Help me find a 3dprinter heatbed.

There is 120V AC going into the power supply?
there is 120V AC powering your hair dryer --- they are generally safe

Relay or SCR controlled by standard printer heater firmware / software to control it

A transformer would increase / decrease AC voltage NOT make it any safer.

Current Kills NOT voltage!!

You could power it with 120V DC
It is a big resistor that heats up with currect going thru it.


Most Heated bed 3D printers use glass plates as printing surfaces
ABS or PLA
Rare to find a 3D printer without a flat smooth Glass printing surface!!
Very inexpensive very flat surface

Quote
the_digital_dentist
Connecting 110V to the printer isn't a good idea because of potential safety problems. In order to be safe you'd have to connect through a transformer, but if you';re going to do that, you may as well use a lower, safer voltage.
Glass plates are fine for unheated beds, but glass is a poor conductor of heat and you'll end up with hot and cold spots. Some people use an aluminum bed to spread the heat and then use thin glass plates on top of the aluminum to print. That allows you to take a finished part and plate off the printer and replace it with another piece of glass while the first one goes into a freezer to release the printed part.

Quote
cozmicray

Current Kills NOT voltage!!

[/quote]

No offense but I am tired of seeing this. While it is true current kills, as a human we would have a hard time dying by touching a 1000amp 1.5v power supply, vs a 500v 3amp version. They both emit the same energy, 1500W and both can potentially do the same amount of work. Its all relative, the voltage has to be high enough to penetrate skin, I believe its in the neighborhood of 35-50v is when you start to get skin penetration. While true you can kill someone with only 1.5v volt, you would have to probably install cathodes into their heart to do so.

The real answer is, It depends on the circumstances. Ever wonder why they leave the terminals of a car battery exposed in basically every vehicle? Well those batteries can produce well in excess of 1000amps for a few seconds.... 1000amp x 12.8v nominal you have 12.8KW of power temporarily. Not many have died from car batteries.....

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Modicum V1 sold on e-bay user jaguarking11

jaguarking11

Point taken -- you sound like an electrical engineer

Please comment on the use of a 120V AC heated bed on a 3D printer
since the expert, the_digital_dentist, has stated that it isn't a good idea?

Thanks

Look;

Personally I went through great pains to ensure I had enough amperage to run every accessory on my printer at 12v.... The reason is simple as I am too lazy to properly wire a heated bed for mains power and having a readily available 12v heating element reduces the amount of work I need to perform.

A transformer or not, 120v ac or 50v dc or whatever adds unneeded risk to the printer. If I were to go for a large printing surface, 24inch x 24 inch or larger I would probably go for a mains powered unit, I would ensure i have met the proper requirements of safety. This means the AC mains power would be isolated, with proper terminals and FUSED. Everything would run very heavy gauge wire if it needs it or not. There would be a separate controller for the bed, again on isolated circuits. In my 30inch round bed I did not bother, it heats to 90c with the 160w 12v bed just fine. Things to consider are also the grounding, because you added a ground wire, adding a proper ground to equipment you need to ensure the ground is not being fed voltage, its hard to insulate a 1500w heating element.....

The real answer is again it depends, an engineer knows each solution has compromises. Need to squeeze more than 300W of heat into a bed? Its suddenly easier to do so by mains rather than 12v. For my needs my 1300w 12V psu is more than double what I need. I only need about 35A at 12.3v to feed everything I need and want. that is peak draw, the PSU happens to be capable of supplying about 110Amps if I need it, but I need to use 220v input for that much. @ 110v it happily supplies about 60A if necessary. Also heavy gauge wiring gets expensive fast. For a 300w bed you draw 25A @ 12v or thereabout. I would use at least 8 gauge wire for that to make sure the resistance of the wire is not a factor. Probably would use 6 gauge to be sure. I would also keep the length under 3 feet...

The only stone to grind I have is people perpetually saying its the amperage that kills. that is certainly true, but only sometimes..... Stay safe and don't fry anything but bacon.

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Modicum V1 sold on e-bay user jaguarking11

Quote
cozmicray
jaguarking11

Point taken -- you sound like an electrical engineer

Please comment on the use of a 120V AC heated bed on a 3D printer
since the expert, the_digital_dentist, has stated that it isn't a good idea?

Thanks

Before I was a dentist I was an electrical engineer for 22 years. I can state unequivocally that low voltage is safer than high voltage.

Comparing commercial products that operate from 117VAC and are designed to meet multiple electrical and fire safety standards to work done by amateurs, especially amateurs who don't understand the relationship between current, voltage, and power, is comparing apples to oranges.

Finally, with regard to current and wire size, wires are rated for current by gauge, insulation material, and allowable temperature rise (OK, also whether they are exposed to air or are in a bundle of other wires). Since all wires have resistance, all wires warm up when they carry current. It becomes a problem if they get so hot as to be a skin safety hazard or the insulation melts off and/or burns. Below that sort of temperature rise, wires can be used safely. PVC Insulated Wire and Teflon Insulated Wire have information about maximum currents. Note that Teflon insulated wire is considered safe up to 200C so has a higher maximum current limit (at least in free air) than PVC insulated wire. Of course, 200C would be a serious burn hazard, so you'd never operate that hot in any place where someone might contact the wire with their bare skin.

