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Injection machine – help on electronics

MakingADifference ha-ng

Injection machine – help on electronics

09/04/2020 at 15:47

Hi all,

I’m making an injection machine and I’m struggling to make it work.

Please find attached a photo of the different components I put together.

The PID controllers are turned on, which means there’s electric current going through, but the band heaters don’t heat up.

I tried holding the temperature detector in my hand and the number on the PID screen went up progressively so I supposed it does detect temperature change.

These are the components I’m using:

– band heater: https://www.amazon.co.uk/gp/product/B0821CT5T3/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

– PID controllers: https://www.amazon.co.uk/gp/product/B07HJ5GQ2L/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

I can really use some advice on how to fix this, thanks in advance!

Ha Tao

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09/04/2020 at 18:12

Your band heaters are rated for 110V I don’t think they will survive 230V. I also would not run them for very long in the desk top configuration, there is no temperature feedback.

With the SV higher than the PV the output light (top left, second LED down?) on the PID should be on.

I would disconnect the heaters and measure the resistance. You may have burned them out. With them disconnected, I would disconnect the 230V from the SSR’s and check that they are switching properly.

As an aside, in your diagram, you have the SSR’s connected to line without a switch. I would run them through a switch just so you can safe the entire assembly.

How do you plan to mount the thermocouples to the tube and nozzle. People have had problems with the PP approach. Using a mounting block approach may be better.

Good luck

10/04/2020 at 09:38

It’s hard to see on the photo, but is your cabling correct from the output SSR to the bandheaters? Means the neutral goes dirctly to the heaters while the live passes via the SSR? You could also measure if you have AC on your heaters when the SSR/PID is supposed to heat.

10/04/2020 at 13:28

have a look at this video, it seemed to have help beginners. as last resort there is another “Wiring” diagram, a little more illustrative.

21/04/2020 at 13:20

Thanks for your suggestions guys! Sorry for the late reply, but I took a break from the project for family reasons but now I’m back on it.

: Yes it could be that the bandheaters don’t work because it’s 110V. I’ll try to order 220V ones. I actually I’m looking for ways to mount it properly. Do you have visuals for the mounting blocks you could share? Thanks!

: i’m rewiring the system using the wiring diagram you provide to try. Do the numbers indicated on it correspond to the numbers at the back of the PID controllers? There’s no place to wire it to n°3 on the PID though (there’s a gap on n°3 as you can see on the photo).

21/04/2020 at 15:45

I just realized that the drawing was for another PID, here’s one for the REXC100

21/04/2020 at 18:33

@ha-ng I would set those 110V heaters aside. At 220V you would be pushing 4X the power through them. If they have not fried yet, they will. Before you wire everything up, I would check things individually. The PID controller should work just fine with just the thermocouple attached. The displayed PV temperature should look right and respond to holding the TC tip in you fingers. If you set the SV to 30 C, the output light should be on and you should have low DC voltage on the output terminals of the PID. When you hold the TC tip in your fingers, the PV should rise above 30C and the output light should come off and the output voltage turn off as well. If all that works, you can connect yous SSR’s and repeat the process. If you suspect the SSR’s I would check them separately using a DC source (battery?) to activate them.

The blocks I was talking about was for mounting the TC’s to the tube. I think the original PP approach for mounting the TC calls for removing the threaded mount on the TC and clamping under the edge of the heater. I didn’t like that approach. First, the TC bead in the tip can be fragile and second, I don’t want to measure the heater temperature, I want to control on the tube temperature. So in my implementation, I used a block with a threaded hole to mount the TC using the original threaded mount and press the tip of the TC against the tube, near the heaters. The picture below shows my build. It is a little different and uses an aluminum tube. For your application I would not bother screwing the block to the tube you can just clamp it with a hose clamp and install the TC through a hole in the hose clamp. You can even just use a nut for the block. At one point there was a picture on the forum where a really clever builder used the hose clamp approach. He welded the block to the hose clamp for a very professional look but that is not needed for DIY.

Also, there have been several threads recently troubleshooting injection machine builds and electronics.

Good luck

23/04/2020 at 11:24

Thanks guys! The diagram makes more sense now. I just ordered the 220V band heaters, they will take a while to come.
For mounting i’ll just use a hose clamp.

I’ll let you know how it goes!

Take care and stay healthy 🙂

28/04/2020 at 18:38

If your heaters are not dead yet, you could put 2 in series, then you can use them on 220 volts. Just in case you don’t want to wait.

10/05/2020 at 13:57

Thanks for the tip @sonik!  It saves me some cash and I finally got it working.
Now I just need to build a box for the electronics, probably using cardboard because I don’t have access to any workshop right now.

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