Become a Creator today!Start creating today - Share your story with the world!
Start for free
00:00:00
00:00:01
Bridging Design and Machining: How to Create Effective Technical Drawings
66 Plays4 months ago
In this episode, host Jill Fennell talks to Dr. David Smith, lecturer in the Woodruff School of Mechanical Engineering, and Scott Elliot, manager of the Machine Shop at the Montgomery Machining Mall about the importance of creating technical drawings that communicate information effectively between engineers and machinists.
Show Notes and Timestamps:
- 00:54 - Welcome and Introductions
- 02:56 - Thinking about technical drawing as communication
- 05:40 - what engineers need to know about the role of the machinist
- 07:43 - examples of students not knowing the machinist’s needs
- 11:45 - Importance of anticipating communication needs between engineer and machinist
- 13:39 - Contracts and Machinist’s response to questions or uncertainties in a drawing
- 16:18 - Information that should (and should not) be included in technical drawings
- 21:34 - Machine Design assignment David gives to refresh specific skills
- 27:26 - Advice for students in ME 1670 to best understand the genre
- 32:02 - what is the most important aspect of technical drawing from the machinist’s point of view
- 34:28 - what is and is not the machinist’s job?
- 38:36 - recommendations for students working with Montgomery Mall for the first time
A transcript of this episode is available here.
Edited by Lee Hibbard
Recommended
Transcript
Introduction to Technical Drawings
00:00:40
Speaker
Whether you're tuning in for the first time or returning for another season, we're excited to have you with us.
00:00:54
Speaker
When students create technical drawings, it's not just about design, it's about communication. These drawings are the blueprint machinists rely on to bring engineered parts to life.
00:01:05
Speaker
Today, we'll explore how to bridge the gap between design intent and the practicalities of machining by talking to both an academic expert in technical drawing, Dr. David Smith,
Meet the Experts: Dr. David Smith and Scott Elliott
00:01:16
Speaker
and Scott Elliott, the machine shop manager here at GT.
00:01:20
Speaker
We'll dive into what students need to know to make their drawings usable and effective for machinists who will be cutting and assembling their designs. David is a lecturer at the Woodruff School of Mechanical Engineering here at Georgia Tech.
00:01:33
Speaker
Prior to returning to academia, he worked for two decades on large telescopes, including your own firm, right, David? Yeah, yeah, that was at my own engineering firm here in Georgia.
00:01:44
Speaker
We also have Scott, who is the machine shop manager at the Montgomery Machining Mall. Scott is responsible for managing the resources and personnel that assist researchers, educators, and students in fabricating equipment.
00:01:58
Speaker
Scott, thank
Role of Machine Shops in Education
00:01:59
Speaker
you for being here today. And you serve a lot of schools here at Georgia Tech, right? That's correct. We not only support ME, we support material science engineering, biomedical engineering,
00:02:11
Speaker
computer and electrical engineering at all the college of science, earth and atmospheric science, physics, biology. When I say we support, we actually train the students for running manualizing manual lays and manual mill in the Montgomery Machining Model, and we also manufacture parts for the faculty and researchers.
00:02:33
Speaker
Nice. Well, I invited you guys here to talk today about technical drawings, and my hope is that this episode might be really useful to students who are taking our and ME 1670 class, to students who are taking machine design, even capstone.
00:02:50
Speaker
But I could also see how it might even be useful for engineers who are early professionals in their field. My first question is to both of you, which is why should engineers think about technical drawings as communication? Well, I don't
Effective Communication Through Drawings
00:03:03
Speaker
want them to think about it as communication. It is.
00:03:06
Speaker
The whole purpose of a technical drawing is that I have some design. It will do something that I want to do, but I need to be able to have that made. I need someone to be able to take this idea. I'm even going to use the word from your introduction. I need to take this intent. I have some design.
00:03:25
Speaker
It has some design intent, it needs to accomplish something, and now i need to I need to have that realized. I need to have it brought into some physical being. And even if I'm the one making it Once it's more than two or three things that need to be kept track of, I won't be able to keep track of it. So even if I knew how to make it, then what I would need to do is record it in some way. But usually it won't be me that's going to make it. I'm not that skilled.
00:03:52
Speaker
So I need to convey to someone else what it is that I need and enough about how it is that it will be used, that they're able to make that in some way that will meet my original design and intent. So the drawing is entirely the communication.