My printer has a 450W heater that operates at 24V (so it takes about 20A). I use a buck/boost transformer to power it from 24VAC. The wire connections to the print bed heater consist of two 16 ga wires on each side. Those wires warm by about 5-10C when the bed is first turned on and the duty cycle is 100%. Once the PID controller senses that the bed is at print temperature (105C) the duty cycle drops and the wire temperature drops with it. There is no need to use heavy gauge wires because the bed does not require power continuously. You can see the wires in this photo:



The wires in question are the twisted white wires that go into the terminal block on the undercarriage of the printer's Y axis.

Edited 1 time(s). Last edit at 11/21/2014 08:12PM by the_digital_dentist.

What free 3d program can i use for a 20 " by 20" printing surfaces

Any CAD program should be OK for any size bed. I have been using DesignSpark Mechanical a lot and find that I rarely run into its limitations. If you're looking for really simple, try Sketchup.

Thank you,ill stay with sketch up because i know how to use it.

Is there a limit of how many stepper motor i can connect to ramps 1.4 control board

I would like my 3d printer to have 7 stepper motor

Quote
nick6765
I would like my 3d printer to have 7 stepper motor

There was a thread just the other day that asked almost the same question. If you really need 7 steppers, Deut with Duex4 was the only one that I knew of. If any of those 7 steppers could be doubled up (e.g. dual lead screws for the z-axis) then you have a few more options with 6-stepper electronics.

the. Y ax will have 2 ,x will have 1,z will have 1,extruder will have 1.its more simple if i use 5 instead of 7 .I was also fund out i can make my heat bed with strip board but i did see good instruction to build it,i was think about my 3d printer to print about 20"x20" is the max but know that i think alittile more how about 40"x40" and the height 50"

What material is good to hold my heatbed ,something that can heat resistant and cheap enough were i can buy large squires of it

You can print with ABS on PIR (polyisocyanurate) foam without heat. I have not tried printing on it with PLA.
PIR foam is sold in big sheets for building insulation. In the US a 4' x 8' x 1" sheet costs about $15 (PIR foam sheet at Home Depot). You can cut it to the size you need with a razor knife.
Stratasys FDM machines print on polyurethane foam. I've been told they charge about $70 US for a single piece of foam about 250x250x30 mm.

Advantages:
1) no heater, power supply, kapton tape, ABS juice, hair spray, or glue sticks needed
2) low mass, great for large build envelopes
3) cheap
4) reusable- can print on one piece of foam multiple times
5) no bed leveling required- just bury the extruder nozzle about 1mm into the foam for the first layer

Disadvantages:
1) must print on a raft- no super smooth, shiny bottom surface on your print.
2) ?

I did some tests about a year ago and posted a couple videos to Vimeo:
[vimeo.com]
[vimeo.com]
[vimeo.com]
[vimeo.com]

As you can see, there's no problem with getting parts to stick!

I used double sided tape to stick the foam to my machine's glass print bed because I was testing. There's no need for the massive glass bed- just a light weight undercarriage to support the foam and keep it from moving.

I am just dipping my toes into 3d printing, so apologies that I haven't read everything on this forum, my background is in homebuilt aircraft, I believe in keep it simple.

The more I look at 3d printers, the more it occurs to me that printers especially those designed for larger objects should be enclosed.

I guess a big printer means very, very slow builds, unless you are using very large nozzles, so warm up time for the bed is not really an issue,

How about this as a way to do it.

Build a cabinet to be a fairly close fit around the printer, I would make it out of 15mm plasterboard and 2x4 timber, and use insulating foam to fill in between the wood.

Use a double glazed window unit for the front door - befriend any window installer he will have stacks of old ones reclaimed from house refurbs.

The bed could be made from 15mm MDF - unheated. as ABS and PLA are relatively good insulators, the heat from the bed isn't actually doing anything after the build is more than 2mm high, so a hot bed seems pretty pointless to me.

I am uncertain about using PIR foam as the bed, the idea of digging the nozzle in seems odd, it may work for small models, but the foam will certainly spring back to it's original position on a large build - I guess it could take a minute per layer on a 20 inch model. If the foam has sprung back, the nozzle will bash into the first layer when doing the second layer - that could be quite messy.

The heating could he suitably sized mains powered halogen lamps and a small circulating fan you can experiment until you get the number right.

I am unsure what temperature you need inside the box to get the best rate of cooling, but I bet it does not need to be anything like 100c, you could have several GU10 lamps in the box and switch some off once the box is nice and toasty. I reckion it won't need more than 100w to get the box up to temp, and probably a lot less to maintain steady state. The whole model then stays at the same temperature, and you can control the cool down by gradually reducing the heat

A further benefit of this appoach is you don't have wires to come detached from the bed.

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Note
it could turn out to be impossible to unglue a 15ix15 inch model from the MDF, you probably want to spray it with release agent rather than hair spray.

