MOI cad. It looks good, is it?

[JasonBModerator @jasonb]

Dave, how do you know there is nothing inside that record player?

I really just depends on what you want to design, some may be happy with a barstock engine that looks just like it was made from barstock, others may want it to look like it was made from castings others designs may be very organic I'd call myself a model engineer not a model artist and would find the options in MOI quite useful when trying to replicate old or new cast parts

If you pay for the render option with alibre that record player is no problem to get the same look, I'm tight and would use F360 to do the renderings

I've only set the glass jam jar fuel tank as transparent but all the workings are inside the shiny outer layer

 

Also worth looking at the MOI model of that turntable, when you break it down it is far more of an "engineering" job made up of basic geometric shapes that could just as easily be done in Alibre, Fusion, etc The rendering of the turntable was not actually done in MOI 

 

Edited By JasonB on 19/05/2023 16:34:07

[Peter Cook 6Participant @petercook6]

As Jason says there is no problem modelling parts and assembling them in MOI, but which tool you choose depends both on what you want to do, AND which ones you find easiest.

I use MOI simply because I "get on" with its underlying design paradigm. Never having ben trained in engineering design or technical drawing I struggle to get my head around the paradigm that underlies the majority of the 3D CAD programs.

This is an MOI model of a clock I plan to make. All the parts can be separated from the whole, and drawings or diagrams created to take across t the workshop. Drawing each part in MOI makes me think about the design choices, while putting them together in MOI makes sure that they fit together.

One approach is not better than the other – they are just different, and at the limits are capable of different things. I will never reach the limits, so I stay in the middle with the tools that I find easiest to use.

[blowlampParticipant @blowlamp]

Dave.

Remember that these are just renders of the solid models produced by MoI.

I'm not trying to claim MoI is anything more than it actually is. You wouldn't design the Space Shuttle in it, just as you wouldn't try to do that in Fusion 360 or Alibre products.

What I am able to do in MoI is produce both solid model files, STL and DXF files, along with dimensioned drawings for my own use. I can send its output to my CAM systems and create excellent gcode for my CNC lathe & milling machine.

"The last MOI example represents a record turntable. It's a broadly correct and scaled external view that could be 3D printed as a model, used to illustrate a forum post, or published in a glossy magazine advert.

Great, so far as it goes, but tell me if I'm wrong: the turntable isn't an engineering model. It's an outer view of a turntable with nothing inside."

You are almost certainly wrong:

As I didn't model the turntable myself I can't tell you how well it has been constructed, but I can tell you that if I had modeled it, then each part of it would be to correct size and ready for transfer to Solid Edge, Fusion 360, Alibre or any CAM system.

The Cars you have posted do give a good indication of some of the nice shapes you can make in MoI that would be manufacturable directly from the MoI file output.

The models I make in MoI can be imported into your favourite mechanical CAD app and edited there – they are just the same NURBS models.

Martin.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Peter Cook 6 on 19/05/2023 16:34:48:

As Jason says there is no problem modelling parts and assembling them in MOI, but which tool you choose depends both on what you want to do, AND which ones you find easiest.

I use MOI simply because I "get on" with its underlying design paradigm. Never having ben trained in engineering design or technical drawing I struggle to get my head around the paradigm that underlies the majority of the 3D CAD programs.

This is an MOI model of a clock I plan to make. All the parts can be separated from the whole, and drawings or diagrams created to take across t the workshop. Drawing each part in MOI makes me think about the design choices, while putting them together in MOI makes sure that they fit together.

One approach is not better than the other – they are just different, and at the limits are capable of different things. I will never reach the limits, so I stay in the middle with the tools that I find easiest to use.

Looks like I have to retreat in confusion: I couldn't find anything on MOI's website suggesting it can do Assemblies, and yet here's Peter's clock. Must have missed it. Does the clock model animate?

Oh dear, sackcloth and ashes, I shall have to buy Martin a pint…

Dave

[JasonBModerator @jasonb]

As we are talking about renderings here are a couple of images, one of a model New Holland hit & Miss engine, the rights of which were bought by Littlelocos but the patterns were missing so he had to recreate them from the existing inventory that he bought as well as bringing them upto a standard that buyers expect these days not what they were like 30 odd years ago.

If Nigel is following the work to reproduce the main casting was done in Turbocad and allowance has been added for double shrinkage so metal masters can be made, machining allowances etc. It will be cast in a gun metal type metal. This is a good example where compound curves, blending of parts etc is all part of the engieering process

 

Bit more on their FB page

Edited By JasonB on 19/05/2023 16:48:51

[Peter Cook 6Participant @petercook6]

Posted by SillyOldDuffer on 19/05/2023 16:41:34:

Looks like I have to retreat in confusion: I couldn't find anything on MOI's website suggesting it can do Assemblies, and yet here's Peter's clock. Must have missed it. Does the clock model animate?

