I have decided that I'm going to leave the Bulldog extruder and E3D V6 Lite hot end on the Two-Up and keep it operational. As a result, I'm going to try the new(ish) E3D Titan extruder. I like that it's lightweight, and can use a very small NEMA17 motor to keep the weight down even more. The Bulldog has been extremely reliable, but being all aluminum, it is a bit of a lump. With this direct drive setup being so light, the idea of a dual extruder setup is becoming very appealing.

Extruder, hot end (E3D v6 @24v), stepper and mount will be ordered this weekend.

 

The way I see it, you get a slight efficiency gain using the 110v AC heater as you don't waste energy converting it to DC first. Also, you now don't need nearly as large of a power supply, saving money and reducing heat in the electronics.

 

All extrusions are standard off the shelf 500mm lengths. I designed it so that you could essentially order everything you need and bolt it all together. The only custom fabrication will be in the heat bed platform and the extruder/hot end mount.

 

Then fuse it. You should do that anyway with high current DC too. As well as covering all exposed connections and conductors. That's just general safety, regardless of the voltage. Grounding the build plate when working with AC will also add another layer of safety.

As someone who works with 700v DC battery packs daily, I don't see either approach being a safety risk, provided the proper precautions are taken. 24v DC can kill you just as easily if it can find a route to ground/earth (yes, I know that higher voltage will break the skin isolation barrier more easily than 24v DC). Remember, it's the current that will do you in, not the voltage.

If something were to short with your 24v setup, it would be more than just sparks if that 33A power supply were to be allowed to deliver all 33A.

I know for some people that working with AC just instills the fear of God in them, but DC is fine to work with. Really, both are just as safe or as dangerous as you make them, but if you aren't comfortable with AC, then the choice is easy.

 

Well, it is actually. It's the current that clamps your muscles and puts your heart into defib. The voltage has be high enough to cross the isolation barrier we call skin. Sure, there is a little difference in how much voltage it takes to penetrate the skin between AC and DC, but so many other elements can affect that (like sweaty skin, cuts on the skin, abrasions, etc...), it becomes a moving target. Static electricity is low current (nano/pico-amps), but the voltage is high. Still breaks the skin barrier, but it's not enough current to cause any problems.

Anyway, we are moving WAY off target here Use what you feel is safe to you. That's really the most important thing. Just make sure to take the proper safety precautions, be it with AC or DC.

 

400W should be more than enough to heat a bed that size to temperatures higher than you would ever need. Plus, with the large aluminum bed, it will be very stable thermally (lots of thermal mass). The only thing you may want to do once the printer is running is set up a dwell time after the heater gets up to temperature. This is assuming you are going to use the thermistor that is mounted to the back of the heater mat. If you don't add the dwell time, the edges of the plate will be cooler than the middle. Adding this dwell time will allow the entire aluminum plate to equalize in temperature. If you want to put the thermistor on the aluminum bed itself (top side towards the edges), then the dwell time isn't as critical, as the thermistor will be measuring the temperature on the coolest spot on the plate (where the heater isn't).

 

I'm looking into that myself. I'll let you know when I find out. I'm still new to G-Code, but I don't think it's that hard to implement.

 

It would seem that there is a delay function in G-Code.

G4 PXXX

or

G4 SXXX

Where PXXX is the length of the delay in milliseconds, and SXXX is the length of the delay in seconds. According to the Reprap wiki, only Marlin and Smoothieware supports the SXXX parameter. Add the delay to the top of the G-Code either manually, or using a startup script.

 

It might take some experimenting with a thermometer, but a minute should get you pretty close. When I get mine running I'll get my thermal camera on it to see the progression of the heat through the plate.

 

Smoothieboard 5x ordered. That should be the last of the parts needed to get this up and running.

 

Many of the questions you have have been answered already, but I'll go through them one by one anyway.

