How do you know when to CAD vs draw up on paper quickly

[CamFam1]

How do you decide which design items must be CAD'ed before proceeding with building and which things can be drawn up on paper with quick dimensions?

It seems there are different views on whether everything must be CAD'ed before proceeding or using a low tech solution of "paper, pencil, and ruler" to get a design that's good enough to build off of.

When time is running short do any of you let go of the desire to CAD and use paper and pencil?

In managing the project, how do you know which things need to be dependent on CAD-ing most and which things can be good enough on paper and pencil?

[EricH]

It depends on time available and accuracy needed. It also depends on whether nearby items need CAD.

If I'm low on time, and I don't have a CAD, I'll grab paper and pencil/pen and do a freehand or ruler-assisted drawing. This is also good for a quick concept model. I do pretty well at freehand perspective drawings, though.

I'll often turn the items drawn up into CAD models, too.

A good perspective drawing course and some practice can really help you make crisp, clear drawings. I've been known to make two quick sketches in half an hour to an hour that wound up in a PDR slideshow after conversion to electronic form. One of them had to show internal structure as well as outside skin.

The time (and maybe money) investment in learning to draw with pencil and paper is well worth it. You might not produce full-on shop drawings, but you'll be pretty close.

[artdutra04]

I usually only draw things on paper when sketching initial ideas (I'll fill up dozens of D size sheets during the first two weeks of the build season doing this), or if making a quick drawing to give to the machinists if there's no printer around.

Otherwise on Team 228, everything mechanically is modeled in SolidWorks. Part numbers are assigned* and official drawings created for every manufactured component on the robot. From there, exploded assembly drawings are also created for some of the critical sub-assemblies, while others are just assembled using laptops with the CAD model open as reference.

Doing this, we were able to machine almost 70% of all components for both of our robots before anything was even bolted together. Ironically, the battery holders (http://www.team228.org/media/pictures/view/4602) were the first completed sub assembly of our 2009 robots (they fit perfectly into the robot chassis' once they arrived back from the machine shop earlier this week). ;-)

Why do we go this far and model everything now? Because for years we did minimal CAD modeling and relied almost entirely on hand-drawn drawings. Without out a doubt, they worked well. But at the same time, it's a lot harder to tell if there is interference between two components in an assembly when it's drawn on paper instead of SolidWorks. And that came back and bit us. A lot. And because of it, there was a lot of "redoing" parts over again (which frustrated our machinist).

This year, by doing everything in SolidWorks ahead of time, we haven't had to redo anything. On the plus side, we now have an entire binder full of SolidWorks drawings for every part on the robot; so if anything breaks and we need another, we're covered.

* I really did give part numbers to everything. Need another Delrin spacer for the rear mounting of the pneumatic cylinder on the right side of the ball intake mechanism? That's 09-BI-026. Need another transmission housing with corresponding bearing spacer? They're 09-STR-006 and 09-STR-007 respectively.

[AdamHeard]

I'm of the belief that every team that can should CAD 100% of the robot, then build from properly dimensioned drawings. The properly dimensioned is the hard part for most.

If this is done, assembly should be painless. Our base went together this year in about 30 minutes, tops. The only interference or fit issue was our battery tray hitting a driveshaft.... and you guessed it, it's location had been changed on the spot from the CAD.

Compared to years past with non-CAD designed bases I've worked with, or even CAD designed ones without proper fits and dimensions, it was awesome.

[mplanchard]

Orginial brainstorming with sketching on a white board or on paper works well.

But I agree with the other designers, if you create your parts and assemblies in CAD, then you will be so much better off in fit. You can check interference in SolidWorks between components and simulate how components are assembled.

I see you are from MN. There is a southern SolidWorks Minnesota Users Group http://www.swugn.org/pages/calendar/calendar.html that meets in February. There may be some engineers there that can give you suggestions. SolidWorks users are very helpful to each other - no matter what their age. It may be too late for this year but you have to think about the future. Marie

[CraigHickman]

Here's a good way to think about it: Would you trust yourself riding in a car you didn't do CAD for, and only sketched it roughly out?

There's a fun exercise you can do to test this out. Have one of your team members go grab a random part from an old robot, mainly one that was Milled simply. Have him/her sketch it out "quickly" on a piece of paper, with all the dimensions THEY think you'd need to make it. Give that drawing to a team member who has not seen what part it's drawn from, and have them try to make it. Unless your student has taken some drafting courses, or is quite gifted in conveying all the details of the part on a sheet of paper, I'm pretty sure there will be errors.

