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MOI cad. It looks good, is it?

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JasonB22/05/2023 20:39:14
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I would have thought the head complete with jacket would be a rotated sketch and then just add the inlet "bends" as swept circles, valve stems, plug boss and side bosses. all as extrusions

Edited By JasonB on 22/05/2023 20:40:17

lee webster22/05/2023 21:08:15
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If I do a rotated sketch to create a hollow head, I can't see inside it to create the other features. Unless I'm missing something. Things get so tight in a head that's only 54mm dia internally, that adding 5 deg draft to say the plug boss could have it interfering with other parts. Thats why I always leave the top till last. But, I will give it a go! I can turn the faces off to create a wireframe environment, but new parts are created as solids, so a mixture of the two.

I also saved a file as an STL and imported it into my slicer. It looks perfect. I didn't print it as it would take hours and serve little point.

Edited By lee webster on 22/05/2023 21:11:38

blowlamp22/05/2023 21:55:28
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I whizzed through a video of your cylinder head(ish). The video is a bit messy, but should serve its purpose. It's pretty much done as Jason describes. You'll see I defined some of the curves and then hid them, so I just remade them on the fly - sorry if that's a bit confusing.

Try turning off individual faces by double-clicking on them and hiding them. If you give them their own colour, you can switch them on & off at will under the Scene Browser>Styles.

As you have found, STLs from MoI are very,very good. They can be treaked to get the right resolution for curved areas, without a massively high number of triangles too.

Martin.

blowlamp22/05/2023 22:16:10
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I didn't do the booleans properly in the previous video, so the cores are wrong. It's better in this snippet. smiley

Martin.

lee webster22/05/2023 23:25:33
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Very interesting videos Martin, thanks for taking the time. I tried a rotated sketch this evening as suggested by Jason. It did not go well. I drew a closed curve.

head outline.jpg

And then revolved it around the right hand side.

revolve 180.jpg

The head was solid, no internal void. I undid that.

I then drew a vertical line 1/2mm to the right of the sketch and revolved around that.

head outline 2.jpg

revolve 2.jpg

I got a hollow head, no jokes please!, but of course it's wider and has holes in. I then extruded the sketch to make sure it was valid.

head extrude.jpg

I am missing something, but I can't figure it out. I did try different variations of the revolve, and managed to get two solids. The head, and the void, by deleting the two small uprights on the right hand side of the sketch. I boolean cut the void from the head to get a hollow head. Before posting this I tried the same sketch in FreeCAD and it worked perfectly. In your first video you revolved the base of the head and that worked OK. I tried full 360 deg revolves and it made no difference. The 180 deg revolve is to make the inside visible.

Thanks for making it clear that I have spent so long without a mirror function in Designspark, that I have been drawing things like the inlet/exhaust tracts twice. Mirror will take some getting used to!

blowlamp23/05/2023 00:01:48
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Lee.

I think you've found a bug! I've never seen this myself, but I can repeat it. I'll post a notice on the MoI forum and see if Michael will take a look.

Well done! wink

Martin.

lee webster23/05/2023 00:05:00
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Thanks Martin. If he wants may original file I can post it to him. Maybe version 5 has a fix?

blowlamp23/05/2023 00:46:38
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Posted by lee webster on 23/05/2023 00:05:00:

Thanks Martin. If he wants may original file I can post it to him. Maybe version 5 has a fix?

I'm using v5 and can easily repeat it, so it's one of those 'obvious' bugs that only new users seem to find. smiley

I've done a video of the problem for Michael so I'm sure he'll look into it. I know he's busy integrating the ACIS kernel into MoI at the moment, so we'll see what he says.

Martin.

blowlamp23/05/2023 01:15:02
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Lee.

Here's a link to my post to Michael and his reply.

 

Martin.

Edited By blowlamp on 23/05/2023 01:15:38

JasonB23/05/2023 06:57:29
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Does Moi not have the option to make the part transparent or give a sectioned view so you can see inside? Or even supress the initial rotation.

 

Though knowing you want to make a core box I think I would approach it buy modelling the core and then using a boolene to remove that from the solid head. That way you can also use the same core model to make your core box. It does need a different approach depending if you simply want to model the finished part or model what is needed for casting

On the last video the core which comes up from the bottom would not need to be as complex as things like the valve stem holes, plug hole and probably the recess would be machined not cast. So only needs a main core for the water void and then the two curved passages which would not need to increase in Dia behind the valve head leaving you metal to bore out and also machine the angled seat.

 

Edited By JasonB on 23/05/2023 07:19:46

lee webster23/05/2023 07:35:45
383 forum posts
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Martin, I read the reply by Michael and that's the way I got it to work.

Jason, as far as I know, there isn't a tranparancy or section option, only wireframe.

blowlamp23/05/2023 11:43:47
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There's no transparency (yet) in MoI, but take a look at the script in this thread to see if it might help.

