3D and RC parts

[ALEXKYRIAK 1046]

I have to say that the combination of 3D printing and RC is a fascinating combo. I have never tried it before but I can use 3d modelling very well.

If you were to make parts that replace or utilise existing Tamiya parts and designs, how does one go about ensuring the shape and accuracy of the geometry is maintained to the original? 

Do you need to 3D scan existing parts first? Is there a database of 3D models for parts on the net?

Or is it just hard graft with photos and very careful measuring, with test prints until the final outcome is achieved?

lets say for example I wanted to create a custom chassis to mount existing gearbox and suspension to. How do I go about creating the model for this, ensuring a tight fit and accurate alignment of surfaces and bolt holes to accept the existing parts?

thanks.

[Pintopower 1456]

On 4/23/2017 at 3:13 AM, ALEXKYRIAK said:

I have to say that the combination of 3D printing and RC is a fascinating combo. I have never tried it before but I can use 3d modelling very well.

If you were to make parts that replace or utilise existing Tamiya parts and designs, how does one go about ensuring the shape and accuracy of the geometry is maintained to the original? 

Do you need to 3D scan existing parts first? Is there a database of 3D models for parts on the net?

Or is it just hard graft with photos and very careful measuring, with test prints until the final outcome is achieved?

lets say for example I wanted to create a custom chassis to mount existing gearbox and suspension to. How do I go about creating the model for this, ensuring a tight fit and accurate alignment of surfaces and bolt holes to accept the existing parts?

thanks.

Well, I am glad you posted! My secret is measuring. That is all man. Measuring. There is no easy way to do it sadly. If you are trying for a repro and want it to look stock then it is a bit harder as many of these parts are plastic and therefore molded and therefore have draft. Draft screws all the measurements up so what you need to do if find critical datums and features and go from there. 3D scans would be amazing if they worked the way most people think. We had a mouse scanned recently at the office. The scan was around $25,000 plus the reverse engineering software to take the useless tessellated image and parameterize it. For what you and I are interested in, this is not a viable option. Give it a couple years and that will be different. I will be doing an episode on just this topic in a couple weeks on my Youtube channel if you are interested. I have some tricks that could help. 

[casethejoint 296]

I will be doing an episode on just this topic in a couple weeks on my Youtube channel if you are interested. I have some tricks that could help. 

I'm interested in seeing that.

I wonder if 3D printing will also push down the cost of decent CNC milling equipment which for many things is as good/better than 3D printing?

[ALEXKYRIAK 1046]

Hey Pintopower, thanks for the response. OK so it's the hard graft option! That's cool, I guess.... do you have any special tricks for doing the measuring? Is it a slide rule/calliper and eyeballs job, or do you have something more sophisticated, laser measuring or similar? Reading about the concept of being able to create custom 3D parts in a hard material, it makes me wonder about a semi custom car where in basic terms, I design a chassis, but utilise the gearboxes and suspension from standard Tamiya cars and parts.

[Pintopower 1456]

21 hours ago, casethejoint said:

 

 

I'm interested in seeing that.

I wonder if 3D printing will also push down the cost of decent CNC milling equipment which for many things is as good/better than 3D printing?

I have seen that happening already. We are on the upswing of an exponential curve. 

 

18 hours ago, ALEXKYRIAK said:

Hey Pintopower, thanks for the response. OK so it's the hard graft option! That's cool, I guess.... do you have any special tricks for doing the measuring? Is it a slide rule/calliper and eyeballs job, or do you have something more sophisticated, laser measuring or similar? Reading about the concept of being able to create custom 3D parts in a hard material, it makes me wonder about a semi custom car where in basic terms, I design a chassis, but utilise the gearboxes and suspension from standard Tamiya cars and parts.

I have many tricks that are next to impossible to describe lol! All I use is a digital caliper and yes, my eyeballs. Rulers are no good though. You need something precise. In terms of the car, you a dead on! Make the chassis but not the gears or gear boxes. That is a waste of time given the options available. 

[ALEXKYRIAK 1046]

Would love to hear about the tricks!  Have you ever used flat bed scanning to create a "flat" image of a component? Is that even possible? Do you ever combine other fabrication techniques - for example,  flat plane "2D" materials such as carbon fibre plate to create the chassis / floor of the car, or shock towers, sort of like an Egress, for example?

