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  1. #101
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    Jul 2018
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    Re: Yet another epoxy granite mill

    Hi Thomas - I'm too far away to help bit would there if I could!! Looking fwd to your news! Peter

  2. #102
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    Aug 2006
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    Re: Yet another epoxy granite mill

    uh....this arrived just today....
    Click image for larger version. 

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    ...things are really coming together now...

  3. #103
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    Re: Yet another epoxy granite mill

    Quote Originally Posted by badhabit View Post
    Well, i'm an engineer by heart and education, so i kinda "just wing it"
    Do Engineers have hearts? Peter

  4. #104
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    Re: Yet another epoxy granite mill

    Quote Originally Posted by peteeng View Post
    Do Engineers have hearts?
    I'm pretty sure that a lot of my professors back in my university days didn't have one ;-) So you might be right? Maybe i'm not a real engineer after all...hm... :-D

    /Thomas

  5. #105
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    Nov 2020
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    361

    Re: Yet another epoxy granite mill

    Quote Originally Posted by badhabit View Post
    I'm pretty sure that a lot of my professors back in my university days didn't have one ;-) So you might be right? Maybe i'm not a real engineer after all...hm... :-D

    /Thomas
    Same thing happened to me when I did an internship at a local company that made sheet metal products, the soulless environment made me realize I do not want to work in the industry...well failing programming and electronics helped a bit too.

    I'm surprised you ordered a ready made ATC, were you not interested in making your own?

    Anyway this is the best I could find so far when it comes to counterbalancing.(attachment)
    Attached Files Attached Files

  6. #106
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    Jul 2018
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    6254

    Re: Yet another epoxy granite mill

    Hi Thomas - You've clearly put your heart into this project so I'm sure you have one Peter I remember a Scottish hydraulics prof that definitely didn't have a heart... he must have had a swash plate....

  7. #107
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    Aug 2006
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    Quote Originally Posted by ardenum View Post
    I'm surprised you ordered a ready made ATC, were you not interested in making your own?
    Yeah, well, in principle all components can be made by myself if i put enough energy into it. One could also make the spindle, ballscrews, etc… but i have to draw a line somewhere… i’m also going to buy the table for the machine…

  8. #108
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    Aug 2006
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    258

    Re: Yet another epoxy granite mill

    A little progress today aswell, finished up the inside of the moulds with anchors and stuff:
    Attachment 467828Attachment 467830
    ....you really can't tell it from the images, but there is also small inserts at the very bottom for attaching the enclosure, way covers etc. Here is a picture from another angle, it's the stainless ones at the bottom:
    Click image for larger version. 

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    I got the small inserts from UK: https://www.anchorinserts.co.uk/stai...ed-inserts.php

    Casting is tomorrow...fingers crossed!

  9. #109
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    Aug 2006
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    258

    Re: Yet another epoxy granite mill

    The casting is done! Took around 4 hours give or take...
    Attachment 468048
    We started with 15% epoxy ratio by weight which was too wet, then went to 12% and it seemed good, could probably have gone to 11% or a tad under...but 12% worked really well so we just went with that, i think it is very reasonable...

    It went very well, no problems at all and it looks awesome! :-) Can't wait to the curing is done so i can get those forms of...!

    /Thomas

  10. #110
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    Re: Yet another epoxy granite mill

    During the preperation for this project i did a lot of testing with this epoxy and it was NEVER warm...not even the slightest... in contrast with many of my other epoxies...

    .... i guess this changes with the amount used:
    Attachment 468052


  11. #111
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    Nov 2020
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    361

    Re: Yet another epoxy granite mill

    Quote Originally Posted by badhabit View Post
    The casting is done! Took around 4 hours give or take...
    Attachment 468048
    We started with 15% epoxy ratio by weight which was too wet, then went to 12% and it seemed good, could probably have gone to 11% or a tad under...but 12% worked really well so we just went with that, i think it is very reasonable...

    It went very well, no problems at all and it looks awesome! :-) Can't wait to the curing is done so i can get those forms of...!

    /Thomas
    With the color you could've fooled me that its UHPC.

  12. #112
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    Re: Yet another epoxy granite mill

    Quote Originally Posted by ardenum View Post
    With the color you could've fooled me that its UHPC.
    yeah, i considered pink color paste, but ended up taking "boring grey" ;-)

  13. #113
    Quote Originally Posted by badhabit View Post
    During the preperation for this project i did a lot of testing with this epoxy and it was NEVER warm...not even the slightest... in contrast with many of my other epoxies...

