Author Topic: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE  (Read 543 times)

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Offline NY2KW

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Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« on: September 25, 2019, 12:16:11 pm »
I am restoring a 45 yo transceiver and one large capacitor is fitted into a slot with special hardware holding it place.  Modern capacitors are about 1/2 the size so I wanted to build a plastic sleeve of sorts the dimensions of the old cap, about 4" h x 3" d and create a cylindrical pocket about 2" deep and 1.5" diameter.  I got a free copy of Autodesk Fusion360 and created STL files for 3D printing as well as ige files for CNC.  I went to a few sites to get quotes and was blown away with quotes ranging from $400 to $800 for 1 piece.   

What would be the least expensive method (other than a block of wood turned on a lathe) and least expensive material to use?

Thanks
Jerry 
 

Offline martin1454

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #1 on: September 25, 2019, 12:33:06 pm »
Look up a local 3d print hub - The local private hubs are way cheaper than professional prototype service
 

Offline SMTech

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #2 on: September 25, 2019, 12:34:23 pm »
wrap the modern smaller capacitor in some cardboard or other thick pliable material, optionally secure with double sided tape  :box:
 

Online Macbeth

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #3 on: September 25, 2019, 12:52:38 pm »
Why not restuff the old capacitor?

Here's an example
 

Online Ian.M

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #4 on: September 25, 2019, 12:56:16 pm »
wrap the modern smaller capacitor in some cardboard or other thick pliable material, optionally secure with double sided tape  :box:
*DONT* do that if the capacitor carries any significant ripple current!
From a cooling point of view, I'm not even too happy about the O.P's plastic sleeve idea.

Edit: Macbeth beat me to it: Antique radio restorers commonly 'restuff' caps, replacing the guts with a whole new capacitor to maintain an authentic period appearance.   That may be the easiest approach if the cap doesn't carry enough ripple current for self-heating to be an issue.

@NY2KW: Please post a photo of the clamping arrangement.

 
 

Offline SMTech

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #5 on: September 25, 2019, 01:37:43 pm »
wrap the modern smaller capacitor in some cardboard or other thick pliable material, optionally secure with double sided tape  :box:
*DONT* do that if the capacitor carries any significant ripple current!
From a cooling point of view, I'm not even too happy about the O.P's plastic sleeve idea.

Edit: Macbeth beat me to it: Antique radio restorers commonly 'restuff' caps, replacing the guts with a whole new capacitor to maintain an authentic period appearance.   That may be the easiest approach if the cap doesn't carry enough ripple current for self-heating to be an issue.

@NY2KW: Please post a photo of the clamping arrangement.

Very true, but something that crude but less insulating could work as could any number of pipe or capacitor brackets depending on how it fits/where it is.
 

Offline NY2KW

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #6 on: September 25, 2019, 02:14:55 pm »
Thank you to all for the advice.  The operating voltage is 14.5vdc with a specified ripple no more than 1vdc but the maximum current draw at peaks is 30A.  I have to rethink this in terms of heat dissipation.  I have attached a picture so you can get an idea of the lack of room to maneuver.  The cap has to be reasonably secured so that when the radio is place upside down or on its side for servicing/tune-ups the cap can't just wobble around... don't want the top terminals coming into contact with the radio cover, etc.  There is a bottom clamp around the base of the cap - maybe 3/8" high strap so not for heat dissipation. 
As you can see there is also an aluminum ground strap (0.5"w x 4" h ) that comes up vertically and at the top has a small horizontal tab that gets screwed to the (-) cap terminal.  This ground bar appears welded to the chassis and there is just no room to get in there to shorten it and re fabricate that horizontal tab.  But your comments made me think of a simpler solution.  I need a 3" cylinder (wood would work as well) to up the difference in height between old cap and new cap and then I can place the new cap off-centered on top and the ground strap when screwed down should hold the cap in place fairly still allowing for air circulation.

Jerry
 

Offline sokoloff

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #7 on: September 25, 2019, 02:48:59 pm »
Many 3D printer hobbyists would do that for cheap. I think turning one out of wood would also be a fast (and cheap) operation as well.

Finding one local to you is probably the best plan, mostly because it's quite possible that your rev 1.0 isn't going to be the final part.
 

Online Ian.M

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #8 on: September 25, 2019, 02:56:28 pm »
@NY2KW (Jerry): You failed to attach the picture!   :'(

Its going to be difficult and expensive to find a modern cap that will be happy long-term with approx 17A RMS ripple current. 

You may well be better off building an assembly of smaller caps in parallel to improve the surface area to dissipation ratio, reducing their internal temperature, even though it will vastly complicate designing a compatible mounting solution.
« Last Edit: September 25, 2019, 03:01:26 pm by Ian.M »
 

Online Kjelt

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #9 on: September 25, 2019, 03:04:52 pm »
Look for a hobbyist with a cnc lathe around your vicinity.
They usual hang out in these kind of forums.
Sometimes they just ask the price for the material and a six-pack for the trouble, esp. when it is a quick one time thing.

https://www.cnczone.com/forums/usa-rfq-s/
 

Offline NY2KW

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #10 on: September 25, 2019, 04:06:13 pm »
Here's a picture
 

Offline Kilrah

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #11 on: September 25, 2019, 04:45:55 pm »
What services did you get 3D print quotes from?? Those prices sound like engineering grade SLS, not common hobby level FDM that would be more than enough. You can buy 2 printers for that price and print it yourself....
« Last Edit: September 25, 2019, 04:48:06 pm by Kilrah »
 

Offline ebclr

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #12 on: September 25, 2019, 08:47:02 pm »
It'very cheap to have 3d printer parts, you can easily find something between 20 to 60 Buck per a cigar packet size print ( this is a big generalization ), But you need to make a model first , and upload the STL file to get a quote, have at many services that do that on the internet, especially in USA and China.  One thing you must consider is 3D printer is plastic, don't expect a huge mechanical strength
 

Offline NY2KW

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #13 on: September 26, 2019, 03:16:54 am »
Can you recommend some "hobby" grade 3D printing companies?
 

Offline ebclr

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #14 on: September 26, 2019, 06:57:11 am »
Here you have a 3dprinter service price comparator

https://www.craftcloud3d.com/

Just upload your files, and see which one is better for you
 

Offline Nusa

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #15 on: September 26, 2019, 09:34:40 am »
I do have a 3-d printer, but if re-stuffing a real cap casing isn't an option, this sounds easier to just fabricate.

I'd probably run down to the hardware store and look at plastic pipe options for a starting point. I'm thinking a 2.5" schedule 40 pipe (OD is larger than nominal ID) might be about right. Or a 2.5" coupler, which in that size should be long enough and a bit larger than the pipe. Then cut to length if required and figure out what to glue on the ends to make it look right.
 

Online No.Mad

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Re: Need to CNC or 3D Print an object about 3" x 2" - EXPENSIVE
« Reply #16 on: September 26, 2019, 11:42:41 am »
Can you recommend some "hobby" grade 3D printing companies?

I am not a company, but ping me a PM and we could sort it out somehow ;)
 


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