plastic shrinkage compensation Q?
Greetings all;
From those of you doing 3d printing, cura, and likely most slicers, has
a setting to scale up the part to compensate for shrinkage on cooling.
Can I ask a question of those trying to do precise work, the factor your
slicer is using for PETG?
With 15 to 16 teeth engaged, I'm beginning to see an accumulating pitch
error between what's carved by a well calibrated milling machine for
wooden threads in hard maple, and the supposedly matching nuts created
by OpenSCAD. Its not huge, and the use of a better compensation factor
in cura could fix it nicely.
It might be possible to calculate if the shrinkage is a linear relation
ship, but such data seems to be had to come by.
Thanks all. Take care & stay well
Cheers, Gene Heskett.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page http://geneslinuxbox.net:6309/
I use a factor of 1.0057 i.e. 0.57% on XY and nothing on Z. It is a value
I measured on a large PLA print on Hydraraptor that uses ball screws, so I
know the axes movements are exact. It seems to be close enough for all
other plastics I have tried.
On Tue, 9 May 2023 at 08:05, gene heskett gheskett@shentel.net wrote:
Greetings all;
From those of you doing 3d printing, cura, and likely most slicers, has
a setting to scale up the part to compensate for shrinkage on cooling.
Can I ask a question of those trying to do precise work, the factor your
slicer is using for PETG?
With 15 to 16 teeth engaged, I'm beginning to see an accumulating pitch
error between what's carved by a well calibrated milling machine for
wooden threads in hard maple, and the supposedly matching nuts created
by OpenSCAD. Its not huge, and the use of a better compensation factor
in cura could fix it nicely.
It might be possible to calculate if the shrinkage is a linear relation
ship, but such data seems to be had to come by.
Thanks all. Take care & stay well
Cheers, Gene Heskett.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page http://geneslinuxbox.net:6309/
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
On 5/9/23 04:16, nop head wrote:
I use a factor of 1.0057 i.e. 0.57% on XY and nothing on Z.
So acc that, I'm overdoing it by about 3x at 100.145. Thanks.
Cheers, Gene Heskett.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page http://geneslinuxbox.net:6309/
If it is a percentage you are under doing it. Expressed as a percentage I
use 100.57. which is nearly 4 times more expansion than 100.145.
As there is a phase transition between molten and solid I don't think
normal thermal coefficients apply.
On Tue, 9 May 2023 at 09:25, gene heskett gheskett@shentel.net wrote:
On 5/9/23 04:16, nop head wrote:
I use a factor of 1.0057 i.e. 0.57% on XY and nothing on Z.
So acc that, I'm overdoing it by about 3x at 100.145. Thanks.
Cheers, Gene Heskett.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page http://geneslinuxbox.net:6309/
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
On 5/9/23 05:57, nop head wrote:
If it is a percentage you are under doing it. Expressed as a percentage I
use 100.57. which is nearly 4 times more expansion than 100.145.
As there is a phase transition between molten and solid I don't think
normal thermal coefficients apply.
Could well be so. What I actually see looks like I'm overdoing it, so
I've a nut pair under construction at 100.135 to see if it fits any
closer. I've also added some stuff that make the tooth shape polygon
numbers more easily visualized, so the next set of nuts I make will have
a slightly more fine-tuned tooth shape. The angles seem exactly correct
so I'm moving points .05mm at a time. Part of the problem is the
availability of cutting tools, they don't make them small enough to
approach what I'm doing with enough DOC to do it, too fragile, so I'm
using a 1/16th" ball nose with a .250" DOC. A bit big to try and cut a
perfectly symmetrical male & female fit with. Tool life with the 1/16 bn
2 flute has been excellent, only broke them with coding mistakes. Like
running into the tailstock while homing. :o(> I'm learning to park the
mill in a safe place when the job is done. Stupidity, hope its not
contagious.
Thanks nop-head, take care & stay well.
Cheers, Gene Heskett.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page http://geneslinuxbox.net:6309/
I calibrate for XY scale by printing a large L shape and measuring the
inside dimension. That is independent of flow rate and backlash, so is
purely contraction and XY motion.