    .... i guess this changes with the amount used:
    Attachment 468052


    Wow, who has a FLIR just sitting around to check that lol!

    Yeah, if you'd cast that full thickness at 100% epoxy it could easily result in self ignition. Thickness means more reaction mass and lower thermal transfer and thus why any good epoxy supplier will list maximum volumes for a given mix percentage. Even filled for thermal conduction, epoxies are great insulators, but reactions mean heat is moving...

    I've seen 2mm thick beads burn themselves at >250°C because we couldn't read the label on a magbonder and used it as a gap fill.

  14. #114
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    Aug 2006
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    258

    Re: Yet another epoxy granite mill

    Quote Originally Posted by StrawberryBoi View Post
    Wow, who has a FLIR just sitting around to check that lol!
    They are built into CAT smartphones :-) Very usefull!

  15. #115
    Quote Originally Posted by badhabit View Post
    They are built into CAT smartphones :-) Very usefull!
    I had to look that up, thought you were pulling my leg! I'm a basic $100 smartphone kind of guy, but then again, I have cracks all through the screen and I'm setting it down where it gets chips and cutting oil on it sometimes...

  16. #116
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    Aug 2006
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    258

    Re: Yet another epoxy granite mill

    Post-curing in progress... I threw together an oven of sorts:
    Attachment 468156Attachment 468158Attachment 468160

    ...and a very safe and wife-approved PID controller for the 2kW heater inside the tent:
    Attachment 468162
    ...i seperated the fan itself and the heatingelement, so the fan always runs and then the heating element is controlled via the PID controller...

    The resin manufacturer states >40c in 12hours or more, however for maximum strength 70-80c is recommended. I was hoping for 70c, but i'm not sure that 2kW is enough... i'll see....

    Note for others: Remember to put your temperature sensors in the casting... i had it planned, but forgot it :-(

    /Thomas

  17. #117
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    Jul 2018
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    6254

    Re: Yet another epoxy granite mill

    Good oven Thomas - Will take a while to get the heat into the centre. With metals its recommended to heat 1hr per 25mm (Then the required soak time) and plastic is an insulator compared to metal... shame about the missing sensor you must have got excited... You can't overcook it so let it run for as long as you can stand the suspense...2kW will get to 70-80C easily with that insulation.. I used to heat treat aluminium with a 2kW oven, 50mm of rockwool and it got to 200deg C... Peter

    Is there wool on the floor? The floor will absorb heaps of heat.... I had a top hat oven once (so we could trolley things into the oven) and the floor was the biggest pain. Couldn't get to temp until I put in a false insulated floor and a ramp...

  18. #118
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    Aug 2006
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    258

    Re: Yet another epoxy granite mill

    Quote Originally Posted by peteeng View Post
    Good oven Thomas - Will take a while to get the heat into the centre. With metals its recommended to heat 1hr per 25mm (Then the required soak time) and plastic is an insulator compared to metal... shame about the missing sensor you must have got excited... You can't overcook it so let it run for as long as you can stand the suspense...2kW will get to 70-80C easily with that insulation.. I used to heat treat aluminium with a 2kW oven, 50mm of rockwool and it got to 200deg C... Peter

    Is there wool on the floor? The floor will absorb heaps of heat.... I had a top hat oven once (so we could trolley things into the oven) and the floor was the biggest pain. Couldn't get to temp until I put in a false insulated floor and a ramp...
    I also think the floor is the main-problem, as it has no wool on top. It is however isolated below the concrete with 300mm styrofoam, but nonetheless the concrete also absorbs heat(and transfers it outside the tent)... this is also why i doubt i'll get to 70-80c with the 2kW heater... but lets see... i checked the airtemp this morning and it said 47c after it has been running for around 10'ish hours at full tilt...

    My plan is to remove the molds sometime during the coming weekend, so i'll turn it off and remove the tent half a day prior to let it cool a bit so i can handle it without issues...

  19. #119
    After the >12h cure completes, which with your thickness going overlong is always better because like pete says it will take a bit to reach that in the core, you can move the solid castings onto insulation and heat again for the full curing temp.

    Doing the elevated temperature cure as much as possible will add dimensional stability as well as strength.

  20. #120
    Join Date
    Aug 2006
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    258

    Re: Yet another epoxy granite mill

    …52 degrees after 20’ish hours…

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