Oh dear, sackcloth and ashes, I shall have to buy Martin a pint…

As I don't use the other CAD systems, for the reasons explained above, I am not 100% sure what you mean by "doing assemblies". That model is put together part by part – in almost exactly the way I would do it in the workshop.

Each part is created individually (in my case mostly by hiding the rest of the model while I do so), then connecting or associated parts are unhidden using the browser and the bits put together, then the rest of the model is unhidden. That model was actually created by designing the three trains as separate MOI models, then combining them into a single one.

It doesn't do animations, although I often use stepwise rotation of parts to ensure things don't interfere with each other.

[lee websterParticipant @leewebster72680]

I am still plodding on with MOI, I won't give up just yet!

I drew an engine cylinder with water jacket. Now I want to create a water inlet on the side of the jacket. I drew a rectangle 3mm away from the surface.

And then tried to extrude it up to the surface with 5 degrees of draft.

I couldn't find a way of doing that except to run the extrusion past the cylinder face and boolean union the two parts. On virtually all other cad programmes I've used, a simple extrude would have done the job. Am I missing something? Or does MOI use boolean for all add/subtract operations?

Also, I couldn't find a "project to surface" function, it would have made drawing the initial outline of the water inlet a bit easier.

Still early days.

[Peter Cook 6Participant @petercook6]

Posted by lee webster on 19/05/2023 17:24:43:

Also, I couldn't find a "project to surface" function, it would have made drawing the initial outline of the water inlet a bit easier.

I think the function you want is in Construct/Curve which has four choices Project – Isect- Silhou – ISO

Although have never used them, they seem to do what you want.

I do use Boolean for most add/subtract operations – but then I am still learning.

One other thing to be aware of, there are available ( for free via the forum) a lot of add-in functions that can be used in MOI. I use the one that creates threaded fasteners, and one that creates gear wheels (specify Mod & Tooth count). There are many others.

 

Edited By Peter Cook 6 on 19/05/2023 17:52:08

[SillyOldDufferModerator @sillyoldduffer]

Posted by Peter Cook 6 on 19/05/2023 16:55:59:

Posted by SillyOldDuffer on 19/05/2023 16:41:34:

Looks like I have to retreat in confusion: I couldn't find anything on MOI's website suggesting it can do Assemblies, and yet here's Peter's clock. Must have missed it. Does the clock model animate?

Oh dear, sackcloth and ashes, I shall have to buy Martin a pint…

As I don't use the other CAD systems, for the reasons explained above, I am not 100% sure what you mean by "doing assemblies". That model is put together part by part – in almost exactly the way I would do it in the workshop.

Each part is created individually (in my case mostly by hiding the rest of the model while I do so), then connecting or associated parts are unhidden using the browser and the bits put together, then the rest of the model is unhidden. That model was actually created by designing the three trains as separate MOI models, then combining them into a single one.

It doesn't do animations, although I often use stepwise rotation of parts to ensure things don't interfere with each other.

My retreat may have been premature, because that's not what I mean by an Assembly. I'd call it a group, that is a selection of bodies, each drawn individually, positioned adjacent to each other. In FreeCad the parts are identified in a tree from which they can be hidden or reworked. They are only related by their position in space.

Here's an example of what SE means by an Assembly, Fusion is similar. It's a rough start at a Lazy Tong Riveter:

 

It's an assembly of 4 parts: a Brass "handle", an Aluminium pin, which runs in the slot, and an arm, 6-off. The arms are connected by 7 rotating joints, plus 1 rotating joint at a hole in the handle, and a non-rotating joint to the Aluminium pin, which has a tangent joint with the slot.

As shown in the next mage, I've extended the arms by sliding the pin up the slot. Moving the pin operates moves all the other joints.  This is the same model, except the joints have operated,

Pulling the pin down moves all the joints and retracts the tong:

Note the pin hasn't travelked the full length of the slot because an arm has collided with a corner on the handle.

Joints are modelled too, allowing the Assembly to move realistically, and can detect when distant parts hit each other, as a result of the movement of 'n' joints away.

All the parts can be used by other assemblies, and this assembly (with joints), could be assembled within another assembly, also with joints. If I change the original arm part, all the arms used in the assembly change. If the change breaks a joint, the assembly won't animate until the joint or other relationship is fixed.

The model supports step-wise refinement, divide and conquer, and part re-use. As parts and sub-assemblies are independent, projects can be developed by teams, not just singleton developers.

Next step in this riveter is to connect the far arms to a hinged cam that pulls a shaft and clutch that grips the pop rivet, all inside some sort of head. Then I'd add fasteners to join the tong arms together, and either drill and thread the cam to the pull shaft (two parts), or tap the shaft for a bolt (three parts). Both methods can be tried, because many cam and shaft variations can be modelled independently, and – provided they fit – can be swapped around. This is important in production : might be cheaper to bolt, because that removes one threading operation, or could be more convenient to thread the shaft. Or maybe the whole thing should be cast, drop-forged, or force fitted.

