BeTrue3D Printer build part 4 – Printbed
This post is about my brand new super nice PEI-Coated black oxidized 5mm aluminium plate with lasered logo/url and about a lot of wiring I’ve spent time doing.
I also put in the last paneling. I ran out of the white 5mm card board material and am using some whiteish acrylic I had untill I can get some more of the white plates.
First up is the printbed. This is the single most expensive item in my printer at around €85 including shipping! Especially when combined with the 500w AC heater at around €35. You can get the plate much cheaper if you get it in natural color instead of black though.
Here’s the finished result, which I’ll go through in steps, to show how I did it.
I’m very pleased with the result, if I might say so 🙂
Keenovo heater used
I’m using a 500w AC heater from Keenovo. You can get it in custom sizes at no extra prize, and they really deliver high quality. Included is 1 big pad of preapplied heat resistant and -conducting 3M MP486 tape, which is the best for the job.
It comes with premounted 2 wires for AC power and 2 wires for the build in thermistor. It generally reads 10c above actual surface temp of the printbed.. guess its due to heat dissipation. You can get other sensor types as well
The CE is “China Export”, so it doesn’t mean it is CE certified
Ground and sleeving
I wanted to ground/earth my Z-gantry directly, in case of a mishap, so needed an extra wire. I also enlarged one of my 3mm holes to 4mm to make it fit perfectly.
I drilled an extra small hole where I can zip-tie the cables onto the lift-plate for stress-relief for the wires/headpad. It is places so the wires does not grind on the edge of the plate.
I originally wanted to use a cable drag-chain, so hadn’t planned on using zip ties.
I braided the cables and sleeved the part that’ll be visible ind the print chamber.
I do not insulate the bottom of the plate, as I want the increased heat output to act as a sort of “passive” heater element for the heat-chamber effect I’ll get by doing this.
I’ve planned to use the Ultimaker 2 fingerscrew system. I really like it, as it is discreet and runs very nicely, while at the same time can be tightened down really tight so the bed doesn’t wobble.
It means I’ve had 3 holes at 6.5mm made in the lift-plate for the fingerscrews, which lines up with corrosponding countersunk holes on the print bed.
The fingerscrew assemblies are made up of the fingerscrews, spacers, springs and m3 scews.
For best result I have put on lithiumgrease between the fingerscrews and spacer, and again on top of the spacer.
Note: I’ve used some other types of grease on other printers with great result as well, so no need for special grease. Just use something.
After fixing the cables at the back edge of the bed, as shown in photo a bit above, I placed the springs at the right spots, and placed the bed on top of them (took a bit of balancing in order not to knocking around the springs with the plate).
The springs are 20mm long and has an inner diameter of 7mm.
I used a caliber I can lock into place and put it at 10mm. This means I can do a rough calibration of the bed. It’s not precise, but close enough to start calibrating using printer software.
Note: The distance I used might not fit on other printers, due to thickness of plates and length of m3 screws and springs. So tighten down the springs untill you can depress the corners with your fingers, but not so easily that the bed can wobble. The springs must be tightened down good, but not all the way.
The give in the sprigns is an insurance if you accidentailly have the hotend smash down onto the plate. If the plate can’t move, something else is likely to break.
Clean it up using Acetone or Isopropyl alcohol when done. Can see my sticky fingers on the photo above 🙂
I originally wanted to use a dragchain… but I’m just not that big a fan of them, and found it looked bulky in there.. even a thin one. I know this is a subjective view, but there it is. I liked the sleeved version I made, so stuck with it.
I drilled an 8mm hole for the wires to get out to the back compartment, along with 2x 3mm holes for a ziptie to hold the cable in place.
The cable can flex up behind the z-stage.. even if it wanted to get under the bed, there is plenty of space for it in there, so it can’t cause any troubles.
Cables out back
I couldn’t get good photos of cables out back, but one of the AC wires went to the Load side of the SSR module at the connector labeled 1. The other AC cable went to my PSU at the AC N connector.
The Ground/Earth cable went to the AC earth connector, while the 2 thermistor wires went to the bed thermistor.
Cabling – Wire harness.
So much wiring when custom building printer!
As I created a connector plate for the 5 extruder motors, I did the same for my wire harness going to the carriage/hotend. It’s a LOT of wires for sure, but they are needed.
The 6-pin plug to the left is for BLTouch. 2 of those pins are for z-min and 3 for servo. 1 is unused.
The big 9 pin plug is for heater (2), heatsink fan (2), printobject fan (2), thermistor/thermocoupler (2-3 – some thermocouplers has 3 or even 4 wires)
The handdrawn “labels” are meant for my reference untill I get it working. I plan on printing some nice versions at some point.
Here we can see how the new connectors looks; with and without the matching wire-harnesses hooked in.
I havn’t put connectors on the far end (at hotend) which’ll wait till I get the last parts I need to make the Y axis and carriage in order to make the correct length.
That’s it for now.
Hope you liked it, and thank you for following my proejct. 🙂