And some imponderables

I guess a large 15x15 model could take more than a single spool of filament, How is that handled.

A big model has lots of inertia, presumably that means you have to move it very slowly or use big steppers and big belts, if you take the second route, how do you stop it shaking itself to bits?

Pete

A few comments:

One of the first problems 3D printing noobs run into is getting the prints to stick to the print bed. Some people spray their bed with hairspray, others use "ABS juice", others use glue sticks. Kapton tape works well and isn't as messy as any of those, but costs a little more. The heated bed is necessary to keep the ABS part stuck to the kapton tape on the surface of the bed. If you kill the heat the plastic on the bed shrinks as it cools and breaks free of the bed. That kills your print. Normally you set the temperature to about 105C for the first layer then back off to maybe 90C for the remainder of the print. I have doubts about getting ABS to stick to MDF, and if it did, you'd probably destroy the soft surface of the MDF trying to get the print off.

I have found that 40-45C is sufficient to prevent delamination in relatively large prints, but if the base of your print gets to 15" x 15", maybe you need higher temperature. The enclosure doesn't have to be much more than a cardboard box, and it doesn't have to be sealed particularly well because the printer provides plenty of heat to make up for any lost to poor insulation or sealing. I wouldn't bother with wood framing, insulation, and double glazed windows. My enclosure is made of foam insulation board held together by printed clips. I actually prop the door open while printing to prevent the temperature from getting above 45C because I still have the electronics and motors inside the box (soon to change). All the heat is provided by the print bed heater and, to a much lesser extent, the extruder heater and rest of the electronics/motors. My bed heater is a 450W kapton heater glued to the underside of the 1/4" aluminum print bed.

For really big prints that will require more than one spool, you splice the filament as the first spool ends. You just have to heat the two ends up and stick them together.

If you're going to do really massive prints, a printer architecture that doesn't move the bed or only moves the bed in the Z axis is the best way to go.

Excellent advice from the dentist as usual. I would add that MDF is not stable enough to use for the bed. Use a glass or thick anodised aluminium plate instead.

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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].

Does anyone know were i can buy online this things,
smothrod m8 hardened steel height 55" and 35"
Threadedrod m8 steel height 55"

Quote
nick6765
Does anyone know were i can buy online this things,
smothrod m8 hardened steel height 55" and 35"
Threadedrod m8 steel height 55"

Offtopic for this thread, but google is your friend. Or ebay, aliexpress, McMaster-Carr, Mitsumi, etc... You'll probably want to search for metric lengths when specifying metric rods. 1m 1.5m, are probably going to be your most likely length options and then cut them down, but you may need to go up to a 2m rods if you can't find any at 1.5m for the 55" length.

What deos the smoth rod have to be made of,i think hardend steel will be good but i can found the right one with the length i need.how about aluminum ,but i think the ball bearing will scratch them?

Steel balls will chew grooves into aluminum very quickly.

Look into something like this: [www.ebay.com]

You can often find used ones for reasonable prices and they are much more precise than round rails.

Quote
the_digital_dentist
Connecting 110V to the printer isn't a good idea because of potential safety problems. In order to be safe you'd have to connect through a transformer, but if you';re going to do that, you may as well use a lower, safer voltage.
Glass plates are fine for unheated beds, but glass is a poor conductor of heat and you'll end up with hot and cold spots. Some people use an aluminum bed to spread the heat and then use thin glass plates on top of the aluminum to print. That allows you to take a finished part and plate off the printer and replace it with another piece of glass while the first one goes into a freezer to release the printed part.

I have used 240 volt heated beds on over 70 builds with no problems at all. The power is switched by a SSR which is controlled by RAMPS the same way a 12 volt heated bed is attached.

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[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

Everything is OK until it isn't. I hope you have continued good luck with no one getting injured or killed.

Edited 1 time(s). Last edit at 01/20/2015 12:29AM by the_digital_dentist.

Could you please be so kind to indicate where specifically?

Thank you so much.

Little bit late to the discussion, but I made mine out of paperclips, nichrome wire from a dead hairdryer, a fiberglass ceiling tile and some high temperature tape. heats up in a couple minutes, and havent had any ABS warp from it.

I just realize something,why cant i just buy lots of small heatbed tell i reach the dimmesion i want and place aluminum on top of them.

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Quote
ocina
I just realize something,why cant i just buy lots of small heatbed tell i reach the dimmesion i want and place aluminum on top of them.

Yes, you can do that. If they are all the same model of heat bed (in particular, they have equal resistances - which also depends on the manufacturing tolerances), you can connect them in series as well as in parallel so as to avoid needing a very high current power supply. For example, if you use four 12V 10A heated beds, you could wire them as 2 chains of 2 each and connect the chains in parallel - so the power needed would be 24V @ 20A. This is still a lot of power, and the power supply will be expensive.

For very large heat beds, mains voltage is the only realistic option - but then you need to address the additional electrical safety issues, as others have pointed out. It's easier on a delta printer, because the heated bed is non-moving.

Edited 2 time(s). Last edit at 02/20/2015 06:40AM by dc42.

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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].