Delta 3D Printer Heated Bed - Heavy Duty

I recently purchased a Delta 3D printer kit from a Chinese manufacturer. The heated bed that came with it was thin and warped (I wish this was the only problem with this expensive printer kit!). A glass plate on top of it was high centered and could not be clipped down easily. The manufacturer sent me a replacement heated bed, but it too was warped. Realizing that I'd never get the printer to work with a warped bed, I decided to make a high quality heated bed that would not warp.

This particular printer has a 310 mm diameter print bed that is secured on printed plastic brackets, below which are the electronics for the printer. Following the instructions in this article you should be able to make a similar heated bed of a similar or smaller size.

Regardless of the type of 3D printer you are working with, this type of heated bed upgrade will serve you well. The silicone heater heats rapidly and the thick aluminum plate holds the heat well.

Parts List

• Two pieces of 1/4" to 3/8" thick aluminum plate that are at least 12" x 12" (unless building a smaller plate). I recommend 6061-T6 aluminum for the heated bed. I used 3/8" 5052-H32 for the base plate and 1/4" 6061-T6 for the heated bed.
• A 2" to 3" pieces of 1 to 2" aluminum (or other machinable metal) round bar
• A Keenovo silicone heat pad. I used a 400W, 110v A/C heater. I bought this one from E-bay:

  http://www.ebay.com/itm/281996626702

• An A/C Solid State Relay like this one that I used:

  https://www.amazon.com/gp/product/B0087ZTN08/ref=o...

• Aluminum Foil tape

• Kapton Tape

• Six #6-32 flathead screws, 1.25" long (1" long for use with garolite spacers)

• Six springs or if you have an auto-leveling printer, 6 garolite spaces 1/2" tall for #6 screws. You might also opt for higher priced ceramic spacers.

• A thermistor that matches the one your printer electronics is programmed to use - typically these are 100k thermistors.

• Glass capable of being cut to size to cover the aluminum print bed. Borosilicate glass would be best but I used this acid etched glass from Home Depot.

• An A/C power cord

• Wire to connect the Solid State Relay to the printer's control board

• Large binder clips to secure glass plate to aluminum heated bed

Tool List

• A band saw or another saw capable of cutting 1/4" to 3/8" aluminum plate
• A lathe with enough swing-over-bed capacity to round your cut plate. I use a Grizzly G9729 lathe.
• Metal turning tools - I used both a left and right hand turning tool
• A drill press or hand drill
• A circle glass cutter. I used this one but you might want to find something of higher quality.
• Various drill bits, specifically though I used #36 (for #6 tap holes) #25 (for #6 through holes), #29 (for #8 tap), and #7 (for 1/4-20 tap)
• A center drill / countersink bit. I used pieces from this set.
• An 6-32 tap
• An 8-32 tap
• An 1/4"-20 tap
• A Sharpie

Cut the plates on the band saw
Mark the circle on each aluminum plate. You could use an existing heated bed as guide. After marking the circle, mark the center of the circle. I used the glass circle cutter to find and mark the center of the circle.

Then cut the circles on a band saw or something similar. The edges will be rough and will be turned on the lathe

Drill a #7 hole through each circle center and thread them with a 1/4"-20 tap.

Make a turning tool

Face and turn a piece of round bar stock about 2 inches long (maybe 1.5" diameter). Then use a center drill and a #7 drill bit to drill about 1 inch into the center.

Next use a 1/4"-20 tap to thread the hole. The aluminum plate will be attached to this piece with a 1/4"-20 bolt. Another hole can be drilled through the aluminum plate and into the bar, and then threaded (I used a #8-32 tap) so that another bolt can secure the plate to the bar and prevent it from coming loose during turning. See the photos for an example of this tool.

Turn the plates

After attaching the turning tool / post, secure it in the lathe chuck and carefully (slowly) turn the plate and remove the rough edges as shown in this video:

Do this for each plate to produce nice, round, smooth plates the right diameter for your printer. A deburring tool will take the edge of each side of the plate, or your can use a file while turning, or a bit to give a slight chamfer.

