// Recesses for nuts

I am designing a part where I need recesses for nuts. So I put in a pair of differences as follows: // Recesses for nuts translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad, h=Nut_High,center = false, $fn=6); translate ([Screw2_X,0,Nut_Offset]) cylinder (r = Nut_Rad, h=Nut_High,center = false, $fn=6); Nut_Rad is defined as 4.5 The actual part is measuring 6.93mm across the flats and 7mm at the corners. My outer dims on the part are perfect, the printer is calibrated. So how do I get these recesses to be 9mm across the flats? -- View this message in context: http://forum.openscad.org/cylinder-radius-problem-tp11703.html Sent from the OpenSCAD mailing list archive at Nabble.com.

// Recesses for nuts
translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad,

On 02/22/2015 11:17 AM, dbvanhorn wrote: > I am designing a part where I need recesses for nuts. > So I put in a pair of differences as follows: > > // Recesses for nuts > translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad, > h=Nut_High,center = false, $fn=6); > translate ([Screw2_X,0,Nut_Offset]) cylinder (r = Nut_Rad, > h=Nut_High,center = false, $fn=6); > > Nut_Rad is defined as 4.5 > > The actual part is measuring 6.93mm across the flats and 7mm at the corners. > My outer dims on the part are perfect, the printer is calibrated. > > So how do I get these recesses to be 9mm across the flats? i'm confused as to what you want. if you want a "nut capture" recess, where it prevents the nut from turning, then the $fn=6 "cylinder" should have a radius of 3.5, as you mentioned it's "measuring 6.93mm across the flats". if you get a perfect print, it would fit. however, the actual size of the nut capture depends upon your printer settings. i've had to add between 0.25mm and 0.5mm (typically) to get stuff to "fit right". but what is really confusing is that you have a hex nut that's 6.93mm across the flats and "7mm at the corners". that's pretty round, imo. are you sure you measured your hex nut correctly? i have a 6/32 (hex) nut i measured. it's 8mm across the flats, and 9mm across the corners. hth yvette

     // Recesses for nuts
translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad,

Divide the a/f radius by cos(30) to get the a/c radius, which is what cylinder takes. On 22 February 2015 at 19:25, Yvette S. Hirth, CCP, CDP <yvette@dbtgroup.com > wrote: > On 02/22/2015 11:17 AM, dbvanhorn wrote: > > I am designing a part where I need recesses for nuts. >> So I put in a pair of differences as follows: >> >> // Recesses for nuts >> translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad, >> h=Nut_High,center = false, $fn=6); >> translate ([Screw2_X,0,Nut_Offset]) cylinder (r = Nut_Rad, >> h=Nut_High,center = false, $fn=6); >> >> Nut_Rad is defined as 4.5 >> >> The actual part is measuring 6.93mm across the flats and 7mm at the >> corners. >> My outer dims on the part are perfect, the printer is calibrated. >> >> So how do I get these recesses to be 9mm across the flats? >> > > i'm confused as to what you want. > > if you want a "nut capture" recess, where it prevents the nut from > turning, then the $fn=6 "cylinder" should have a radius of 3.5, as you > mentioned it's "measuring 6.93mm across the flats". if you get a perfect > print, it would fit. > > however, the actual size of the nut capture depends upon your printer > settings. i've had to add between 0.25mm and 0.5mm (typically) to get > stuff to "fit right". > > but what is really confusing is that you have a hex nut that's 6.93mm > across the flats and "7mm at the corners". that's pretty round, imo. > > are you sure you measured your hex nut correctly? > > i have a 6/32 (hex) nut i measured. it's 8mm across the flats, and 9mm > across the corners. > > hth > yvette > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

When you make a hexagon, the radius is the distance from the center to the corners. To get a hexagon with a specified dimension from the center to the flats (called the apothem), divide your radius by cos(180/6). This works for other polygons too if you change the 6 to whatever $fn value you're using. To get the nut to fit, you'll probably need to add a bit of tolerance as well. On Sunday, February 22, 2015 at 11:17, dbvanhorn wrote: > I am designing a part where I need recesses for nuts. > So I put in a pair of differences as follows: > > // Recesses for nuts > translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad, > h=Nut_High,center = false, $fn=6); > translate ([Screw2_X,0,Nut_Offset]) cylinder (r = Nut_Rad, > h=Nut_High,center = false, $fn=6); > > Nut_Rad is defined as 4.5 > > The actual part is measuring 6.93mm across the flats and 7mm at the corners. > My outer dims on the part are perfect, the printer is calibrated. > > So how do I get these recesses to be 9mm across the flats? > > > > -- > View this message in context: http://forum.openscad.org/cylinder-radius-problem-tp11703.html > Sent from the OpenSCAD mailing list archive at Nabble.com (http://Nabble.com). > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org (mailto:Discuss@lists.openscad.org) > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > >

     // Recesses for nuts
translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad,

That was measuring the printed cavity. The actual part measures 8.48 on the flats and 9.59 on the corners. 8/32 So my confusion is that I thought a six sided cylinder of radius 4.5 would be 9mm diameter either on the flats or across the corners, but it's small on both. On Sun, Feb 22, 2015 at 12:25 PM, Yvette S. Hirth, CCP, CDP < yvette@dbtgroup.com> wrote: > On 02/22/2015 11:17 AM, dbvanhorn wrote: > > I am designing a part where I need recesses for nuts. >> So I put in a pair of differences as follows: >> >> // Recesses for nuts >> translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad, >> h=Nut_High,center = false, $fn=6); >> translate ([Screw2_X,0,Nut_Offset]) cylinder (r = Nut_Rad, >> h=Nut_High,center = false, $fn=6); >> >> Nut_Rad is defined as 4.5 >> >> The actual part is measuring 6.93mm across the flats and 7mm at the >> corners. >> My outer dims on the part are perfect, the printer is calibrated. >> >> So how do I get these recesses to be 9mm across the flats? >> > > i'm confused as to what you want. > > if you want a "nut capture" recess, where it prevents the nut from > turning, then the $fn=6 "cylinder" should have a radius of 3.5, as you > mentioned it's "measuring 6.93mm across the flats". if you get a perfect > print, it would fit. > > however, the actual size of the nut capture depends upon your printer > settings. i've had to add between 0.25mm and 0.5mm (typically) to get > stuff to "fit right". > > but what is really confusing is that you have a hex nut that's 6.93mm > across the flats and "7mm at the corners". that's pretty round, imo. > > are you sure you measured your hex nut correctly? > > i have a 6/32 (hex) nut i measured. it's 8mm across the flats, and 9mm > across the corners. > > hth > yvette > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >

     // Recesses for nuts
translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad,