Just thinking about how to create a chassis from 3D printed materials, it's quite interesting to review various chassis designs from Tamiya and to think about how they could be adapted. In another thread on this forum I am wondering how to make something similar to a Mad Bull in terms of it's wheelbase, wheel size, track, centre of gravity, etc, as the base Mad Bull is quite flimsy. I am half tempted to see if I can create a similar set of parameters, but using a custom 3D printed chassis/tub, utilising an off the shelf rear gearbox and suspension, and a front suspension/steering (possibly even a front gearbox also....  a 4wd Mad Bull...!).

 

[VagabondStarJXF 350]

I've just received notification from Shapeways that they've got the new HP MultiJet Fusion Printer which should be able to print in full colour plastic (instead of white plastic that is dyed afterwards) and with a comparable Z axis strength to that of X and Y. At the moment it's being offered up for testing and print colours are only grey and black. It is, apparently, more efficient (less material wastage) which should bring printing costs down a bit and it also looks like greater detail can be achieved with this printer too. The next couple of years in 3D printing are going to be fun. I've had ideas that have been relegated that I might now reconsider if this printer is as good as Shapeways seem to think it is.

[Dangerseeker 162]

3D printing is indeed fascinating and opens infinite possibilities to restore/upgrade our rc cars. the one thing i am not sure about is the strength/durability of the 3D printed parts compared to the injection molded ones. the latter feel stronger and i am afraid they are, but i have not directly compared such parts.

[VagabondStarJXF 350]

Just the differences in the processes would mean that injection molding would mean stronger parts than 3D printed ones (assuming the quality of the material is high for both processes). That being said, there have been cases where the quality of the injection molded part isn't good, whether that be due to the quality of the material or the design of the part. This is where, I think, 3D printing gets to shine. I think Pintopower's King Cab suspension arms can be used as an example. In his video he shows just how much flex there is in the original arms and his redesigned arms eliminates most of the flex to improve the model.

[ALEXKYRIAK 1046]

Has anyone looked into 3d aluminium components? Been reading up a lot lately on custom plastic printed parts, but then started wondering how far one could go...!

[ThunderDragonCy 7886]

You can get aluminium and stainless steel on Shapeways but price is about 10-20 times plastic. Depending on complexity of the part I still think it is borderline on 3d metal vs getting a metal part custom made by an engineering firm.

[ALEXKYRIAK 1046]

Ah yes I see that now, interesting, didn’t realise they provided that service.

Description of the aluminium says that its slightly rough surface. Has anyone here ordered one or had one made? How do they perform in terms of rigidity? 

And in terms of performance, how does the plastic that shapeways provide perform in comparison to the standard Tamiya plastic?

And is Tamiya plastic less sturdy than that say the likes of HPI Hot Bodies or Tekno? I would presume so given the target markets?

Having aluminium or even carbon machined seems intriguing. 

What is also very interesting that I hadn’t realised is how many pre-made free parts are available online as STL files, and how many 3D RC cars have been built. Thingiverse and Instructables are amazing websites.

[ThunderDragonCy 7886]

There won't be much difference in stiffness at all between 3D aluminium and CNC machined. It's fundamentally the same material so the intrinsic stiffness (the Youngs Modulus) is the same. They don't say what grade the aluminium is which is how you figure out the strength. Some aluminium alloys are barely stronger than plastic, some are stronger than mild steel. I don't know how far things have come with this recently but z-axis stability used to be a real problem with early metal 3D parts. This is where the part is built up in layers by the process vertically (the z axis) and the layers didn't fuse quite as well as they could gave so it wasn't as strong in that direction as the parent metal.

3D printed nylon isn't as strong as the ABS plastic used in Tamiya cars. If you want durability then stick with original parts in vulnerable places or overbuild the 3D part.

Yeah there are tonnes of STL files out there. It is an interesting subject. I have made a few parts for my Thunder Dragon and rising fighter inspired by Ampro engineering.

[Tizer 606]

Actually, I've experienced many times already that the 3D printed nylon parts are actually stronger than the original plastics. Mostly with vintage cars where even all the new parts you buy are 20+ year old New Old Stock items and have turned very brittle over time. Compared to new plastic parts it depends on the application really, as the nylon is a bit more flexible and therefore a bit more forgiving but not always 'stronger'.

