Accuracy with 3D files.

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Accuracy with 3D files.

Postby Zootalaws » Fri Jul 06, 2012 1:09 am

On a friends recommendation I am trialling Aspire.

I make furniture, picture frames, 'art', etc and was looking for a good app that combined all my needs instead of half-a-dozen bits and pieces.

I start with a model designed in 3D CAD, from there I 'flat pack' all the components, export them, bring them into Aspire. But the results I am getting are terrible. Bad enough that I can't see me ever wanting to use it - which is a bust - it's a great product!

Despite turning my DXF, OBJ and STL resolution up really high (for the compound curves), the results in Aspire are really blocky and lo-res.

Am I doing something wrong?

Here are my files:
Screen Shot 2012-07-06 at 8.04.16 AM.png
CAD image of table end

First is a screen shot of a component, second is the actual component (in mm) in STL (which seems to be Aspire's preferred medium, from what I have read). I have tried ASCII and binary STL, 2D and 3D DXF, basic and 'fiddled with' exports, it all seems to come out the same - crap! (pardon the French).

Designing in Aspire isn't an option, I need to make them in 3D for a number of reasons - perfecting 'fit', producing schematics and brochure art, among others.

I have tried PDF, but can't get the scaling right - too much mucking around and the results aren't accurate enough for the tight fit I need.

I use AutoCad Designer and Sketchup - AutoCad for bigger, more detailed pieces, Sketchup for quick and simple flat-pack no-more-screws-type furniture. It slots together, so tolerances are critical.

Any help gratefully received.
End.stl.zip
STL CAD export
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Re: Accuracy with 3D files.

Postby ger21 » Fri Jul 06, 2012 2:36 am

Importing 2D vectors via .dxf would probably give the best results. Using an .stl would be terribly inefficient for that type of part.
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Re: Accuracy with 3D files.

Postby Zootalaws » Fri Jul 06, 2012 8:11 am

Thanks Ger - I will give that a try.

Although in this case all my 'products' are made from sheet goods, I also make a range of woodworking 'machines' and jigs that have quite a few multi-axis machined parts - how would I manage with Vectric products?

The '3D' bit of Cut3D would tend to indicate its intent, but from what I have seen, all the Vectric products use common code - I can't see it handling 3D CAD files any differently.
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Re: Accuracy with 3D files.

Postby Adrian » Fri Jul 06, 2012 8:42 am

As Gerry says those aren't 3D parts. You need to export them as a 2D DXF or EPS in plan view and then toolpath them with profile toolpaths.

For parts like that you don't really need Aspire either. You could do it all in VCarve instead.

I've create an Aspire file to show you how it could be done for this part. The scale may well be wrong but it will give you the idea of how it works when moving from 3D cad to cnc.

For the the other items you describe they could be done with Cut3D or with Aspire.
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Re: Accuracy with 3D files.

Postby Zootalaws » Fri Jul 06, 2012 1:00 pm

Thanks Adrian.

That makes sense for sheet goods.

For my 3D parts, like these machined 2x4 blocks, what is the best way to import them? This one is relatively simple, so I could make it in Aspire, but there are hundreds per unit and they are already drawn, having to redraw them in Aspire would be a no-go.

Screen Shot 2012-07-06 at 8.12.07 PM.png
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Re: Accuracy with 3D files.

Postby Adrian » Fri Jul 06, 2012 1:14 pm

Cut3D would be better for that as it supports four side machining. It can be done in Aspire but it's not something I do.

It's best to work through the tutorials on the main site - http://www.vectric.com - as it's not the sort of program you can really learn by having a go. There are important concepts that, if not understood, will lead to lots of frustration and an incorrect view of what the software is capable of.

Not sure what 3D package you're using but it created a lot of redundant geometery on the STL file you posted.
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Re: Accuracy with 3D files.

Postby tmerrill » Fri Jul 06, 2012 1:22 pm

Not knowing what the unseen sides have, but that part can be completely done with Cut2D, VCP or Aspire using 2D toolpaths. Cut3D will not drill holes or machine good slots and it can be challenging to get good vertical sides with 3D toolpaths.

The challenge with any program will be stock alignment and rotation. Again, going only by what I see, I would do two sided machining (very easy) and create a positioning jig for a drill press to do the small holes. Next step up may be some type of indexing device that is under software control.

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Re: Accuracy with 3D files.

Postby Mike E » Fri Jul 06, 2012 4:48 pm

I tied to import the STL file into Aspire 2.5 and kept getting "out of memory" error.
Also tried importing to Solidworks, it went through the import process but nothing came in. Seems like the STL file isn't valid???????