00:04:07
Speaker
Without that, I will never be able to have it realized into an actual product. And I'll also throw in there that while we're doing that, we're documenting it for the future. This is something that once I design it and I get it built, I don't want to have to do all that work again. So I would like to make it, have it as a permanent piece of communication that somebody can make it now, somebody can make it in the future, and we can reuse it for even future things.
00:04:34
Speaker
And I'd like to push that second thought. So often that's what happens when we have students and even researchers that will bring prints and they maybe made a mistake on the fits. Uh, maybe there was a tolerance issue.
00:04:49
Speaker
or you whatever the mistake was, we will correct it. And in the Montgomery Machine Mall, we have a mechanical engineer on staff to assist with the different schools.
00:05:00
Speaker
And we will actually email them the corrected and say, is this what your intent was? So, like David said, for further posterity or for making sure we're doing the services, like you said, re-engineering, that's where we're We can have that.
00:05:20
Speaker
Right.
Engineer vs Machinist: Roles and Trust
00:05:21
Speaker
As you said, then, we're not thinking about this as communication, but it is communication. This is not something that that we are imagining. communication 101, you have a c sender of the information and a receiver of the information.
00:05:38
Speaker
Imagining that, what does the engineer need to know about the role of the machinist? Like, for example, what is their job? What is not their job? I think the most important thing for sorry, I'm used to thinking about what the engineer needs to know, but what the engineer needs to know about the machinist is that one,
00:05:59
Speaker
They know how to build it. These are your skilled professionals. And so when you're when you're writing to them, what is most important for you to convey to them clearly is what the part they're making must meet, what what it must look like, what dimensions it must have, what tolerances it must have in order to do what you want.
00:06:22
Speaker
It's usually best for you to not start out by deciding how they're going to make it. Again, these are people who know they're in every shop, any foibles of those machines, what machines they have access to, they'll know that.
00:06:37
Speaker
So you need to trust that they'll know how to build it, and if they have questions, that they'll come back to you with it.
Common Student Mistakes in Drawings
00:06:43
Speaker
But the main thing that you're going to need to do to get to there is you have to have clarity on what you wanted.
00:06:48
Speaker
And then you have to remember that you're the one saying what you want and they're the ones that will know how to make that into something real. And with that, not only do we think about machinists, but we do have welders and fabricators. So there's different aspects as far as that.
00:07:07
Speaker
The one thing the engineer does the stress analysis, any of the, I don't want to say math, but any of the edge distance issues that goes back with stress or the material, any of that needs to be already set up for the machinist, that or the fabricator.
00:07:30
Speaker
So that to I think is a more important, I don't say more important, but the engineer needs to do the front end work and I think the back end work is done by the fabricator.
00:07:42
Speaker
Building on that a bit, do you have maybe any examples of students who were trying to get something built by the Montgomery Mall and they didn't really maybe understand what the machinists need from them in order to do their job properly? the Perfect. That's a good one.
00:08:00
Speaker
David and I actually had a short conversation yesterday. And one of the things that I think is so great As a machinist, we break inches up into thousands.
00:08:12
Speaker
So when you talk to machinist and he says a half an inch, when we break it down, it's 0.5, but we say 500 thousands.
00:08:23
Speaker
A quarter inch is 250 thousands. We only break it down even further. 3 16ths is or and eighty seven and a half.
00:08:42
Speaker
there's no edge distance issues, there's no stress analysis. Why do you need that hole at specific size? And they said, this is just what I came up with. Well, let's go with 3 16ths which is 187 and a half because we can drill and ream it fit it exactly right quickly so that's one of the Principles of thinking on the nominal sizes I want to touch a little bit on when you said they come in and they say well I need this drawing and they have a drawing and it says point one five zeros I need a hundred and fifty thousandths hole if There was a good reason they needed that then what you would hope is that when the shop says back to them Why do you need that?
00:09:24
Speaker
there should be a reason. And if there's not, that's part of where your intent has to be clear. I'm sure we'll hit other aspects of this, but the communication with your fabricator is going to be important because if you're in a place where you can ask that question, they'll even tell you, wait a minute, why do you need that? That's not that's not a standard or preferred size.
00:09:46
Speaker
And this isn't an English versus metric thing. a Let's pick on something strange. A 17 millimeter hole is weird. But a 16 millimeter hole is pretty common.