To add the script in MoI: Copy it straight from that linked page, go to Options > Shortcut Keys and click Add, press the key you want to use and then paste the scrip into the box.

There's also Display Hidden Lines under View in the tools menu.

Martin.

blowlamp23/05/2023 11:59:16
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Jason.

Good point about the cores being a bit complex in the last video, but bits could be added or deleted pretty easily. Using the Merge tool can be a real help for making patterns from the model.

Martin.

lee webster23/05/2023 14:38:36
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I had another go at the head. This pic shows the head ready for capping off. The yellow parts are the tops of the spark plug and valve guides which are 3mm down from the top surface of the head. The head has a water jacket.

1.jpg

This pic is the top filled and and joined to the head with a rectangle ready to boolean cut through the head.

2.jpg

The water jacket has been filled in. I selected it and pressed delete.

3.jpg

This pic shows that the rest of the water jacket is left in place. It too could be deleted to leave the head with a water jacket.4.jpg

I then tried an experiment to see if it was the boolean cut creating the filled water jacket. I created a head that had no plug or inlet/exhaust tracts, cut a hole in the side, and filled in the top.

5.jpg

It looks as though there is no bottom to the head, there is, it's just the angle. But the point is, it proves that the water jacket isn't filled in by sealing the top. I pressed ctrl z until the hole was gone, filled in the top and cut through.

6.jpg

The water jacket has been filled in again. The water jacket solid could be cut from the head to leave a void. I am not sure if this will cause problems later on, so I will carry on with creating a head and making core moulds and patterns from it.

Should I start a new post? It might not be of interest to many.

JasonB23/05/2023 16:35:58
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I wa sinterested when you posted on MEM and still am.

This is how I went about it in Alibre. I drew the overall head, then the cores for the inlet & exhaust and finally the water space core including passages that will link to the cylinder water jacket, changing how opaque the part is allows me to see inside.

I then boolene subtract the water space and passage cores to leave me with the as cast part. I can also subtract these from blocks to mould the cores in.

Finally I add the machined features like valve seats, valve guides, plug hole etc And use the section option to see what is going on.

lee webster23/05/2023 18:10:13
383 forum posts
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Jason.

If only Atom 3D had those features, I would have bought it by now. I think the version you are using is £1,000 or so. I can't justify that sort of outlay unless I know I can produce good castings.

MOI is proving to be a challange, good or bad, I don't yet know. I have 84 days to find out. This afternoon I produced a simple nameplate. It looks better on screen. I have produced an STL of the file, and it looks very good in the slicer. I might print it out. There is 5 deg draft on the lettering and plate. The letters protude 1mm from the surface, and are about 8mm high. I think the 7 is 15mm high.

a7badge.jpg

I watched a video on youtube by a man scratch building a Spitfire. He used MOI to produce the engine cowling, spinner and a double bladed prop, from some old drawings. That showed what MOI is really good at.

blowlamp23/05/2023 18:46:11
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Posted by lee webster on 23/05/2023 18:10:13:

Jason.

If only Atom 3D had those features, I would have bought it by now. I think the version you are using is £1,000 or so. I can't justify that sort of outlay unless I know I can produce good castings.

MOI is proving to be a challange, good or bad, I don't yet know. I have 84 days to find out. This afternoon I produced a simple nameplate. It looks better on screen. I have produced an STL of the file, and it looks very good in the slicer. I might print it out. There is 5 deg draft on the lettering and plate. The letters protude 1mm from the surface, and are about 8mm high. I think the 7 is 15mm high.

a7badge.jpg

I watched a video on youtube by a man scratch building a Spitfire. He used MOI to produce the engine cowling, spinner and a double bladed prop, from some old drawings. That showed what MOI is really good at.

Did you use the Flow tool to position the text?

Martin.

JasonB23/05/2023 18:57:37
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You could save yourself £700 and do the same head using basic features that can be found it Atom, no Boolenes in this one I just copied the sketches I used for the cores and pasted them into the head model and simply extruded or cut them.. It's just a case of getting to know a program to get the best out of it.

lee webster23/05/2023 19:08:37
383 forum posts
71 photos

Hi Martin, Yes, I used the flow tool. The help file explained it enough for me to have a go, but the curve I flowed the text on was too big and I had to backtrack and shorten it. Then I found the stretch option. That helped, but the curve still had to be close to finished size. I couldn't see a way to center the text, yet. I also chose flat text so I could extrude it with draft.

Jason, I suppose I am so used to doing my designs in Designspark, that I found Atom 3D awkward. At least MOI has familiar functions, sort of.

Lee

blowlamp23/05/2023 20:45:11
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Lee.

The length and position of the base curve in relation to the items to be flowed is significant, as is its length in relation to the target curve. I've tried to give a few hints in the attached video.

Martin.

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