Basic question on Part Design workflow (cut vs. loft)

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iwbnwif
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby iwbnwif » Mon Sep 24, 2018 9:41 am

Thanks guys for the explanations.

I was able to roughly reproduce the slopes by creating two datum planes and pocketing away from the material, like this. It is only an approximation of the original form, but I think I understand the method now.

@chrisb - thank for the cross reference. I am happy now to use the subtractive tools, although sometimes drawing and cutting helps visualise what is [going to be] removed. Of course this is the great strength of FreeCAD that you can choose the tool to suit your own personal workflow.

Out of interest, is there a way to visualise the pocket as opposed to seeing what is left after the pocket action?
nozzle2.png
nozzle2.png (30.32 KiB) Viewed 200 times

I may be able to be more accurate with positioning the datum planes by inspecting the dimensions and angles in the OpenSCAD import. For example, I tried with the TechDraw workbench as follows:
techdraw.PNG
techdraw.PNG (33.46 KiB) Viewed 200 times

This is my first time to use TechDraw so still exploring.

Thank you again for the help.
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HarryGeier
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby HarryGeier » Mon Sep 24, 2018 10:23 am

One idea..

You can CONTROL the angle of the Sloping Datum Planes by using named constraints and using them in the parameter sheet of the Datum planes.

here: https://www.youtube.com/watch?v=8Bmcgn2RBGI&t=2s

at about 15 minutes i use a parameter from a master sketch as the Z offset of a datum plane..
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chrisb
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby chrisb » Mon Sep 24, 2018 12:32 pm

iwbnwif wrote:
Mon Sep 24, 2018 9:41 am
Out of interest, is there a way to visualise the pocket as opposed to seeing what is left after the pocket action?
No, well and yes. It is not in the way as with loft and sweep, where the subtractive thing is shown as a light pink half transparent solid. But if you tick the "Update preview" checkbox the result of the pocket is displayed immediately while you change the parameters.
iwbnwif
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby iwbnwif » Mon Sep 24, 2018 1:50 pm

You can CONTROL the angle of the Sloping Datum Planes by using named constraints and using them in the parameter sheet of the Datum planes.
here: https://www.youtube.com/watch?v=8Bmcgn2RBGI&t=2s
Hi, yes I'm a subscriber and learned about datum planes from your video :) Actually, I have been meaning to post a couple of questions in the comments, will do it now.
No, well and yes. It is not in the way as with loft and sweep, where the subtractive thing is shown as a light pink half transparent solid. But if you tick the "Update preview" checkbox the result of the pocket is displayed immediately while you change the parameters.
Thanks, I can imagine that probably isn't that useful in the end. It was to see the effect of 'through all' on a complex structure (e.g. something in the model gets pocketed that I wasn't intending to).
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HarryGeier
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby HarryGeier » Tue Sep 25, 2018 1:42 pm

iwbnwif wrote:
Mon Sep 24, 2018 1:50 pm
Hi, yes I'm a subscriber and learned about datum planes from your video :) Actually, I have been meaning to post a couple of questions in the comments, will do it now.
Better ask me here.. in the end it will help more and maybe more answers come ...
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iwbnwif
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby iwbnwif » Wed Sep 26, 2018 8:33 am

Better ask me here.. in the end it will help more and maybe more answers come ...
I see, that makes sense. To save anyone who is reading through this thread from jumping to the video - here are the questions and answers:

Q1) What is the advantage of using a master sketch over a spreadsheet for named parameters?

A1) Well, there is no advantage, just a difference. With a master sketch you can directly see what is where and how values influence your design.

Q2) Is it possible to use construction lines from another sketch in the same way as you used the master sketch's part lines?

A2) No, not at that time. this has been discussed a few times in the forum. This is also the reason why you would normally create a master sketch and do not use it directly for features, so you can put in whatever you like without needs that it builds a single solid.
iwbnwif
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby iwbnwif » Wed Sep 26, 2018 9:48 am

No, well and yes. It is not in the way as with loft and sweep, where the subtractive thing is shown as a light pink half transparent solid. But if you tick the "Update preview" checkbox the result of the pocket is displayed immediately while you change the parameters.
Out of interest, I found that the material to be removed is displayed when using a subtractive primitive, however I couldn't achieve the same with a subtractive loft.

The following is created with a subtractive primitive cylinder.

subtractive.PNG
subtractive.PNG (50.77 KiB) Viewed 151 times

Please can someone give an example of a subtractive loft with the loft displayed?
chrisb
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby chrisb » Wed Sep 26, 2018 10:30 am

It does not appear on creation, only on editing a loft; perhaps it's a bug.
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iwbnwif
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby iwbnwif » Wed Sep 26, 2018 10:48 am

It does not appear on creation, only on editing a loft; perhaps it's a bug.
Ah, yes thank you - got it now.

subtractive2.PNG
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NormandC
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Re: Basic question on Part Design workflow (cut vs. loft)

Postby NormandC » Sun Sep 30, 2018 3:12 am

chrisb wrote:
Wed Sep 26, 2018 10:30 am
It does not appear on creation, only on editing a loft; perhaps it's a bug.
IMO it is a bug, or at least an UI inconsistency. All PartDesign features should perform the same in regard to the live preview, but they do not... Some features display the end result (Pad, Revolution, Pocket), while others display a translucent yellow/red shape (primitives, transformation features). In some cases, when the parameters are active, two separate features are visible at the same time: the one being created, and the one before it. This definitely should not happen.

It would be a good idea to make a list of how all the tools perform, and make a report about it... Too lazy to do it now I'm afraid. :oops: