for the daily WTF, I wonder why the 3d printer hot plate ... - Page 1
Forum section: electronics / general

author: legacy
author_rank: Super Contributor
timestamp: June 19, 2018, 09:37:39 am
content: Recently I have been playing with 3d printers, developing kits and hacks, among which the replacement of the standard hot-plate with a custom one, and I got a lot of questions, thus I really wonder why people insist they want a 3d printer hot plate made with the same technology of Electronics PCB Circuit Board, rather than a plate made of aluminium?an aluminum plate costs just 4 euro and it's for better at conducting heat than PCB, it's more mechanical resistant, and doesn't need to be painted.copper is better at conducting heat than aluminum, but PCB plates only come with a thin copper plate, say a quart of the thickness is made of copper, the rest is resin and glass powder, that is rather heating insulationthere is up to 100 C degree on the hot plate, it needs to be of the same kind possible in every point of the plate, thermal gradiends are not good when you print, and there are 3d printers that need a special mechanism to balance out the plate, this mechanism consists of five conductive areas on the plate, and the extruder head moves on the plate looking for these points to balance the plate by software, or by hardware if behind the plate there are 3 motors used to correct the roll on the X and Y axes.so, why they insist on PCB-hot-plates?

author: mikerj
author_rank: Super Contributor
timestamp: June 19, 2018, 10:06:09 am
content: How do you heat the aluminium plate without significant thermal gradients?

author: legacy
author_rank: Super Contributor
timestamp: June 19, 2018, 10:08:12 am
content: Quote from: mikerj on June 19, 2018, 10:06:09 amthe aluminum plate is 100% made of aluminum.the PCB plate is made of copper for 1/4 and 3/4 of it are made of a thermal insulation material.also, the copper does oxidate: how to solve it? with a protective spray?

author: legacy
author_rank: Super Contributor
timestamp: June 19, 2018, 10:14:09 am
content: anyway, when I was talking about thermal gradients, I was referring on the printing surface: ideally, you want the same temperature at every point on the printing surface. If the copper does oxidate, it's even more far from the ideality.which treatment can you use to avoid that? to print, you need a spray to anchor the object you are printing, when you remove the printed object, you might remove the treatment for the copper.that is bad.

author: sleemanj
author_rank: Super Contributor
timestamp: June 19, 2018, 10:16:39 am
content: Because a PCB based heated bed is cheap and easy to construct, very easy, you can make one yourself if you wanted, just like etching any other PCB, just a fairly large one.If you make a heated aluminium bed, you have to heat the aluminium some how, how do you propose to do that, to construct a heating element which is appropriately bonded to the plate, this is not a trivial manufacturing task.

author: legacy
author_rank: Super Contributor
timestamp: June 19, 2018, 11:00:25 am
content: Quote from: sleemanj on June 19, 2018, 10:16:39 amAluminum heated bed costs 4-5 Euro, already cut and you only need to drill 8 holes for the support.The surface is electrically conductive, that makes it perfect for the auto-balancing mechanism (if the 3d printer supports it).NOTE:you have only to choose "untreated" aluminum plates, there are some with a protective film on the top, and this protective film is not electrically conductive.Quote from: sleemanj on June 19, 2018, 10:16:39 amas easy as aluminum, but, to do a proper job, cutting PCB requires special tools, you can cut it with a common cutter, but after a while, it destroys the blame since the PCBs are made of glass powder and it's abrasive.Quote from: sleemanj on June 19, 2018, 10:16:39 ambut the copper does oxidate, and you need to protect it. How to do so?Quote from: sleemanj on June 19, 2018, 10:16:39 amthe heater is a component, it stays below the aluminum plate, these parts are in contact, and the heater transmits the heat to the aluminum plate that diffuses it on the printing surface.Thus you mechanically have a heater plate, and you have the aluminum plate on the top.They are blocked with screws, and it's very easy to be assembled.

author: mac.6
author_rank: Regular Contributor
timestamp: June 19, 2018, 12:08:26 pm
content: my printer (ender 3) has an aluminum heated bed, with printed heat track on the back.The issue is that it's warped, 0.15mm bend in the middle. With much seating, some precision rods and a granit surface plate I have been able to reduce it to <0.1mm, but glass is generaly <0.05mm out of the box.

author: bob225
author_rank: Frequent Contributor
timestamp: June 19, 2018, 12:15:40 pm
content: why Pcb/wire elements ? cheap and easy to mass manufacture, proven to work, cheap heatpads are cheap for a reason, they are not made to lasteg.https://reprap.org/wiki/PCB_Heatbed#MK2_A4Even high end machines use a pcb or wire element with a aluminium sheet on top to dissipate the heat, even the Ultimaker use itbuilding a heating element on a aluminium sheet is a no go as the aluminium will expand and contract at different rate to the copper or carbonI started out with a ooznest prusa I3 with a Pcb MK2 heatbed what was a major learning curve, I now have a Ultimaker 2+ thats been flawlessif you want to really learn have a look around the openbuilds forum

author: legacy
author_rank: Super Contributor
timestamp: June 19, 2018, 01:02:56 pm
content: Quote from: bob225 on June 19, 2018, 12:15:40 pmthat is close to my idea.anyway, copper oxidizes, and you need a copper plate to auto-balance the plate, to correct the bend on the X and Y axes: how do you solve this problem with a copper plate?here I need 5 electrically conductive points on the surface, moving the extruder on the Z axis, these points are checked before printing.