Drill, countersink and tap mounting holes

Use some double sided tape to hold the plates together. You may also want to use a 1/4"-20 bolt through the center to keep them centered. Then mark and drill the holes around the edges. I used the old warped heated bed (pressed flat) to mark the drill holes. I then drilled each mark with a center drill to start the hole and followed through both plates with a #36 drill bit.

Select one plate to be the base plate. This one will sit at the base of the printer and will bear up the heated bed plate. Thread each of the previously drilled holes with a #6-32 tap. BE CAREFUL when using the tap. A #6 tap breaks very easily! Go slow, use a lot of oil and a lot of reversing and clearing.

For the heated plate, re-drill each of the holes with a #25 drill bit to allow free clearance of the #6 bolt. Then use an appropriately sized countersink drill bit, to drill the top surface allowing flat head screws to sit level or slightly below the surface of the plate. Use a #6 flat head machine screw to test each countersink hole.

We will place a glass plate over the top of the heated bed. The 1/4"-20 hole left in the center will be used to allow the thermistor to touch the glass plate so that our temperature reading will reflect the temperature of the glass rather than that of the aluminum plate.

The Keenovo silicone heater has a paper backing under which is a sticky surface. Peel the paper and then careful place the heater on the bottom side of the aluminum plate, as centered as possible. Before applying it, make sure your countersunk holes are facing down (on the table surface)!

Once attached, apply pieces of aluminum tape over the heater and the aluminum plate to provide additional holding, as well as to help reflect heat upward into the plate. Clean-up the edges with a pair of scissors.

Use the scissors to open the center hole in the plate, clearing away the tape pieces. Then run a piece of Kapton tape (2" wide is good) from just past the center all the way to the edge where the A/C wires are. Puncture the center hole again to clear it. You may want to use 2 pieces of Kapton tape to provide extra insulation for the thermistor wires.

Placing the Thermistor

Place the thermistor through the hole so that the glass end will touch the table top and not the sides of the aluminum plate. You may want to first wrap ends of the wires near the thermistor with Kapton tape for added insulation against the heat and the sharp edge of that center hole. Secure the thermistor in place with pieces of Kapton tape and run a piece all the way along the wires to the edge. Remember when placing the thermistor that the goal is to have it touch the glass plate the will be secured to the top of the plate. This way we have a temperature reading from the glass, not the aluminum.

Wiring is very simple. You will attach the thermistor exactly the same way it was (or was intended to be) for your old heated bed. Since there are a variety of RAMPS and similar boards out there I'm not going to show the details on this - consult the manual for your board.

The heater however is A/C powered. Connect one wire of your heater to an A/C power cord. Connect the other one to the A/C side of a solid-state-relay. Connect the other side of your A/C power cord to the other A/C terminal on the solid state relay.

The DC terminals on the solid state relay are polarized. Connect the +3-32 volt side to the positive output for the heater on your RAMPS (or similar) controller board. Connect the other DC terminal to the ground terminal of the heater from your controller board. If you use the same Solid State Relay that I listed in the parts list, you should be good to go for almost all controller boards, because most of them will deliver 12 or 24 volts to the heater and the relay can be driven by anything from 3 (including a Raspberry Pi GPIO) to 32 volts.

The base plate attaches to the printer using the same mounts that were there for the cheap fiberboard base plate.

Flathead #6-32 screws pass through the top, heated bed and through a spring or a heat resistant spacer and into the threaded holes in the base plate.

Springs allow for easier leveling. Spacers may be used if the printer has an auto-leveling feature. This printer has an auto-leveling feature so the springs will be replaced with Garolite spacers.

You may wish to wrap the top of the screws (where they pass through the heated bed) with Kapton tape to help prevent too much heat transfer through the screws into the base plate.

