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Open-Encoder-MG995
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jharvey
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Joined: 15 Mar 2009
Posts: 359
Location: Maine USA

PostPosted: Fri Jan 08, 2010 11:22 am    Post subject: Reply with quote

First I heard about a feature being too small. The key concern they pushed with me was the probably of breaking the webbing between the parts. I inquired about submitting the part without the webbing, such that they are free standing. The fellow I was talking to couldn't get past the webbing. He eventually changed his concern to breaking the parts when cleaning off the support material. I inquired if I could remove it, such that it would minimize their labor, and remove their liability for breaking the parts. He then started to complain about breaking the webbing again.

At one point early in the conversation, I had inquired if the issue was a small feature. He didn't reply, but I don't think he had the file open at that point, so I don't think he was able to reply then. After he got the part open, he didn't bring up that concern. I didn't bring it up again, because I was addressing his other concerns.

I had expressed that I'm willing to change the files and I'm willing to be as flexible as I can. I noted I could change the features of the part, I could also change the qty from 250 to something lower, and I could change the length and width of the array. However, instead of getting a list of issues that I might be able to resolve in term of the model, I got the no bid e-mail posted below. Perhaps there's a variation in opinion from the folks that work 8-5 vs those that are there at 6:30 to 7:00 when I was able to call, not sure.

Quote:
I apologize for missing your phone calls last night. I was hoping to get you after 7pm but when I called you were unavailable.

Sean Perkins spoke with me this morning regarding the conversation you had last night. It is
difficult to express in email the subtleties of my concerns with your designs, but I will try
below.

To begin with, I would like to let you know that we will have pass on this project and no bid the
work. This design is not well suited to the prototyping processes we offer for a variety of
reasons.

My recommendation would be to find a local university or small company that has a prototyping
machine with plenty of excess time and a willingness to experiment with the process. Your design
is beyond the limitations of the process and will likely require many attempts to get a workable
piece, and even then, the machines may not be able to build the design at all.

The basic design of the part is far below the minimums that we have found for getting a good
result using our rapid prototyping processes. Being so small raises problems beyond just what the
machine can build. In order to remove the support structure we would likely destroy, damage or
lose, the majority of the parts in the model.

We also do not have the capabilities to efficiently finish, as these processes require
significant hand finishing, all the parts. Your design may be too small for today's technology to
properly replicate.

I apologize that we cannot be of more assistance with this project. Good luck with your future
work and should you have any questions, please feel free to contact your Sales Manager, Wes Wilson
(wwilson@quickparts.com). I have copied him on this email as well.

Thank you,


About my unavailability when he called, I have no record of a call, and I was available after about 6:15 of the two days he may have tried to call. He did leave me a message the first time he called, so he has the correct number.

I posted the SLA file. Caution they are in the 50 meg to 150 meg range in size. There are several files because they are different sized arrays. The QTY is noted in the name.

http://jaredharvey.com/openservo/open_encoder/2010-01-01_sla_arrays

[EDIT]Do you think this fellow your working with can or is willing to get these through the system? I'm certainly willing to make changes if required.
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barryfzr



Joined: 27 Aug 2008
Posts: 13

PostPosted: Sun Jan 10, 2010 5:38 pm    Post subject: Reply with quote

The plot thickens.... Smile

I decided to try and stick a h bridge in as well


just waiting for parts now Smile
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robotjay
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Joined: 01 Aug 2006
Posts: 225
Location: Nebraska, USA

PostPosted: Mon Jan 11, 2010 6:12 am    Post subject: Reply with quote

jharvey wrote:
Do you think this fellow your working with can or is willing to get these through the system? I'm certainly willing to make changes if required.


I will talk with Duffy at Quick Parts again, but I will also look into other shops. Considering QP has an online quoting system, the actual order system seems to be a pain. Regardless, this should be cleared up shortly. Talk to you soon.

