making a curved shape (part for my car)

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making a curved shape (part for my car)

Postby keastab » Mon Jul 31, 2017 4:31 am

I have Aspire (rank newbie here) I am reading /watching the tutorials one by one but I have not been able to wrap my thoughts around making a specific shape and curving it
it's a finish piece for my convertible and I need to make at least 3 sets of molds to vacuform the left ad right pieces from, I know I could just slather an epoxy on the inside of the shape and make the mold ,BUT I also want to be able to jig it up and cut it out.
here is a picture and the basic DXF I have
DXF finish pieces for convertible.dxf
(39.16 KiB) Downloaded 22 times


I've watched the molding video(man, I really get some weird shapes that way) a couple of them I might want to cut just to hang it on the wall for abstract art.
also the extrude and weave. different results but still weird shapes.
I go into the modeling and do a basic shape and can get a flat raised part the correct height. But I just can't figure out how to slope it down to another level using the line I have on the side of the shape for the actual bent shape that the part need to go.

I know it's me not knowing what setting or operation to use. Can any one point me into the correct direction for this seemingly simple part.
!finish!.jpg
the actual pic
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Re: making a curved shape (part for my car)

Postby highpockets » Mon Jul 31, 2017 5:20 am

I'm still having problems with the molding toolpath also. Just haven't sat down and tried to master it yet.

I modeled this, not sure if it's close or not.... You might try modeling it instead of using the molding toolpath.

Image 37.png
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Re: making a curved shape (part for my car)

Postby Leo » Mon Jul 31, 2017 1:14 pm

I have played around with two rail sweeps a little in the past.

I see that part as a 2 rail sweep, but with many sectionals to describe the shape along the sweep.

Many times we think of a 2 rail sweep as just 2 rails ans one cross section, but in fact you can have a LOT of cross sectionals.

Like in a shape of a hull of a boat. The gunalls are the rails, and the ribs are the sectionals. Each sectional would be spaced some distance apart, like the ribs in a boat.

The drive rails are pretty straight forward. The cross sectionals would be a little more difficult.

There is a section in one of the tutorials somewhere, but I don't know precisely where. You add additional nodes along the rails. They are not nodes like node editing, and they are color coded. Then you draw the cross sectional shape for each of the sectionals and attach that cross section to the node. One set of nodes along the rails for each cross sectional.

I have no idea the size of the model you are creating, so I cannot take about sizes.

Your shape CAN be created in Aspire. I would not consider it to be a simply shape
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Re: making a curved shape (part for my car)

Postby keastab » Mon Jul 31, 2017 3:29 pm

Thanks Highpockets and Leo, I'll try both ways(after watching some more videos) and see if I can get it to the shape I'd like. It's a 4" x 6" plastic piece that hides the hydraulic rams on an old dodge convertible. I happen to own 2 of them and no one makes good quality replacements for most of the plastics so I'm slowly making parts for mine and others. That is one of the reasons I did buy Aspire for the 3d modeling stuff, now all I have to do is learn enough to use it effectively(or try to anyway) :)
I hd an easier time creating my speaker kick panels from a flat 2d dxf than I'm having with this thing my first attempt at a custom kick panel for my car.
20160119_152051.jpg
kickpanels vs finish panel


and the final version 2 tries later
DSCF4514.JPG
final version made by CNC for the mold ,vacoformed and then cut out by the CNC,


that what type of process I'm working to create here since I can NOT cut or follow a line free hand anywhich way I try :mrgreen:
Last edited by keastab on Mon Jul 31, 2017 3:39 pm, edited 1 time in total.
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Re: making a curved shape (part for my car)

Postby Leo » Mon Jul 31, 2017 3:32 pm

So, please do NOT think this is the shape. I did NOT put any real effort into creating YOUR actual shape. I just wanted to demonstrate that the 2 rail sweep CAN create multiple cross sectionals in this case 5 to create a shape. Your part would be 30 or 50 cross sectionals. I just threw lines on the page.

What I did to place the cross sectionals was to select the cross sectional vector and (i forgot how already, may have been right click) place it on the rails. Must be done in the 2 rail sweep workbox.

image.jpg


You would need to measure the cross sectional shape("Z") and intervals of every - say 1/8" or so - along the drive rail axis (say - "Y"). Your sectional vectors would be the "X" and "Z"
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Re: making a curved shape (part for my car)

Postby keastab » Mon Jul 31, 2017 3:42 pm

Leo wrote:So, please do NOT think this is the shape. I did NOT put any real effort into creating YOUR actual shape. I just wanted to demonstrate that the 2 rail sweep CAN create multiple cross sectionals in this case 5 to create a shape. Your part would be 30 or 50 cross sectionals. I just threw lines on the page.

