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Hey, Great Work!
You made a lot of progress in improving the safety, reliability, and effectiveness of the PP machines.
Yeah, the – what to make – and how to make it cost effectively (molds) is the next step to go beyond educational demonstrations.
I’m curious who your customers were (categorically) education/universities, government or NGO sponsored workspaces, or self sustaining workspaces.
Good luck going forward and thank you for all that you’ve done.
Nice design. I think if you were to reduce it to basic functionality the cost would be pretty low. All the 3D prints and bearings are nice but could be done in other ways. Printing the timing pulleys and the grinder mount is convenient. Here the grinders can be bought for $15. You can skip the chuck if you are willing to size the hole in the timing pulley to your part.
The Robodigg parts are nice, but if you need something local.
Do you really need super polish? Isn’t there always going to be shear within the plastic? Of course you could use polishing wheels on the grinder and use a router speed control (<$20) to slow down the grinder.
Interesting, I have SDS concrete bit that is waiting in the project cue.
It is hard to tell, but if the white wires are going to your load, it looks like you have going and returning to the same connection (1) on the PID, instead of what is shown in your second diagram.
If that is the common online PID bundle, with the BERM brand PID, I don’t think there are any PID parameters to adjust. But you don’t need to for this.
It is difficult to see your wiring in the photo. This discussion may help you.
If it is a smooth sphere, for a low cost mold you could try one of these, Carefully cut it in half and encase each half in something strong like mesh reinforced concrete and a steel box.
I’m not sure how you avoid bubbles or voids. I think the compression approach would do several flat melt/press/fold cycles and then compress in the mold. Probably depends on how efficient the process needs to be and how many you want to make.
If you are going to use an injection machine, there is a lot of pressure. Even if you encase the mold in something rigid, I’m not sure you can hold shape or detail.
Also, a 12 cm sphere is about 900 cc. That is a lot for an injection machine.
You might check with the local gardening people. Depending on what the local soil is like, it can be used as a soil additive. We just put ours into our compost bin. I’m sure the worms work faster when they hit the espresso grind.
The PP approach to mounting the TC to the tube may not be the most reliable. Take a look at my suggestion (April 21 post) in this thread and see if it makes sense.
Just to confirm, When you use the screw type temperature sensors (type K thermocouples) that came with the controller, you have them attached blue to 9 (-) and red to 10 (+). Also your controller model number has a K after the F, indicating it is for type K thermocouples. I can’t tell what your other temperature sensors are but if they are resistor type, they won’t work.
Interesting, Could you provide the steps. Are you using plaster and a bakeout oven?
Did you buy the temperature sensors with the temperature controllers as a kit? Does the temperature controller part number call out the type of sensor you are using? Take a picture of the sensors, the part number and your connection. Something is not matching up. If you are using thermocouples, are the tips undamaged?
Hopefully, since both are doing it, it should be easier to find the cause.
Yeah, I noticed the other day that the only activity was a spam post to a spam topic.
Agreed, there was some good discussion and excitement when this forum was active.
Looks great, what force does the cylinder produce?
I believe you. For general purpose, large area compression you need lots of force. The thought was for the relatively small, pyramid shaped mold that a 2 ton jack might work. 3 broken jacks say otherwise.
Those look really great. I really like your “engineered with what’s cost effective locally” approach to building your machines.
Would a motor (drill?) driven scissor jack work as a replacement for the log splitter?
Thanks for the update.
I am not personally involved in these efforts so I don’t have any direct information but here are a couple of links to get you started.
Sorry but if you search the forum, there have been several attempts at working with PET. The only successes I remember are the finely shredded PET used in direct 3D printers. The general observation appears to be that PET is both moisture and temperature profile sensitive and may be too difficult for simple DIY recycling.
@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.
There should be drawings and a bill of materials in the download kit. The important thing is what is available in your area. The inside one (piston) is usually a solid rod, though if you find a way to close off the end and the walls are thick enough so it does not bend, you could make a tube work. The outside tube and the band heaters you can find need to be consistent in size. As the instructions say, check the outside tube to make sure it is smooth (no weld seam). You could use aluminum if you have a good way to attach sturdy mounts.
The heater bands and controller/SSR/TC part of the system is probably a must buy, though you may have some heater equivalents. They are relatively cheap.
If you have a way to provide a low speed/high torque drive with your current equipment that is safe to operate, you may be able to save that part. If you search the forum, there are a lot of discussions on speed/torque/couplings.
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.
Let’s say you got your hands on an industrial robot. You could raise your environmental karma by sorting plastic http://onearmy.world/community/forums/topic/sorting-plastic-with-robotics-v4/ or you can do this https://www.youtube.com/watch?v=_P4xiNx-hc4 (you can skip to 2:10)
If you need more pressure using the current levered design, @andyn made a clever change in his version where he could change the piston diameter without changing the tube. Of course, you trade injection volume for pressure but for small molds with narrow passages it may be an option.
It should just be the area of the piston face pushing on the plastic. In your case
I get 5.3e-4 sq meters and about 39.6 bar. I think to get to 45 bar, the PP guys eat more chocolate.
Sounds like a great project. Is there a link to a more detailed description?
I’m curious what is the predominant plastic type that will be processed and what will they be making?
Thanks for posting.
Well, if you are building a machine to the specifications on that page, it states that it has a leverage of 3. So if you are 70 Kg (about 700 N) and hang of the end of the bar, you will apply 2100 N of force on the piston. If you divide that by the area of the piston in sq. meters, you will get the pressure in Pascals.
If you take more accurate measurements of the machine you are building, you will get more precise estimates for your machine.
If you need more pressure, the rack and gear designs are an alternative.