All Things BOXZY *Unofficial*
Register Calendar Latest Topics
 
 
 


Reply
  Author   Comment   Page 1 of 2      1   2   Next
CKP343

Junior Member
Registered:
Posts: 20
Reply with quote  #1 
Buy a heated bed or some form of heating the aluminum plate you have now. After waiting hours and hours on prints that warp from cooling I have had tons of trouble with getting them to stick and stay stuck. Yes I did everything from the best tape and glue sticks right down to maple syrup which is messy. Some of the prints were not terrible but pretty much everything had an issue with warp. Once I put a heated bed on and cranked it to 70c I have had ZERO warping issues If this is something you are experiencing I just thought I would let you know it is easily solved with heat. P.s. If you tape a paper shield around it to keep the heat in you will have much better prints as well.
0
Gary

Avatar / Picture

Senior Member
Registered:
Posts: 116
Reply with quote  #2 
Are you using a separate power supply for the heater or are you running it through the heater port on the controller?
0
Drunken Boxzer

Avatar / Picture

Moderator
Registered:
Posts: 327
Reply with quote  #3 
Are you printing on to glass over the heated bed?
0
CKP343

Junior Member
Registered:
Posts: 20
Reply with quote  #4 
I am using a separate power supply and a separate controller. It's my heated bed from my old printer so I just disassembled it. It is an aluminum heated bed. I clamped it in place and leveled it then turned it to 70c and while hot I applied glue stick to the surface of the aluminum. I am printing directly on the aluminum. The cleanup is super easy just use a razor and the parts "pop" right off the build platform. I would like to find a way to heat the factory bed using boxzy.
0
Stealth

Junior Member
Registered:
Posts: 12
Reply with quote  #5 
Can you post a picture of this?

I used the BoXZY guide to install your own heated bed, but its very cumbersome to use as removing the aluminum plate for cleaning and putting it back goes from taking seconds to minutes. I don't like this method at all. Its not very usable and the way the heated bed is secured is just not viable for long term printing. I am currently trying to figure out a different method.

Team BoXZY did get back to an inquiry I made about a heated bed, and informed me they do plan on making one after fulfillment and selling it. Here is hopes it will offer a much needed better solution than the guide provides.
0
CKP343

Junior Member
Registered:
Posts: 20
Reply with quote  #6 
This setup is not permanent but it works amazingly well.

Attached Images
jpeg image.jpeg (1.39 MB, 50 views)

0
Gary

Avatar / Picture

Senior Member
Registered:
Posts: 116
Reply with quote  #7 

You have convinced me to add a 120V AC heater/controller to my Boxzy. The pad will fit on the underside of the stock aluminum plate.

I'll let you know how it turns out when I get it!

0
SpasticKen

Moderator
Registered:
Posts: 51
Reply with quote  #8 
I plan on starting the Heated Bed tutorial that they posted in the forums, but I don't know how great it is going to turn out. I will let folks know when it is done.

In the meantime, Octoprint is still the way to go to eliminate needing the BoXZY interface. I can print with no problem, and if I am careful, I can also laser etch.
0
CKP343

Junior Member
Registered:
Posts: 20
Reply with quote  #9 
Be careful heating the aluminum plate boxzy came with. I doubt the heat will damage the paint but removing parts may scratch or peel the paint with the heat combined. It would be really awesome to do it with an unpainted bed from boxzy
0
Gary

Avatar / Picture

Senior Member
Registered:
Posts: 116
Reply with quote  #10 
The 3D printing plate is anodized, not painted, but I'd still use the painter tape/kapton covering over it because I like being able to replace the surface easily.
0
stantm1

Junior Member
Registered:
Posts: 1
Reply with quote  #11 
Does anyone know if the BoXZY will support a Keenovo 12V 200W heated mat? I purchased one and installed it per the BoXZY guide, but as soon as I turn on the heated bed setting everything shuts down. I'm suspect the mat is drawing more wattage than the BoXZY will support.
0
dewhisna

Avatar / Picture

Senior Member
Registered:
Posts: 158
Reply with quote  #12 
You won't be able to run the heater with the stock power supply.  The stock power supply on the BoXZY doesn't even produce enough power to run the motors and the extruders (see this discussion: https://boxzyunofficial.forumchatter.com/post/pushing-power-supply-limits-overloading-supply-8187295), let alone a bed heater.