The 3D printed aluminium and steel is pretty cool. The aluminium really is just aluminium, while the steel is actually ~30% bronze because of the printing process. The biggest issue I've found with using these two materials is the dimensional accuracy. The aluminium polishes up quite nicely so the rough surface isn't really an issue, but the fitment is.

I tend to stick to nylon for all my parts, or maybe the Jet Fusion HP stuff or even carbonfibre reinforced nylon in the future.

[ALEXKYRIAK 1046]

Tizer, so what issues are you finding with the fitment of the aluminium and steel? Is it a poor tolerance? Is it a predictably poor tolerance? Ie  - if you want 5mm thickness, design in 4mm? Or is it just random?

thunderdragon, I guess I’ll make enquiries on the grade of aluminium they do. I’d be interested to know if certain pieces are better achieved in aluminium  - if the tolerance is right. 

I think i read somewhere that if you want to have a threaded shaft made (to accept a screw of corresponding thread) you’ll need to go to full CNC as this is the only way to achieve the precision. 

[ThunderDragonCy 7886]

For relatively straight forward things like shafts that could be done on a lathe it would be worth trying to find a small engineering firm local to you. We have guy next door to us at work who knocks up small parts for prototypes for reasonable money. If you have a part they can measure up to check tolerances so much the better. I'm a design engineer in Real Life so it might be that I am more comfortable with this kind of thing than most but it is work considering. The power of 3D printing comes in for one off complex shapes which would require hours of setting up on a CNC mill.

[MadInventor 3884]

On ‎24‎/‎04‎/‎2017 at 8:44 PM, casethejoint said:

 

 

I'm interested in seeing that.

I wonder if 3D printing will also push down the cost of decent CNC milling equipment which for many things is as good/better than 3D printing?

I can't see 3D printing pushing down the cost of CNC machine tools. 3D printing it still far from being able to reproduce the accuracy and surface finish of industrial machine tools, and as the above post has pointed out, if you're making one offs, most of the cost of machining is in the setting up of the machine. I quite often have to make jigs first before making parts on my mill, which if someone was paying for it would also push the cost up.

If anything, I see 3D printing pushing up the cost of getting things made in a machine shop, as 3D printing will be taking work away from machine shops in some instances, causing them to increase prices to meet overheads.

With regard to the original post and the subsequent ones about measuring, I've noticed from several years of making bits for Tamiya cars, or using their components in scratch builds, that all their dimensions seem to be metric, so when measuring with the callipers you will soon notice that a lot of measurements are in whole or half mm, allowing for the injection moulding tolerances. These are surprisingly large, I've seen variance in parts of easily 0.2mm, particularly with parts made from flexible plastics such as wheels.

[MadInventor 3884]

On ‎26‎/‎04‎/‎2017 at 10:26 PM, ALEXKYRIAK said:

Would love to hear about the tricks!  Have you ever used flat bed scanning to create a "flat" image of a component? Is that even possible? Do you ever combine other fabrication techniques - for example,  flat plane "2D" materials such as carbon fibre plate to create the chassis / floor of the car, or shock towers, sort of like an Egress, for example?

Just thinking about how to create a chassis from 3D printed materials, it's quite interesting to review various chassis designs from Tamiya and to think about how they could be adapted. In another thread on this forum I am wondering how to make something similar to a Mad Bull in terms of it's wheelbase, wheel size, track, centre of gravity, etc, as the base Mad Bull is quite flimsy. I am half tempted to see if I can create a similar set of parameters, but using a custom 3D printed chassis/tub, utilising an off the shelf rear gearbox and suspension, and a front suspension/steering (possibly even a front gearbox also....  a 4wd Mad Bull...!).

 

Mad Bull wheels fitted on a thundershot give a car only 1 cm wider than a Mad Bull, all you need to do is get a custom motor plate made to fit small pinions and fit the body shell and hey presto

[yogi-bear 2321]

12 minutes ago, MadInventor said:

I can't see 3D printing pushing down the cost of CNC machine tools. 3D printing it still far from being able to reproduce the accuracy and surface finish of industrial machine tools, and as the above post has pointed out, if you're making one offs, most of the cost of machining is in the setting up of the machine. I quite often have to make jigs first before making parts on my mill, which if someone was paying for it would also push the cost up.