If you sketch it out as you go, you'll always be building under the pressure of the clock. If you CAD it entirely, all you have to do is put the model together. Motion can be tested, speeds can be calculated, and interference can be looked for before hand. You'll end up with a more honed and precise machine, which should elevate your level of competitiveness.

[CamFam1]

Thanks for all your guidance everyone. Please consider another dimension to the question.

If you are running short on time, when would you come to a point where you would say do it in paper and pencil and forego putting pressure on CAD so you can have a robot rather than possibly risking not having a robot?

I see how it's ideal to CAD. When do you let it go and try using paper and pencil? Have you had any experiences like this? How did it go?

[Akash Rastogi]

Thanks for all your guidance everyone. Please consider another dimension to the question.

If you are running short on time, when would you come to a point where you would say do it in paper and pencil and forego putting pressure on CAD so you can have a robot rather than possibly risking not having a robot?

I see how it's ideal to CAD. When do you let it go and try using paper and pencil? Have you had any experiences like this? How did it go?

If you think about it, having full CAD of all the components can save the time you are losing by perhaps figuring out dimensions on paper. The fabrication process goes a lot faster, which is what Adam basically said.

We learn how to create properly dimensioned tool assisted drawings too though.

Graph paper is the shizzz.

[CamFam1]

Maybe I'm asking a different question than I should be asking.

How about this question. In which week do you like to have your CAD work completed by? What should you do if it is taking longer than you had expected?

[artdutra04]

It was only two days ago in which I finished up the CAD of the elevator and shooter on 228's robot. However, the chassis and ball intake were completed over two weeks ago. The date in which the CAD has to be done is entirely dependent on how fast you can fabricate parts and how many revisions you want to go through before you shoot the designers and build it. ;)

Because I was slow on the last bit of the CAD, now I get to spend all my free time running parts on the CNC mill.

[Molten]

AutoCAD, the speed of hand and the accuracy of computer. This makes it where I start. When I don't have it, I'll resort to hand/Inventor. But my start is always AutoCAD.

[s_forbes]

There's a fun exercise you can do to test this out. Have one of your team members go grab a random part from an old robot, mainly one that was Milled simply. Have him/her sketch it out "quickly" on a piece of paper, with all the dimensions THEY think you'd need to make it. Give that drawing to a team member who has not seen what part it's drawn from, and have them try to make it. Unless your student has taken some drafting courses, or is quite gifted in conveying all the details of the part on a sheet of paper, I'm pretty sure there will be errors.


What we do instead is try to make all of the students understand the importance of being able to draw things correctly with proper dimensions. "Did you draw a picture of it?" has kind of become a catch phrase on our team.

As far as our robot design goes, we don't use CAD software as often as we could. If something can be drawn to scale on paper, then we just do that. There are always a few things that are easier to do in CAD though, like our helix this year. It's nice to know that it will actually fit on the robot before we put it there.

[R.C.]

In terms of how to model up designs. The best way to visualize them 3d is too use a simple modeling program such as 3ds Max (Sorry not tooo simple) or Google Sketch Up (I am learning it). We used it for our bot and we got 4-5 concepts drawn up in about a day which made the Cadding easy. And I use paper to start because it makes it easier to CAD.

[Paul Copioli]

Team 217 does exactly what Arthur explains happens on 228. We do everything in CAD and simultaneuosly do prototypes for critical items. If the prototypes find a particular geometry that work, then we will immediately CAD it in SolidWorks to get the manufacturing dimensions. See the attached pdf for an example of one of our assembly drawings.

[Paul11]

Our entire robot was CADed before we cut metal. Hand drawings are good for early design or if a team member must convey an idea or a part placement to the designated CADer.

[AdamHeard]

Team 217 does exactly what Arthur explains happens on 228. We do everything in CAD and simultaneuosly do prototypes for critical items. If the prototypes find a particular geometry that work, then we will immediately CAD it in SolidWorks to get the manufacturing dimensions. See the attached pdf for an example of one of our assembly drawings.

$@#$@#$@#$@# Paul, Being a student on your team working on design like that must be an amazing experience....

I'm trying to work towards that with my students, but I'm probably decades away :ahh:

[JVN]

Team 217 does exactly what Arthur explains happens on 228. We do everything in CAD and simultaneuosly do prototypes for critical items. If the prototypes find a particular geometry that work, then we will immediately CAD it in SolidWorks to get the manufacturing dimensions. See the attached pdf for an example of one of our assembly drawings.

