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Sheet Metal Guru's - Is Flat Pattern Needed on a drawing?

18 REPLIES 18
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Message 1 of 19
SeanFarr
4088 Views, 18 Replies

Sheet Metal Guru's - Is Flat Pattern Needed on a drawing?

Hello All,

 

I have a simple sheet metal part that does not require explicit bend radii. We leave it up to the shop to fab this part up as long as it's final outcome is within tolerance. We don't normally include a flat pattern, simply because it could cause confusion when cutting a blank. I use the default bend allowance and bend radius, which gives the exact blank size and bend locations. But our local fab shop probably doesn't/won't use the correct tooling to provide the exact bend radius, so this will throw off the final outcome if the blank was cut using the flat pattern dimensions.

 

Not sure what should be done so that I can apply the flat pattern to my drawings, because there is some sheet metal components we have that require the flat pattern to show cut profile features.

 

Thanks

 

Sean


Inventor Pro 2012

 

 

Sean Farr
Product Designer at TESInc.ca

Inventor Professional 2014-Update 2 - AutoCAD Electrical 2014
Win7-x64 | ASUS P8Z77-V | i7 3770 -3.4 GHz | 32GB RAM |
240GB SSD | nVidia GTX 670 4GB - 320.49
18 REPLIES 18
Message 2 of 19
JDMather
in reply to: SeanFarr

The last sentence doesn't really make sense.

If you want the flat pattern for only some uses - you could put it on second sheet in the drawing.

 

Also - your first sketch isn't constrained and you are doing too much work.

 

Sketch1.png

 

I recommend using construction lines for clarity (I should have add a horizontal line at the bottom as well).


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Message 3 of 19
SeanFarr
in reply to: JDMather

I understand the sketch is bad format (bad habits, I am getting better though)... but going back to the flat pattern, we have been supplying our fab shop with drawings that don't have flat patterns, well before I started here.The guys would sketch on piece of paper what they wanted and fax it it the fab shop and they would build it. Now I get the sketches, I model it,draw it and then email to the shop.

 

I want to start applying flat patterns to my drawings to show cuts, holes, other features etc. etc. but I don't know if I start applying them if it is going to start confusion because of how exact Inventor is.

 

Or should I not include a flat pattern, and annotate all features off the folded state view in the drawing??

 

I have been through the Sheet Metal section of Mastering Inventor 2012, and was hoping it would help me decide what to do. But after going thought the chapter, I am still unsure if flat patterns are needed or not?

Sean Farr
Product Designer at TESInc.ca

Inventor Professional 2014-Update 2 - AutoCAD Electrical 2014
Win7-x64 | ASUS P8Z77-V | i7 3770 -3.4 GHz | 32GB RAM |
240GB SSD | nVidia GTX 670 4GB - 320.49
Message 4 of 19
jdavis417
in reply to: SeanFarr

Without the shop's input to "fine tune" your bend table and/or tolerances, you'll never "get them what they need" (if you're not already).

 

Give them the flat pattern and insist that they use it.  The shop MUST evalate your Work Orders (the fabricated, bent, finished product) vs. what was ACTUALLY produced from the instructions given.  Having the shop being the only ones who know exactly how to complete your sheet metal part is a very dangerous thing.

 

Finally, what will happen when you need to have your sheet metal part produced out-of-house?  Will they be able to use the "bent", Work Order or will they insist on a flat-pattern?  If they require a flat pattern, will your employees have helped you to insure that your flat-patterns are real-world usable?  Not if they don't use a flat-pattern!

 

"Be not afraid of moving ahead slowly.  Be only afraid of standing still."  Chinese proverb quoted on PBS.

Man Tongue

Message 5 of 19
JDMather
in reply to: SeanFarr

I think most people sending to outside would only send the dimensions of the finished folded part.  The vendor should know how to get the correct part from the finished dimensions.

 

For internal use - or if you have a very very close working relationship with external vendors, you could try to work together to reduce costs by supplying flat patterns, but you have to have information about there manufacturing processes (to get the correct bend allowance) and this works best if you can walk out onto the shop floor and get sample bends directly from the person who will run the job.  On small run jobs there might not be a payoff for the effort.

 


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Message 6 of 19
JDMather
in reply to: jdavis417


@jdavis417 wrote:

Without the shop's input to "fine tune" your bend table and/or tolerances, you'll never "get them what they need" (if you're not already).

 

Give them the flat pattern and insist that they use it.  


 

 

These two sentences seem to contradict each other.

The finished part dimensions are what the customer pays for.  The finished part is what performs the function.

