Re: 3D Design Courses and Resources
Thanks, as a retired software guy with no mechanical engineering background, this is really helpful in the places where I need it.
I don’t quite get what you mean in the final paragraph. I can think of a couple of different ways to interpret what you said.
What’s the deal with "PTFE spray”?
-Bob
Tucson, AZ
On Dec 10, 2022, at 06:32, Roger Whiteley via Discuss discuss@lists.openscad.org wrote:
From: Roger Whiteley roger.whiteley@me.com
Subject: [OpenSCAD] Re: 3D Design Courses and Resources
Date: December 10, 2022 at 06:32:54 MST
To: discuss@lists.openscad.org
Reply-To: OpenSCAD general discussion Mailing-list discuss@lists.openscad.org
Leonard
I’ve got a background [degree] in Materials Science, which I hardly ever used in my professional life in computing and IT, from which I have now retired after 42 years. I consider myself an engineer first, programming is just something I do..
The machines I make are handled by people who often have little mechanical sympathy so sometimes they broke things - but three years of making these machines means I have tuned out all the problem areas where ham fisted operation broke parts. Below is what works for us...
3d prints are a bit like wood, strong in compression, not so good at resisting bending unless sized to suit the load, a 7mm thick walled cylinder with four printed walls inside and out is remarkably strong;
Chamfer every edge, it looks nicer and helps to remove any corner ringing..;
Chamfer every hole, for the same reason and it speeds up finishing,;
Use cylinders, not cubes, they are stronger in bending, just like drinking straws / bamboo canes
Lattice structures print faster than cubes if you need height and reach with minimal weight and good stiffness..;
The strength of 3d prints are directional, so design your parts so when you print them the layers are in the direction of greatest load - which of course you can choose when slicing - have a look at CNC Kitchen and Makers Muse on You Tube;
Fabricate big parts from smaller ones fastened together - if you want to take them apart use flanges so that you can put self tapping screws through the mating faces, if permanent is ok, make the parts to slide together - I always deduct a print allowance from the diameter of pegs which fit into properly sized holes - I use 0.3mm for my print allowance - then use a solvent adhesive to weld the parts together;
Depending upon where you are in the world, you should be able to get Plastruct solvent weld - in the UK I use EMA Model Supplies Plastic Weld which works on PLA and PETG. Its way better than superglue as it melts the faces which then dry as a solid one piece;
Avoid sharp corners - use a fillet - round or straight diagonal between faces;
If you need low friction bearing surfaces, there are low friction 3d printing materials available - or I use flanged bearings pressed into my components - or put thrust bearings in where appropriate;
I did design a large diameter thrust bearing using 6mm stainless balls, complete with cage and a means of removing backlash but never used it in a production machine - the central backlash adjust was a 110mm ISO screw thread with a 2mm pitch, low friction materials work better in sliding surface contact at the rotation speeds involved - you can reduce friction considerably by polishing to 2000 grit and using a PTFE spray on the contact surfaces;
To get extra stiffness or bending resistance embed holes in parts through which you can pass a screw / bolt and put a nyloc nut and a load spreading washer underneath the nut face - this helps to overcome the directional weakness along the layers by putting everything into compression - same principle as pre-stressed concrete;
Getting strength in 3D parts -
You can fix a lot of issues at the slicing stage - increasing the number of walls is better [and faster] than increasing infill density, for example If you need to stiffen up a cylinder, hide another smaller cylinder inside using difference, or create a lattice structure which puts more walls than infill into your component - this is the absolute joy of OpenSCAD IMHO - reusable elements, rescaled without having to consider anchor lines or mess about with edges, I’ve tried FreeCAD, hated it, gave up.
Use gyroid infill - I use Cura for slicing and you’ll hardly ever need more than 15%;
Thicker layers are stronger than thin ones, use multiples of the minimum step 0.04 mm - this is a general rule which I avoid because I need parts that look good, so 0.2 mm is just about all I use now - I take the print time hit in preference for appearance;
If you want to use a captive bolt, make a socket for the bolt head and some of the shaft then print a sleeve which holds the bolt head, over the shaft then solvent weld the sleeve and bolt into the socket, I use M5 hex headed bolts with printed hexagonal sockets and either a regular full nut or nyloc according to the application - the embedded bolt is stronger than a 3d printed thread which has a nice stress raiser all the way around it.
if it looks right it generally is..
good luck,
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
You spray it on a surface you want to make slippery. It forms a dry
lubricating film that is water resistant.
On Sat, 10 Dec 2022 at 17:21, Bob Carlson bob@rjcarlson.com wrote:
Thanks, as a retired software guy with no mechanical engineering
background, this is really helpful in the places where I need it.