00:09:58
Speaker
So how to find that out on the engineering side, there are handbooks and such that will list preferred sizes. Even standard machine design text will have a table in the back that will say preferred sizes.
00:10:11
Speaker
But another way to check that is go to a supplier and look up what they're selling. And if they're selling it, it's probably a common size. But if somebody says, I need hole that's
Professional Standards and Communication
00:10:21
Speaker
0.150, they want to know why.
00:10:23
Speaker
they want to know why And if what they said was, oh, it is a stress issue, so I need it because of where it is near the edge, I need it no bigger than that. then you might turn around instead and say, well, let me recommend an eighth of an inch. That's 0.125, and we can do that.
00:10:39
Speaker
And if they said, no, that um I need at least this big because of the local contact stress of that hole or something, you might say, can we go bigger? This is not a standard size, and this is not easy to do. Right. And there's no, this is something it can be hard for engineers, particularly ones who really love math, because there is no physical reason why We don't design everything around 0.15 and then space it by every 0.05.
00:11:08
Speaker
But the fact remains that we don't. So it would be easier for you to get a precision hole. I'm going to probably get this one wrong. I think it's 0.203 is of an inch But there are pins that are that size.
00:11:22
Speaker
But there aren't.150, even though it's got fewer digits. So if your machinist comes to you with a question about your drawing, he's not trying to challenge your math. He's trying to save you money.
00:11:36
Speaker
Oh, trying to save save the whole enterprise money? Sometimes they're trying to find out just what it was you wanted, because if that hole didn't say where it was, they don't know where to put it. I think this ties into a theme that has become prevalent in a lot of the episodes where I've been talking with different people, which is when you're designing your communication, you really need to be imagining what the person on the other side of the communication is going to do with it.
00:12:01
Speaker
I think this can be some of the difference that we're I'm hearing from you guys, that if you have a machinist shop in-house where they're very open to communication back and forth, then you can have these discussions. Whereas If you're just sending it out to be built, it's almost like a contract.
00:12:20
Speaker
And so what you write is supposed to be emblematic of of what you want. You've included those three significant figures, which is very detailed, and therefore you're connoting to your audience, and that's the level of detail that I want.
00:12:35
Speaker
I'll let David take that, but I did want to bring in... the expense factor, like you said, and the tolerance of the three decimal places to two decimal places.
00:12:46
Speaker
And we treat those very differently because one is usually within, i would say, sometimes three decimal places we have to get within one thousand.
00:12:58
Speaker
Sometimes it's three. It just depends on whatever. But it's a very tight tolerance. So with that, if it's just a piece of material exterior, we have a lot of problem with with capstone.
00:13:14
Speaker
The kids want everything perfect. They want it, everything's three decimal places. That makes no sense. And we have to communicate that with them. Capstone, the research is not quite as bad, especially dealing with a lot of mechanical engineers.
00:13:33
Speaker
We can talk to them about the tolerance. capstone a little bit more in-depth. This is bringing back that question of legality and contracts, but can you expect a machine shop to ask you questions like like the ones we've been talking about? Or should you expect that they're just going to make it the way you sent it to them and they're just doing you a service if they ask you questions?
00:13:59
Speaker
Oh, I've had both happen. Certainly I've had both happen. The closer it is to a a rapid prototyping thing, they just figure you want it. And if you when you send them your your you're drawing, no matter what you put on it, what you might find is that they have some boilerplate the contract that covers them to just be able to make it. And places like that are less likely to call you back.
00:14:23
Speaker
But I've never had an in-house shop that wouldn't talk to you if you let them. And so I did want to answer on contract that generally a machine shop does not want to be dealing with attorneys, right? This is not what they're there for.
00:14:39
Speaker
So it is true. So when you said contract, it's not
Legal and Contractual Aspects of Drawings
00:14:43
Speaker
like a contract. It literally is. So if I send, let's pretend that I'm sending just contract work to the Montgomery Machining Mall.
00:14:50
Speaker
And I'm some outside group. I don't know if y'all can even do that. No, can't. Probably not. Okay. But let's pretend we can do that. And I send them a drawing. And they quote it. And they say, this is what we'll do. And then they make it. And when it comes back, I go to bolt it on to the piece I needed to connect it to. And the holes don't line up.
