OpenServo.com

[robotjay]

I think it looks good. Let's light this candle.

-Jay
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"Nothing is fool-proof; For we fools are ingenious and will find a way."

[jharvey]

It's been a bit of a roller coaster trying to get this STL file ready, but it's almost there. This post is mostly to remind me of what I did to generate it, such that I have it as reference for the next time I have a go at it.

First I made a file that included 110 parts in one file, and it had a min $150. I got over that price point by uping the qty to 2, this put me around $152, and some methods where over $200. The two lowest cost were SLA and Polyjet. Looking at the pictures, it appears the rigid polyjet is slightly more accurate than the SLA. Both claim to have the same offical specs. SLA was $152, polyjet was $160. Machined was an opiton, but I didn't trust it as these parts have some very hard to machine features, so I ignored the machined quote.

I then uploaded a STL of just one part, and got a quote for 200. That came back at about $5k, so about $25 each. I'll assume the materail cost is minimal, so I'll consider them to have a $25 setup fee per part.

So, it would appear that if one can get it done in one file / one job, then it will be the lowest cost. Each setup is probably around $25. Based on the first run it appears the materail cost $100 for 220 parts. So about I expect that for $125, we can get 275 parts. I had a bit of trouble getting 250 parts, kept running out of memory. I'll keep trying. Right now it's uploading the 250 part file. I've also got a 200 part file up there that I've been working with.

Also it appears that the LxW dims play a roll in the cost. I made the array 5x50, and it's costs about half of the 10x10 array. Weird.

More to come shortly.

[jharvey]

I just ordered quote number 435861 from quickparts.com which includes an array of 500 polyjet parts that hare held together by a small piece of webbing. I ordered qty 2 for $160 + shipping. I chose ground, I think that will be lowest cost. So 1,000 parts for not much money. We'll have to see how these come out. Fingers crossed. It notes I'll get a call from them to go over the details of this order. Pending no hiccups there, we should be good to go, and perhaps have parts in a week or two. Fingers crossed.

[barryfzr]

Hi just had some luck with the austria microsystems encoder on our futaba ss3306 servos we use for our boats and thought I would share them with you.

http://www.facebook.com/#/group.php?gid=110062036719&ref=ts

http://www.facebook.com/#/photo.php?pid=10515108&o=all&op=1&view=all&subj=50642505762&aid=-1&id=769460211

we have been using a polulo motor controller for the motor but I would like to stick a microcontroller board in there to make it stand alone.

[jharvey]

Nice boat, and glad to hear you got one working. I'm guessing you used the analog version. I searched for that servo, but it didn't produce a google hit. It it a normal servo? Motor, gears and a POT.

[barryfzr]

yes its a normal analogue servo, its the biggest hobby one futaba do. Sorry I put too many s's in ;o) its a futaba s3306

[jharvey]

I don't think I see the hip bone from the leg bone in your design. In my case I mounted it in the servo, for a fully self contained unit. In your case it looks like you mounted it external. I'm not sure how yours was used. The OE design I have posted above can be made to work with analog, and might fit in your servo. Are you interested in giving it a try?

[barryfzr]

Lol yes I'm sorry I'm quick to make these things and less eager to write them up

heres a picture with it mounted in the servo:

http://www.facebook.com/photo_search.php?oid=50642505762&view=user#/photo.php?pid=10696096&op=1&o=user&view=user&subj=50642505762&aid=-1&oid=50642505762&id=769460211&fbid=402468415211

These servos are soo big that there is plenty of room. There are more pictures on there too.... have a peak at my robot pebble!

We want a complete 360 servo solution for our boats and this encoder is going to help achieve that. I looked into an equivalent Volz servo but was quoted approx. £1000!! Our department could probably stretch to that but it would be a waste of resources. All I need to do now is get a h-bridge/pic in there and we have a very viable robotics servo....any help appreciated ;o)

[jharvey]

That's cool, and I'd bet expensive. Appears you had a custom brass shaft and aluminum POT body made for this.

On a different note, I've run into some problems with the polyjet parts. When I made the array of parts, I used a small webbing between the parts to make them all come out as one file, instead of several files. They appear to be concerned about breaking this webbing. Even after told them I wasn't concerned, they still expressed concern. I also offered make it with out the webbing, as the polyjet isn't concerned, it's just my ability to make a file that was an issue. However that also didn't seem to help. My suspicion is that they real concern is that I'm using prototypes for production. They simply didn't like that. I know they also are pushing short run injection molded parts, so I suspect they don't like productions like this because they are trying to push their other services.

I'm still bouncing back and forth with them. I'm having trouble catching up with the sales guy. He leaves at 5:00 and I get home at 6:00 to 6:30. I caught the production manager last night, perhaps he's more concerned than the sales guys are.

If worst comes to worst, they will put it up as no bid, and I'll have to shop around. I'm sure we can find some one that is willing to do this, it might not be these folks.

[barryfzr]

It was'nt too expensive... I just knocked them up on the lathe in about an hour

I think for the next one though I will try and mount the encoder on a main board with the driver electronics

[jharvey]

Sounds like an interesting approach, perhaps mechanically intensive. I've had good success with putting a hole in the PCB and mounting the magnet under the chip, instead of on top of the chip. So far I've been able to keep it on center, no calibration was required. If you vary off center by a tinny amount, you really need to calibrate it to keep if from producing an semi erroneous result.

Have you see my assembly pages posted here?

http://www.openservo.com/ConstructionTutorial_MG995_open-encoder

[barryfzr]

hey thats a great idea thankyou.....

If I mount the chip upside down as you mentioned I could drill a 3mm centre hole in the pcb to align the shaft holding the magnet. Maybe put a teflon washer in there too.

I have to finish a boat this month ... but more photos to follow soon ;o)

Are you on facebook??

[jharvey]

No face book for me. Haven't really had much interest in it. My wife is into that. I don't know much about it really. I share photos with photobucket.

[jharvey]

Just heard from Quickparts. They put this project on no bid. I can't change the design in a manner to make them happy with it. They didn't list any specific details about what was wrong. My gut tells me they just don't want to do an array of parts. Blasted. I guess I'll have to shop around to see if I can find another company that will give it a try.

[robotjay]

Jared,

I got in touch with my contact at QP and here's what he replied: