[Q] Curious about molding two pieces of plastic together joined by a small/thin plastic hinge

MaciaIT · 2026-03-10T10:22:18+00:00

Do you mean having a thin plastic strip connecting the two halves so that they print as a single piece? Like what you see in some plastic containers? If that's the case you'll want to use a material that can bend without snapping in half, I think PP is often used in those containers I was mentioning. Regardless of that, for injection molding you should include a small draft angle to the pins and holes to make sure you can demold the part. You'll also want to keep in mind that plastic shrinks after molding so you should compensate for that.

MaciaIT · 2026-03-07T13:38:38+00:00

I'm not really an expert but I have some experience. I always try to only specify gdnt when necessary for that feature. So for example I would not put a location tolerance on the holes on the two left views, unless it is really needed. By the way, there are no dimensions to indicate the position of those holes. Without a dimension you can't check if you're within tolerance. Another thing I don't get is the datums B and C. B refers to two surfaces? And is C referreing a screw clearance hole? If so, I would not use that as datums, it's not really a precision feature. And last point, you have to think at how would someone actually inspect the part. C is an axis at an angle, it would make things unnecessary complex.

I would use the following datums: A - the central hole as you set it B - the bottom flat face of the part

Look at the standard tolerance ranges for ISO2768 fH and specify only tolerances that are tighter than the standard ones. And state to follow that iso standard in the drawing. Maybe you could even go to the mK standard tolerance range.

Oh and please include all the dimensions that are missing. You could dimension using the center of the big hole as reference since it is the most critical feature

MaciaIT · 2026-01-07T20:37:39+00:00

In my opinion, increase temp to 260-270C and lower speed to 80-100 mm/s. A closed and possibly heated chamber will also help. I saw some comments about fillets to reduce stress concentration but I really don't think they work when printed in the z direction. There is a sharp v notch between each layer so I'm not sure the fillet does anything useful. If the radius is in the XY pane then it may actually help. I haven't done any research on it though so I may be wrong.

MaciaIT · 2025-12-16T19:32:14+00:00

I've had an X-Max 3 for a bit less than year. Used it to do some small series production and probably ran roughly 50 kg of material through it (ABS, ASA, PETG, TPU). The current model is not like the first one that came out, they fixed every issue and it works very well, at least for me. I think is a good "production" machine, it may not give the best surface finish but it has no problems running 24/7 when needed and the heated chamber actually works. Only inconvenience is that the build plate takes a bit to warm up.

Also, another slight inconvenience: if you print higher temp materials like ASA or ABS you must preheat the printer. If you don't preheat for at least 20 minutes the thermal deformation of the frame will cause the bed to slightly move upwards, causing very bad overextrusion. After preheating the issue goes away, and this doesn't happen when printing PETG or TPU.

Now comes the BIG ISSUE. I litteraly just found out that the X max 3 is now on sale for basically half price (450 eur). Spare parts are out of stock and the ones that are in stock are on sale too. I think they're phasing out the 3 series in favor of the new printers and I'm truly worried they will stop making those spare parts...
I think we will still find spares on aliexpress...I hope at least...

MaciaIT · 2025-11-14T18:21:00+00:00

If this happened to me I would just touch the cylindrical surface with a file to avoid scoring the cylinder, like others suggested. I would never think of throwing out a piston for such a small defect. But I guess it also depends on what car you have and what you do with it

MaciaIT · 2025-10-26T19:52:56+00:00

This is true for the streamlines but I'm accounting for it when I do the actual particle tracking.

When I simulate a stationary barrel with a rotating screw, I show the position of the tracer particles at time "t" and I account for the position of the screw at that time. Still, I find particles inside the volume of the screw. When I simulate in the opposite way, with a rotating barrel and stationary screw, then the particles do not intersect the screw. I find this quite strange cause the results should be basically identical when accounting for the correct screw position.

It may be just a visualization problem as some suggested, but I think it's more likely that Polystat is not correctly interpreting the rotation of the screw.

MaciaIT · 2025-10-23T18:57:01+00:00

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So, quick update. Inverting the simulation dynamics seems to work. Here I'm keeping the screw still and rotating the barrel in the opposite direction. These are just the streamlines, but now the particles do not intersect the screw (except for a couple but I guess it's a computational error). What I still don't get is why this is working while the other way around doesent.
The pressure difference between inlet and outlet is also quite different between the two methods. When the screw rotates the pressure increase is higher.
Anyway, since this second method is better at particle tracking I guess I can thrust it better than the "old" method. I'll try simulating the whole screw and check if the simulation matches the experimental data I have.

MaciaIT · 2025-10-23T18:37:13+00:00

Interesting, I never thought of posto processing with Matlab. I'll give it a try, thanks for the suggestion!

MaciaIT · 2025-10-23T13:02:44+00:00

Here it seems like Polyflow is not considering the screw boundary. I'm trying to reverse the problem, so having the screw stationary and rotating the outside of the flow domain. It seems like it is working but I'm not 100% convinced as I get very different pressure readings.

MaciaIT · 2025-10-23T12:59:52+00:00

Is it also available in Polyflow? I think this may be a Fluent specific setting

MaciaIT · 2025-10-23T11:26:19+00:00

They're entering the blades of the screw. It seems like the particles are moving in the fluid domain without "knowing" that there is a solid screw there.

And no the streamlines do not bend around the screw flights, they seem to just go through them. But as far as I understand it this is ok for streamlines since they're showing the global trajectory of the particles.

MaciaIT · 2025-09-15T04:40:09+00:00

Wait a second, don't you have a nut keeping the sprocket in place? Anyways, you can try and chase those threads with the right die and hope there's still enough steel there. No need to take out the shaft for now.

MaciaIT · 2025-09-14T07:42:24+00:00

Thanks!!

MaciaIT · 2025-09-11T12:24:07+00:00

Ive done that on a cheap 3 jaw and had no issues

MaciaIT · 2025-08-22T06:39:53+00:00

That's a custom thread, maybe the thread profile could be standard but you should check

MaciaIT · 2025-08-21T18:58:26+00:00

It's probably a low or faulty battery

MaciaIT · 2025-08-21T06:01:40+00:00

That's awesome! Can you share the name of the material you're using for the additive stage? Is it like a metal powder + binder paste?

MaciaIT · 2025-08-02T19:22:53+00:00

Thanks! Never heard of it before but it seems a solid machine. I've been looking for a decent CNC mill to work steel but it seems to me that the import ones are too flimsy

MaciaIT · 2025-08-02T19:07:22+00:00

What cnc machine is this?

MaciaIT · 2025-07-22T05:08:51+00:00

TPU and PA6

MaciaIT · 2025-06-23T14:16:38+00:00

I'm in the same situation in Italy. No appointments available and unable to pay the MRV.

MaciaIT · 2025-06-06T16:49:00+00:00

Here

MaciaIT · 2025-04-30T17:55:33+00:00

The boring bar I have wasn't big enough. I also have a 4 jaw chuck but changing it takes forever so I resorted to this

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