Having looked again at the MOI website, I don't believe it does this type of Assembly. But I accept what MOI does is effective too.

Dave

 

 

Edited By SillyOldDuffer on 19/05/2023 20:12:51

[blowlampParticipant @blowlamp]

A video with a few ways to get things properly positioned in MoI, for things like stud or bolt holes and also attaching a boss to the side of a cylinder.

Martin.

[lee websterParticipant @leewebster72680]

Thanks for the video Martin. Believe it or not, that's what I ended up doing. The one thing that isn't obvious from my pics is that I had already created the water jacket inside the block. The dotted lines are barely visible. It was wondering how to do the boolean operation between extrusion and block without leaving a piece imbedded in the jacket that slowed me down. But MOI took care of that itself. The hole I then created in the face of the extrusion caused some concern because I wanted it to stop somewhere in the jacket and not take a chunk out of the cylinder wall. I did it, but it mainly guess work. I can see a more accurate way to do it, but I haven't tried yet. I will have another go later.

I will also get some images of the cylinder head from Designspark that I want to draw in MOI. Not the sidevalve head on the engine I posted earlier, this one is an OHV with sparkplug and a water jacket. I will use the finished head to also produce the pattern and moulds for casting one. This is all an excercise!

[blowlampParticipant @blowlamp]

Lee.

Glad you haven't given up.

Sorry if you are already aware of this, but you can load images of the head for tracing purposes etc, if that helps.

Also, If you get stuck whilst using a particular tool the ?Help icon takes you straight to the information about the tool in use. I find it sometimes gives me a useful nudge.

Martin.

[lee websterParticipant @leewebster72680]

I have drawn a simple water cooled OHV cylinder head in MOI. I can't say it was easy, MOI has it's own way of doing things that I'm not used to. The only thing I didn't do is the water inlet. It would have been easy to add it, but all this is only practise.

This pic is a general view of the head. All lines are hidden and the head is coloured grey-ish.

This is a cut-away view showing inlet tract, water passage and spark plug hole.

Next I have removed the top of the head to show the water passage and other internals.

It's early days yet, 87 days of a 90 day trial to go. I will still look at other packages, including, and I never thought I would say this, monthly or yearly subscription. I could get the latest copy of Designspark Mechanical for a tenner a month that would have all the tools I need, for the price of a mobile phone contract. I will also check out Solidworks student or hobbiest cad package. I think that's about £100 per year.

[JasonBModerator @jasonb]

Looks good, now all you need to do if perfect that casting technique! Have you had any more attempts at that?

[lee websterParticipant @leewebster72680]

Hi Jason.

No time for casting at the moment, all my spare time is spent building the model cars I am making. I hope to start painting them in primer soon. Before I try casting again I want to make new elements for my electric foundry. I will aim for 2.5kw to get up to temp quicker. I am also going to order some oil bound sand to try.

As for MOI, it isn't for me. I have seen what others have done using it, but it isn't like using a dedicated cad programme. The head above took far too many steps to create than with any other cad programme I've used. And thats not because I am new to the programme. I will stick with Designspark and Solid Edge, unless something better comes along.

[lee websterParticipant @leewebster72680]

Strewth! Talk about back-tracking. I have now re-installed MOI, after 100% believing it wasn't for me. When I put a "lid" on the cylinder head (see above) to create the top, I thought everything was going well. I was wrong. For some reason, when I boolean joined the top to the main body, it also filled in the water jacket with a solid. I discovered this when I tried slicing the head to have a look inside. I deleted the water jacket solid, and there was another one under that. I deleted that and was left with a solid head, no water jacket at all. I restored the two water jackets and named the head. I then hid the head, deleted the first water jacket solid, and named the second one. I made the head visible again and boolean cut the jacket from the head which created a void where it should be. I then uninstalled MOI and started to look for another cad package to try, I even looked at Turbocad, which looks really good on paper.

That was yesterday. Today I started to think about MOI again. I don't know if I did something wrong, or if MOI has a certain way of working. Anyway, I reinstalled MOI and tried a new approach. So far, it seems to be working, and I have to admit, for such a tiny programme, it packs in a lot of features. I didn't know the Text feature was so good, and the help file is really good. I did think that I wouldn't want to spend £260 buying MOI, but now…….

I have 85 days left of the trial to make up my mind.

[JasonBModerator @jasonb]

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 websterParticipant @leewebster72680]

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

[blowlampParticipant @blowlamp]

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.

[blowlampParticipant @blowlamp]

I didn't do the booleans properly in the previous video, so the cores are wrong. It's better in this snippet.

Martin.

[lee websterParticipant @leewebster72680]

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.

And then revolved it around the right hand side.

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.

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.

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!

[blowlampParticipant @blowlamp]

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!

Martin.

[lee websterParticipant @leewebster72680]

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

[blowlampParticipant @blowlamp]

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.

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.

[blowlampParticipant @blowlamp]

Lee.

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

 

Martin.

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

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