 


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Message 7 of 19

Hi SeanFarr,

 

I've seen it done many different ways, and it all depends on the capabilities of all involved. But currently, I send out drawings with dimensions of the finished folded part only (no flat pattern), as JDMather mentioned. But I do provide a DXF, STEP and IGES file of the finished folded part along with it. Some of the shops we work with use other software to bring in the 3D files and apply their bend information to it to get the correct flat pattern.

 

On occasion, I have added a "thumbnail" flat pattern to the drawing, with a note that states that the size is approximate, in order to communicate a complex part.

 

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

 

Message 8 of 19
SeanFarr
in reply to: SeanFarr

Thanks Everyone for the input, for now, I have decided to not use flat patterns, unless there is something that would require me to do so. Not exactly sure yet what that would be, haha,  At least I can continue without any issues.

 

Ciao for now!

 

Sean

Sean Farr
Product Designer at TESInc.ca

Inventor Professional 2014-Update 2 - AutoCAD Electrical 2014
Win7-x64 | ASUS P8Z77-V | i7 3770 -3.4 GHz | 32GB RAM |
240GB SSD | nVidia GTX 670 4GB - 320.49
Message 9 of 19
JimSteinmeyer
in reply to: SeanFarr

On the other hand, since our holes and contured edges are done on the laser table the exported DXF file of the flat pattern is important.

 

Jim

Inventor Premium 2013 SP1.1
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HP G71 notebook
celeron cpu w\ 4gb RAM and 64 bit system
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Ya, my boss has me running my personal machine at work.
Message 10 of 19
SeanFarr
in reply to: JimSteinmeyer

I did read that flat pattern files can be exported and used for that purpose, but wasn't sure if all or most automated cutting machines could accept files such as DXF. Do most automated cutting machine set-ups require there own specific file formats and inputs or does the majority accept exported files such as DXF (from Inventor)?

 

If I send a drawing of a sheet metal product without a flat pattern to a shop that utilizes a laser cutting machine, are they capable of using the information on the drawing to input whatever info they require into the program/software to cut? or is a flat pattern required?

 

I don't have any experience with automated cutting tools and there software, what can be used as inputs or how to input data to produce and accurate cut.

 

I imagine there is a certain percentage offset to allow for precise cutting, example; cutting a square, the laser cutter would not line up directly on the line of the drawing, the cut has a certain thickness, is this taken into account by the machine or does it have to be calculated by the operator and applied?

 

Thanks for bringing this up JimSteinmeyer!! Any help or direction is appreciated.

 

Sean

Sean Farr
Product Designer at TESInc.ca

Inventor Professional 2014-Update 2 - AutoCAD Electrical 2014
Win7-x64 | ASUS P8Z77-V | i7 3770 -3.4 GHz | 32GB RAM |
240GB SSD | nVidia GTX 670 4GB - 320.49
Message 11 of 19
jdavis417
in reply to: SeanFarr

I suppose you should put it through the old drafting crucible of "does it communicate something useful"?

 

The flat pattern is, at least, useful for expressing the extents of the material reaquirement.... and... okay, it's flashy!

Please don't take away my flash.Smiley Embarassed

Message 12 of 19
jdavis417
in reply to: JDMather

Thanks for giving me the opportunity to edit that, JD!

 

I probably shouldn't take over this post, but I was really trying to get at "manufacturing capability"... also an opportunity to build relationships and exchage knowledge through the refinement of the Bend Table and Tolerences.

 

I think you gave me a segue with your closing statements... I suppose the goal of a flat pattern should be to avoid the two "prototypes" that the customer didn't pay for!

Smiley Wink

 

Message 13 of 19
JimSteinmeyer
in reply to: jdavis417

Sean,

The best answer I can give you is "it depends". All automated cutting equipment (laser, plasma or flame cutters) that I have run into use their own file format but are able to import DXF files. If you send a vendor a set of drawings of formed parts only the vendor will have to redraw your part into his system to be able to cut it. The DXF gives them a shortcut there. Depending on the system, most take into account the kurf of the cut and that is automaticly done. The concern deals largely with hohw the vendor bends the parts. depending on the bend allowances and how the material works. your flat pattern may give the vendor a flat sheet that is either to wide or to narrow. Often times a vendor will cut and form a part once or twice to ensure that they have the correct dimensions. If you have a close relationship with your vendor and know their equipment you may be able to enter the bend allowances to meet their system so the flat pattern is "right". But if you provide a flaat pattern that uses different allowances, you are in effect giving them two different sets of drawings that can create two different formed parts. If your trolerances for the formed parts are not too tight this may work for you. However if you need the formed parts "exact" you may be better served providing only the formed drawings and making sure they are very well documented. Which they should be anyway.