If anything, I see 3D printing pushing up the cost of getting things made in a machine shop, as 3D printing will be taking work away from machine shops in some instances, causing them to increase prices to meet overheads.

...

I have a slightly different perspective. Without the current batch of 3D printers or cnc machines, I would probably just drop a lot of my projects as I don't have the kind of money needed to pay a shop to machine parts.

So these machines won't mean work from a machine shop will get cheaper. But what has changed is cost of the entry level and getting started into cnc machining and 3D printing. Especially in the last 4 or 5 years, its a lot cheaper to get into either, and with the slow improvements in software, that seems to only be getting better. While these machines are not going to be used in professional workshops, they are good enough for someone like me to tinker, learn and even use in a small business.  This has in part been driven because 3D printers and cnc machines share many of the same base components - stepper motors, controller boards, rails etc. Many people even do cross conversions from a cnc to 3D printer or vice versa, although I would say there are often dubious results. Plus the amount of information out there is enough such that someone like me can build a small machine for a relatively small amount of money that can machine wood, plastic and soft metals like aluminium and brass without too much trouble, with a reasonable accuracy (certainly better than 0.2 mm) and a fairly large work area. So in that context, machining is getting cheaper.

[ThunderDragonCy 7886]

2 hours ago, MadInventor said:

Mad Bull wheels fitted on a thundershot give a car only 1 cm wider than a Mad Bull, all you need to do is get a custom motor plate made to fit small pinions and fit the body shell and hey presto

Note also that a grasshopper 2 body shell fits directly onto a thunder shot chassis 😉

[Tizer 606]

On 30-10-2017 at 11:44 PM, ALEXKYRIAK said:

Tizer, so what issues are you finding with the fitment of the aluminium and steel? Is it a poor tolerance? Is it a predictably poor tolerance? Ie  - if you want 5mm thickness, design in 4mm? Or is it just random?

Unfortunately the tolerances are random. Holes are not round, and the surface is sometimes very rough. Getting the parts machined would be a much better option.

[ALEXKYRIAK 1046]

So on nylon 3D printing, what’s the general advice for tolerances?

For example, if designing a wheel with a 12mm hex hub, do you design the hex in the 3D model at 12mm? Or do you have to make it an offset to account for the fabrication process? Ie 12.2mm? I have noticed wheel models on thingiverse seem to do this.

Similarly with a standard M3 screw which is 3mm diameter, I have read that the hole this will screw into should be of a diameter of 2.5mm. Is this the correct diameter to design in on a nylon 3D printed part? Or does it need to be offset? 

I guess it’s a different scenario if a hex hub piece is fitting into a wheel there may need to be a slight bit of clearance, whereas a screw just needs to bind into the material tightly so no additional tolerance is required?

[VagabondStarJXF 350]

I've done a few wheels this year and designed them all with an extra 0.1 for nothing but clearance and haven't needed to make them any bigger for any other reason. Variations in the printing process have been minimal in my experience with Shapeways SLS Nylon/Strong & Flexible Plastic so far. Admittedly I have had one wheel out of set be a little snug compared to the others, it might've been just be a thin layer of excess powder for all I know, but nothing more than any of my Tamiya or HPI made ones have sometimes been.

[ThunderDragonCy 7886]

For holes I tend to follow @Pintopower example and size all the holes on the low side and then drill them to an accurate size when you get the part. You get a better finish and tighter tolerance doing that. So for holes you are threading into model them at 2.2mm and drill out to 2.5mm. For through shafts size at 2.8 and drill with a 3mm bit. I sometimes use a sharp 3.1mm drill for pivots so they are definitely free moving.

[VagabondStarJXF 350]

1 hour ago, ThunderDragonCy said:

For holes I tend to follow @Pintopower example and size all the holes on the low side and then drill them to an accurate size when you get the part. You get a better finish and tighter tolerance doing that. So for holes you are threading into model them at 2.2mm and drill out to 2.5mm. For through shafts size at 2.8 and drill with a 3mm bit. I sometimes use a sharp 3.1mm drill for pivots so they are definitely free moving.

Yep. Thanks to @Pintopower I do the same. It's very good advice to follow.