# Penn Foster Sheet Metal drawing project

## Recommended Posts

Hi CADTutor folks! It appears PF has changed the drawing project in the HVAC section after searching for some topics. The project is to draw a multiview drawing and flat pattern for a bracket made out of sheet metal. I'm getting tripped up on the flat pattern when it comes to calculating the bend deduction with the formula they give (pg 12 in attached pdf). Right after the formulas for bend allowance and deduction, they say "you should find that the bend deduction is 0.0633" and the bend allowance is 0.2867". I had no issue getting the same bend allowance number, but I'm not getting what they said for the bend deduction. Pg 6 lists K-factor(K)=0.33, bend radius(R)=0.1", thickness(T)=0.25", and says all bends will be 90°(A).

I've found a considerable amount of typos in the course up to this point, so it really wouldn't surprise me if there was a typo in these instructions as well. I have an email submitted to PF asking for clarification, but I figured I might get a quicker answer on here.

So for those of you who enjoy a good math problem, can you get the bend deduction they have of 0.0633? I even busted out my trusty old TI-86 graphing calculator to figure it out. I've been out of school for way longer than I care to admit to myself, so it's definitely possible that my advanced math skills are bit rusty. Any insight would be appreciated!

Thanks!

Amy

##### Share on other sites

I am not familiar with this particular project but I'll pass along this advice.  You will find that Penn-Foster projects are indeed riddled with typos, errors, incorrect information and evening missing information.  You signed up to learn AutoCAD and that is the main thing you have to remember.  You did not sign up to learn how to become a HVAC design draftsman.  I'll take a look at what you have posted and see if I can offer any assistance.  I am glad to hear that you emailed your instructor asking for clarification.  They don't have the best reputation however for timely results however.  I hope your instructor is the exception.

##### Share on other sites

I've started reading through the project and have one comment.  P-F asks the student to create a top, front and side view, in 2D, of the bracket.  Then it goes on to ask the student to create a 3D model.  This is backwards.  Create the 3D model first then extract the 2D views from the model.  In essence, as one forum member used to say, your 3D model is the basis for all truth.

Edited by ReMark

##### Share on other sites

I have two other points of contention I'd like to address.

The first is P-F instructs the student to use the ROTATE3D command to rotate the 3D model.  The axis and the degree of rotation are specified as X axis, –90 degrees / Y axis, 45 degrees  / X axis, –35.2466 degrees.  Shouldn't the three axis be X, Y and Z?

The second is the student is instructed to modify the 3D model by deleting lines, substitute hidden lines for continuous lines, extend some lines and redraw a hole that penetrates the bracket using an arc instead of a circle because it's view is partially blocked by one leg of the bracket.  Unless one were to explode the 3D model this would be impossible.  To create a 3D model then explode it for the purpose of constructing a perspective view of the bracket, in my opinion, would be a huge waste of time.

I have not completed the reading of the full PDF.

##### Share on other sites

No reply yet from PF. They did send a survey asking how satisfied I was with my recent interaction with their student support. I don't know if they'll really value my opinion as stated they would in the email.

In any case, I appreciate the advice. I'm having zero problems actually using AutoCAD, so I guess I'm doing alright!

I also inquired about the X/Y/X rotations as I also thought it should be X/Y/Z.

I finished the drawing to get what was in the image they provided at the end of what the drawing "should" look like. I'm just waiting to submit it in case they did screw up on any of the given values and they decide to get back to me about it. If I don't hear anything by Monday, which will be a full week since my inquiry, I'll submit what I have.

Again, thank you for taking the time to read through it! I appreciate it.

##### Share on other sites

Can I inquire as to what you got for the bend deduction?  I got .4133 and for the bend allowance I got .2866.

##### Share on other sites

If I used the equation for BD that they gave, I get a negative number. -0.2483?

I found a different equation after some google searching that has it as

BD=2*(tan(A/2)*(R+T)-BA

I got 0.2867 for the BA and 0.4133 for BD using the equation above.
I didn’t see the BD equation in any of my searching.

##### Share on other sites

It's 5:35 a.m. and nothing better to do so I searched the Internet for a bend allowance formula and came across this site that has a bend allowance calculator.

It also has a bend deduction calculator as well.

Using the information you are given in the PDF and plugging the numbers into the calculator I can confirm that both you and I arrived at the same answers.

##### Share on other sites

So I can still perform advanced math calculation properly. Awesome!

The two websites you posted links to are the sales ones I came across.

I guess my real dilemma now is whether I should submit the drawing with the numbers PF provided or the correct numbers.

Thank you for checking on this for me!

##### Share on other sites

I would submit them with what we assume is the correct bend deduction number and explain to your instructor that 1) you did the math using a different formula and 2) you checked it against a website where you found a bend deduction calculator and it matched what you came up with.  Then ask him to explain how the P-F bend deduction number was arrived at.  Perhaps we're missing something obvious although I doubt it.  Please let us know what grade you receive.  Good luck.

##### Share on other sites

I submitted it with the numbers we came up with and included a note explaining how I calculated the bend deduction with a different formula and asked if someone could explain how they got their value with their formula. I just logged on and saw my project was graded. Here's the project exam feedback:

So I guess no one there could explain how they got their bend deduction value either.

Never got a response from the email I sent a week ago either.

I only have one more project to go and them I'll be done with them forever!

##### Share on other sites

Well done!

Unfortunately their response or lack thereof is about what I expected.  When presented with information that runs contrary to what they say in their project descriptions they chose to ignore or deflect.  I'm saddened but not surprised that you never heard back from your instructor.  Apparently he is only going through the motions of being a "teacher" and someone students can turn to when they have questions.  So much for their "instructional staff".  I would rate them an "F".

##### Share on other sites

Thanks!

The last drawing project is an electrical and electronic schematic drawing project. I haven't searched the forums yet to see if this one changed like the HVAC one did, as I'm doing ok with it so far. I can pass along the instructions for your amusement if you'd like!

##### Share on other sites

That would be very kind of you.  Thanks.

##### Share on other sites

Here you go! I just got my grade for it. 100.

If you want the remainder of the "current" instructions for the drawing projects, I can post those too. I got 100 on all five of them. If you want any of those files to help future poor, unfortunate souls, I would be more than happy to send them to you.

I am so thankful I came across this website and for you and all the others for providing guidance when PF did not. Thanks again!!

##### Share on other sites

I would happily accept any files you are comfortable sharing.  Once again, thanks.

##### Share on other sites

Here are the rest of the drawing project instructions; check your PM for what to do about the dwg files

In the Ocean Avenue project, there was clearly a typo in one of the coordinates given for the center of the cul-de-sac (pg 15) when I saved these pdfs. I'm sure it will jump right out at you when you see it!

Edited by gogrey34
typo

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.