Need to make a desktop injection molding machine for batch production of parts of the same size specifications

cardin6

Need to make a desktop injection molding machine for batch production of parts of the same size specifications [Copy link]

 

My friend has some engineering parts (non-standard parts) that need to be processed. He originally used a 3D printer to make a batch for demonstration and testing. But unfortunately, the efficiency of 3D printers is not very high and it is best to use nylon materials for such engineering parts (nylon does not have resin packaging... only solid forms such as wire, particles, and powder) So he prepared to make a desktop-level small and medium-sized injection molding machine In fact, for diligent people, they can be made with a vertical press + heat pipe, etc. But in line with the principle of not tossing and not being cheap, you will die. . . I decided to make a semi-automatic desktop injection molding machine similar to a fully automatic one (except for taking out the injection molded parts, the rest is automated) So I started to draw a picture and refer to the method of the FDM3D printer wire extruder I made before (which came first, the injection molding machine or the wire extruder prototype? I have always been following the principle of ignoring this boring question of which came first, the chicken or the egg) The structural part is okay, it's just a matter of rationality, accuracy and other issues. The key is the control part, which I can't do anything about So the original intention of this post came up The control part can record the heating temperature of several different materials (melting temperature but not reaching the crystallization temperature), and can be manually switched according to the material put in, such as ABS or nylon, the melting temperature is different After putting in the raw materials, preheat the reduction motor to drive the screw to rotate and push the raw materials to the heating pipe. Because no matter ABS, PLA, PC or nylon, they are still very viscous after dissolution (non-crystallization), so the gas is easily eliminated. This does not need to be considered (the test of the wire extruder has already shown that this method works. The key is to leave a space in front of the screw). The dissolved raw materials are squeezed out from the pagoda head and enter the mold (the mold needs to have an injection port and a vent, otherwise it will fail. For large molds, a heating pipe should also be reserved, otherwise the dissolved raw materials will solidify before reaching the position, which is also a failure. Of course, if you say to increase the injection pressure, it’s ok, no problem, but you must pay attention to safety. After all, it is a DIY machine to prevent high-temperature dissolved raw materials from splashing out) When the raw material enters the mold, its pressure gradually increases. At this time, if the reduction motor still needs to rotate at the previous speed, it is necessary to increase its torque. However, if the torque is increased continuously, the excess raw material will flow out from the vent, causing waste. Not to mention that the machine will not stop, it needs to be operated manually. This is a mechanical and cumbersome operation. It is necessary to replace it with a combination of software and hardware. So there is the torque sensing device in the figure. When it reaches XX Nm, the reduction motor stops working and the platform for placing the fixture moves to the right away from the injection port of the pagoda head. The reduction motor reverses and withdraws some raw materials to avoid waste. As for how to make the mold. . . I downloaded a CNC machine when I first came to the forum. Many of you may still remember it. Although I downloaded this CNC machine myself, I still used CNC to make parts with high precision. I replaced the water-cooled spindle motor and there was no problem milling aluminum-magnesium alloy. The strength of aluminum alloy is also enough to make such plastic-like parts. Please help me with the problem I mentioned above! . .

qwqwqw2088

The idea is good, but there is a problem. The injection molding machine uses the maximum glue weight as the main parameter. For example, a 500g injection molding machine means that the maximum glue weight of this injection molding machine is 500 grams. This involves mold making. A 500g plastic body means that the mold body is already very large. It is recommended that the mold body be taken into consideration when designing this injection molding machine.

cardin6

qwqwqw2088 posted on 2017-11-23 15:12 The idea is good, but there is a problem. The injection molding machine uses the maximum glue weight as the main parameter. For example, a 500g injection molding machine means that the maximum glue weight of this injection molding machine is 500 grams. ...

I don’t know if I didn’t express it clearly. . . Maybe the mold for each injection is different, so I personally feel that this is not very meaningful. In order to meet this similar demand, I used the word "torque" in the structural design to increase the injection resistance after the mold is filled, so that the reduction motor stops running after reaching this torque (no matter how big the mold is, as long as the mold is properly designed, the resistance threshold after the same raw material is filled is the same). And as mentioned before, the parameters of several different materials are recorded separately, including the melting temperature - not higher than the crystallization temperature (to avoid excessive bubbles and crystallization) - the viscosity and density after melting, the resistance value range after normal injection, etc. are customized according to the different raw materials used. However, before the injection resistance value is reached, the silo will continue to feed. In this case, it seems that the statement about the 500g injection molding machine is invalid, right? I don't understand this thing. I just need to use it suddenly and I'm a bit blind. . .

qwqwqw2088

cardin6 posted on 2017-11-23 15:28 I don’t know if I didn’t express it clearly... Maybe the mold for each injection is different, so I personally feel that this is not very meaningful...

