[ckelloug]

DAK3333,

Here's the epoxy we settled on due to our ability to obtain it cheaply. Thanks for the help. Damned molecules are out to get us macro guys. I hear cobalt acetyl acetonate helps increase the crosslinking.

--Cameron

[walter]

It would be nice to find out that epoxy is at fault. Personally, I think it's my poor mixing/curing technique.

[brunog]

Here in the lab (back in double door land) the house vac is a water ventury backed vane system. We get about 26 mmHg at the bench. This has been sufficient to degass my samples. I would guess that near 28mmHg for about 15 min would do it. Yes it will expand to great volumes (kinda neat). I have used a refridgeration compressor at home with good results in other ventures.

For the Shore hardness. These are good questions. If someone could share again the epoxy being used and a data sheet, I would like to see the chain length to crosslink position ratio. It may be a simple matter of the wrong epoxy chemistry. A good adhesive may not be a good binder and vise versa.

DAK,
Please take a look at East system 9482 epoxy and hardener.

Thanks, best regards

Bruno

[Adam M.]

Would everyone slow or stop adding to this thread, please? I have been reading for a few days now and am only at page 31. If people keep adding, I will never catch up.

Since this is my first post ever, let me say, great website. Very informative, but I see I have a lot to learn before I get to build the machine of my dreams.

Okay, back to page 31.

Take care.

[ckelloug]

Guys,

Here is an index I compiled of interesting ideas. I haven't had time to edit it, spell check it etc. The format is poster, post number summary. If the post number has an A or an R after it then it is an answer or a reply to the given post number.

Materials

Mcgyver 84 water filtration sand
WilliamD 267 Us Composites EPOX-1505563 the #635 epoxy everyone is talking about
lgalla 537 Cabosil from Cabot
jsage alumina material
walter 551 Zeospheres
walter 593 quartz
brunog 596 pool filter sand


Suppliers

Episs 10R-5 Accures 3 cu ft casting kit 360$ 435 punds
Episs 12 www.sika.com epoxy grout
lgalla 44 www.shopmaninc.com a.k.a. www.uscomposites.com
lgalla 52 http://www.reade.com/products/sand/granite-aggregates http://www.kafkagranite.com/
walter 551 The Cary Company www.carycompany.com
walter 593 www.u-s-silica.com quarts
sposl 949 http://www.r-g.de/ R&G epoxy in Germay

Methods

lgalla 163 degassing with a blowtorch
lgalla 167 vacuum degassing with paint pot foaming overflow and big vacuum pumps.
lgalla 212 Poly vinyl alcohol with water soluable tendancies as a mold release, paste rather than sprayed
lgalla 497 Chopped Kevlar makes the viscosity go up very quicly therefore not suitable.
lgalla 503 Kevlar absorbs moisture in raw form and deterioates under UV exposure
lgalla 527 Epoxy spraying is dangerous without body suit and air supplied respirator
lgalla 558 Carbon Black will make a black cloud when you open it and a little goes a long way.
Stepper Monkey 794R791 IN-Situ Vacuum compaction of the mixture (This post is worth reviewing).
lgalla 795 R794 DOesn't this need perforated release film and bleeder material?
lgalla 855 Watch out for amine blush and sand off before repouring on that part