I don’t quite get what you mean in the final paragraph. I can think of a
couple of different ways to interpret what you said.
What’s the deal with "PTFE spray”?
-Bob
Tucson, AZ
On Dec 10, 2022, at 06:32, Roger Whiteley via Discuss <
discuss@lists.openscad.org> wrote:
*From: *Roger Whiteley roger.whiteley@me.com
*Subject: *[OpenSCAD] Re: 3D Design Courses and Resources
*Date: *December 10, 2022 at 06:32:54 MST
*To: *discuss@lists.openscad.org
*Reply-To: *OpenSCAD general discussion Mailing-list <
discuss@lists.openscad.org>
Leonard
I’ve got a background [degree] in Materials Science, which I hardly ever
used in my professional life in computing and IT, from which I have now
retired after 42 years. I consider myself an engineer first, programming
is just something I do..
The machines I make are handled by people who often have little mechanical
sympathy so sometimes they broke things - but three years of making these
machines means I have tuned out all the problem areas where ham fisted
operation broke parts. Below is what works for us...
3d prints are a bit like wood, strong in compression, not so good at
resisting bending unless sized to suit the load, a 7mm thick walled
cylinder with four printed walls inside and out is remarkably strong;
Chamfer every edge, it looks nicer and helps to remove any corner
ringing..;
Chamfer every hole, for the same reason and it speeds up finishing,;
Use cylinders, not cubes, they are stronger in bending, just like drinking
straws / bamboo canes
Lattice structures print faster than cubes if you need height and reach
with minimal weight and good stiffness..;
The strength of 3d prints are directional, so design your parts so when
you print them the layers are in the direction of greatest load - which of
course you can choose when slicing - have a look at CNC Kitchen and Makers
Muse on You Tube;
Fabricate big parts from smaller ones fastened together - if you want to
take them apart use flanges so that you can put self tapping screws through
the mating faces, if permanent is ok, make the parts to slide together - I
always deduct a print allowance from the diameter of pegs which fit into
properly sized holes - I use 0.3mm for my print allowance - then use a
solvent adhesive to weld the parts together;
Depending upon where you are in the world, you should be able to get
Plastruct solvent weld - in the UK I use EMA Model Supplies Plastic Weld
which works on PLA and PETG. Its way better than superglue as it melts
the faces which then dry as a solid one piece;
Avoid sharp corners - use a fillet - round or straight diagonal between
faces;
If you need low friction bearing surfaces, there are low friction 3d
printing materials available - or I use flanged bearings pressed into my
components - or put thrust bearings in where appropriate;
I did design a large diameter thrust bearing using 6mm stainless balls,
complete with cage and a means of removing backlash but never used it in a
production machine - the central backlash adjust was a 110mm ISO screw
thread with a 2mm pitch, low friction materials work better in sliding
surface contact at the rotation speeds involved - you can reduce friction
considerably by polishing to 2000 grit and using a PTFE spray on the
contact surfaces;
To get extra stiffness or bending resistance embed holes in parts through
which you can pass a screw / bolt and put a nyloc nut and a load spreading
washer underneath the nut face - this helps to overcome the directional
weakness along the layers by putting everything into compression - same
principle as pre-stressed concrete;
Getting strength in 3D parts -
You can fix a lot of issues at the slicing stage - increasing the number
of walls is better [and faster] than increasing infill density, for example
If you need to stiffen up a cylinder, hide another smaller cylinder inside
using difference, or create a lattice structure which puts more walls than
infill into your component - this is the absolute joy of OpenSCAD IMHO -
reusable elements, rescaled without having to consider anchor lines or mess
about with edges, I’ve tried FreeCAD, hated it, gave up.
Use gyroid infill - I use Cura for slicing and you’ll hardly ever need
more than 15%;
Thicker layers are stronger than thin ones, use multiples of the minimum
step 0.04 mm - this is a general rule which I avoid because I need parts
that look good, so 0.2 mm is just about all I use now - I take the print
time hit in preference for appearance;
If you want to use a captive bolt, make a socket for the bolt head and
some of the shaft then print a sleeve which holds the bolt head, over the
shaft then solvent weld the sleeve and bolt into the socket, I use M5 hex
headed bolts with printed hexagonal sockets and either a regular full nut
or nyloc according to the application - the embedded bolt is stronger than
a 3d printed thread which has a nice stress raiser all the way around it.
if it looks right it generally is..
good luck,
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
Roger Whiteley: Thanks! Some really good stuff there!
On Sat, Dec 10, 2022 at 11:27 AM nop head nop.head@gmail.com wrote:
You spray it on a surface you want to make slippery. It forms a dry
lubricating film that is water resistant.