-Jay
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robotjay
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Location: Nebraska, USA

PostPosted: Tue Jan 12, 2010 12:56 am    Post subject: Reply with quote

Jared,

After speaking with QuickParts again, their main concern is that the triangular wedges rise only .008" above the part, and that the wall thickness of the tip of the shaft is only .003". From the picture of the part file they have (below), it appears their file is much different than the one I have access to. They also mentioned that your STL file's resolution is too high, and that from now on we should just send the native solidworks files.



Talk to you soon,
Jay
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jharvey
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Joined: 15 Mar 2009
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Location: Maine USA

PostPosted: Tue Jan 12, 2010 10:14 am    Post subject: Reply with quote

Awesome, and glad to hear the news. It appears there is a small change from the picture above and what I have currently modeled. That wall thickness dim is currently .010, not .006 and not .003. I just uploaded what I have now. Here's a link.

http://jaredharvey.com/openservo/open_encoder/shaft_array_2010-01-12.zip

I wonder if they miss placed a decimal on the .003 note. The hole down the center is .035.

Did they say what thickness would be acceptable for those features? I know they specify a min feature size of .025, and a tolerance of .005. Perhaps they are pushing for a min dim of .025?

When I made the STL file, I set the tolerance to .001. Where the default was .012. My theory was that it can't be .005 accurate if it's working file tolerance is .012. So I set the file tolerance under .005. I wonder if perhaps their objection to an increased file accuracy is perhaps a source of their concerns about failed part creation. STL is a file format specifically made for the STL process, which is very similar to what the PolyJet is doing. I know the PolyJet uses it's own material, where most STL's will simply melt plastic like a hot glue gun. When you melt plastic, there is a physical tolerance you can't get past because of shrinkage while cooling, ect. I believe the special PolyJet material allows the PolyJet to offer a higher accuracy than the original STL process allowed. How much did they object to the more accurate file? Do you think we can get them to use a file with a higher accuracy? If they want it lower that's fine. My gut tells me we might have a better result with the higher accuracy file.
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jharvey
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Joined: 15 Mar 2009
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Location: Maine USA

PostPosted: Tue Jan 12, 2010 10:54 am    Post subject: Reply with quote

I just spent some time looking at the STL file format. I had some theories about why a .005 tolerance might be better than .001 tolerance. I wondered if the STL format was a sliced format such that the machine didn't have to post process the file, but I got to find out that STL is a form of a tetrahedral mesh. When I specify the tolerance in Solidworks, I'm specifying how accurate those triangles are relative to the actual part. So .001 is in fact more accurate.

[url] http://en.wikipedia.org/wiki/STL_(file_format) [/url] Hmmm, can't seem to get this URL to work correctly.

As we can see in the below image, this mesh like format will get very large when using circular objects. Especially when features protrude in or out of a circular feature.

http://www.engtran.com/Keyway/MESH.gif

The slice and fill operations are done by PolyJet software.

So with a .001 file tolerance, and a .005 machine tolerance, I believe then end tolerance is .006. I could be wrong though. I think we really want to keep that .001 if we can. With out it, I don't see how it's possible for them to maintain a .005 tolerance.

If the concern is that the file is to larger for their machine to open in a reasonable amount of time, perhaps we can offset file opening time and general file size by using the qty 110 file instead of the 250 file. Another possibility to reduce the file size would be if I made the rivet like feature out of a triangle instead of a circle with several protruding features.
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robotjay
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Joined: 01 Aug 2006
Posts: 225
Location: Nebraska, USA

PostPosted: Wed Jan 13, 2010 11:13 pm    Post subject: Reply with quote

Here's the message I got back from Quickparts:

Quote:
Jay,

All of the tips measure .006”.
Also, the height of the locking mechanism is .008”

These are too small to print in any process.
Please adjust to a minimum of 0.025”

Finally, the resolution of the STL is too high.
Send in the Native CAD to us when the changes are made.