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Re: Accuracy with 3D files.

Postby ger21 » Fri Jul 06, 2012 10:27 pm

Zootalaws wrote:Thanks Adrian.

That makes sense for sheet goods.

For my 3D parts, like these machined 2x4 blocks, what is the best way to import them?


As Tim says, it really depends on what's on the other side. But, the simplest and most efficient would be to use 2D drawings again. One for each side of the part. That's how I'd do it. Machine one side, and make a fixure to hold the machined side while cutting the other side.
(I just looked at your part a little closer, and it looks like you might need to machine all 5 or even 6 sides. But I'd still do it as 2D drawings)
2D machining is far more efficient than 3D machining. Machining time will typically be 50-75% faster using 2.5D toolpaths.

If you want to import a 3D model, you're probably going to need machine all 4 sides independently, unless you have a 4th axis to rotate the part.
3D models and toolpaths are really only needed when doing more organic type surfaces, or carvings. Any shapes with flat surfaces should be done with 2D toolpaths, imo.
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Re: Accuracy with 3D files.

Postby Zootalaws » Sat Jul 07, 2012 4:15 am

Adrian wrote:Cut3D would be better for that as it supports four side machining. It can be done in Aspire but it's not something I do.

It's best to work through the tutorials on the main site - http://www.vectric.com - as it's not the sort of program you can really learn by having a go. There are important concepts that, if not understood, will lead to lots of frustration and an incorrect view of what the software is capable of.

Not sure what 3D package you're using but it created a lot of redundant geometery on the STL file you posted.


I used a conversion program to create the STL file from a DAE (ex Sketchup.)

I have pretty much moved over to Autocad Inventor now - that learning curve was steep, but no more having to convert, so swings and roundabouts.

I am never happy with conversions - I prefer the data path to be as short as possible between design and implementation, but in that case it was a purchased plan that was in Sketchup SKP format (bleah!).

So, it looks like another weekend of tutorials :) Oh well, plenty of rugby and motogp in the background - not too much of a chore.

Thanks very much for your advice Adrian - much appreciated. It is a new venture for me having come from a computing / electronics background into 'manual' woodworking, and now to CNC. But I love learning and trying new technologies. I have a lot of experience of computer-controlled things like printers (large - 6-colour offset, dye-sub, etc.), scanning, laser cutters, engravers, so the concepts aren't entirely new, but learning how to translate what's in my head, to a 2D design and actually cutting that out, finishing and selling the products is a whole new ball-game.

I have already upgraded my CNC from 4x4 to 8x4 and could probably justify 6x10 if I sat down and did the figures.

The reason Aspire attracted me was the ability to add further strings to my bow in the nature of wood engraving, lithophanes, etc. and potentially to branch out into supplying the sign industry. What started out as routing picture frames and making bookcases for friends has completely changed, now I have 'found' CNC

I live in a small SE Asian nation, there isn't another CNC machine in the country and I am just beginning to scratch the surface of the potential markets. What started out as a hobby to keep me out of trouble has ended up more than paying or itself. I haven't even though about metal cutting, it is an area so far outside my expertise, but there is a booming construction and boat-building industry that is ripe for the plucking :)

I am lucky in that I don't need to make money to live - I have a hard-working wife, free housing, power and a very low cost of living, so I have the time and breathing space to develop this business without having to worry about feeding hungry mouths :)

Onwards and upwards!
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Re: Accuracy with 3D files.

Postby Zootalaws » Sat Jul 07, 2012 4:19 am

tmerrill wrote:Not knowing what the unseen sides have, but that part can be completely done with Cut2D, VCP or Aspire using 2D toolpaths. Cut3D will not drill holes or machine good slots and it can be challenging to get good vertical sides with 3D toolpaths.

The challenge with any program will be stock alignment and rotation. Again, going only by what I see, I would do two sided machining (very easy) and create a positioning jig for a drill press to do the small holes. Next step up may be some type of indexing device that is under software control.

Tim


Thanks Tim, yes that part is normally 'finished' by hand - drilling, etc. THe back side is flat but before it is cut there is a hole bored parallel to the back side.

I am fine with jigs and have a full workshop of things like bandsaw, drill press, bench saw, router table, etc.

You say "it can be challenging to get good vertical sides with 3D toolpaths." - can you elaborate? I haven't done any 3D work up to now, that was why I thought to give Vectric products a try.
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Re: Accuracy with 3D files.

Postby Zootalaws » Sat Jul 07, 2012 4:20 am

Mike E wrote:I tied to import the STL file into Aspire 2.5 and kept getting "out of memory" error.
Also tried importing to Solidworks, it went through the import process but nothing came in. Seems like the STL file isn't valid???????