On Sat, 10 Dec 2022 at 17:21, Bob Carlson bob@rjcarlson.com wrote:
Thanks, as a retired software guy with no mechanical engineering
background, this is really helpful in the places where I need it.
I don’t quite get what you mean in the final paragraph. I can think of a
couple of different ways to interpret what you said.
What’s the deal with "PTFE spray”?
-Bob
Tucson, AZ
On Dec 10, 2022, at 06:32, Roger Whiteley via Discuss <
discuss@lists.openscad.org> wrote:
*From: *Roger Whiteley roger.whiteley@me.com
*Subject: *[OpenSCAD] Re: 3D Design Courses and Resources
*Date: *December 10, 2022 at 06:32:54 MST
*To: *discuss@lists.openscad.org
*Reply-To: *OpenSCAD general discussion Mailing-list <
discuss@lists.openscad.org>
Leonard
I’ve got a background [degree] in Materials Science, which I hardly ever
used in my professional life in computing and IT, from which I have now
retired after 42 years. I consider myself an engineer first, programming
is just something I do..
The machines I make are handled by people who often have little
mechanical sympathy so sometimes they broke things - but three years of
making these machines means I have tuned out all the problem areas where
ham fisted operation broke parts. Below is what works for us...
3d prints are a bit like wood, strong in compression, not so good at
resisting bending unless sized to suit the load, a 7mm thick walled
cylinder with four printed walls inside and out is remarkably strong;
Chamfer every edge, it looks nicer and helps to remove any corner
ringing..;
Chamfer every hole, for the same reason and it speeds up finishing,;
Use cylinders, not cubes, they are stronger in bending, just like
drinking straws / bamboo canes
Lattice structures print faster than cubes if you need height and reach
with minimal weight and good stiffness..;
The strength of 3d prints are directional, so design your parts so when
you print them the layers are in the direction of greatest load - which of
course you can choose when slicing - have a look at CNC Kitchen and Makers
Muse on You Tube;
Fabricate big parts from smaller ones fastened together - if you want to
take them apart use flanges so that you can put self tapping screws through
the mating faces, if permanent is ok, make the parts to slide together - I
always deduct a print allowance from the diameter of pegs which fit into
properly sized holes - I use 0.3mm for my print allowance - then use a
solvent adhesive to weld the parts together;
Depending upon where you are in the world, you should be able to get
Plastruct solvent weld - in the UK I use EMA Model Supplies Plastic Weld
which works on PLA and PETG. Its way better than superglue as it melts
the faces which then dry as a solid one piece;
Avoid sharp corners - use a fillet - round or straight diagonal between
faces;
If you need low friction bearing surfaces, there are low friction 3d
printing materials available - or I use flanged bearings pressed into my
components - or put thrust bearings in where appropriate;
I did design a large diameter thrust bearing using 6mm stainless balls,
complete with cage and a means of removing backlash but never used it in a
production machine - the central backlash adjust was a 110mm ISO screw
thread with a 2mm pitch, low friction materials work better in sliding
surface contact at the rotation speeds involved - you can reduce friction
considerably by polishing to 2000 grit and using a PTFE spray on the
contact surfaces;
To get extra stiffness or bending resistance embed holes in parts through
which you can pass a screw / bolt and put a nyloc nut and a load spreading
washer underneath the nut face - this helps to overcome the directional
weakness along the layers by putting everything into compression - same
principle as pre-stressed concrete;
Getting strength in 3D parts -
You can fix a lot of issues at the slicing stage - increasing the number
of walls is better [and faster] than increasing infill density, for example
If you need to stiffen up a cylinder, hide another smaller cylinder inside
using difference, or create a lattice structure which puts more walls than
infill into your component - this is the absolute joy of OpenSCAD IMHO -
reusable elements, rescaled without having to consider anchor lines or mess
about with edges, I’ve tried FreeCAD, hated it, gave up.
Use gyroid infill - I use Cura for slicing and you’ll hardly ever need
more than 15%;
Thicker layers are stronger than thin ones, use multiples of the minimum
step 0.04 mm - this is a general rule which I avoid because I need parts
that look good, so 0.2 mm is just about all I use now - I take the print
time hit in preference for appearance;
If you want to use a captive bolt, make a socket for the bolt head and
some of the shaft then print a sleeve which holds the bolt head, over the
shaft then solvent weld the sleeve and bolt into the socket, I use M5 hex
headed bolts with printed hexagonal sockets and either a regular full nut
or nyloc according to the application - the embedded bolt is stronger than
a 3d printed thread which has a nice stress raiser all the way around it.
if it looks right it generally is..
good luck,
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
OpenSCAD mailing list
To unsubscribe send an email to discuss-leave@lists.openscad.org
PTFE = Poly Tetra Fluoro Ethylene aka "teflon"
On Sat, Dec 10, 2022 at 12:20 PM Bob Carlson bob@rjcarlson.com wrote:
Thanks, as a retired software guy with no mechanical engineering
background, this is really helpful in the places where I need it.
