouTube vids for how to mix and pour concrete table tops and garden planting boxes.* To slow down the "set",,) of a motars or concrete mix, you can purchase retarders* from CTS as needed or as below.*
    INCREASING CSA mix/set/poor/clean up TIMES*
    *to 1hr or more is possible using chemical retarders and temperature control of the admixture.* * An extensive but long YouTube video from* Jeff Girard P. E @ Concrete Countertop Institute* *- - you tube* * "How to use CSA cements for rapid production of countertops". :* * *Jeff appearsc to be in the business of teaching and selling products used in concrete counter table top manufacture.* Very* extensive tables etc.* Take home lessons below

    a. Water/cement 35-50 % for CSA, 40 % ideal.*



    b. use 0.1% to 0.4% by weight* powdered citric acid* from the web or health food store prolongingworking times, think 30 minute to 1 hr extension. 2$ /lb.*


    c. use combinations of water plus ice to lower tenofovir of mixture to about 47 degrees to 55 degrees slow the setup to 45 min to 1hr.


    *

    a. Minutes. 21-24* * strengths of CSA*

    *

    Water/cement a 35-50% w/c* for CSA (lower water, more strength). , 40 % about the ideal between strength and flow ability. with water @ 35% to 50% (strength vs flow ability) and he recommends about 40 % w/c. Includes tables of strength vs time vs w/c* vs Portland cements. BTW these water/c* % corelates with the CTS literature also. .


    For slowing down the setup of the mix* to get 45 minutes to an hour or so working time with these products, he* uses 2 different* methods- chemical retarders and controlling* the temperature of the water and the mix.* *


    b1. Minutes 28-30 -* *For a simple, widely available inexpensive chemical retarder using widely available powdered citric acid* mixed in @ 0.1% to 0.4% by weight (of cement). .*

    *

    *b2. Minutes 31-34* * use of water temp and ice to drop mix temps to about 50 degrees tp 60 deg Fahrenheit.* *ex. each 1 lb of ice generates* 162 btu of cooling (144 for phase change and 18 btu to go 32up to 50 deg F.,* 28 btu to go to 60 F.*



    .*



    Also major disclaimer, CTS Cement Corp doesn't know me from atom,* doubt I could get any Alibaba supplier (aside- - CSA started in China) to ship me the small* quanties I would use* or not use >> then eventually have the CSA show up in So Cal all doa from moisture intrusion,* in probably no less than 8 months shipping,* cost of shipping to N. A. from China etc .




    Also a really interesting post grad masters thesis by Michael* G Simpson in June 1974 " Fatigue of Ferro-Cemet".

    This is an early paper about fatigue strength.* There are many subsequent papers and books on feroconcrete. There are some takehomes that are relevant for machine building in this 120 page research paper.**


    P17* one of first studies of cyclic loading (10*7* cycles 10 million cycles and where failures occurred.


    P35* galvanized mesh INFERIOR* to plain mesh


    P48-49 fatigue strength is* 15% of the vultimate* compression strength after 10 million cycles.*


    "Failure of ferro-cement in either fatigue or monotonic flexure

    appears to be prfimarily a function of the mortar strength and elasticity. The reinforcement serves to distribute the loading throughout the mortar as long as the load-carrying capability of the wire ts sufficiently high.". In P48



    Hope these observations help

    Chuck Menz



    Sent from my SM-N986U using Tapatalk



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    Default Re: Milli a new composite mill kit

    Hi Chuck - Thanks for the summary. Rapidset grout has come up in a few discussions here over the last year. The Material data sheet shows its CSA with no portland. Most DIY epoxy granite and mineral castings get between E30 and E40. This is because they use sand and granite in various ratios. Sand is worn granite and mainly SiO2 which has a modulus of around 70GPa. If you use the CSA grout with a high loading of blue metal (say 3mm and 20mm grading) you can get it up to E40. Some companies quote higher values but these are compression stiffness's. This means the aggregate is transferring load via contact. Tensile stiffness is usually lower. Onward and upward... Peter



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    Default Re: Milli a new composite mill kit

    Evening All - Update on water infused block.... After I fixed the vac pump I waxed the mould and I stacked the dry excess steel/csa mix I had from one of the blocks. I set up the vac with a bypass to control the vacuum so I didn't get to the saturation pressure (around 30000pa abs) . When I opened the water valve the water charged in! In a few seconds the 600g of water was in.. I'm used to waiting 45mins for the epoxy to fill such a volume. I released it early to see what I had. Its very dry. I'll have another look in the morning. But I think I'll stick to mix and pour solutions for CSA. Infusion for epoxy.... Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-bag-release-1-jpg   Milli a new composite mill kit-bag-release-2-jpg   Milli a new composite mill kit-bag-release-3-jpg   Milli a new composite mill kit-bag-set-1-jpg  

    Milli a new composite mill kit-bag-set-2-jpg  


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    Default Re: Milli a new composite mill kit

    Hey Peter

    Looking good!

