Working on a custom Shapeoko 2

discussion of design changes / improvements / suggestions
Woodworker
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Re: Working on a custom Shapeoko 2

Post by Woodworker » Tue Jul 01, 2014 11:34 pm

Here is a voltage drop calculator. Appears if you draw 2.5 amps at 10' the drop is .5 with 20 gauge wire. Industry standard appears to be 10% so you would be well within limits.

http://www.supercircuits.com/resources/ ... calculator
BRuce - SO2 #4798 - IC's Z axis upgrade, customized Z rail and Z motor mount, spindle Dewalt 611

cvoinescu
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Re: Working on a custom Shapeoko 2

Post by cvoinescu » Wed Jul 02, 2014 12:45 am

10% of what? The voltage drop on a 2.5 A NEMA17 motor is around 3 V; that's why I'm saying that 0.5 V is a significant drop.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

Woodworker
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Re: Working on a custom Shapeoko 2

Post by Woodworker » Wed Jul 02, 2014 1:09 am

Not sure I understand your question. Supply wires have voltage drop, not motors. 10% of the supply voltage is what the recommends.
BRuce - SO2 #4798 - IC's Z axis upgrade, customized Z rail and Z motor mount, spindle Dewalt 611

cvoinescu
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Re: Working on a custom Shapeoko 2

Post by cvoinescu » Wed Jul 02, 2014 1:30 am

Agree: the supply here is the driver, and the load is the motor. The driver is, effectively, a switched-mode power supply that feeds 2.5 A at 3 V into the motor. Do you want to drop 0.5 V of that? It will work, because the driver is current-regulated, not voltage-regulated, but the MOSFETs will have to be on longer, dissipating more heat -- which is already a problem in many cases.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

Woodworker
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Re: Working on a custom Shapeoko 2

Post by Woodworker » Wed Jul 02, 2014 2:25 am

I'm confused, why is there a 24VDC power supply for a 3 volt motor? Using 18 gauge the drop is .32, only .18 volt difference. I will have to study the stepper motors and drivers more. My background is standard AC motors.
BRuce - SO2 #4798 - IC's Z axis upgrade, customized Z rail and Z motor mount, spindle Dewalt 611

cvoinescu
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Re: Working on a custom Shapeoko 2

Post by cvoinescu » Wed Jul 02, 2014 9:22 am

The driver acts as two buck power supplies, one for each motor coil (well, more complex than that because they have H-bridges, so they can reverse polarity, but that's besides the point). Such a supply takes a relatively high voltage at a low current, and, by chopping it (turning a switching element on an off very quickly) and using an energy storage element (normally a coil, but the motor's own coils do the job in this case), it turns it into a higher current at a lower voltage.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

eldad87
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Re: Working on a custom Shapeoko 2

Post by eldad87 » Fri Jul 11, 2014 9:51 pm

Hey LouisV,
Thank you for a great thread! the images and videos were very impressive.
I'm new to this field, and I'm looking for a mid-range CNC machine (just like you) and I wonder if you can share the part list of your modifications.

Thanks!

chmedly
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Re: Working on a custom Shapeoko 2

Post by chmedly » Tue Sep 02, 2014 4:40 pm

Hi LouisV and all,

I've been thinking through some design ideas for a 5'x5' model (so I can cut baltic birch in it's native size) but something tells me I should build a smaller one first to work out some concepts before attempting the big boy. I have had several somewhat novel ideas (I think) about how to do the big model but several of those ideas need to proven out in some manner before making a mess out of a bunch of wood and metal. Also, there is a chance that a small unit might be what I really need. So, I'm planning to put together a mostly stock Shapeoko 2 but with 2 important changes: a 16" x 24" cutting area, an 800W frequency control spindle. I'm fine with the X axis being the short one which means the gantry is "safer". That said I do want to make it decently strong to begin with. LouisV, the machine you've written about in this thread (soon to be your old machine) is pretty close as far as actual parts to what I'm envisioning so I've got a few questions. Anyone else please feel free to chime in as well. I'm definitely looking for ideas.

One of the concepts for the heavier duty gantry was putting an extra piece of extrusion between the 2 pieces of makerslide. What extrusion did you use? What motor mount plates did you use? I see that Inventables has part number 26029-01 "Upgraded Shapeoko Motor Mount" plates. Are these compatible with this concept? Did you have to drill extra holes in the plates to make this work?


Thanks!

LouisV
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Re: Working on a custom Shapeoko 2

Post by LouisV » Tue Sep 02, 2014 4:56 pm

chmedly wrote: One of the concepts for the heavier duty gantry was putting an extra piece of extrusion between the 2 pieces of makerslide. What extrusion did you use? What motor mount plates did you use? I see that Inventables has part number 26029-01 "Upgraded Shapeoko Motor Mount" plates. Are these compatible with this concept? Did you have to drill extra holes in the plates to make this work?


Thanks!
Hey there. I haven't seen this thread in a while lol.

Anyway, I used a 2040 extrusion to put in-between the 2 pieces of makerslide. I used the stock Shapeoko 2 motor plates. The upgraded Shapeoko Motor Mount plates are identical to the stock Shapeoko 2 plates so yes those plates at Inventables are compatible. I did not have to drill extra holes in the plate, but I did have to buy longer screws and spacers to accommodate the thicker gantry. I believe I bought 90mm long M5 socket head cap screws and two 1" and one 7/8" aluminum spacer for each screw.

chmedly
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Re: Working on a custom Shapeoko 2

Post by chmedly » Tue Sep 02, 2014 5:44 pm

It sounds like you're saying that the motor plates (on each end of the gantry) where designed with the 2040 sandwich in mind.

When you say 2040 extrusion, was that a piece from misumi or from somewhere else? I'm wondering if there is enough room to use a domestic sized piece of rectangle aluminum tubing instead of fancy extrusion. It might be easier to drill... But I'm still not clear on how those pieces all line up since I don't have them in hand.

Also, if you were to do it over again, would you use the openbuild v-wheels instead of the Inventables? Do they really seem any better?

Lastly, am I asking for trouble if I go with a Nema 17 motor on the Z axis? It seems that Inventables doesn't have Nema 23 motor mount plates for the Z axis at the moment.

Thanks!

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