I don’t quite get what you mean in the final paragraph. I can think of a
couple of different ways to interpret what you said.
What’s the deal with "PTFE spray”?
-Bob
Tucson, AZ
On Dec 10, 2022, at 06:32, Roger Whiteley via Discuss <
discuss@lists.openscad.org> wrote:
*From: *Roger Whiteley roger.whiteley@me.com
*Subject: *[OpenSCAD] Re: 3D Design Courses and Resources
*Date: *December 10, 2022 at 06:32:54 MST
*To: *discuss@lists.openscad.org
*Reply-To: *OpenSCAD general discussion Mailing-list <
discuss@lists.openscad.org>
Leonard
I’ve got a background [degree] in Materials Science, which I hardly ever
used in my professional life in computing and IT, from which I have now
retired after 42 years. I consider myself an engineer first, programming
is just something I do..
The machines I make are handled by people who often have little mechanical
sympathy so sometimes they broke things - but three years of making these
machines means I have tuned out all the problem areas where ham fisted
operation broke parts. Below is what works for us...
3d prints are a bit like wood, strong in compression, not so good at
resisting bending unless sized to suit the load, a 7mm thick walled
cylinder with four printed walls inside and out is remarkably strong;
Chamfer every edge, it looks nicer and helps to remove any corner
ringing..;
Chamfer every hole, for the same reason and it speeds up finishing,;
Use cylinders, not cubes, they are stronger in bending, just like drinking
straws / bamboo canes
Lattice structures print faster than cubes if you need height and reach
with minimal weight and good stiffness..;
The strength of 3d prints are directional, so design your parts so when
you print them the layers are in the direction of greatest load - which of
course you can choose when slicing - have a look at CNC Kitchen and Makers
Muse on You Tube;
Fabricate big parts from smaller ones fastened together - if you want to
take them apart use flanges so that you can put self tapping screws through
the mating faces, if permanent is ok, make the parts to slide together - I
always deduct a print allowance from the diameter of pegs which fit into
properly sized holes - I use 0.3mm for my print allowance - then use a
solvent adhesive to weld the parts together;
Depending upon where you are in the world, you should be able to get
Plastruct solvent weld - in the UK I use EMA Model Supplies Plastic Weld
which works on PLA and PETG. Its way better than superglue as it melts
the faces which then dry as a solid one piece;
Avoid sharp corners - use a fillet - round or straight diagonal between
faces;
If you need low friction bearing surfaces, there are low friction 3d
printing materials available - or I use flanged bearings pressed into my
components - or put thrust bearings in where appropriate;
I did design a large diameter thrust bearing using 6mm stainless balls,
complete with cage and a means of removing backlash but never used it in a
production machine - the central backlash adjust was a 110mm ISO screw
thread with a 2mm pitch, low friction materials work better in sliding
surface contact at the rotation speeds involved - you can reduce friction
considerably by polishing to 2000 grit and using a PTFE spray on the
contact surfaces;
To get extra stiffness or bending resistance embed holes in parts through
which you can pass a screw / bolt and put a nyloc nut and a load spreading
washer underneath the nut face - this helps to overcome the directional
weakness along the layers by putting everything into compression - same
principle as pre-stressed concrete;
Getting strength in 3D parts -
You can fix a lot of issues at the slicing stage - increasing the number
of walls is better [and faster] than increasing infill density, for example
If you need to stiffen up a cylinder, hide another smaller cylinder inside
using difference, or create a lattice structure which puts more walls than
infill into your component - this is the absolute joy of OpenSCAD IMHO -
reusable elements, rescaled without having to consider anchor lines or mess
about with edges, I’ve tried FreeCAD, hated it, gave up.
Use gyroid infill - I use Cura for slicing and you’ll hardly ever need
more than 15%;
Thicker layers are stronger than thin ones, use multiples of the minimum
step 0.04 mm - this is a general rule which I avoid because I need parts
that look good, so 0.2 mm is just about all I use now - I take the print
time hit in preference for appearance;
If you want to use a captive bolt, make a socket for the bolt head and
some of the shaft then print a sleeve which holds the bolt head, over the
shaft then solvent weld the sleeve and bolt into the socket, I use M5 hex
headed bolts with printed hexagonal sockets and either a regular full nut
or nyloc according to the application - the embedded bolt is stronger than
a 3d printed thread which has a nice stress raiser all the way around it.
if it looks right it generally is..
good luck,
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