00:15:08
Speaker
And when I look at it, say, wait, these holes don't line up. And this will mostly be a problem if if it's expensive. But I come back and say, I just paid you $20,000 for this custom part, and it doesn't bolt up.
00:15:20
Speaker
Nobody wants to deal with attorneys. But if they say, well, here's your hole pattern. You gave us holes on the drawing. It said this size. It said this distance. It said this tolerance. Let's put it on a gauge real quick. If it meets that, I have to pay for it.
00:15:34
Speaker
They built what I told them to. Now if they missed, if I said that has to be within three thousandths and they were off by fifty thousandths, then no really, if we wanted to go to court over it, they have not met it. So in that sense it really is a contract. When we send it off and say make this, the tolerances on that drawing are part of that contract.
00:15:54
Speaker
And if they meet it, I got to buy it, even if it's my mistake. And if we're making a thousand of them, Because we didn't even test it. know, whatever. I'm not saying that I would ever have it. But if we do something like that, then we're buying all of them.
00:16:09
Speaker
But ultimately, if they buy what we put on the drawing, and if we left something off the drawing, then we can't hold them to it. So then I have a question for you, for both of you.
00:16:21
Speaker
Is it possible to include too much information on a technical drawing? Because think I remember i was having conversation with you once, David, where maybe your brother was complaining about a drawing that had, what is it, 98 different annotations or something? Yeah, it was an assembly drawing, and it was an A-size print, and it had 90 call-outs. And the lines pointing to the individual pieces were we' at very shallow angles, so you couldn't actually follow the arrows even. So these are the sort of things that do happen. You can put too much on a drawing. yeah but What would be an example of too much information? I think it's perfect when everything's too tight.
00:17:00
Speaker
I think sometimes when people try to put section views and then maybe an isometric and all these in one, it just gets too crowded. Yeah, that's a really good point because our students are going to be using SOLIDWORKS lot because it's really useful in certain things, but it's useful for those certain things because that's the view that that audience would want.
00:17:23
Speaker
But they need
Historical Practices and Modern Standards
00:17:24
Speaker
to understand that while that might be really useful for the customer, and the person who you you are doing the engineering design for, that view could be completely misleading for the machinist.
00:17:38
Speaker
or at least it just takes up real estate on the drawing and crowds everything to make everything else harder to see. Increasing cognitive load, then. Yeah, yes, fair, absolutely.
00:17:48
Speaker
That is the, in some ways, it sounds like I'm dunking on Cellarworks, it's not its fault that it has made it easy to create lots of extra views. The question is, did you need that extra view, or are you just doing too much with it?
00:18:01
Speaker
But there's something I can't believe I let it go this far, but remember the drawing is not just... ah contract and it isn't just an attempt to communicate to someone else it's also this document that has to go somewhere else someone else might need to know about it including yourself even as the person who designed it one week one month one year 15 years later someone might need to know what's going on and for all of these the most important thing to put on the drawing is your name Because when we are having this conversation, if you walk up to somebody and you're talking to them, you can say, well, right. But, you know, I saw Scott in the hall. We've got this all cleared up and now I can get that part made.
00:18:47
Speaker
But in terms of long term documentation. Now, if that drawing manages, and universities are places more likely to tolerate this than any workplace, then what they're going to do is, if you say, oh, I've got this drawing, this is from an old capstone project, meaning last semester. If they say that and someone has a question and there's no name on it,
00:19:10
Speaker
Now I don't know who to ask. And because I don't know who to ask, I'm going to have to do a lot of rework on things that have been done. In a former life, so it wasn't even in the in the bio, but as ah as a grad co-op, I worked at Babcock and Wilcox for a brief time.
00:19:26
Speaker
And they had lots of pieces that this wasn't what I thought would be the fun part of mechanical engineering, but they had lots of drawings. and they were trying to automate a database system to be able to pull up those old drawings.
00:19:39
Speaker
The drawings were old enough, they're not in CAD, so they had pictures of their drawings. they They knew where to pull them once they had the drawing number. But what they found was, as especially as we started trying to compile these so we could search it,
00:19:53
Speaker
We found that often they could not find prior designs. And since they couldn't find it, their engineers would say, i can either go hunt in the library all afternoon or I can redesign the part.