What I did to place the cross sectionals was to select the cross sectional vector and (i forgot how already, may have been right click) place it on the rails. Must be done in the 2 rail sweep workbox.

image.jpg


You would need to measure the cross sectional shape("Z") and intervals of every - say 1/8" or so - along the drive rail axis (say - "Y"). Your sectional vectors would be the "X" and "Z"



I'm watching the video right now on the 2 rail sweep. dang this part is a lot harder than the kick panels just by the different processes I am having to understand(I didn't say learn yet)
thanks again. I'll finish watching and give it a try. ahh part is 1.5" tall
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Re: making a curved shape (part for my car)

Postby Leo » Mon Jul 31, 2017 5:21 pm

There is a bit more about cross sections in the Manual, under 2 rail sweep.
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Re: making a curved shape (part for my car)

Postby Leo » Mon Jul 31, 2017 5:41 pm

I thought I saw a video demonstration but I cannot find it. sorry

It's all a matter of the "Z" height at many points along each cross section.

If you lay the part down, as in the picture you show, and orientate it the way you want to machine it, I would orientate it with the longest axis being "Y".

Then on the plane under the part scribe lines in the "X" axis 90 degrees to the "Y" axis.

Then measure the "Z" at points, say at 1/8 intervals along the "X" axis.

Draw a line between the points

What you will create is a 2 axis line that describes the "X"-"Z" cross section at intervals of 1/8 along the "Y" axis.

So then you have 3 dimensional information you use to create a 3 dimensional model.

I don't know if you are familiar with boating, Americas Cup or 12 meter sailboat racing. Herreshoff was, ans still is, a very historic name in that arena. This method I am describing, though not very clearly is the method used by Herreshoff to document their designs. It's a time proven and accurate method.

I am a bit old school, so there may be better and easier methods.

Anyone else can point out easier ways.

It's a bit of work to do it, but it is doable.
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Re: making a curved shape (part for my car)

Postby dwilli9013 » Mon Jul 31, 2017 6:05 pm

Just throwing it out there.
This is a method I have used many times with very favorable results for recreating solid models.
I use a xbox kinect sanner. Hook it up to your computer via usb. Download and install the free software ReconstructMe from the internet.
Scan the piece your are trying to model. The Kinect will turn the data into a point cloud this is very usable in Aspire.

Bonus: there are lots of youtube videos on using the Kinect this way.

Leo's method is a very tried and true method for interpolating 3d objects for modeling. Just thought I would add another method that is also doable. :lol: :lol: :lol:
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Re: making a curved shape (part for my car)

Postby Leo » Mon Jul 31, 2017 6:52 pm

You can also use your machine to measure all the points, using the digital readout and a pointy tool in the spindle. With the spindle OFF, do the same as I described and set zero to the table top (bottom of part) with "X" somewhat mid point and "Y" zero nearest to you.

Move the "Y" axis .125 and touch the points along "X" and "Z" to record your points. YES - it IS a tedious job and will take time, but it is doable.

If you had a probe, you could also use that.
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Re: making a curved shape (part for my car)

Postby highpockets » Mon Jul 31, 2017 7:21 pm

Dwayne and Leo are both giving good alternatives to creating a piece from scratch.

I've used a probe to do modeling before and it's great for 2.5d stuff, but a bit more fiddly for true 3D. I highly recommend the probe from Crafty CNC http://www.craftycnc.com . The guy is great, there was a conflict between the software he ships with his probe and Screen 2010. He worked with the Screen 2010 guy to resolve the issue. Big thumbs up to both!!!!

As for Dwayne's suggestion of Kinect, from what I've seen (not used) it looks like it would do a great job and give you a true 3D part. I've been looking into getting this setup for a while now.
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Re: making a curved shape (part for my car)

Postby martin54 » Mon Jul 31, 2017 7:54 pm

While you have been given some good options to make this part on the CNC & I also understand that you are also wanting to learn how to use the software I can't help thinking you would be better using an epoxy mould (as you have already mentioned) for a job like this. Far easier & quicker to make & the mould will still be able to produce multiple parts :lol: :lol:
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Re: making a curved shape (part for my car)

Postby TReischl » Mon Jul 31, 2017 9:34 pm

Mr HighPockets. . .

I checked out the probe site. He references that he sells on eBay and Etsy. But I could find anything on either one. Maybe it is just me, or maybe he has stopped selling.
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Re: making a curved shape (part for my car)

Postby keastab » Mon Jul 31, 2017 9:49 pm

Leo wrote:There is a bit more about cross sections in the Manual, under 2 rail sweep.

I've got it marked and am playing with it now. I'm close to getting what I want THANKS
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Re: making a curved shape (part for my car)

Postby keastab » Mon Jul 31, 2017 9:54 pm

martin54 wrote:While you have been given some good options to make this part on the CNC & I also understand that you are also wanting to learn how to use the software I can't help thinking you would be better using an epoxy mould (as you have already mentioned) for a job like this. Far easier & quicker to make & the mould will still be able to produce multiple parts :lol: :lol:



I know it would be faster (and easier) to make the mold with casting epoxy. but my problem lies in the fact that I can not cut a straight line to save myself. This way I can learn to make the part,position the part and cut it out (correctly and straight) using the CNC. I end up with something super ugly if I try to cut them out.
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