Observations
lgalla 4-A1 epoxy granite
lgalla 6-A5 Expensive damping properties 10 times cast iron
lgalla 8 Polyester shrinkage and brittleness make it unsuitable
lgalla 9 Establish Terminology E/G to avoid confusion with polyester
RotarySMP 11 Fill rate between 80% and 85% aggregate, aggregate bears weight, mix of aggregate sizes
lgalla 26 Forklift accident problem is a concern
dansutula 20 Zanite up to 6 mm aggregate size
Mcgyver 21 E/G strength may be too low to replace steel in machines
Geof 22 accrues casting claims .0005 tolerance on parts and better damping
Mcgyver 36 Metalworking vs. woodworking rigid metal frame with e/g damping
the4thseal 45 epoxy steel fiber anyone?
RotarySMP 46. A mix of aggregate sizes is needed
lgalla 47A46 skepticism about the larger aggregates.
RotarySMP 49 8% epoxy, all grades of aggregate, vibratory table, vacuum degassing
greybeard 51 spherical packing ratio mixtures and difficult 3 part system
greaybeard 61 spherical packing 1: .2 :x ratio for tetrahedral packing
lgalla 62 aggregates are generally a local product
nMotion 63 is making a commerical mill out of E/G composite
RotarySMP 66-R30 12% epoxy had epoxy pooling in german machine
Geof 72 Steel structure filled with E/G will likely be easier DIY. Fewer problems pertaining to voids. No steel frame requires special attention to aggregate ratios.
Chris-Jennings 78 aggregate ratio 10 mm :5mm : 3mm
lgalla 82 need thin epoxy 600cps, reactive dilutents smell bad. Makre sure it ships non-hazmat
nMotion 85-R63 3/8 to sand aggregate, low viscosity slow cure epoxy, accurate steel or aluminum molds for accurate parts. (Post is worth referring back to.)
lgalla 89 milled glass fiber to keep epoxy aggregate ratio down and lower viscosity
lgalla 92R90 Problems have to jig all inserts and bolt holes to be cast into the epoxy
RotarySMP 94 aggregate from .1 to 16 mm. resin 7%-10%; 70Hz 2.5g shaker. make parts same size as cast iron but solied instead of cored (post is worth referring back to).
Geof 95 Anything will work if you are just trying to damp conventional machines.
RotarySMP 96 list of E/G properties that is useful (Post is worth referring back to)
Geof 97 Doesn't believe that E/G is practical for DIY machine frames.
RotarySMP 102R30 The german site shows that something quite workable can be done well with improvised equipment
digits 103 Bury an 80/20 frame in E/G leaving the top exposed.
Geof 113 E/G and aluminum match well thermal expansion wise and good for embedment of 80/20 etc.
lgalla 125 Solid frames must be aligned accurately as they will not deflect to cover imperfections.
walter 145 steel tubing is expensive and also has to be normalized which is also expensive
brunog 188 E/G may need reinforcement with steel and will need inserts for bolts etc.
the4thseal 230 post-tensioning
Geof 231-A230 post tensioing may cause the vibration damping properties to be decreased.
skippy 240 points out bottom is in compression, top is in tension.
lgalla 244 entrapped air expands when the epoxy goes exothermic
JerryFlyGuy 257 Moglice ways and rails repair compund is expensive and bad value.
brunog 349R347 aggregate size and mixing is the critical point fill density is better when the ratio is right
brunog 369 Calculation for the 1/5 by volume ratios for E/G aggregate.
martinw 380 theoretical packing density for quaternary structure is 1:7:38:316 for 95%
zumba 383 Area moment of inertia of square beam
lgalla 387 What is stiffer 4" of E/G or 1/2" of cast iron?
ger21 407 Use a truss to make a 16 foot unsupported beam
martinw 408 Hollow core slabs
ger21 416 West System Epoxy publishes magazine epoxyworks so beware of bias
Zumba 418 Hollow E/G beam thin steel on the outside E/G filled but empty center around neutral axis (Worther referencing)
jsage 420 Crystallize approach to rebar
martinw 425 Analysis of beams by lever arm method
lgalla 443 Use of foam filled tubes to minimize deflection.
martinw 444 Foam filled beam Helps in preventing slenderness ratio column collapse.
martinw 444 Single part foam is useless at filling voids unifoemly in closed parts.
brunog 447 Create foam core E/G
brunog 453 Foamed epoxy filled aluminum
lgalla 456 Foamed epoxy outrageously expensive.
Zumba 467 Mold a vacuum grid into the table.
jsage 472 IF overall engineering is good perfection of the fabrication becomes less critical
greybeard 473 Use of Glass Microspheres.
brunog 489 Kevlar shortage and dupont.
jsage 492 Chopped kevlar strands