    Anyway, you had some concerns about mounting the columns to the side of the bed, here's a video of an Okuma that is mounted just like that.




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    Default Re: Milli a new composite mill kit

    Morning All - Been looking at costs and the current estimated material modulus. If I use epoxy/alox at V=60% alox then the its ~E85 and $17,206AUD/m3. If I use grout and alox its E80-90 and $9,940AUD per m3. So its a no brainer to use the CSA at the moment. I have a quote from china for alumina that is 1/4 the price of here but it costs lots to get it here unless I bring in tonnages. I can get smaller grains of alox and grade the mix to bump up the alox % but the csa is always going to be cheaper then the epoxy or the alox... So onward to testing to prove the modulus figures. I made a little model to see what's needed. I think a 100x6mm aluminium benchmark 1m long would be good. So I need to go find some extrusion. It deflects 15mm under gravity and takes quite a bend before it yields so should be able to load it up in various increments.... see what the local shops have...Peter

    re concrete - been reading up on its chemistry and it needs excess water to begin with vs its volumetric size. So a slurry is needed. Infusion will never produce a slurry as it will only fill the voids available so the grout path is not with infusion. That's cool I want a mix and pour solution....



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    Default Re: Milli a new composite mill kit

    Hi Ard - I looked at the video closely and they weld the columns to the foundation or at least pads for the jacks.... There are steel beds within the concrete. You can see them prep them before they stand the columns. Same with the bed. Would be good to know what the jacks look like. But doesn't really apply to DIY machines... Even though its a multi million $$$ machine it comes down to grinders and crowbars. Then there's always someone on the planet doing the Titanic thing!

    Funny story - last night I drove a friend home and half way there it started to rain so tried to put the passenger window up. No GO! so park under a cover and get out the plastic and tape and tape it all up. This morning I pull the door trim off (2 hrs work) and poke around nothing I can find... so I ring an autoelectrician and he can't get to it for days ARGGGGHHH So I ring the local Toyota dealer and he says have you tried the child lock? I say what lock? He says the small red button on the armrest that people put their elbow on? I say no but I'll have a look... bingo it works, now I have to put the door back together again... HaHa cheers Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-crowbar-jpg   Milli a new composite mill kit-welding-jpg   Milli a new composite mill kit-grinder-jpg   Milli a new composite mill kit-welding-jpg  

    Milli a new composite mill kit-titanic-jpg  


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    Default Re: Milli a new composite mill kit

    Afternoon All - Been a while since I have looked at Milli. We've been trundling down the material development rabbit hole and lost sight of the machine. So I looked back and Milli-Gram was waiting patiently for review. On top of that my main computer died last week and its being rebuilt. Its motherboard went on holidays when I went away so I've had to migrate data to my newer machine. Software and data migration is always a bore! Waiting for the machine maybe today.... its like a second date the tech never seems to call back...

    So I'm pretty sure I can get E70 plus so I'll stay with that for now. Looking at Milli-Gram it screams for me to rotate the table 90deg. We may have been there before. I think this is what happened with the Vulcan machine. Once you trim down the double gantry table to a certain size you look at it and ask why go thru the columns? If I turn the table 90deg the big dim is then in line with the X axis and its stiffer. Which is what I'm trying to do... Hmmmm

    In summary:
    1) assuming I can make E70+ material continue machine development
    2) the triangular gantry has been very good
    3) Turn the table 90deg and the base is a bit shorter and lighter. Current table and envelope 500x275mm
    4) question do I still use the double column or combine into a single?
    5) so many more rabbit holes to not fall into
    6) current model is 327kg and I'd like to par that back a bit by making the machine smaller.... 500x250mm table
    7) the current throat depth column to tool centre is 275mm so a 250mm wide table would fit as is

    onward and rotate . Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-gram-1-jpg   Milli a new composite mill kit-milli-gram-2-jpg   Milli a new composite mill kit-milli-x-jpg  


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    Default Re: Milli a new composite mill kit

    Evening all - Been waiting for some data to come through so did the Mill-Gram-2. Didn't work out, Milli-gram-1 stats 25/27/38um/N and Milli-Gram-2 stats 19/17/27 um/N so Milli-gram-1 holds up. So a bit of refining to be done now... I even put in a second bridge and that didn't help... Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-gram-1-x-axis-jpg   Milli a new composite mill kit-gram-1-y-axis-jpg   Milli a new composite mill kit-gram-1-z-axis-jpg   Milli a new composite mill kit-gram-2-x-axzis-jpg  

