New Delta Heated Bed Options & Arm Length

I am 90% of the way through my new Delta build and the last pieces of the puzzle are the heated bed and delta arms. The goal was to use as few printed parts as possible, and so far there are no structural pieces at all. I am really pleased with how it's come out so far and want to make sure I get the arms & heated bed right.

Here's a few pictures to introduce you...

Here you can see the base frame with Smoothieboard. The custom front panel. has USB, Ethernet, LEDs for power, bed and hotend. There is also a reset switch (top hole)


Here's how I conceal the wires going up the corner of Z frame...


I went for simple endstop switches for starters, you can also see I am using a 20T idler pulley at the top.


I made a bracket for the dial test indicator, after homing and then sending the carriages down to 0. The deflection was never more than 0.02.


So far, so good.

I think the build looks really clean, and using the metal corners, carriages and effector with the acetal trucks, everything fits snug and feels solid.

The last pieces of the puzzle are the delta arms and bed. (For reference the horizontal profiles are 330mm and the uprights are 740mm)

So i guess the first thing, is to decide the bed size. Edge to edge is approx 265mm diameter...


Is is the best practice to stick within this size or is it OK to have a small overhang?

Lets say I wanted to go for 300mm dia, as it's a nice round number. I had a play with the Delta Simulator to try and calculate the arm length. However, I wasn't sure about the beam_int_radius, is it this?


If the above is correct, then it says my arms should be 345mm for a working dia of 300mm, and a min angle of 20 degrees. Does that sound correct?

A couple of things to note.

• While I am unlikely to print anything that big, I would like to maximise the print radius.
• Height is not important, 200mm would be ample.(I am sure the highest thing I have ever printed in 3 years was 80mm tall!)

Finally, there is the heated bed. I am using a Smoothieboard, and while the big mosfets are rated at 20A the connectors are only 12A. I like a bit of a safety margin, so I really want something that is no more than 10A. I am struggling to find something to correct size and power rating. Suggestions are welcome.

Notes...

• I have definitely ruled out a mains voltage heater.
• I did order a cheap SSR but I am worried about the heat/voltage drop. (would bolting it onto one of th e60x20 extrusions be a good enough heatsink?)

If anyone is interested, I can create a BOM and supply the STLs for the few printed parts.

Regards,

Les

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345mm length for 300mm print area sounds about right. You can make the bed as large as you like as long as it doesn't hit the belts. Enclosing the printer is harder when the build plate extends past the horizontals.

I'd turn your printer upside down as it makes wiring and maintenance a lot simpler.

A non-fake Fotec SSR makes using mains electricity safe. I'm using a Keenova 300mm 120v 500w heater. Warm up to 115C takes about 5 minutes (build plate is 8mm).

Quote
etfrench
345mm length for 300mm print area sounds about right. You can make the bed as large as you like as long as it doesn't hit the belts. Enclosing the printer is harder when the build plate extends past the horizontals.

I'd turn your printer upside down as it makes wiring and maintenance a lot simpler.

A non-fake Fotec SSR makes using mains electricity safe. I'm using a Keenova 300mm 120v 500w heater. Warm up to 115C takes about 5 minutes (build plate is 8mm).

Thanks for the reply.

I ended up going for 340mm arm length and have just glued the 3rd arm this morning. Stupidly, I only ordered 6 x M4 grub screws, so I can't finish the arms until some more arrive.

I personally have no problem working with mains voltage, but I do want to keep this all 12V. Also, as I am only going to print PLA with this Delta, it seems silly to have a super high powered heated bed. (I am not sure what in my Ormerod,I think it's a MK2, but the heat times are only a few minutes for 65 degrees)

I have contacted a supplier on AliExpress, as they say they can make silicone heaters to any size, voltage & power requirements, but I haven't received a reply yet.

Regards,,

Les

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Pointy's Things
Pointy's Blog

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Pointy
I personally have no problem working with mains voltage, but I do want to keep this all 12V. Also, as I am only going to print PLA with this Delta, it seems silly to have a super high powered heated bed. (I am not sure what in my Ormerod,I think it's a MK2, but the heat times are only a few minutes for 65 degrees)

Why not 24V? If you will be using 0.9deg stepper motors for the towers, you should definitely use 24V power.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42

Quote
Pointy
I personally have no problem working with mains voltage, but I do want to keep this all 12V. Also, as I am only going to print PLA with this Delta, it seems silly to have a super high powered heated bed. (I am not sure what in my Ormerod,I think it's a MK2, but the heat times are only a few minutes for 65 degrees)

Why not 24V? If you will be using 0.9deg stepper motors for the towers, you should definitely use 24V power.

Because I have the 300W 12V PSU already with 12V fan/hotend heater and I have already spent too much on this project..

I am also just using the standard stepper motors, but maybe in the future I will consider the 24V/0.9deg motor upgrade.

Regards,

Les

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Pointy's Things
Pointy's Blog