Most people are running AC powered heaters and not controlling it from the main board.  But, you could also use your DC heater if you get another power supply to run it.  The MOSFET transistors on the main board are adequate to drive it (STP55NF06L part rated at 55A and 60V), but you'll need to tie a nice beefy ground connection between your secondary power supply and the main board, and tie the positive lead on your secondary power supply to your DC heater, and connect the other side of the heater to the MOSFET side of the connector on the main board (leaving the other side of the connector open), that way the two power supplies will be at the same potential and the main board's MOSFET can switch and control it.  You'll have to be careful to connect things correctly and not short the two power supplies or something.

You could also just get a decent power supply for the BoXZY in general, though you'll want to use much heavier gauge wire to feed things.  Most heaters are rated for their wattage at their target temperature.  Since the resistance increases as they heat, that means they actually pull a lot more power initially at startup than they do at operating temperature.

For example, a typical 130W heater pulls around 8.7 amps (on a 24 volt system) when first powered up, which is closer to 210 Watts.  When it's at operating temperature, it drops to about 6-6.5 amps, close to the 130W rating.

A 200W heater at 12V is going to pull at least 20 amps at startup, and require an absolute minimum of around 250-300 Watt power supply just for the heater.  The BoXZY power supply is only about 190W to start with -- which isn't even enough to properly drive the motors and extruders (let alone the heater)....  But if you switched up to a 500W power supply, you'd at least have a chance to power the whole thing.

0
mikeinfodoc

Avatar / Picture

Junior Member
Registered:
Posts: 5
Reply with quote  #13 
Agreed.

I wound up making a separate 3D printer Heat Bed controller, via a 30A Max power supply.  I use a relay (controlled by a cheap arduino nano) to control when the heat bed is on/off.   I also included an ammeter to track how much power this was consuming.

Here is a very short video of it working during a print:

http://michaeldockery.me/videos/HeatBedDesign.mp4

ammeter_and_lcd.png 
It basically turns the heat bed on, until it reaches a certain min threshold temp, and turns off when it exceeds a max threshold.


Many heat bed silicone pads/mats come with an embedded thermistor.   The thermistor adjusts its resistance value based on the temperature of the mat (aka: heat bed).

glass_n_heat.jpg 
I basically bought a piece of glass to set on top of the mat, and the glass heats up nicely.  Not perfectly uniform from corner to corner, but it seems to work pretty well so far.

I put some/most of the details here (if interested):
  http://michaeldockery.me/files/HeatBedDesign.pdf


It includes the parts I used to create this. 


BTW - The black case which the circuits are in, is a 1 dollar plastic tool box case I got from the dollar tree :-)



__________________
Respectfully,

Doc
0
dewhisna

Avatar / Picture

Senior Member
Registered:
Posts: 158
Reply with quote  #14 
Nice!  At first, I was really concerned with your design and how you were switching the relay from the Arduino and was thinking you needed a driver transistor and a clamping diode, but then, I followed the link for the relay and realized it was actually a relay module with an optoisolator between the control signal input and the relay.  And that should work OK.

I'm not totally sure you need all of the 7805's.  You could probably get by with running the relay directly from the 9V.  And since the 7805 is rated for 1A (assuming it's a 7805T or a 500mA if it's a 7805L), one regulator by itself should power all of the Arduino and LCD circuit.

On the thermistor code in the Arduino, you may want to take a look at the code that various printer firmwares are using for linearizing them.  The thermistor itself is a logarithm function and isn't linear, so it may benefit to go through a lookup table to convert it to the actual temperature, assuming you have plans to extend your code to allow for setting other temperature control ranges.