00:20:06
Speaker
And so you have people redesigning things that in fact already exist on their own equipment because they couldn't find it. So the group I was working with was shaking their heads and saying, we've got to do better. And as they did that, while I was there, I even got to see an example of where they said, we have a competitor, actually.
00:20:25
Speaker
They built the thing that we also built. And we have a customer that said, we need this and we need it now. can you do it? And they happened to have heard that we might be able to find it they said, well, go put it through the search system.
00:20:38
Speaker
And they put it through the search system, found out that, yes, they had it. It looked like it was all OK. And all you had to do is, I think, you had to cut up the other piece that had like an extra half inch on one end. And they said, well, we can cut that off.
00:20:51
Speaker
But even more importantly, it had the drawing of the engineer who was still in the group. And they could say, We know we can make it out of this standard alloy, but we have this other stuff. Will that still be okay? And because they knew who to talk to and they could find the drawing, it was even another piece of business for them where they got to swoop a competitor, which made them the bosses very happy. But if you don't have a name on it, then no one knows who to talk
Teaching Technical Drawing: Methods and Applications
00:21:18
Speaker
to.
00:21:18
Speaker
And without that, you can't have the communication of having the shop go back and forth. So always put your name on your drawings. Right. i mean, we were just talking the other day about how names and titles of things are themselves communications.
00:21:34
Speaker
Our conversation... so far has been really interesting because I think that we've been oscillating back and forth between larger concepts like understanding your audience to smaller details like whether or not asking for measurements to three decimal points is actually important, those those smaller details. but I'd like for us to continue this conversation maybe through a very specific frame. So Scott, have you heard about the assignment that David does in machine design? Is this the one with the plate? The board? oh Yeah. it's just
00:22:10
Speaker
Can you explain that assignment? Okay, it isn't always the same, however, in my sections of machine design, to give them the opportunity to again dust off their solid work skills before they graduate, I require on two of the design problems that they do a drawing.
00:22:28
Speaker
And each of those drawings is to be produced suitable for quote or fabrication. And that said, this is not a SolidWorks class, and in fact, I'm not showing them any tutorials, I'm not talking about it.
00:22:41
Speaker
We have, in theory, all had 1670, the drafting class. And so the first one is, this time around, what it was, was a rectangular plate. It's a pretty simple piece.
00:22:53
Speaker
And that means that we need to draw a rectangle, we need to put a couple of holes in it. Now, the way that the holes interact with the rest of the design, they've been told that it needs to be something that we can put together without a hammer, but it needs to be...
00:23:09
Speaker
close enough that we're getting a nice well-located fit. Some of that is those words will let you, if you're looking at a table of typical fits and tolerances, those words will actually let you select. This is not a press fit, it's not a transition fit, but I wanted it pretty close so it's also not a really wide clearance fit. This will be close running fit or it'll be a locational clearance or something like that.
00:23:32
Speaker
And They have at least in theory heard about tolerancing and fits and dimensioning before. However, within the machine design textbook, there are tables that will give some recommendations. We live in the future here in the 21st century. So they can also then Google to see what the tables are to see what these tolerances are.
00:23:50
Speaker
So then all they have to do in quotes is produce this drawing. This is something that then it's not a lot of the credit. This really is mostly an opportunity I say opportunity because it has no points on it, nobody will do it. So it's not many points, but this way we can go off and say, let's do this. Let's try to remember what we're doing.
00:24:12
Speaker
And these issues, the reason I'm so delighted to be able to talk about this here is that There will be problems ranging from not putting any tolerances on the drawing, to missing critical dimensions, to not even saying what it's made out of, and the very common leaving out the name.
00:24:31
Speaker
You mentioned that titles can be communication. It is very common. also to leave out any the appropriate title. The title will say something like, since it's design problem one, the title of the drawing will say DP1, which is completely nondescriptive.
00:24:47
Speaker
You yourself will have no idea what this was for in in six weeks. So this is something that they have seen in 1670, and what I find is by doing two of these, the first one, in all honesty, is often horrible.
00:25:02
Speaker
And do I take time out of the lecture to cover it? I do not. We have the actual material of the course to cover. But by doing that, when the grading team goes through to to review it, it gives an opportunity to surface these things that they've seen again.