_______________________________

Duffy Cink
Low Volume Sales Manager


I would just send them the .sldasm and .sldprt file, and let them sort it out. The picture they sent is weird and I have no clue what they're pulling those dimensions from, but I am certain that whatever their size restrictions, we can make it work, as long as they're still willing to let us do this at all.
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jharvey
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Location: Maine USA

PostPosted: Thu Jan 14, 2010 10:50 am    Post subject: Reply with quote

How about this approach? Theory being that we use some fishing twine or equivalent in the V grooves to fill in and make a semi pressed fit. That twine would be around .010in (.25mm) diameter.



I uploaded that part file to this link http://jaredharvey.com/openservo/open_encoder/POT_shaft_B_2010-01-14.zip

The array assembly file is the same.
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robotjay
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PostPosted: Thu Jan 14, 2010 6:59 pm    Post subject: Reply with quote

I like this idea. I will personally forego the fishing line in favor of super glue, but having the option to make these non-permanent is ideal. Nice work.

-Jay
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jharvey
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PostPosted: Thu Jan 14, 2010 9:45 pm    Post subject: Reply with quote

Glad to hear you like, can you pursue Quickparts about this version?
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ginge
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Joined: 14 Jan 2006
Posts: 1031
Location: Manchester, UK

PostPosted: Sat Jan 16, 2010 6:04 pm    Post subject: Reply with quote

Hi guys,

I have just committed to CVS the OpenEncoder source code:

The OpenEncoder is now in the live AVR_OpenServo_V3 tree, but disabled by default.

CVS Message:
"Addition of Darius Rad's i2c bitbanging support for Jared Harvey's OpenEncoder addon project. This patchset, once enabled with ENCODER_ENABLED will enable a bit banged i2c connection from the potentiometer interface to the I2C position encoder connected."

This implementation is excellent and small.

No encoder support:
text data bss dec hex filename
10648 264 313 11225 2bd9 ATmega168_OpenServo.elf

With encoder
10844 264 318 11426 2ca2 ATmega168_OpenServo.elf

Jared, you might want to use the version of the source in CVS, as I had to tweak some minor details and patch a couple of issues.

Fantastic work guys!
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jharvey
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Joined: 15 Mar 2009
Posts: 359
Location: Maine USA

PostPosted: Sun Jan 17, 2010 1:50 am    Post subject: Reply with quote

Great and glad it's up there for others to use if they want to use it.

Darius does good work. I'm very happy I was able to get him to work on this. The quality of his software is far better than mine.

Thanks for getting that up there.
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robotjay
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PostPosted: Fri Jan 22, 2010 6:47 am    Post subject: Reply with quote

Just to keep you guys updated, the last message I got from QuickParts was this:

Quote:
Jay,

We are trying to get a smaller STL converted on this one.
Didn’t want you to think you are falling on deaf ears.

Right now the STL is 198MB which is too large to process in the RP machine.
Our CAD team is on it.

Duff


*Sigh* This was two days ago. I'll let you know when I get a final quote back. Talk to you soon.

-Jay
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jharvey
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PostPosted: Tue Jan 26, 2010 9:25 pm    Post subject: Reply with quote

Any luck with quickparts or other?
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jharvey
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Joined: 15 Mar 2009
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Location: Maine USA

PostPosted: Tue Mar 23, 2010 12:35 am    Post subject: Reply with quote

I just got an e-mail from a fellow inquiring about how OE was going. So I thought I'd share an update. I've made a little video showing OE working in a servo. That video can be found here.

http://vimeo.com/10364526 (Vimeo notes it will take about half an hour to process before it can be watched. Current time is 8:30 EST)

That servo is using the Amazing magnet clued on to a hand machined and modified brass shaft that came with the servo POT. The program sets the P, I, D, velocity, ect values. Then it prints to STIO and commands to seek a position. It then waits until OE note's it has reached the position, then commands and prints the next position. The firmware is the same that can be compiled from the V3 non-dev source code posted on the CVS.

The above noted SLA shafts are in the mail and I should receive them any day now. Robotjay has had good things to say about the shafts before he sent a pile of them my way. I'll have some picts of these parts in a couple days.
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