If you do that, you'll want to get some additional measurements at higher temperatures.  Based on the temperatures you are showing, I assume you are using only PLA?  On the bed of my FlashForge Creator Pro printers, I generally run 60-70 degrees Celsius (140-158 Fahrenheit) for PLA and 110 degrees Celsius (230 Fahrenheit) for ABS.  Most printers measure all of their temperatures in Celsius, so on various forums when you see people quote their temperatures without giving units, generally they are in Celsius.

Unless you speed up your BoXZY and enclose it to hold in the heat, you really don't need to worry about hitting the temps required for ABS.  The BoXZY itself isn't designed for ABS and prints come out "brittle" (from layer separation due to the slow print speed) and/or you will encounter serious warping problems.  So unless you do some serious mechanical redesigning, you probably don't need to worry about hitting the bed temperatures required for ABS.

14.4 amps seems about right.  At 12 volts, that would be about 173 watts.  I haven't done as much experimenting and measuring on the silicone heaters as I have with PCB heaters, but I'm guessing the silicone ones behave somewhat similar and that it probably pulls around 16 to 17 amps when it's still cold and initially starts heating?

If I were doing it, I don't think I would have done as much work as you did.  Rather than use the separate processor, I would have tied the ground of the secondary supply to the ground on the BoXZY's main board, tied the +12V of the secondary supply to the silicone heater, and tied the other wire of the silicone heater to the drain pin of the MOSFET transistor on the BoXZY's main board so that the BoXZY could control it (as the transistor on the BoXZY's main board is a negative-side switch).  And then connect the bed's thermistor to the heat-bed thermistor input on the BoXZY's main board, and tweak the BoXZY's firmware to enable the heat-bed and select the correct thermistor table and control it from the computer via gcode commands.  The transistor on the BoXZY is more than adequate to switch power to the bed-heater without needing the relay, it just needs the secondary power supply to power it.

But I do like the external ammeter that you used to monitor it.  That's a neat addition.

So nice job!  Glad you got things set up to work for your heater.


0
dewhisna

Avatar / Picture

Senior Member
Registered:
Posts: 158
Reply with quote  #15 
I was also just thinking, there's two additional features you need to add...

The first one is extremely important, as it's safety critical, and can be done entirely in your software.  That is, the code needs to detect some fault conditions.  It needs to look for sensor voltage out-of-range-high and out-of-range-low.  If it is out of range, in either direction, it needs to set a fault code (like flash an error on the screen) and shutdown the heater, as an out-of-range usually means you either have a thermistor wire that broke or came loose or the sensor went bad or the wires shorted out.

And additionally, part of item one is to add a timer in your control loop to check for temperature rise when commanding the temperature on.  If the temperature hasn't changed by a minimum delta amount in a certain delta amount of time when commanding the heater on, it should set a fault and shutdown the heater.  If there's no temp rise, it usually means the tape holding the sensor to the silicone pad came loose and the sensor fell off.  Or it could be a bad thermistor.

I didn't see those checks in the code you posted, unless I just overlooked it.  In any case, failure to implement item one could result in a fire.  It would be horrible to accidentally burn your house down over the BoXZY.

The second feature you could implement is to tie an input on your Arduino to the heat bed transistor output on the BoXZY's main board so that you can control your heater via gcode.  The big gain is being able to shutdown the heater at the end of the print should you not be there to do it so it doesn't just sit there "baking your print", and as slow as the BoXZY runs, that's a much needed feature.  It won't be quite as easy to do if the main board isn't controlling the temperature and all too, but it can still be done.

Both of these features are already implemented in the BoXZY firmware, so if you were to just drive the heater from the transistor on the BoXZY's main board and let it monitor and report the temperature by connecting the thermistor to it, it would be a simple solution to implement both.  And as I mentioned, since your heater is a DC heater, you can have the main board run the heater using the on-board transistor and still power it off your new power supply while powering the rest of the BoXZY on the BoXZY's original supply.  All they need is a common ground (i.e. the negative side of both power supplies tied together).  And connect the new supply's positive to the heater board and connect the other side of the heater to the MOSFET's drain pin, which is the negative side of the main board's heat-bed connector, leaving the positive side of the heat-bed connector disconnected.  And then enable the heater in the firmware.


0
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.