lgalla 497 use of chopped glass fiber or other fiber to resist microcracks
mhasting2004 499 questions using E/G on beams based on imagesetter design
mhasting 2004 509 description of Anocast process for imagesetter
ger21 514 add graphite
Geof 515-R514 add CarbonBlack, Not graphite. (Actually they can be quite similar according to cabot CK)
walter 521 Sportiness reference
lgalla 537 Thixotropic epoxy and Cabosil
BobWarfield 552 comment about nobody doing anything
davo727 561 filling in castings on an R45 Mill.
jsage 567 note problems with 90 degree angle cuts. Want v Grooves to avoid stress concentration.
walter 583 commercial countertop 95% granite 5% epoxy
brunog 585 fillet right angles at 3/4 inch radius
lgalla 588 clept Epoxy Quartz E/Q
sposl 592 Announces his experimentation start with E/Q
martinw 599 Epoxy might vaporize at low vacuum and hose pump
davo727 606 describes results filling machine base and parts with epoxy.
davo727 606 problems with air bubbles with small sand. West105 resin and 206 hardener had low exotherm.
jsage 610 quartz lamps to heat the epoxy for cure
lgalla 614 Vibration at the correct frequency will cause the material (which is thiotropic) to liquify
greybear 619 Cast self leveling epoxy tiles as load bearing portion. Fill center with E/G and cast final surface
brunog 621-R619 Moldmaking for inserts anchors plates and replicaton
Zumba 627 Playsand plus epoxy?
davo727 629 1 part epoxy one part playsand and 3 parts rock work better than just sand.
Zumba 631 Epoxy natural sand tests pictures.
jsage 633 concern on high freq vibration
jsage 641 Calorific absorption in epoxy causing it to draw into spaces.
Zumba 648 sledge hammering paper cup cast samples.
Geof 653 higher frequencies are less likely to disrupt the aggregate mix. Better Air bubble release.
jsage 663-R660 We've probably reached the end of the possibilites
ahlbebuck 664 Non-Polymer Concrete/Mild Steel probably the way to go. (Concrete designer)
Zumba 667 Concrete takes a long time to cear and be stable along with iron castings. E/G if done well is fastlgalla 678 Thermal expansion issues with concrete.
ahlbebuck 688 Structureal Civil engineer speaking about aggregate sizes 6mm 13mm 19mm 25mm 32mm sand 250 micron to 3mm
ahlbebuck 688 post-tensioing of frame.
ahlbebuck 692 Bigger aggregate is natually desnse. Must use graded aggregate to fill gaps.
ahlbebuck 695 quartz is good: fines from 6mm to about 25 - 32 mm.
MikeMattera 717 Hermle Machine makes mills with E/G bases .00003 precision if properly cared for
sposl 719 an excellent post describing making a mixture which is likely to be the right stuff.(Worth referring to again)
pupa 729 Many remarks about vibrating concrete
sposl 732 Approximately 30% of his samples appears to be air.
walter 733 using a press for compaction
wjfiles 739. Muchh less than 29 inches of vacuum is not enough to deair the mixture.
Stepper Monkey 741 Applying impulses may be the best means of agitating.
Stepper Monkey 759 Epoxy with viscosities as low as water
brunog 767-R30 Vibration apparently has to be in the up and down direction.
walter 777 Sacrifice strength for practicality. Use more liquid mix and more reinforcements.
pupa 779 Talk to manufacturer app engineers as they know more about this stuff than we ever will.
walter 785-R404 Reference to the rebar cage idea
LeeWay 796-R794 Use thermally safe bag material.
Zumba 812 Thinking about practical solutions with bucket mixing degassing, pouring and the lack of thermal probs.
walter 822 Epxoy Surface Plates
gt3073b 847 Ultra low viscosity epoxies for resin injection using vacuum bagging/vacuum infusion.
walter 853 pictures of some plates with carbon black
walter 859 formula used that was working was 60% large quartz/ 25% zeospheres/15% fine quartz
walter 861 picture of fabulous surface plate type.
speed33317 879 Pictures of polymer concrete samples.
sposl 889 pictures of E/G samples 12% epoxy .18mm 15.85% .49mm 26.06% 1.52mm 46.09%
walter 907 Forklift Theory is out. Sample is gummy.
walter 919 incredible results with zeospheres and 3 micron quartz
lgalla 920 need to get external lab involvement.
martinw 937 Deflection is far more important than Ultimate Strength in E/G because if we are ever near ultimate load it's bad. E/G mixes for this designed to deflect none at all .
ckelloug 944 Importance of understanding load on parts to be made. Bottom is in tension, top in compressions
LeeWay 945 Heat parts for cure with IR lamps.

