New three regulation point aluminium bed

  • Hi guys, I would like your opinion regarding my future heated bed / bed for a D-bot corexy printer.
    The bed is a cast aluminium sheet 3303408mm covered with PEI on both sides.
    Heating element is a Keenovo 300x300 silicone pad 220v 750W.
    I was inspired to make this three point bed by Mark Rehorst
    I am planning to replicate the Mark 's system using a mount made by an aluminium peace or Vslot peace witha M5 ball head screw.I woould like to have some suggestions from you

    Head screw type
    option 1 metal .heat resistant but current capable
    option 2 bachelite. heat resistant only till 120 C°but insulating and this can help using a 220v heating bed

    How level it?
    option 1 an hole on the bed and I can reach the head of the ball which is provided with hex
    but I'll lose some printable surface
    0_1555615492014_hole.jpg !
    option 2 buy ordinary m5 screw and a simple m5 ball , regulate the bed underneath using the regular head screw
    0_1555615535794_head screw.jpg
    cons , maybe not to comfortable to reach
    option 3 another ball or regulation roller underneath
    I made three scenshoots about it

    Next things to do is how to make the ball slot in the bed.

    option 1 CNC machining a slot under the bed
    option 2 glue a machined peace underneath, this second option could lead in the possibility ov reverse the bed in case of the first side gone scratched but I really don't know withc kind of reliable glue I could use. Heat resistant silicon?

    Thank you for your help

  • Instead of the ball head screw I am thinking about using this cheaper and a lot more easy to buy in different threads

  • Acorn nuts should work fine instead of spherical head screws. I'd put a long screw through the teflon block and put the acorn nut on the end of the screw (with a drop of locktite or even epoxy to ensure it can't come loose). Adjusting the screws from under the bed shouldn't be a problem as long as you can reach them easily. Adjustment will probably only be needed when you first set up or modify the Z axis.

    The mounts for the leveling screws should hold the screws without allowing them to wobble, and it needs to be heat resistant because the screws are going to get hot. I find Teflon/PTFE works great. It is very easy to work with and all you have to do is drill a slightly undersized hole for the screw and it will roll its own threads into the PTFE. Even though it grips the screw tightly, you'll find it easy to turn the screws for leveling. Your design for the blocks is a cube that will be easy to make using just a saw and a drill.

    My stock was depleted, so I just ordered a block of PTFE via ebay (search "PTFE block"). The listings for the stuff vary widely in price, just like the linear guide listings. Take out your calculator and run the numbers and you'll quickly find a good deal. PTFE weighs 0.08 lb/in^3. Most of the PTFE listings give dimensions in inches, so just calculate and compare the cost per lb including shipping. I ordered one of these which will probably be enough PTFE to meet my needs for the next 5 years or more. It was about $6.50/lb- cheaper than printer filament.

    If you can't get PTFE for some reason, look for Delrin/acetyl. It should be OK for this purpose. Whatever you do, don't use nylon (I made that mistake, once). There's a reason they use nylon for nylock nuts...

  • @mrehorstdmd thank you again for your such great help.
    I wa thinking to use a spare 4020 Vslot for making the support , but I'll investigate the PTFE suggestion it should a lot easier to work .

  • in case you have not bought the bed yet.

    There is a shop that pei powder coates aluminium plates. Since they are manufactures to order they even do bed according to spec.

  • I drilled and tapped the side of my bed, and mounted it with 3 ball joints, like used on the rods on delta style printers, they were made of nylon with a metal "ball". I considered using nylon screws, but used some precision sholder bolts i had for the ball joints instead. So far so good.

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