00:25:16
Speaker
And I am pleased to say that when they do the second drawing, This time around, it will be of something cylindrical. It's of a shaft they're designing with some details on it. um Those tend to be much better because they've hit it one more time. And this is something that, that's why I consider it to be an opportunity and a service, is it means that when they're turning in that first horrible drawing, it wasn't to their boss. It wasn't to somebody who is paying them and who they might, well, they might feel embarrassed handing it to me.
00:25:45
Speaker
but at least they're paying least they're paying for the privilege of having somebody tell them that their drawing needs work instead of being paid and then having that, wait, this is embarrassing, I look like I know what I'm doing. One of the things I've heard you say is that the students who have been in industry, maybe with an internship or something, their drawings are always really good.
00:26:03
Speaker
It is unfortunate that because of the way learning works, where we learn something and we forget it and we have to learn it again, and somewhere after some number of times it sticks, It is common that if our students have only had 1670, if they haven't been drawing in between, then by the time I see them in 3180, they've forgotten a lot.
00:26:23
Speaker
It's two years later. It's a couple. It might be it might be three or four. Depending on internships. It's been a while.
Advice for Engineering Students
00:26:30
Speaker
But any of them who in an internship have had to draw, all of the things that I've been mentioning that they leave out,
00:26:38
Speaker
By that time, they've they've done that. And maybe it was embarrassing, maybe it wasn't, but they've done that. So you can always tell the people who have seen more drawing, and it may not be an internship out. It might be that they've done something with a research group here and that the folks who have trained them up are Scott's team by saying, you know, you have to tell us how big the plate is or we can't make it.
00:26:59
Speaker
And I think all of the communication that we're doing here in the web communication program is really centered around usability and in order to make a usable communication you have to know and empathize with your audience.
00:27:13
Speaker
um So I'm hoping that a lot of the things that we've talked about today and by having you Scott on today, students can know more about what this audience's expectations are.
00:27:26
Speaker
We talked a little bit about em ME 1670 which is engineering and graphics design and as you said David this course covers For our students, it's their first entry into technical drawing. It's where they learn CAD. It's where they're supposed to learn how to do their technical drawings.
00:27:43
Speaker
And some of them might not get this again until they take your class in machine design in their junior year. What advice would you give them, the students who are in 1670 right now listening to this episode,
00:27:56
Speaker
What advice would you give them so that they can create better drawings in that course, sure, but really understand the genre more and are able to succeed later when they take your class and even maybe more importantly, whenever they're in Capstone and they're going to be working with Scott and his team.
00:28:13
Speaker
Playing with it is good, but the best for the communication there is practice. Right. and before you give somebody a drawing, give it to another audience and as ask them what's happening. What will that person need?
00:28:29
Speaker
and But in terms of what I'd tell somebody from 1670 is look for opportunities to need to draw things. Look for opportunities to practice communicating. Also, and you know going to your 2110 example where the students will need to CAD some aspects of their machine that they're building.
00:28:48
Speaker
Even if you're not the one doing the CAD, if someone else in your team just absolutely loves it and you're like, okay, yeah, ah you can do it, I'll do this other thing. review the drawing for them. Pretend that you're a machinist.
00:29:01
Speaker
Would you be able to go down to the mall and machine that's giving the information that's there? I know it's really hard whenever you're on the project as well to kind of separate because there are things you can't forget that you know, but you can try your best to empathize with that audience.
00:29:18
Speaker
The 2110, when the COVID happened, when the covid before they did a lot more manufacturing with the lathes and needles. COVID came in, they actually, for obvious reasons, they mostly all 3D print, laser cut.
00:29:36
Speaker
We're trying to get back into We've actually moved the lays and mills into the machining mall and we'll have a trained staff member, not just a TA, a but a trained staff member to help and we're hopefully we're pushing forth the more manufacturer to where they can understand the lays, the mills,
00:29:59
Speaker
not saying that the communication and the practice of the 3D printing is not, but we are pushing for that in the manufacturing aspect as well for 2110. Because it's an important part of being an engineer.
00:30:15
Speaker
It is an essential part of any design work to be able to convey what your design intent was to anybody else who's helping you at all. But
Engineer-Machinist Collaboration Insights
00:30:26
Speaker
if you're trying to fabricate a part, they need to know what that has to look like. And that's that's fundamentally what your drawing's buying you, is having someone else even without you standing there, able to know how to make something that will do what you needed it to do.
00:30:43
Speaker
I think that's a great point, what you just said, with nobody else there. With me not, the actual here, you make this and walk away. I think that's a huge step right there.
00:30:57
Speaker
was going to ask, is that why you make students practice technical drawings in your machine design class? Yes, that is 100% why. Again, what happens when you're learning something is you don't hear it and get it. The worst thing is we look at it and we say, that makes perfect sense, but we don't have it. So everybody draws in 1670. Everybody draws.
00:31:23
Speaker
And the computer won't communicate for you. You have to do the communication. Your communication comes from you making this happen and it won't solve it that you have the package.
00:31:38
Speaker
But if you're comfortable with that package, if you practice with it, then it lets you more easily communicate with it. And so that's that's why I do... It's just two drawings. Anybody listening to this that hadn't taken machine design?
00:31:51
Speaker
It's just two of them and actually if you say maybe I better go dust off my my solid work skills before I show up to the class that'll be good for you. I have no regrets. I'm okay with that. From the machine shop's point of view what do you consider the most important aspects of a technical drawing?
00:32:09
Speaker
The most important? Like the but things that can't be left off. material as we were talking about uh the tolerancing we can usually get away with as long as we have the pertinent information as far as the assembly as far as the different fasteners the more information is there i really can't put a finger on one thing if you put more information obviously We'll get it.
00:32:39
Speaker
It's not uncommon for maybe someone from the College of Science or maybe material science, which they may give us just a sketch. And then from that, we have to facilitate a better communication slash drawing for them.
00:32:59
Speaker
And that's when we were talking about we actually work directly with the different schools to get them good drawings. we are there to help. If you need support as far as like what is the tap drill size, things like that, those are information.
00:33:17
Speaker
NPT, I want to seal this off. One of the bigger problems that we see, I spent over 10 years in aerospace as a machinist, light materials.
00:33:29
Speaker
If you have stainless steel male and stainless steel female threads and you screw them together, The way the friction is, they will gall up and they will actually seize up and they will not come apart.
00:33:44
Speaker
So for me to tell the engineer, wait, hold a second, are you sure you want stainless steel light materials? Can we do something else?
00:33:55
Speaker
Those are some of the issues that you get into with the manufacturing. One the worst things you can say to machinists, I don't care. I just make it whatever. I have to know what to make it to because I can't make it to just anything.
00:34:11
Speaker
I need to know a specific size. That's the way the machinist looks at things, and that's where that, I'm so glad to talk about the 15 to the 30,000ths to the differentiation that is we're still going to try to make it to that half inch.
00:34:28
Speaker
Well, that was one of my initial questions, which is, what is the machinist's job and what is not the machinist's job? It's not your job to make that decision. It's their engineer's job to tell you. Very well said. And that's exactly right.
00:34:40
Speaker
And the machinist will accept that. The machinist knows, like we started off this with, the stress analysis, all those type of work. That's the engineer's job.
00:34:53
Speaker
The machinist's job is to manufacture or make this part to the specification that's provided. It
Working with Machine Shops: Best Practices
00:35:01
Speaker
sounds from this conversation that to be an effective engineer who's really good at technical drawings, it would probably be a good idea to get to know your machine shop or whatever shop that you solicit from often so that you can make better drawings.
00:35:18
Speaker
You can find out what they want and how they want it. um One thing that shows up from people who have interned in certain places is, I don't know how much y'all deal with this, but on this example of have a rectangle with two holes in it, there is a there is a type of of setup where what the students will do is they will just indicate station points along it. So this is clearly, it's been indexed to a certain point, and they're saying this hole is here, this hole is here, this notch is here, whatever, and they just, they put a series of numbers.
00:35:52
Speaker
And maybe they're just doing this. I have known some places that they say that's the way we want to we want to set it up. And if that's what your shop wants, do what the shop wants. They're making it. You want to communicate.
00:36:03
Speaker
There are issues with doing it that way, depending on how you've toleranced it, that if that means that you wanted particular dimension is more important to you than others. There's a difference between knowing how long, but saying the part is six inches long and there's a hole in from each end by an inch is not the same as saying the holes are four inches apart.
00:36:24
Speaker
Because each of those dimensions has a tolerance. And so if what... Four inches on center line. Four inches on center line. Oh, oh my goodness. That's something else that I don't know if you run into that I see even in 3180 is people di dimensioning to the side of a hole. Yeah.