Zumba 818 McMaster Carr pneumatic rotary ball vibrator
Speed 33317 Qualitative Results
lgalla 833 Epoxy Suface plate good to .003 in 16x14 ft!
sposl 956 Perhaps reinforcement not used in order to keep parts from warping due to differential thermal expansion
fyffe555 976 An excellent calculation of strength (Should be referred to again)
fyffe555 979 An excellent explanation of shear.
ckelloug 981 compressive and tensile moduli are substantially different and flexural is also different
fyffe555 986 E/G effect on torsion in small cross section member isn't very high
ckelloug 997 Strengthen the mixture by the effects of dispersion hardening using Carbon Black
ckelloug 1000 Silica Fume for dispersion hardening
ckelloug 1019 .1 micron limit of small paricles Tensile strength limits unreinforced beam
ckelloug 1031 $175 for a test of modulus or compressive strength
yugami 1035 Shop Press and a pressure guage easiest way to apply known force.
walter 1107 Walter is testing with improvised screw press and torque wrench


Purpose

walter 28-A21 90% of the people here don't build metal working cnc's or metal parts.
walter 141 build a solid 1ft to 12 ft CNC frame table or gantry with leveled precision surface for linear rails. No metal saw milling machine welding or drill pressing.
walter 334 E/G is brilliantly simple to use- can be done in your garage, requires no tools can be used by virtually anyone. Try that with mild steel anocast or granite.
walter 450 Heavy E/G Gantry
walter 942 Picture of router we'd like to be able to build
lgalla 963 References on what he wants to build
sposl 965 CNC mini Mill 300mm by 500mm x 500mm
leeway 966 36 inch bridge mill and dampening of steel structures.
BobWarfield 967 E/G based CNC table
brunog 16x32 E/Q gantry mill with 12 inch Z axis
lgalla 100 lb gantry 4ft long 50 lb Z axis most interest here.
walter 1088 My current project is 36" x 36" fixed gantry hybrid (E/Q with aluminum guts). The beam will probably be in the 4"x6" area, carrying 50lbs max.
ckelloug 1129 Purpose statement gleaned form all the conversations

Questions/Answers

walter 1 Anyone built anything form polymer Concrete.
walter 1-A1 Dewayne Harelow cnncbridges.com
Mcgyver 2-A1 Hardinge and precision optical equipment but no diy
Mcgyver 70 What is the effect of aggregate size on strength, what aggregates for other applications, techniques for dealing with mixtures of aggregates.
Mcgyver 159 Do we know how much more E/G than granite is needed to make a 12 foot router have comparable deflection in bith materials? Do we know the cost differential if we don't know the materials required?
brunog 220 What aggregates, aquarium sand, glass beads, glass fiber? Molding: vibration? Antifoamin additives?
lgalla 360 why are some of the calculations by weight and others by volume?
lgalla 403 4x4x1/4 tube with and without e/g which will be stiffer of will added weight cause more deflection?
Zumba 406-A399 description of deflections in beams at 4 feet.
lgalla 434 How do different modulus materials in a beam's construction effect it?
jsage 442-A434 Example of composite boat building.
jsage 578 What degree of precision does everybody need.
jsage 578-A578 1/16 inch
lgalla 580-A578 light duty vs. heavy duty light duty is 1/16th. E/G unnecessary at 1/16. Reproducibility and vibration damping.
Zumba 761 Liquids and solids aren't compressible so why the press?
lgalla 787 What's better a low ratio pice full of bubbles or a high ratio pice that's deaired.
lgalla 948 Why is a cast iron tabletop 1 inch thick while the same part in E/G is 4 inches thick.
lgalla 948 will hoolow E/G improve the deflection issues
ckelloug 954 What is the largest member to be considered in the machines being built?
walter 955-A954 4ft usupported 20 ft supported.
brunog 999 What ratio of carbon black and does it affect viscosity?
ckelloug 1010-A999 Cabot sends Carbon Black, should stiffen the material
jkeyser 1016 Has anyone considered using Garnet?
ckelloug 1051 dispersion hardening with nanoparticles
walter 1052 What is the right stuff in epoxy?
ckelloug 1072 Critical length for fiber reinforcement
ckelloug 1082 Rule of mixtures determines strength by ratio of parts in composite materials
DAK3333 1156 DAK (Materials chemist) reccomends ignoring silating agents (worth referring back to) Also mentions the purposes of microreinforcement.