Did you measure it in software to make sure it is the size you think it is, or just in the print? Your printer may not be as finely calibrated as you think it is. Netfabb basic has a measuring tool that works for this, or you can just place a cube in openscad with the background modifier to compare. On Sunday, February 22, 2015 at 11:34, david vanhorn wrote: > That was measuring the printed cavity. > > The actual part measures 8.48 on the flats and 9.59 on the corners. 8/32 > > So my confusion is that I thought a six sided cylinder of radius 4.5 would be 9mm diameter either on the flats or across the corners, but it's small on both. > > > On Sun, Feb 22, 2015 at 12:25 PM, Yvette S. Hirth, CCP, CDP <yvette@dbtgroup.com (mailto:yvette@dbtgroup.com)> wrote: > > On 02/22/2015 11:17 AM, dbvanhorn wrote: > > > > > I am designing a part where I need recesses for nuts. > > > So I put in a pair of differences as follows: > > > > > > // Recesses for nuts > > > translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad, > > > h=Nut_High,center = false, $fn=6); > > > translate ([Screw2_X,0,Nut_Offset]) cylinder (r = Nut_Rad, > > > h=Nut_High,center = false, $fn=6); > > > > > > Nut_Rad is defined as 4.5 > > > > > > The actual part is measuring 6.93mm across the flats and 7mm at the corners. > > > My outer dims on the part are perfect, the printer is calibrated. > > > > > > So how do I get these recesses to be 9mm across the flats? > > > > i'm confused as to what you want. > > > > if you want a "nut capture" recess, where it prevents the nut from turning, then the $fn=6 "cylinder" should have a radius of 3.5, as you mentioned it's "measuring 6.93mm across the flats". if you get a perfect print, it would fit. > > > > however, the actual size of the nut capture depends upon your printer settings. i've had to add between 0.25mm and 0.5mm (typically) to get stuff to "fit right". > > > > but what is really confusing is that you have a hex nut that's 6.93mm across the flats and "7mm at the corners". that's pretty round, imo. > > > > are you sure you measured your hex nut correctly? > > > > i have a 6/32 (hex) nut i measured. it's 8mm across the flats, and 9mm across the corners. > > > > hth > > yvette > > > > > > _______________________________________________ > > OpenSCAD mailing list > > Discuss@lists.openscad.org (mailto:Discuss@lists.openscad.org) > > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org (mailto:Discuss@lists.openscad.org) > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > >

     // Recesses for nuts
translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad,

The outer dims of the part are 25 x 70 and I measure 25.12 x 70.30 With a little surface roughness on the edges, that's about perfect. My holes for the screws are what they should be, the screws are barely scraping as designed. I suspect there's something I don't know about how cylinders work with low side counts. On Sun, Feb 22, 2015 at 12:39 PM, whosawhatsis <whosawhatsis@gmail.com> wrote: > Did you measure it in software to make sure it is the size you think it > is, or just in the print? Your printer may not be as finely calibrated as > you think it is. > > Netfabb basic has a measuring tool that works for this, or you can just > place a cube in openscad with the background modifier to compare. > > On Sunday, February 22, 2015 at 11:34, david vanhorn wrote: > > That was measuring the printed cavity. > > The actual part measures 8.48 on the flats and 9.59 on the corners. 8/32 > > So my confusion is that I thought a six sided cylinder of radius 4.5 would > be 9mm diameter either on the flats or across the corners, but it's small > on both. > > > On Sun, Feb 22, 2015 at 12:25 PM, Yvette S. Hirth, CCP, CDP < > yvette@dbtgroup.com> wrote: > > On 02/22/2015 11:17 AM, dbvanhorn wrote: > > I am designing a part where I need recesses for nuts. > So I put in a pair of differences as follows: > > // Recesses for nuts > translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad, > h=Nut_High,center = false, $fn=6); > translate ([Screw2_X,0,Nut_Offset]) cylinder (r = Nut_Rad, > h=Nut_High,center = false, $fn=6); > > Nut_Rad is defined as 4.5 > > The actual part is measuring 6.93mm across the flats and 7mm at the > corners. > My outer dims on the part are perfect, the printer is calibrated. > > So how do I get these recesses to be 9mm across the flats? > > > i'm confused as to what you want. > > if you want a "nut capture" recess, where it prevents the nut from > turning, then the $fn=6 "cylinder" should have a radius of 3.5, as you > mentioned it's "measuring 6.93mm across the flats". if you get a perfect > print, it would fit. > > however, the actual size of the nut capture depends upon your printer > settings. i've had to add between 0.25mm and 0.5mm (typically) to get > stuff to "fit right". > > but what is really confusing is that you have a hex nut that's 6.93mm > across the flats and "7mm at the corners". that's pretty round, imo. > > are you sure you measured your hex nut correctly? > > i have a 6/32 (hex) nut i measured. it's 8mm across the flats, and 9mm > across the corners. > > hth > yvette > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > >

     // Recesses for nuts
translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad,