By far the easiest option for this step will be to purchase a pre-cut Borosilicate Glass plate, cut round to the right size. If you have access to Borosilicate glass you can cut your own sheet. In this step I will show you how I cut the far less expensive acid-etched glass that I obtained from Home Depot. Be warned however that this glass does not hold up well to the heat required for printing with ABS. It did seem to hold up fine to PLA temperatures (around 70 C), but at 100 - 105 C I've had two pieces crack. So far both are on an edge where they can still be reused with prints that don't extend past the crack.

In the photos for this step you will see that I first cut the glass to the approximate length needed. I then mark the circle using the old heater as a guide. After that I mark the center and attach the glass circle cutter. Unfortunately for this round of photos, my glass cutter was already failing to hold in place (stripped threads), so I ended up cutting a little bit too big and leaving some flat edges. I did not have that problem the last time I cut a piece of this glass. With the cutter suction cup in place and after verifying that the circle will fit properly, spray the glass around the markings with some oil. I've used WD-40 and this last time cooking olive oil spray. They both work fine. Make a single pass with the glass cutter all the way around. Then flip the glass over. Using the ball end of the cutter, gently press it along the cut line. The glass should snap right where the cut line is found.

NOTE: If you have a large capacity CO2 laser you can cut the glass with it. My CO2 laser cutter can't do a circle this large, otherwise I'd get perfect circles. I was able to use it to cut a plate for my JG Aurora Z 605S (Prusa i3 clone).

After cutting the glass you will want to dull and round the edges. In the photos you will see that I used a combination of the disc sander and belt sander to do this. Wear safety goggles and gloves!

Once the glass can be handled without fear of being cut, clean it up with some window cleaner. Use binder clips to clamp it to the heated bed.

The heated bed should now be ready for printing. When printing with ABS I still apply a layer of Elmers Glue from a glue stick as seen in some of the photos.

The temperature of the top of the glass is generally within about 5 degrees C of the temperature reported by the printers control panel.

You will know when the heater is being powered because the red light on the solid state relay will be on. You can see this in action as a few bag clips (thingiverse:212117) are printed in the following video.

Glass Plates

Though I am happy with this new heated bed there are a few things yet to work out. Obviously I need to find better glass plates if I continue to print ABS. If you have had good experience with round glass plates please add a comment and tell us what you have used and what it cost.

Heat Transfer

I also want to find a better way of keeping the base plate cool. When the heated bed was 100 C, the base plate was still warmed up to about 50 C. I'm sure that can be improved and thereby help to keep the electronics underneath of it cool.

The Delta 3D Printer

Finally, you will notice that printer in question here is an He3D DLT-600 (a.k.a. He3D Mega). I'm not providing a link to it because I can't currently recommend it. I'll likely post an article in the near future outlining my experiences with 3 different Chinese made 3D printer kits. Unfortunately, this printer is very expensive as kits go. That would be okay if it had proven to be worth the price. So far however I get higher quality prints from the JG Aurora Z 605S that I assembled. It took several days to get that printer working because of issues with the motor wiring harnesses being backwards. The model shown in the article however has been in the works for 6 weeks, with several items from the hotend to the electronics having to be replaced due to various problems with cheap equipment. Before I cast any final judgement though, I've presented all of the issues to the manufacturer and I will give them a little more time to make things right. Until then, if you are looking to build a large Delta 3D printer, you may wish to start from scratch, or try another model. Either way you are likely to benefit from building your own heated bed as documented in this Instructable! It will be more durable and will heat far faster than the printed circuit board and other inexpensive heated beds, and it will hold the heat very well.

The Printing Materials and Spool Holder

The items printed in the photos and videos were made with Hatchbox ABS in Red. Most of the printer parts were also printed with this material on the JG Aurora Z 605S (using a Flexion Extruder), because it made superior parts to those that shipped with the printer kit. (The printed parts that I made for the printer itself were made with 100% fill using the Hatchbox ABS.)

The Spool Holder that may appear partially in some of the photos is documented in another Instructables.com article.