References


walter 1 http://www.cnczone.com/modules.php?n...threadid=24879 cncbridges thread
Episs 5-A1 http://www.itwpolymercastings.com/ E/G machine parts
Episs 5-A1 http://www.accurescasting.com/index.html E/G machine parts
lgalla 8 www.moglice.com moldable bearing holder
Geof 22 http://www.accurescasting.com/polymer.html on properaties of accres material
Geof 25 Zanite www.itwpolymercastings.com/faqzanite
turmite 23/37 http://www.machinedesign.com/ASP/vie...MDSite&catId=0 link to machine design magazine on all polymer machines
schrupphobel72 30 http://5128.rapidforum.com/topic=110...6&search=beton German CNC machine site
BobWarfield 73 http://www.mech.utah.edu/~bamberg/re...e%20Design.pdf Bamberg's theis on principles of rapid machine desing with concrete damping of metal machines
Xerxes 74 http://video.google.com/videosearch?q=datron datron router with E/G frame
Chris-Jennings 79-R78 http://books.google.co.uk/books?id=h...ct=result&cd=1
Aramon 134 http://www.epucret.de/files/EPU_News_NR_26.pdf epucret is a french copany that makes e/g machines
walter 157 http://www.moldmakingtechnology.com/...es/040401.html moldmaking technology magazine hard milling
Aramon 158 http://www.epucret.de/maschinenbau_anwendungen.html more epucret stuff.
ger21 http://www.joewoodworker.com/ making a venturi vacuum system
walter 174 a whole bunch of machine frame pictures attached to article for reference
brunog 198 http://www.microplan-group.com/pagin.../celith_gb.htm celith french epoxy granite company
JerryFlyGuy 203 http://www.cnczone.com/forums/attach...6&d=1170207942 lgalla's table design
vger 215-R212 http://www.diamond-drill-bit-and-too...Drill/MAIN.htm diamond drills for granite
walter 241 summary to post 240 www.precisionepoxy.com - Awesome Epoxy Surface Plate! - DIY Instructions

brunog 242 http://www.ktm-reiseenduro.de/tz/mg2.htm http://5128.rapidforum.com/topic=110...6&search=beton german machine designs in german
JerryFlyGuy 254 http://diamant.ph/en/produkte/dwh/ an E/G manufacturer link
brunog 258/259 http://www.nist.gov/ nistir 6361 The NIST fire science report on polymer concrete optimizationmartinw 351 http://www.adhesivestoolkit.com/Docs...%20Testing.xtp explanation of epoxy creep
walter 364 summary posting. (Good to refer to again)
martinw 380 http://www.blackwell-synergy.com/doi...1961.tb13716.x (Good to refer to again)
jsage 436 Drawing of potential way of doing hollow core rebar tube (Worth referring to agin).
martinw 444 http://www.sae.org/technical/papers/960435 sae paper on column collapse
mhasting2004 http://www.rockwellautomation.com/an...o/anocast.html Anocast imagesetter info
jsage 525 http://www.rockwellautomation.com/an...df/Anocast.pdf Further anocast information
jsage 536 http://www.velocityseriesinsider.com...11%20November/ http://www.velocityseriesinsider.com...12%20December/ http://www.4spe.org/pub/journals/index.php http://www.vitroco.com/discovery/polymer.pdf http://www.skk-banjaluckapivara.com/...composite.html
jsage 548 http://www.vitroco.com/discovery/polymer.pdf aluminosilicate
walter 551 http://www.cnczone.com/forums/attach...7&d=1174281201 micosphere selction guide
walter 553 http://www.cnczone.com/forums/showthread.php?t=33434 WilliamD's thread on his tests
BobWarfield 560 machine design in post http://www.thewarfields.com/cnccookbook/CCEGGantry.html
martinw 587 Google FU-TUNG CHENG lifestyle countertops for interesting materials
davo727 589 pictures prepping mill for filling base with E/G
brunog 600 http://www.colouredaggregates.com/
walter 632 Brenton (Breton?) Stone and how they make it. AkA manufactured quartz countertops 4.5 inch slab is vibrocompacted down to 3/4 inch
walter 634 Terastone Technology 2000 to 4800 Hz vibration between 720 and 680 mm of vacuum
RogerH 640 http://www.chockfastgrout.com/indextwo.html
walter 649 Pictures of German machine without E/G in it yet.
walter 658 http://www.freepatentsonline.com/20060283136.html Breton Stone Patent info
walter 660 http://www.surfacefabrication.com/Si...ant%20Tour.htm Bretonstone fabrication (Worth referencing again)
walter 705 pictures of carbon black
lgalla http://www.cnczone.com/forums/attach...9&d=1175483284 research paper on polymer concrete properties
brunog 726 http://www.cnczone.com/forums/attach...7&d=1175565278 aggregate size calculator
pupa http://www.sullair.com/corp/details/...TI5905,00.html concrete vibrator labelled for 18,0000 hz (however careful reading of the datasheet shows its 18000VPM!!!!!!)
pupa 737 E/G aggregate contents and silane treatment papers http://jrp.sagepub.com/cgi/content/abstract/1/4/370 http://jrp.sagepub.com/cgi/reprint/1/4/370
pupa 775 Quote form Cincinata Milicron about 95% quartz and 6x damping ratio.
walter 839 http://www.precisionepoxy.com/NPS%20plate.htm Naval postgraduate school epoxy surface plate
walter 846 Pictures of 400-700 micron quartz, 200 micron zerospheres, 3 micron fine quartz, carbonblack
lgalla 891 http://www.cnczone.com/forums/attach...6&d=1176348307 Vibratory table for glass recycling
ger21 930 http://www.canadacool.com/COOLFACTS/...ftCarrier.html An aircraft carrier made from ice and wood pulp designed during the second world war.
lgalla 934 Paper by walker showing larger aggregate does not improve concrete strength
brunog 935 http://www.fire.nist.gov/bfrlpubs/build99/art032.html nist lab report on optimizing E/G E/Q but does not address aggregate sizing.