1. The parts list isn't really all that complicated, as I'm using all standard cut length extrusions and actuators from the OpenBuilds store. There aren't any hidden parts, so you can easily determine the parts from the pictures. I'll create a more detailed parts list once I have the build complete. The short version is as follows (all parts from Openbuilds unless otherwise noted):

• 4x 500mm C-Beam Linear Actuators w/NEMA 23 motors
• 2x 500mm 20x80 V-Slot
• 3x 500mm 20x60 V-Slot
• 2x 90 degree corner brackets
• 2x "T" brackets (Misumi part)
• 2x 120mm 45 degree brace extrusions (Misumi part)
• 16x cast corner brackets
• A pile of M5 screws and t-nuts
• Various spacers for build plate, Y-axis mount, etc...
• 1x 12"x12"x1/4" cast aluminum tool plate (eBay)
• material for Y-axis mount (I used carbon fiber that I had laying around, but dealer's choice)
• 300mmx300mm 750W 120v AC heater mat (with SSR) (Amazon)
• 12"x12" PEI sheet (Amazon)
• E3D Titan extruder (Filastruder, but there are other options)
• E3D v6 hot end (24v) (Filastruder, but there are other options)
• Smoothieboard x5 (Uberclock)

​

2. Final print surface will be a 1mm thick sheet of PEI. I've had great luck with it on my other printer. I had tried bare glass, painters tape, and kapton tape before (worked fine for PLA), but couldn't reliably get ABS to stick to anything but PEI.

3. As stated in the original build description, I'm trying where possible to keep this to a bolt on build. Meaning that most of the parts will be something that you can buy from one site or another without having to modify anything (cutting, machining, printing, etc...). Openbuilds posted a 2:1 belt reduction kit a while back but has since pulled it to make some updates. Hopefully they took my advice and made it so that the mounting position was variable, and that they would offer alternate pulley options to be able to do 2:1, 1:1, or 1:2 depending on what pulleys were used. @Mark Carew was nice enough to send me a few of the original kits, but they still don't have the alternate mounting positions, or the option for different ratios. Hopefully all these things will be taken care of soon and they come out with a very versatile kit. In the meantime, I'm just running the lead screw directly.

4. Yes. I don't see there being much of an issue at this point running both Z motors from the same driver seeing as they never experience long or rapid movements. If it becomes a problem, it won't be an issue to run an external driver slaved from the Z-axis control pins to run the second motor.

5. Yes it will, and was something that I addressed a few posts up. I cut the heating element and re-routed the wire around the standoff positions. This isn't something that I would recommend to most people to do, but it is possible with a little careful work. For most people looking to do a 12"x12" build platform, I would recommend using a 250mm or 200mm heating mat so that it clears any mounting points. You will just have to make sure that you allow some time for the build plate to equalize in temperature before printing.

Please feel free to ask any questions you may have. This build is coming along well and should be operational soon. I did some work on the extruder assembly over the weekend since I got the Titan extruder and the v6 hot end on Friday. I'll have some pictures posted tonight or tomorrow morning.

 

It sounds a lot like PEI (at least from the ease of use and the durability), but some pictures I have seen of it make it look micro textured (that's probably the secret sauce). I can definitely tell you that PEI is tough as nails. I've buried the nozzle of my Two-Up into it a number of times (no limit switches) and hasn't left a mark.

 

Sticky as in, the tackyness of the build surface, or the adhesive that holds it down gives up after a while?

 

I used 3M 468MP adhesive, which seems to be the go to for many different build materials. I haven't had any issues with it letting go on my Two-Up yet (knock on wood), and will be using it for this build. I saw on a few reviews that they recommended carpet tape to stick it down. I'm sure that may be an issue, as it's not really intended as a high temp adhesive (3M 468MP can run for weeks at 150C).

 

Oh! I thought you were talking about the Printbite lifting from the adhesive. I haven't seen any issues on my end. I also don't hang out on any 3D printer forums (other than this one), so I haven't seen word about the PEI not holding. I wonder if the people that are having issues with this are using borosilicate glass, where people who aren't are using other materials (regular float glass, aluminum, etc...). The ease of release on materials like this is generally due to the material shrinking when it cools. Borosilicate is very dimensionally stable through the temperature ranges we use, so I wonder if it's shearing after repeated thermal cycling (again, I'm just speculating as I haven't read into this). I use regular float/picture glass and it does expand and contract as it heats and cools. PEI and float glass may have similar rates of thermal expansion which would limit the shearing force on the adhesive. Just spitballing here.

Now, on Mutley3D's site, they state their sheet comes with adhesive already mounted. Are people not using the adhesive and just clipping it down the print bed like you would glass to a pcb style heater? If that's the case and it works, I don't see why you couldn't use PEI in the same way (provided you could keep it flat).