Heated bed options for a Prusa-inspired delta printer

Hi all,
I'm designing a delta style printer that takes a lot of design inspiration from the Prusa i3 Mk3.
This is the first printer I've built from scratch, so I'm sure there will be several other posts I'll make about it.

One of the features I really want to include is the magnetic removable bed.
The print surface seems fairly simple, it looks like a 22 ga spring steel plate with .25 mm PEI sheets on both sides.
The heater is a lot harder to replicate. I'm not even sure what it's made of, so I guess that's my first question.
If anyone knows more about it's construction and where to find more information on Prusa's BOM that would be extremely helpful.

Right now I'm thinking of using a 250mm silicone rubber heating pad or a pcb heater stuck to an aluminum plate with magnets glued into machined slots on the bottom.
I've seen a few other posts on here discussing the plate thickness and it looks like 6mm is a decent thickness for an aluminum plate, but that thickness seems like it would take a while to heat up.

Also any help sourcing this stuff would be greatly appreciated.
I'm also trying to find some good linear rails, but I'm having a hard time finding some that are good quality, but wont break the bank.
Does anyone know what's a typical price for 500-600mm lengths and what width is usually used for deltas?

I use a magnetic foil on an aluminum bed for my removable bed, it works just fine. At first i feared the magentic foil would pose a problem with heat conduction, but thermal imaging revealed that it actualy only evens out heat distribution.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

That's in interesting idea. How well does it hold the bed on compared to the Prusa?

Quote
Raxius
Hi all,
I'm designing a delta style printer that takes a lot of design inspiration from the Prusa i3 Mk3.
This is the first printer I've built from scratch, so I'm sure there will be several other posts I'll make about it.

One of the features I really want to include is the magnetic removable bed.
The print surface seems fairly simple, it looks like a 22 ga spring steel plate with .25 mm PEI sheets on both sides.
The heater is a lot harder to replicate. I'm not even sure what it's made of, so I guess that's my first question.
If anyone knows more about it's construction and where to find more information on Prusa's BOM that would be extremely helpful.

Right now I'm thinking of using a 250mm silicone rubber heating pad or a pcb heater stuck to an aluminum plate with magnets glued into machined slots on the bottom.
I've seen a few other posts on here discussing the plate thickness and it looks like 6mm is a decent thickness for an aluminum plate, but that thickness seems like it would take a while to heat up.

Also any help sourcing this stuff would be greatly appreciated.
I'm also trying to find some good linear rails, but I'm having a hard time finding some that are good quality, but wont break the bank.
Does anyone know what's a typical price for 500-600mm lengths and what width is usually used for deltas?

I have a scratch design Cartesian 300mm area printer with a 1/4" thick al plate for the bed.
I drilled and counter sunk that plate for a three-point leveling attachment scheme. I used M8 screws with heavy springs so it wouldn't move around. I have a 3mm borosilicate glass plate on that which I use with hairspray. I do PLA and PETG on this printer.

Originally I used a PCB heater - it worked poorly to heat that massive piece of metal. I replaced it with a 12V silicone rubber heater that I attached with strips of 3M 9473PC tape. That tape will hold with continuous temperatures of 149C and transfers temperature really well. The PCB heater would take 20+ minutes to reach 60C, this silicone heater will do in abut 6 minutes to 65C. BIG improvement.

Heater: (Amazon.com) "Signswise 200x200mm 12v 150w Silicone Rubber Heating Heater for 3d Printer Heated Beds"
Tape: (Amazon.com) "3M VHB F9473PC Adhesive Transfer Tape - 1 in. x 15 ft. Transparent Tape Roll for Permanent Bonding. Adhesive Tapes"
My 1/4" plate would be a bit over 6mm.

I have been using this for two years, and it seems to just get better.

DLC

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

A Prusa inspired delta ??? Like a cone inspired by a cube ?

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

How big are you planning to make the bed? I recently backed a Kickstarter that, well wasnt' successful. But they're releasing anyway. It for a spring steel sheet, that's powder coated with PEI on both sides like the Prusa bed, and a sheet magnet to hold it down that's good up to 150C. They're currently up to 380 mm diameter. I spoke a lot with Ken from the company and I'm looking forward to his product.

https://subtle.design

I'm using a round silicone heater that I ordered from Keenovo on Aliexpress. I ordered a 120V, 360W heater. I ordered it without a thermistor, and with 1m long leads. It's 275 mm in diameter with a 25mm hole in the center for a thermistor. It heats my 304.8 mm x 6.35 mm (1/4") MIC6 plate to 60C in about a minute. 95C in a little under 4.

For linear rails, I'm using 600 mm rails from Robotdigg. I got the stainless steel versions cause they say they're made to higher tolerance as well as the rust resistance. I can say I've been happy with them. They're inexpensive, though I'd say to order one or 2 more as well as a couple of spare bearing blocks just in case you get some that have play. I managed swap around the blocks between different rails to get 3 that had no play and moved super clean.

Take a look at my machine

https://reprap.org/forum/read.php?178,788150,page=4

Edited 6 time(s). Last edit at 08/20/2019 12:39PM by blt3dp.

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I don't know how to compare the prusa and my solution. Both just work. There are some companies offering such a flexible magnetic solution, many claim that you can't use them at ABS temperatures. Mine works fine @105°C without loosing magnetism.
I use this foil [www.smagtron.de]
Since using two foils on top of each other is not optimal (stripe shape of the magnetic fireld) a flexible solution should use a ferromagnetic foil under a PEI, FR4 or whatever sheet.
For me the optimal solution for ABS is a magnetic stainless steel plate with a PEI foil on top. For TPU i prefer the flexible solution with ferromagnetic foil and a PEI sheet.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Using the aluminum plate with the magnetic foil definitely seems like a good plan. I don't really plan on printing ABS so the bed probably won't get above the 85^oC for PETG. I'm not too concerned with the textured bed, but it might be worth trying that kick starter. As far as the bed size goes, the plan right now is to do 250 mm diameter print area with a 10 mm border for mounting. I think that's a good medium between my current Kossel delta, which is 220 mm, and something like the Lulzbot TAZ at 280x280. For leveling, I want to use a PINDA probe like on the Prusas. Since this printer is going to have sheet metal frame with Plexiglas or lexan windows and door, so having that built in thermister will definitely help in calibration and I won't need any exposed surface. Does anyone know a good place to get a PINDA probe without high shipping from Europe or a good clone?

I am currently building a peek/ultem delta printer based on spatialone, it has a magnetic bed that has been tested to 150 degrees without loss of magnetism. I will post pictures of its progress.