"The injection resistance increases after the mold is fully filled..." That's what I mean. I hope you can calculate how big the injection force is. In addition, the injection molding machine needs to melt the plastic, right? After melting, after it is injected into the mold cavity, does it need to hold the pressure for a certain period of time? Does it also need to be cooled quickly? How do you consider the heating part and the cooling part? 500g is just an analogy. A 500g plastic part is too big. It's okay if the plastic part you need is only 5g, 10g, 15g,,,

cardin6

qwqwqw2088 posted on 2017-11-23 15:46 "The injection resistance increases after the mold is fully filled..." This is what I mean. I hope you can calculate how big the injection force is. In addition, the injection molding machine needs...

Well, after finite element analysis, it is about 2.7 Newton. Because it is a desktop machine, according to 1:1.13 nylon, each part should not exceed 30 grams. Because the parts themselves are small in size, heat dissipation can be directly solved by physical methods. For example, the aluminum block can be slightly larger and thicker to solve the cooling problem and prepare to use a rotating wheel. Place 4-5 molds on a wheel so that the cooling time of each mold is also improved accordingly. As for holding pressure, I did not calculate the time. I thought that the injection molding of such small parts would be completed in a few seconds, as long as the molded pagoda head and the mold are not separated for a few seconds. Is this actually the case?

qwqwqw2088

After the injection molding is completed, the pressure is maintained because the unfixed material in the product is not allowed to flow back after injection. This is not the point. The OP wants to make this machine, but I just want to remind you that there should be a function to control the pressure maintenance. The time of pressure maintenance depends on the material of the plastic.

cardin6

qwqwqw2088 posted on 2017-11-23 17:27 After the injection molding, the pressure is maintained because the unfixed material in the product is not allowed to flow back after injection. This is not the point. The original poster is not going to make this machine...

OK, I will pay attention to this and prevent the pressure from withdrawing before solidification.

边际力度

The original poster should take a look at the real injection molding machine first, and then think carefully before posting.

cardin6

Marginal strength posted on 2017-11-24 10:39 The original poster should take a look at the real injection molding machine first, and then think carefully before posting.

This must have been seen and the drawings drawn are the actual injection molding machine modification parts. Asking this shows that you have not understood my needs.

fsyicheng

I admire you so much. There is no industry you cannot conquer.

cardin6

fsyicheng posted on 2017-11-24 21:56 I admire you so much. There is no industry that you cannot conquer

There really is... Forensic medicine... I faint at the sight of blood...

395qav

This should work, but there are a few points: 1. It needs a certain temperature and pressure before solidification; 2. Will the excess material harden inside the screw, which makes it difficult to remove; 3. If the screw pushes a piston structure to inject plastic, it would be more ideal.

cardin6

395qav posted on 2017-11-25 08:06 This should work, but there are a few points 1. It needs a certain temperature and pressure before solidification 2. Will the excess material harden in the screw, which is very...

Before, we have considered the situation that the residual material will solidify after it is not taken out. Therefore, it must be heated to the original melting point before the reduction motor is turned on. If a piston type is used, it is also possible. For slightly larger molds, it is necessary to add a mold heating device and a cooling tank to prevent it from prematurely cooling and solidifying before the injection molding is completed. Comprehensively considering the materials needed, such as nylon, ABS, PC, etc., aluminum-magnesium alloy should not be suitable from the perspective of density, pressure, deformation temperature, price and many other factors.

chunyang

For desktop injection molding, the structure should be simplified as much as possible to control the volume and weight. It is unnecessary to use the feeding system of a conventional injection molding machine. Just make a fixed material box, add materials manually each time, close and heat, push the mold with a piston, and finally manually operate water cooling and demolding. Although this is inefficient, the structure is simple and can be made into standard detachable components. It can be removed and stored when not in use, and it does not take up space. If it is a small batch continuous production, it is better to use a standard small injection molding machine. In addition, the injection molding pressure of nylon and the like is relatively high, and it is not easy to miniaturize the structural design, so the plan needs to be carefully demonstrated.

cardin6

chunyang posted on 2017-11-25 20:48 For desktop injection molding, the structure should be simplified as much as possible to control the volume and weight. I feel that the feeding system of a conventional injection molding machine is unnecessary. Just make a fixed material box. Every time you manually...

OK Thanks to Brother Chunyang for the tip. I should first start with making a simple version of the manual molding machine. For example, use a press + steel column + steel pipe to try how much pressure is needed for nylon material to be injected, which will also be a reference for making a semi-automatic one later

陇上客

Brother, please leave me your contact information. I need a simple injection molding machine.

cardin6

Longshangke published on 2017-12-15 06:36 Brother, leave me your contact information. I need a simple injection molding machine.

Not for sale

许一凡

Can I learn from you?

许一凡

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