Open Source Rotary Attachment

Bearings/Motors/Belts/Gears/Etc.

Re: Open Source Rotary Attachment

Postby lasersafe1 » Fri Dec 31, 2010 3:01 pm

I didn't think about the image stretching. I just engraved an apple and it seemed to work fine. Now that I think about it, If I were engraving a basketball it would indeed be a different story, but then again the basketball wouldn't fit. I think my unit was optimized for wine glasses and mugs. After all it was designed for commercial use by trophy and engraving companies.

Why not take the first design and introduce some rubber pads on the interior face of the first set of wheels. That way it could perform both functions. :P
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Re: Open Source Rotary Attachment

Postby trwalters001 » Fri Dec 31, 2010 4:01 pm

I hate it when I'm an idiot...
:lol:
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Re: Open Source Rotary Attachment

Postby macona » Fri Dec 31, 2010 9:18 pm

trwalters001 wrote:The "height adjustment" end of the fixture slides along the rail (I think.)

It seems that we'd need some way to adjust the spacing between the wheels too.

.


An option for making the jack side of the rotary is using a lab jack. You can get them in all sorts of sizes and will save a lot of time vs building one yourself:

http://cgi.ebay.com/Lab-Jack-/120660512 ... _500wt_922

The spacing between the wheels does not need to be adjustable.

The advantage of the wheel drive is that it is diameter independent. Since it drives the surface of the work the setting never need to be changed. I have engrave things as small as a cigarette to 8" cardboard tubing with one.
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Re: Open Source Rotary Attachment

Postby trwalters001 » Fri Dec 31, 2010 10:29 pm

I've already got a few different sizes of lab jacks. That's what I was going to use for starters.

So really - the spacing between the wheels needs to be as close as your smallest object. Everything else larger works automatically. Nice!
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Re: Open Source Rotary Attachment

Postby bdring » Fri Dec 31, 2010 11:57 pm

Do you think both wheels of the surface roller version on the stepper end need to be powered? That makes things a little tricker.
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Re: Open Source Rotary Attachment

Postby trwalters001 » Sat Jan 01, 2011 3:25 am

I can't think of a reason to power both of them. One drive wheel and the other is an idler.
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Re: Open Source Rotary Attachment

Postby bdring » Sat Jan 01, 2011 11:02 pm

Here is an el-cheapo solution that gets very close to within 5% of 1000 dpi. This is a $8.00 stock drive pulley with a 3.5mm silicone o-ring. The groove is a little small for 3.5mm but it should hold firm. The beauty of this, is the pulley directly mounts to a 200 pole stepper running at 10 microsteps which is the same as a lot of machines trying to get the 1000 dpi FSE resolution. It is also small diameter which helps on small Z range machines.

79002245.jpg


o-ring_pulley.JPG
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Re: Open Source Rotary Attachment

Postby macona » Sun Jan 02, 2011 4:20 am

All of the ones I have seen drive both wheels. Pretty good reason for this too. There is very little surface in contact. Drive both wheels and you have twice the power being driven to the object being turned. Another thing if you hit a slick spot you still have a drive in contact with the surface.

Its not hard to drive both. Just put a timing pulley on each drive roll. The stepper is to one side.The belt just wraps around both. There is enough contact with the teeth to get more than enough power transferred to the roll. This is how the epilog unit we had work as well as the chinese one.

Another thing is use silicon o-rings. They are much stickier.
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Re: Open Source Rotary Attachment

Postby macona » Thu Feb 24, 2011 6:42 am

Sure, just install a DPDT switch to swap the step/dir lines from your X axis drive to the rotary drive. There is no need for a X axis when running the rotary attachment.
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Re: Open Source Rotary Attachment

Postby twehr » Mon Feb 28, 2011 8:05 pm

bdring wrote:Things with a different diameter will engrave differently unless the software knows about it. Surface length per degree depends on diameter.

The other style does not care about diameter because it uses the surface of the item to drive the motion.


The DSP does know about varying diameters. I have not tried it yet (don't have the rotary attachment yet), but know that when you set up to do rotary work, you have to tell it the diameter of your work piece. So should not be an issue for the v2 DSP (v1.x does not natively do rotary work).
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