BobWarfield 974 http://www.mech.utah.edu/~bamberg/people/bamberg.html Link to Principles of Rapid Machine design PHD thesis by Bamberg
ckelloug 1010 http://www.michaelengineering.com/index.htm Epoxy metering equipment
ckelloug 1051 http://www.nanoresins.com Also bilbiography of texts and materials used.
ckelloug 1053-A1052 Hardener data sheet for epotuf 37-606 Us composites 635 hardener
ckelloug 1060 http://www.cnczone.com/forums/attach...7&d=1177647171 Beamer java applet for deflections
ckelloug 1064 http://www.cnczone.com/forums/attach...4&d=1177701256 datasheet for epotuf 37-127 the epoxy used in us composites 635
ckelloug 1129 http://www.cnczone.com/forums/attach...1&d=1178124508 DOWz6040 coupling agent data sheet

[walter]

Thanks for joining the thread Adam! Ideas and comments are always welcomed :-)


Cameron,
Great work on the summary, I really appreciate it.


Note to New Members: Get on with reading while the thread is still relatively lightweight. I am not joking!
_

[the4thseal]

Walter how do i send you the samples that i have made? Address? i have never sent anyone anything on this forum so i do not know the protocall ect.

[walter]

Please enable your PM box.

[Zumba]

See and See.

[martinw]

Guys,

Here is an index I compiled of interesting ideas.
Questions/Answers

That is pretty heroic!

Top dog.

Best wishes,

Martin

[walter]

walter,
feel free to post your design
Best regards
Bruno

Hi,
This is the rough version, showing the part count (taken from something I saw online). It fits the Greybeard's EG Lego category and allows me to make heavier/thicker parts. 200-300 lbs total(?).

top beam ± 5" x 5" x 36" with ballscrew hidden inside this (load bearing) structure ---> Π

Backplate is optional, I may or may not use it. All E/G parts will feature some sort of internal bracing/plate/metal junk that will hold it together. 20 bolting points identified so far.

1 bottom table- EG with weight lowering PVC pipes
3 top tables - solid EG, ballscrew&rails inside the center piece (the actual moving table not shown).

Machine will feature the infamous 1kW P5 motor, powered by Fluxeon AC servo made by none other than Granite Devices!

Anyway, that's all I got so far.

Comments?

[ckelloug]

Wow, walter,

This looks pretty darned awesome. Are you planning on using steel channel or E/G for the top beam? I'd be worried that in either material that it won't be stiff enough if you leave out that reinforcing plate.

As for the table, unless this whole think is sitting flat on a bench, I'd be a bit worried about the table collapsing under it's own weight. I'd suggest making the base of the table from steel box channel which can also be used as an integral mold. See the diagram attached. The critical load on the machine base is tensile load on the bottom of the base so it better be pretty strong so it doesn't want to fail.

[walter]

Thanks!

All E/G pieces will have some kind of internal structures or plates. Some metal/aluminum junk- whatever I can find- this is my junk yard design. So no fancy fabrication- quite the opposite!

Top beam- junk aluminum structure with rails and ballscrew, like this Π. E/G jacket overwrap.

Bottom table needs reinforcement, and there's a weight limit- some foam or pvc piping will have to be used. Three top tables are bolted to the bottom table, adding mass, X axis drive train and second bolting surface for gantry sides. Yes, four bolting points for gantry 'legs'. Plus, all 20 bolting points metal to metal contact- through the entire thickness of the composite.

Good thing you mention the tensile load, I haven’t really think about that...
_

[the4thseal]

walter ....I think i have done it .....give it a try. if it does ot work where do i go for the instructions

[walter]

You haven't. That was AOL instant messaging

Please go to User CP, Edit Options, Enable Private Messaging.

[ckelloug]

walter,

Your design is on the right track I think. If you overwrap the beam with E/G, this is good as it puts the metal where it's strong and the E/G on top where it is in compression. I don't know how I'd cast that piece but what you said is sure how I'd want to cast it.

Steel channel is likely a better choice than aluminum channel for both cost reasons and the fact that aluminum's Q factor for vibration is worse than steel.

Metal reinforcement will help you very little in the upper table pieces. A bit of wire mesh in the bottom of each of these table pieces is probably enough. Your big problem is in the bottom of the base. The E/G has very very little tensile or flexural strength so it is unlikely to hold if a bunch of individually reinforced blocks are simply bolted together.

I'd still suggest steel channel for the base and then I'd make columns of E/G by cutting PVC pipe 2 or three inches long and using it vertically to mold the E/G columns against the channels on the bottom to hold up the upper table pieces up. You can then run your bolts through the E/G columns. The upper table pieces can probably use a small amount of reinforcement in their bottoms but if the lower table is sturdy, then they can sit on the columns. I've attached a diagram of the idea.

[the4thseal]

I think i have enabled my messenging try it now.

[walter]

Cameron,

Thank you for your suggestions, they are very useful.

I went back to some of my E/G samples, please have a look at them.

This time I tried some new things - sweating the epoxy, heating it and heating aggregates in the oven. The results are not much different but the heating seems to help. I also noticed that tightly packed large aggregate samples are weaker than my 'regular' mix.

So what I did is mix the epoxy/hardener and leave it for a while in the container. It helped to get rid of the air. Some of the aggregate was heated in the oven. Have a look at the pictures.

Sample A - mostly large/medium aggregate. The mix was barely pourable, hard to work with; heat gun used during pouring. Strength test- very weak, 10 ft*lb after 1 screw turn.

Sample B - similar mix but aggregate was heated in the oven; I couldn't get the temp right and did 'smoke' some of the epoxy (uneven epoxy temp weakens the structure). A lot more epoxy was used to make it pourable; heat gun used during and after pouring. Strength test- 50% better than sample A, after 1.5 screw turns.

Sample C - random mix of 0.5-5.0mm aggregate with some 10-15mm large rocks. These were the oven aggregate leftovers, very random pile of sand. Also very hot; decent amount of epoxy for good pourablility; heat gun used during and after pouring. Strength test- 100% better than sample A, after 2 full screw turns. Pretty tough sample but no better than pool sand/zeeospheres sample from post #1181.


I could probably get 10-50% improvement (with creative use of heat), but what's the point? I think the epoxy limits have been reached. It's nowhere near the commercial matrix and that's the end of that.

I believe that there is a matrix out there that's 10 times stronger.
There has to be.
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[walter]

Any idea where to get this book?

http://stinet.dtic.mil/stinet/jsp/do...=epoxy+granite

[walter]

"Granitek Precision Granite Castings are produced by mixing high grade angular granite aggregates, which are crushed, river-washed, kiln-dried and carefully sieved to give optimum performance, with an epoxy resin system.
The mixed material and resin system is then poured into an open mould at room temperature (ambient), vibrated and low exothermic reaction takes place over a period of time."


Low exothermic reaction? That sounds new to me..

http://www.granitek.co.uk/materials.html
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