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Granite Print Bed?

Posted by MightyMouth 
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MightyMouth
Granite Print Bed?
December 04, 2015 11:18AM
I was just wondering if Granite would make a good print bed? I ask because I was browsing the ALDI Special buys and next Thursday the 10th of Dec they have Granite worktop savers for just £6.99. They have both round and rectangular. I don't know the dimensions but if building your own reprap you could easily adjust the design to accommodate if they are a reasonable size. They do look a bit thick, I don't know if that would be a problem.
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ElmoC
Re: Granite Print Bed?
December 04, 2015 12:17PM
I don't think granite is a very good heat conductor so might not be good if you want to use a heated bed. Also the weight would limit its use to fixed Z height bed, like delta printers.

Overall, personally I don't think it would be a good bed. I'm pretty sure those you linked to are not ground to the flatness you want for a print bed.
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MightyMouth
Re: Granite Print Bed?
December 04, 2015 12:35PM
I am pretty sure granite is a better heat conductor than Glass though the thickness may counter that and I agree the weight might be an issue but for a delta they would be fine. I just thought the cost seemed good but if they aren't flat enough then all the other points are moot.
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the_digital_dentist
Re: Granite Print Bed?
December 04, 2015 01:43PM
Only one way to tell- get a steel ruler and stand it up on edge on the surface. If it isn't flat it will be pretty obvious.

Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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frankvdh
Re: Granite Print Bed?
December 04, 2015 02:54PM
I don't think granite would cope well with heat, being basically crystalline.

Basalt would probably be better, being an igneous rock.

But, unless you slice it real thin, it's going to take a lot of energy to heat it up.
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MechaBits
Re: Granite Print Bed?
December 04, 2015 04:00PM
Not to mention negating all the weight saving you might have done, but I saw an interesting chopping board the other day, made from some plastic material with swirly grooves in it, and I wondered could this be like the printbite stuff? might be good for cold bed with pla?

Though I got a 200x200 tempered glass square for 99p from Home Bargains, its gotta be good for something.
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MightyMouth
Re: Granite Print Bed?
December 04, 2015 04:38PM
I really think the only problem with them would be the thickness and maybe they aren't flat. Granite can withstand heat very well, You can put a hot pan right out of a 500° F oven on granite without worry.
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J-Max
Re: Granite Print Bed?
December 07, 2015 04:04PM
Hi guys,

Granite is often used as reference surface, some are dead flat, but also expensive.
I worry about time and energy consuming to raise granite at an even and usable temperature too.
As you print PLA and don't want any heat bed why not, but what about polymer bounding/release on granite ?

++JM
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MechaBits
Re: Granite Print Bed?
December 09, 2015 06:11PM
Not that I dont want heatbed, just first things first, without so as not to fry anything in the arduino too early on, I wouldn't mind using a slab of granite or concrete for the printer base, if I can set some M8 or M12 inserts in it.
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ElmoC
Re: Granite Print Bed?
December 09, 2015 07:57PM
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MechaBits
Not that I dont want heatbed, just first things first, without so as not to fry anything in the arduino too early on, I wouldn't mind using a slab of granite or concrete for the printer base, if I can set some M8 or M12 inserts in it.

Are you serious about the granite and concrete or not?
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kenblu24
Re: Granite Print Bed?
December 10, 2015 01:07AM
I've got a Basalt bed on my Threeup. I would go for a standard glass or aluminum bed over Basalt though, it's really thick and heavy and heats up slowly.

It works quite well as a flat surface though, probably retains/distributes heat quite well too.
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MechaBits
Re: Granite Print Bed?
December 10, 2015 02:01PM
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ElmoC
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MechaBits
Not that I dont want heatbed, just first things first, without so as not to fry anything in the arduino too early on, I wouldn't mind using a slab of granite or concrete for the printer base, if I can set some M8 or M12 inserts in it.

Are you serious about the granite and concrete or not?

I was talking about base not bed, if i had a heavy base, with holes for rods, or better inserts for rods that have threads on the end, it would reduce my current part list quite a bit, maybe a cast resin would suffice.

Why what problems do you forsee besides getting all inserts totally true.
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ElmoC
Re: Granite Print Bed?
December 10, 2015 02:14PM
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MechaBits
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ElmoC
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MechaBits
Not that I dont want heatbed, just first things first, without so as not to fry anything in the arduino too early on, I wouldn't mind using a slab of granite or concrete for the printer base, if I can set some M8 or M12 inserts in it.

Are you serious about the granite and concrete or not?

I was talking about base not bed, if i had a heavy base, with holes for rods, or better inserts for rods that have threads on the end, it would reduce my current part list quite a bit, maybe a cast resin would suffice.

Why what problems do you forsee besides getting all inserts totally true.

My concern was more about trying to use them as the print surface, not a structural component. But even then, that would be a lot of weight to deal with when you have to move the printer.
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MechaBits
Re: Granite Print Bed?
December 10, 2015 02:50PM
Not thinking about moving the first build, figured a heavy base would provide a stable base less prone to vibrations, no need for frame, single Z would have a smaller footprint but if dual Z would need a base about 150x400 so quite slim.
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ElmoC
Re: Granite Print Bed?
December 10, 2015 02:59PM
You will want to move it eventually.
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enastoyashchiy
Re: Granite Print Bed?
December 10, 2015 03:47PM
I also don't think granite is a very good heat conductor so might not be good if you want to use arduino a3144 a heated bed. Also the weight would limit its use to fixed Z height bed, like delta printers.

Overall, personally I don't think it would be a good bed. I'm pretty sure those you linked to are not ground to the flatness you want for a print bed.
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MechaBits
Re: Granite Print Bed?
December 10, 2015 07:23PM
it wouldn't be any heavier than a granite chopping board, slimmer but longer 1" thick, simple, functional, the only problem I see is shipping it, I would rather a simple light mold that could be used to cast a resin base...add some broken watch parts, fossils, old computer parts or what ever.





But as for using as a heatbed?, but I do love a nice juicy steak served on a hot slab of something.

Edited 4 time(s). Last edit at 12/10/2015 07:32PM by MechaBits.
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etfrench
Re: Granite Print Bed?
December 10, 2015 09:07PM
Self leveling epoxy is commonly used when building CNC machines, but you would need to verify it's working temperature range.

Granite is easy to drill with diamond or masonry (carbide) bits. Use running water to keep the dust down as it can cause silicosis.

You can use magnets to hold the inserts at the top level of the granite. I don't think the inserts have to be particularly true, but the pieces they will be holding down need to be true. In other words, it isn't good practice to depend on bolt hole location to true the pieces. Use a fixture or jig for location which can be removed once the bolts are tightened.
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epicepee
Re: Granite Print Bed?
December 25, 2015 07:51PM
I have a stone bed (basalt). I don't recommend it. It takes ages to heat up -- it can only hit 90C after about two hours with an old shirt insulating the top, and it levels off at about 50C with no insulation (i.e. when printing).

OTOH, it is very flat and tough, so it might be nice without a heater.
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