This process is especially AWESOME when you work with a manufacturing facility that works directly off the 3D solid models. We are lucky to have a sheet-metal shop that takes our part files designed in Solidworks, auto flattens them and sends them directly to the laser cutter / turret punch for creation.

I typically send CAD files to the shop late at night, and have parts ready by the end of the next business day. When you combine this quick turn manufacturing with a robot that is well designed and "drops together" it makes for some incredible meetings. It is easy to feel like our team is behind until one day *poof* the robot appears. This quick stuff also helps us do more iterations on our designs as we work to tune in the robot. Design is after all, an iterative process.

To answer the question of the thread, we CAD EVERYTHING.

-John

[Collin Fultz]

On 234, our manufacture and our CAD proceed in parallel paths. If there are complex mechanisms which require CAD before manufacture, we will do that, but again, only if required. This year, we have made an effort to keep the robot simple, yet elegant. Doing this has made it possible for us to build two robots for the first time. Admittedly, R2 has much fewer holes than R1

My advice...do what works for you. If you don't have the people/resources to CAD everything, you don't have to. The great thing about FIRST is that every team has such a unique identity...and they all work. Only in FIRST could so many answers to the same question be right answers.

[MrForbes]

Here's a good way to think about it: Would you trust yourself riding in a car you didn't do CAD for, and only sketched it roughly out?

Hmmmm.....would that include my 55 Chevy? my son's 59 Chevy truck? My other son's 70 Camaro? My wife's 70 Dodge? I didn't design these, I did modify some of them. I know they weren't designed with modern technology, but short answer...yes, I would.

This year we have some students on the team who are enrolled in the new pre-engineering program at our local community college. This is a joint high school/college program. There hasn't been any integration of the classes with the robotics team, unfortunately...they seem to be in different worlds.

But one day, it might all come together, and we'll have a lot of students with CAD knowledge, and computer resources for them to use (all of the Inventor work we've done so far this year has been on a few older student owned laptops). We have no sponsors in the manufacturing business, and no CNC equipment, so the move to computer aided manufacturing is either in the future or just a pipe dream.

Even so, we did use Inventor quite a bit this year for our robot design, and revising the design. We did not do much in the way of using it for making design drawings, it ended up being easier to just make a dimensioned sketch on paper to make parts from.

I'm very impressed with how 217 and 148 and others have managed to get their design process so well organized. It's something we should all aspire to, as it reflects how things are done "right". I agree with Adam that it must be an amazing experience for the students!

[Team 1782]

Sketching is by far the best way to get something made on Autodesk, they're not seperate things, unless you're like a Autodesk Prodigy, I would sketch first.

[Madison]

I design as much as I reasonably can in the time I have available. Usually, I'm able to take care of fit and function for major assemblies and parts and create accurate drawings for parts that require milling or laser cutting. Beyond that, though, we still use paper drawings to quickly communicate requirements and intent. In a lot of cases, I make paper drawings of parts I've modeled since it goes faster, but sometimes we'll develop parts on the fly and I add them to the CAD model later.

If we had a more efficient manufacturing process in place, we'd assuredly rely more on CAD models than we do even now. But, because most of our machine is made from laser cut parts, or with a drill press and saw, I can get away with being lazy.

In fact, so far this year, we've not used our milling machine for anything at all.

[JesseK]

Our design process is whiteboard --> sketch on paper --> CAD spacial representations to get critical dimensions/relations --> Prototype --> Prototype even more --> CAD critical subsystems --> Build, test & integrate. It's amazing we even have that since every one of our mentors, myself included, do software in our careers :ahh:.

We're still learning, and we get hung up on not using solutions that we can't fully envision working for us...even when we're staring at a video of it on Youtube (prime examples this year are our conveyor belt & shooter). We also hate settling for less because we're unwilling to put the effort into venturing into the unknown...that is, it's unknown for us. So really it boils down to the fact that if we don't know something will work or exactly how it will work, it's impossible for us to CAD something with any detail before we prototype it...but we will prototype it to near perfection! We really spend most of our time in the shop improving our prototypes before we do a final CAD on them. Drawings are sometimes made while in the shop, then added to whatever CAD models we have later. It's not really healthy for students to use a computer when they have aluminum shavings all over their clothes anyways :rolleyes: .

Hopefully our "poof, here's your robot" day will be tomorrow since we took so much extra time to prototype & design :p. Cheers!