Mike


Thanks Mike - no doubt it is my conversion from DAE.
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Re: Accuracy with 3D files.

Postby Zootalaws » Sat Jul 07, 2012 4:28 am

ger21 wrote:(I just looked at your part a little closer, and it looks like you might need to machine all 5 or even 6 sides. But I'd still do it as 2D drawings)
2D machining is far more efficient than 3D machining. Machining time will typically be 50-75% faster using 2.5D toolpaths.

If you want to import a 3D model, you're probably going to need machine all 4 sides independently, unless you have a 4th axis to rotate the part.
3D models and toolpaths are really only needed when doing more organic type surfaces, or carvings. Any shapes with flat surfaces should be done with 2D toolpaths, imo.


How I currently do it is to cut out the block, use a forstner bit to get the recessed curve, finish it on the bandsaw and drill press. To make that part from beginning to unsanded, finished takes (Me! Slow, bad eyes) about 20 minutes. There are a lot more parts in that machine, that is one of them that uses more 'axes' than others. For the most part, it is made from sheet goods and 8x1 boards, but there are wheels, gears, laminations - a fully-cut machine takes me about a day to assemble, not including finishing time and drying time prior to assembly, then a few hours tinkering and tuning. So from timber to running, maybe 4 or more days.

If I could shorten that time by getting the bulk of my cutting done by machine, I could probably make two or three at a time in the same cutting and assembly time it currently takes me to make one.

Thanks for your help Gerry, it is really appreciated.

Mike
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Re: Accuracy with 3D files.

Postby Zootalaws » Sat Jul 07, 2012 11:04 am

Zootalaws wrote:
Adrian wrote:...I have already upgraded my CNC from 4x4 to 8x4 and could probably justify 6x10 if I sat down and did the figures. ...


Late night posting - I should have said, redesigned my router from 4x4 to 4x8, now I have to actually break it down and rebuild it... I could sell it and make another from scratch, but that means there would be someone competing with me... :)

It's a hard decision - having so much fun with my new machine, I am loathe to break it down. I guess I will carry on with it, order the new parts and refine the design, then when it's all here and ready, then rip it down and rebuild it in one weekend.

I have just drawn up a bunch of new designs for large corner-unit desks and tall bookshelves that need to be made from a whole sheet of stock - I really didn't think this was going to take off quite so dramatically.
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Re: Accuracy with 3D files.

Postby tmerrill » Sat Jul 07, 2012 11:19 am

You say "it can be challenging to get good vertical sides with 3D toolpaths." - can you elaborate? I haven't done any 3D work up to now,

Hi Mike,

Let's see if this helps.

There are 3 types of toolpaths for machining a 3D object.

The Roughing toolpath is normally run first and it is a simple toolpath normally with an end mill designed to hog out almost all the waste material above and around the model.

The Finishing toolpath is always a single pass normally using a ball nose (round nose) bit and it follows the 3D model surface. To get a smooth surface, the bit's stepover is normally set to a very small amount, which means longer machining times.

Finally, a Cutout toolpath may be used to trim the edges of the model to improve their quality and release the part from the material.

A program like Cut3D only provides these three toolpaths, while a program like Aspire provides these and additional 2D toolpaths that can help in certain situations.

I took your part above and loosely modeled one side of it in Aspire to show you what the program could do. But now try to visualize machining the entire model using just the 3 toolpaths above.

Now balance that with only needing the vectors shown on the left side of the picture and using these to create 2D toolpaths such as profile and pocket. All the cutting would be done with larger diameter end mills and very quickly when compared to the 3D machining times.

Again, just using your part example, the trouble some area would be the vertical semi-circular edge. A 3D toolpath would need to machine this by running the side of the bit up to it, retracting to get over the top, then repeating that in the opposite direction. You seem very comfortable with hand power tools, can you imagine using a plunge router the same way to create that lip? With a 2D toolpath you would create a toolpath that will cut that lip with an horizontal only movement, resulting in better results at a fraction of the time.

You have only given two examples so far, but in both cases they are simple shapes best cut with 2D toolpaths. Go the the Aspire Gallery and look at some of the plaques and projects that people make with Animal/nature models. This is where the actual 3D toolpaths shine and that is where there main purpose is, however do realize you may have parts someday that require a domed top or angled bottom and this is where you could use 3D.

If this hasn't made sense, please ask. I think getting your head around the concepts of the different types of toolpaths and how they are used is going to be very important for what you are trying to do.

Tim
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