    Milli a new composite mill kit-gram-2-y-axis-jpg   Milli a new composite mill kit-gram-2-z-axzis-jpg  


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    Default Re: Milli a new composite mill kit

    Morning all - here's a big epoxy pour!! Peter





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    Default Re: Milli a new composite mill kit

    Morning all & sundry - this mornings exercise was to set up some alox and pour epoxy onto it to see what happens. As expected with the infusion epoxy it seeped through in a few minutes and filled nicely. I filled on one side of the cup so the air had a pathway of escape on the other side. This means I can make parts without setting up vacuum and bags and all that wasted stuff..... Hopefully today I pick up some aluminium to use as a benchmark for the modulus test... Peter

    and I measured the volume of the cup and then calc'ed out the mix using 56% alox volume and it worked out nearly spot on... For real parts I'd warm the alox a bit and the epoxy will flow in really well. The geltime for this one is around 45mins so it has lots of time to soak in. I added some white pigment, should have used red it would have shown the air escape better. By the way if you do this with laminating epoxy it would not work must be very thin eg infusion or river table type resin. But have a go with the resin you have if this is something on your list.

    In this case the epoxy by weight addition is 18% so the next trick would be to get some very fine alox and add it to the mix to improve the Valox ratio and decrease the epoxy addition. With the current alox and epoxy ratio the estimated Modulus is 96GPa which is really good if it translates... onward to testing... If I can get the volume ratio to 0.6 then I have a 100GPa material and I'm super happy with that... at 0.65 its 107GPa....

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-water-volume-jpg   Milli a new composite mill kit-resin-mix-jpg   Milli a new composite mill kit-air-escape-jpg   Milli a new composite mill kit-full-cup-jpg  

    Last edited by peteeng; 03-04-2021 at 06:44 PM.


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    Default Re: Milli a new composite mill kit

    Hi All & Sundry - I released the alox cup and it slipped out really nicely. The surface has no bubbles and it looks great. Even my wife likes it!! I can use a coloured resin and forget about paint... Weighing the cup and knowing the alox weight means theres 360g of alox and 69g of resin. The resin is 1050kg/m3 and the alox is 3920... This means the alox volume ratio is 58% which I'm very happy with. This also means using current calcs its E=99GPa or more.... So its an easy system, dry fill the mould then pour in the epoxy. If I use black pigment it will look like granite sure feels heavy enough. Its calculated density is 2714 kg/m3 which is the same as aluminium. So its high modulus aluminium! Now it just needs to be transparent and it will be amazing...Shouldn't get excited until the modulus test me thinks... Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-alox-cup-jpg  


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    Default Re: Milli a new composite mill kit

    Evening All and Sultry - I tried another batch of alox. This time I added some 430 grit aluminium powder that I have as well. I filled the cup with alox then added Al dust until I thought the volume was growing. So I started with 337g of alox then added 50g of aluminium powder. The powder is very fine. I mixed it a few ways dry and they all seemed to segregate and form layers or spots of al vs dispersing. This is my argument for using one grade of powder. Anyway after playing with it dry for a while I then poured it into the mould and mixed the required amount of epoxy. It filled very slowly compared to the first mix. So the breakdown in volume ratios is 51% ALOX 11% AL AND 39% Epoxy. This is 18% by weight addition of epoxy to the solids, which is the same as before. The solid volume ratio is 62% which is a little better then the first batch. We'll see what the surface finish is like tomorrow.... Peter



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    Default Re: Milli a new composite mill kit

    Great stuff Peter, thanks for sharing. I think it looks great as is. Interested to see your modulus measurements when they happen.

    I think I'd be scared of warming the mix for fear of adding any thermal expansion stresses to the mold or mix while it's curing. But I've been wrong before



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    Default Re: Milli a new composite mill kit

    Morning all, you scruffy lot - By warming I mean to about 40C. In summer here its 30C plus so 40 is not a stretch. The epoxy flows very very well at 40C (but the gel time drops from 1hr to 30mins)... Now back to mixes. Here's the result of the alox/al mix. The grey colour is the Al as it has segregated. I tried mixing it a few ways but found I could not mix it. The alox/al mix has clear resin whereas the RHS has white resin. The LHS cup grey areas are the aluminum powder not the resin colour. This makes me think to keep to one grade not mixed. The solids delta is 58% alox and 62% alox/al so not a great gain. So onward to modulus testing which is the proof of the pudding... These moulds are plastic puddling cups!! Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-alox-test-jpg  


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