00:36:38
Speaker
That's not a thing we dimension to the center line of the hole. But if I said four inch centers between the hole, and that's what really matters to me, there's a difference between that to 15 thousandths and a piece that was six inches long, plus or minus 15 thousandths, with a hole in from the left, plus or minus 15 thousandths, and a hole in from the right.
00:36:58
Speaker
plus or minus 15. So that's the design intent. If I put it out one particular way, they can make it and say, well, this meets this. So that's your intent part comes I'd completely forgotten about seeing dimensions to the side of a hole. that let's let's not Let's not do that. We don't we don't want want to do it that way. When you said talk to, make sure you talk to them, you always want to make sure you're in communication with the people who are going to be fabricating things for you.
00:37:27
Speaker
They will tell you what they want. So if they say, i need this or with this machine, I can now do whatever, then fine. That lets me know what's happening.
00:37:39
Speaker
Something that's important to know, i think we even said this ah ah or much much earlier in here, toma they know how to make it. Machinists are skilled professionals. When you said a laser cutter, you might be able to cut it to three thousandths.
00:37:53
Speaker
I can't. Okay? As you heat up the material, it changes. When he said, i'm getting down to a thousandth, he didn't have to think about it. He's like, well, you know, then I'm going to have to do this in a certain going let the part cool.
00:38:05
Speaker
I'm going have to come back and do a finish cut. These are the sort of things that he's going to know. If you give an engineer a water jet cutter and say, go make me this.
00:38:17
Speaker
That's not the same as taking it to a shop that has a water jet cutter and saying, make me this. So I do want to get out there that when we say, Hey, we have a machine that can do this. We have a machine that in the proper hands can do this. and speaking to my fellow engineers, and that is very seldom you.
00:38:36
Speaker
Bringing this closer to the close. I know oftentimes the machining model make a parts for students for Capstone. So what advice or recommendations would you have for those students who are working with the Montgomery Mall for the first time on how to best understand how you want to be communicated with?
00:38:56
Speaker
Usually the first thing we do, we meet with the teams. Like I said, it's myself. We have Ashley, who's an engineer. Carlos, who I don't know if the anybody's met, Carlos Barrow.
00:39:10
Speaker
We actually stole him from the University of Georgia. he This is true. He worked there for over 15 years and he actually ran the shop and he decided to come join us.
00:39:22
Speaker
So he's one of the he's the day shift supervisor. But his last three years he spent is designing parts for their shop. We sit down and ask what's the application?
00:39:35
Speaker
We send them out. Okay, this is Cherokee steel. This is McMaster car. This is the material. These are the specifications. We send them out, let them do their stress analysis, do their design, meet again, find out if it's manufacturable.
00:39:53
Speaker
That's one of the things that comes in once they come back. And then we talk about the manufacturability, welding, the manufacturing process,
Conclusion: Importance of Communication and Documentation
00:40:02
Speaker
and then Sometimes they actually choose to do some of the work their self.
00:40:08
Speaker
We actually do have classes set up where they can come in and actually lay, mill, or if they've been in a different area where they've got experience, they can come in and do some of the work their self.
00:40:22
Speaker
It's not uncommon. lot of the capstone is more... They don't have to have a working model. Sometimes they do, and usually we'll have... four or five teams in the mall, and they will be in there on each of the tables, and we work with them. So we get real busy towards the end of the semester.
00:40:44
Speaker
Well, it's great that we have someone like you and the rest of the mall here on campus so the students can have this learning experience at the university setting before they get into the real world.
00:40:55
Speaker
David, do you have any final takeaways, perhaps for your own machine design students on how to succeed at technical drawings? If you remember that it's communication and that it has to stand without you, so it must be readable, it must be something that if they needed to get to, if if you've made a mistake, it should stand without you. But if you've made a mistake, that they can find you.
00:41:17
Speaker
And that anybody with just that drawing in their hand with the knowledge of how to build stuff, could build it. then That's the lens you want to look at it through.
00:41:28
Speaker
There are things that are obvious to you. That hole is symmetric. It's not obvious on the drawing. Give us a center line. Do you know where everything is? So it really is about communication. If you handed it to someone else, could they build it without you?
00:41:42
Speaker
And then, of course, if they can't, then do they know how to find you? Well, thank you both so much for being here. I've really enjoyed our conversation. It's been fun.