Then if flowrate is calibrated and backlash is negligible then dimensions
are close to spot on.
[image: IMG_20210323_212659826.jpg]
[image: IMG_20210323_212544674.jpg]
On Tue, 9 May 2023 at 16:16, gene heskett gheskett@shentel.net wrote:
On 5/9/23 05:57, nop head wrote:
If it is a percentage you are under doing it. Expressed as a percentage I
use 100.57. which is nearly 4 times more expansion than 100.145.
As there is a phase transition between molten and solid I don't think
normal thermal coefficients apply.
Could well be so. What I actually see looks like I'm overdoing it, so
I've a nut pair under construction at 100.135 to see if it fits any
closer. I've also added some stuff that make the tooth shape polygon
numbers more easily visualized, so the next set of nuts I make will have
a slightly more fine-tuned tooth shape. The angles seem exactly correct
so I'm moving points .05mm at a time. Part of the problem is the
availability of cutting tools, they don't make them small enough to
approach what I'm doing with enough DOC to do it, too fragile, so I'm
using a 1/16th" ball nose with a .250" DOC. A bit big to try and cut a
perfectly symmetrical male & female fit with. Tool life with the 1/16 bn
2 flute has been excellent, only broke them with coding mistakes. Like
running into the tailstock while homing. :o(> I'm learning to park the
mill in a safe place when the job is done. Stupidity, hope its not
contagious.
Thanks nop-head, take care & stay well.
Cheers, Gene Heskett.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page http://geneslinuxbox.net:6309/
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
On 5/9/23 20:42, nop head wrote:
I calibrate for XY scale by printing a large L shape and measuring the
inside dimension. That is independent of flow rate and backlash, so is
purely contraction and XY motion.
Then if flowrate is calibrated and backlash is negligible then dimensions
are close to spot on.
[image: IMG_20210323_212659826.jpg]
[image: IMG_20210323_212544674.jpg]
Those took pretty good, and closer than what I got on the last nut make,
looking thru a strong glass, with the load face of the thread meeting on
an end tooth, the same place 15 teeth down the stick looks like at least
.15mm clearance, so I'm about 35 minutes from done of a remake at
100.135 comp instead of the 100.145 quoted earlier. If the printer is
repeatable, and it has been so far since switching to klipper, it s/b a
better fit.
At some point I'll have to declare its good enough for the girls I've
gone with and place the for sale adv.
Thinking on ways to rig this cheap mill for a tool changer. That would
save me about 1.5 days per screw.
On Tue, 9 May 2023 at 16:16, gene heskett gheskett@shentel.net wrote:
On 5/9/23 05:57, nop head wrote:
If it is a percentage you are under doing it. Expressed as a percentage I
use 100.57. which is nearly 4 times more expansion than 100.145.
As there is a phase transition between molten and solid I don't think
normal thermal coefficients apply.
Could well be so. What I actually see looks like I'm overdoing it, so
I've a nut pair under construction at 100.135 to see if it fits any
closer. I've also added some stuff that make the tooth shape polygon
numbers more easily visualized, so the next set of nuts I make will have
a slightly more fine-tuned tooth shape. The angles seem exactly correct
so I'm moving points .05mm at a time. Part of the problem is the
availability of cutting tools, they don't make them small enough to
approach what I'm doing with enough DOC to do it, too fragile, so I'm
using a 1/16th" ball nose with a .250" DOC. A bit big to try and cut a
perfectly symmetrical male & female fit with. Tool life with the 1/16 bn
2 flute has been excellent, only broke them with coding mistakes. Like
running into the tailstock while homing. :o(> I'm learning to park the
mill in a safe place when the job is done. Stupidity, hope its not
contagious.
Thanks nop-head, take care & stay well.
Cheers, Gene Heskett.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page http://geneslinuxbox.net:6309/
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
Cheers, Gene Heskett.
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page http://geneslinuxbox.net:6309/