 

Hope this helps

 

Jim

Inventor Premium 2013 SP1.1
Vault 2013- plain vanilla version
HP G71 notebook
celeron cpu w\ 4gb RAM and 64 bit system
Win 7 home premium

Ya, my boss has me running my personal machine at work.
Message 14 of 19
BLHDrafting
in reply to: JimSteinmeyer

I agree with Jim We do both inhouse plasma cutting and folding, but for the thinner sheets (1.2 mm and less) we farm out. Our drawings include fully detailed and toleranced folded parts and a flat pattern view with the bend notes or direction, andgle and radius. But the note also includes "BEND DATA CORECT FOR BKS HACO PRESS #1".

 

When we farm out the work we supply this IDW and the DXF of the part. The outside firm then 'alters' our DXF file to suit their bending machines and what we get back is within tolerance.

 

So it really depends on what youare trying to achieve.

 

Best of luck.

Brendan Henderson

Web www.blhdrafting.com.au
Twitter @BLHDrafting

Windows 7 x64 -64 GB Ram, Intel Xeon E5-1620 @ 3.6 GHz
ATI FirePro V7800 2 GB, 180 GB SSD & 1 TB HDD, Inv R2016 PDSU SP1 (Build 210), Vault 2016 Professional Update 1 (Build 21.1.4.0)
Message 15 of 19
SeanFarr
in reply to: BLHDrafting

Well of course after I decide not to use a flat pattern, our fabricator is deciding to farm out sheet metal panels to be laser cut and asked me for a dxf drawing with flat pattern!!

 

Inventor does make this easy to do, but I have a few quetions now and what is required for a dxf drawing that is to be used for laser cutting.

 

1 -  Is the drawing to be detailed like a normal drawing? I have vaguely read somewhere on google, that laser cutting   

      acts on coloured layers of geomtry and no dimensional inputs? So the dxf will have to be scaled 1:1 when exported.

 

2 -  am I better to provide a fully detailed drawing with flat pattern?

 

3 -  does anyone have any examples of a drawing for laser cutting that they can share or link too

 


I have attached a .ipt file of something that will be laser cut. Does each hole, slot, and cutout need to be detailed?

 

Thanks

 

Sean

 

Version - Inventor Pro 2013

Sean Farr
Product Designer at TESInc.ca

Inventor Professional 2014-Update 2 - AutoCAD Electrical 2014
Win7-x64 | ASUS P8Z77-V | i7 3770 -3.4 GHz | 32GB RAM |
240GB SSD | nVidia GTX 670 4GB - 320.49
Message 16 of 19
rdyson
in reply to: SeanFarr

The laser cutter only knows geometry, not dimensions. The shop will adjust the dxf if anything need changing like colors or layers.

I always give overall dim's. Aids the shop in giving quick cost estimates and eliminates any confusion about scale.

1:1 is best, but the shop can scale if necessary.



PDSU 2016
Message 17 of 19
SeanFarr
in reply to: rdyson

So an ideal drawing would be one view of a flat pattern with some dimensions of size and shape for reference. Positioning of hole, slots, cut-out etc will be based of the geometry of the actual shape and size of the component?

 

I don't have direct contact with the laser cutter company and my fabricator isn't up to date on CAD, or requirements for this.

 

Thanks for any help!

 

Sean

Sean Farr
Product Designer at TESInc.ca

Inventor Professional 2014-Update 2 - AutoCAD Electrical 2014
Win7-x64 | ASUS P8Z77-V | i7 3770 -3.4 GHz | 32GB RAM |
240GB SSD | nVidia GTX 670 4GB - 320.49
Message 18 of 19
blair
in reply to: jdavis417

One normally works backward to calculate the bend-factor for each machine. The attached Excel file may help you in your calculations.

 

Get a pre-measured length the required material and do a ben to the desired angle, get your measurements and then calculate the proper k-factor for the machine and tooling for the materail and bend angle.


Inventor 2020, In-Cad, Simulation Mechanical

Just insert the picture rather than attaching it as a file
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Message 19 of 19
RobJV
in reply to: SeanFarr

I produce models, drawings, and flat patterns for internal and external use.  We have a burn table with oxy and plasma.  The software I use will take in DXF files (from Inventor) and spit out "g-code" cnc language.  I produce a drawing with the bent up part shown and dimensioned.  I also show a flat pattern with some dimensions for reference stating what others have said about the finished part being the objective.

 

Some external customers/vendors also want flat patterns for their machines.  I send them out with a disclaimer about the finished bent up model being the objective.

 

Hope this helps.

 

Rob

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