A 3D printed part will always be smaller across corners than the STL file it is printed from because you get a radiused corner rather than an infinitely sharp one. The corner radius depends on the filament width and how much the plastic is stretched. On 22 February 2015 at 19:44, david vanhorn <kc6ete@gmail.com> wrote: > The outer dims of the part are 25 x 70 and I measure 25.12 x 70.30 With > a little surface roughness on the edges, that's about perfect. > > My holes for the screws are what they should be, the screws are barely > scraping as designed. > > I suspect there's something I don't know about how cylinders work with low > side counts. > > > On Sun, Feb 22, 2015 at 12:39 PM, whosawhatsis <whosawhatsis@gmail.com> > wrote: > >> Did you measure it in software to make sure it is the size you think it >> is, or just in the print? Your printer may not be as finely calibrated as >> you think it is. >> >> Netfabb basic has a measuring tool that works for this, or you can just >> place a cube in openscad with the background modifier to compare. >> >> On Sunday, February 22, 2015 at 11:34, david vanhorn wrote: >> >> That was measuring the printed cavity. >> >> The actual part measures 8.48 on the flats and 9.59 on the corners. 8/32 >> >> So my confusion is that I thought a six sided cylinder of radius 4.5 >> would be 9mm diameter either on the flats or across the corners, but it's >> small on both. >> >> >> On Sun, Feb 22, 2015 at 12:25 PM, Yvette S. Hirth, CCP, CDP < >> yvette@dbtgroup.com> wrote: >> >> On 02/22/2015 11:17 AM, dbvanhorn wrote: >> >> I am designing a part where I need recesses for nuts. >> So I put in a pair of differences as follows: >> >> // Recesses for nuts >> translate ([Screw1_X,0,Nut_Offset]) cylinder (r = Nut_Rad, >> h=Nut_High,center = false, $fn=6); >> translate ([Screw2_X,0,Nut_Offset]) cylinder (r = Nut_Rad, >> h=Nut_High,center = false, $fn=6); >> >> Nut_Rad is defined as 4.5 >> >> The actual part is measuring 6.93mm across the flats and 7mm at the >> corners. >> My outer dims on the part are perfect, the printer is calibrated. >> >> So how do I get these recesses to be 9mm across the flats? >> >> >> i'm confused as to what you want. >> >> if you want a "nut capture" recess, where it prevents the nut from >> turning, then the $fn=6 "cylinder" should have a radius of 3.5, as you >> mentioned it's "measuring 6.93mm across the flats". if you get a perfect >> print, it would fit. >> >> however, the actual size of the nut capture depends upon your printer >> settings. i've had to add between 0.25mm and 0.5mm (typically) to get >> stuff to "fit right". >> >> but what is really confusing is that you have a hex nut that's 6.93mm >> across the flats and "7mm at the corners". that's pretty round, imo. >> >> are you sure you measured your hex nut correctly? >> >> i have a 6/32 (hex) nut i measured. it's 8mm across the flats, and 9mm >> across the corners. >> >> hth >> yvette >> >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >> >> >> _______________________________________________ >> OpenSCAD mailing list >> Discuss@lists.openscad.org >> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >> >> > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > >

nophead wrote > Divide the a/f radius by cos(30) to get the a/c radius, which is what > cylinder takes. By a/c I assume you mean "Across the Corners". The thing is, with specifying 4.5 I should have had 9mm across the corners, and it's not even close. -- View this message in context: http://forum.openscad.org/cylinder-radius-problem-tp11703p11711.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Yes a/c is across corners. But as I stated above it will always be too small unless you use an infinitely thin filament to get a sharp corner and measure it with an infinitely thin calliper. The a/f measurement should be correct if you set the radius to it divided by cos(30) if you printer is correctly calibrated. -- View this message in context: http://forum.openscad.org/cylinder-radius-problem-tp11703p11712.html Sent from the OpenSCAD mailing list archive at Nabble.com.