author: bob225
author_rank: Frequent Contributor
timestamp: June 19, 2018, 05:20:54 pm
content: The pcbs are insulated you just need to wire it uphttp://ooznest.co.uk/Aluminium-PCB-Heated-Bed-MK2B

author: mikerj
author_rank: Super Contributor
timestamp: June 19, 2018, 10:15:36 pm
content: Quote from: legacy on June 19, 2018, 10:08:12 amYou haven't answered the question, how are you planning to heat the aluminium plate evenly to avoid thermal gradients (since this seems to be one of your concerns)?If you stick some power resistors to the back, you will get hot spots = thermal gradients. A PCB can have an etched heating element distributed over the entire surface to get very even heating.

author: sleemanj
author_rank: Super Contributor
timestamp: June 19, 2018, 10:47:44 pm
content: Quote from: legacy on June 19, 2018, 11:00:25 amAnd you also need a heating element of some description.Quote from: legacy on June 19, 2018, 11:00:25 amGood grief if you are doing that many you send it to the PCB factory. And as above, if you are making from Aluminium you need an element too, which is not so easy to make.Quote from: legacy on June 19, 2018, 11:00:25 amWith soldermask, legacy, use soldermask.Quote from: legacy on June 19, 2018, 11:00:25 amI think here we see the problem, you don't seem to understand that a PCB heated bed IS the element, there is no element underneath it, that is all there is.So with an aluminium bed you need the aluminium slab AND a way of heating it up. With the PCB heated bed, you need the PCB heated bed, the end.This is a PCB heated bed, it is A PCB with a long windy copper trace eteched on the underside, and a copper plane on the top side, usually you put a glass plate, or some other printing surface (including an aluminium plate if you want) on top of this..https://reprap.org/mediawiki/images/c/c4/PCB_HEATBED.jpgagain, this is a PCB, that's what it is, if you want to get rid of this then you need to replace it with something else to work as a flat, light weight, somewhat uniform heating element. Can you do so cheaper and easier?

author: Gibson486
author_rank: Frequent Contributor
timestamp: June 20, 2018, 01:19:16 pm
content: Quote from: mikerj on June 19, 2018, 10:06:09 amyeah...if you can do that, you can make a lot of money...

author: thm_w
author_rank: Super Contributor
timestamp: June 20, 2018, 08:09:43 pm
content: Quote from: Gibson486 on June 20, 2018, 01:19:16 pmMy cheap $200 3D printer came with an aluminum heated bed that is even enough. I assume its the usual PCB on Al process, so you have a long length of copper track on the bottom, very thin pcb, then the aluminum.If you want to purchase one alone its about $30 (so more expensive than PCB).https://www.aliexpress.com/item/Funssor-Delta-Rostock-Kossel-3D-printer-240-x-270-PCB-hot-bed-12V/32815266304.htmlThe one advantage I do see for PCB heater is the thermal insulation the PCB provides (helps the bed heat up faster). You can see in the above link, it can be achieved on a Al bed as well, with white thermal sheet.

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: June 20, 2018, 09:05:01 pm
content: Another options is an IMS (Insulated Metal Substrate) PCB. Many PCB fab houses, including PCB Pool, offer this as an option.https://uk.beta-layout.com/pcb/pcb-types/info_pcbpool_alupanel.html

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 21, 2018, 12:48:01 pm
content: Abs wont stick to aluminium even when heated iirc. And possibility of scratching the bed with nozzle when used naked making using sacrificial blue or kapton tape is a good idea and hence conductive contact for bed levelling is not. Anyway my cheapo printer is aluminium plate on top and pcb heater trace below (and blue or kapton changable tape on top top) so this is a 'i don't get this' thread. And i dont see how trying to embed heating element into aluminium plate can end up in 4 euro tooling and labor of commercial product cost except for charity work...ymmv.

author: Gibson486
author_rank: Frequent Contributor
timestamp: June 21, 2018, 01:12:38 pm
content: Quote from: thm_w on June 20, 2018, 08:09:43 pmUnderstood, but other applications would beg to differ. There are some applications where the gradient cannot be more than .01 degree C in an 32 in^2 area while still maintaining a +/-.01 degree C set point with something sitting on it . That being said...I do not think 3d printers need that, but I never made a 3d printer before.