CAD 3D PRINTING MODEL MAKING

Have any questions or tips and advice on how to build those bits that don't come ready made.
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TimberSurf
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Re: CAD 3D PRINTING MODEL MAKING

Postby TimberSurf » Sun Jan 15, 2017 12:52 pm

Have you tried Acetone vapour smoothing?
https://www.youtube.com/watch?v=9qByAGrbmS8
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timbologist
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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Sun Jan 15, 2017 11:18 pm

Hi
No I have not tried acetoning, as most of the items I make would have all the detail removed, as the acetone softens the skin of the item and lets it flow so the highs sink into the lows and the detail would just disappear.
Tony

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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Wed Feb 22, 2017 7:45 am

Hi all.

After discussions on my other thread about 3D printing thought it was about time to put a bit more here. One of the points made was about accuracy, but in actual fact they were talking about the surface finish of the parts they had looked at, which in there opinion was not good enough for what they were wanting to do. When questioned about actual figures for the printers set up. They had no idea.

But first I'll talk about the different type of printers and some of the things to be aware of if you are going to by a printer.

There are 3 main configurations the standard X,Y,Z printer like the one in photo 1 and 2 which is my Ordbot Hadron, which I use for my finer work.

There are 2 types of set up in this Type of printer.
The first is the head moves in the X an Y and the bed rises and falls for the Z axis. Some of the printers use a cantilevered bed, the drive screw and the rails are at the back and there is no support at the front, The front therefore has movement, ( my first printer was of this configuration, Bad move on my part :oops: ).

The second type is like my Ordbot Hadron the head moves in the X and the Z these have 2 screws on the Z axis. And the bed moves in the Y axis, the bed moves back and forth on rails or rods, A lot more ridged construction.


The next 2 configurations I don't know much about them, they are less common than the above type.

The second configuration is the CoreXY with these the head moves in the X and Y and The bed moves in the Z direction, These are very ridged type of printer but the X,Y movement is a bit complex because of the way the stepper work together to get the X and Y movement. And the bed is usually supported and lifted by screws on each corner.

The third configuration is the Delta which has 3 arms that provide the Y,X,Z movement, and the table stays stationary

That will do for today next will talk about the control electronics
Don't forget to ask questions.

Timbologist
Yeah I know it's a mess Mr hart :)
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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Thu Feb 23, 2017 7:59 am

Hello again

Changed the topic slightly, will talk about propriety and open source printers.

The propriety printers can be a real pain in the bit you sit on, if you are like me and want to fiddle.
Some of the propriety printers you can only use there filament which is sold at ridiculously inflated prices as compared to the open market filament.

They have there own software for slicing the models to make ready for printing, and can only be driven with the printer connected to the computer with there software, cannot be used without the computer, ( no sd slot.)
A friend bought one of these type of printers for his business does nice prints, but cannot change much, and need to buy there filament, ( tax deductible wink: :) ) so not a problem written of over x years.

You are stuck with what you bought no upgrades or interchangeable parts, there is nothing wrong with this if you just want to print the odd thing and just want something you take out of the box and it just works.

If the electronics lets the smoke out you cannot put it back in you have to buy a new controller board at inflated prices, And in some cases they won't sell you the board but they have to install it as well at inflated prices.

The first printer I bought was a Flashforge Creator as bought shown in first picture the rest show now, not pretty but does exactly as I want.

This had a controller that was based on Makerbots controller it used .x3g files and not Gcode and trying to change the hardware was nearly impossible. So was not long before I removed that and put in the open source Arduino Mega Ramps set-up. The slicer software you could use the open source ReplicatorG which works quite well.
So my printer now only has one extruder and that is a wades type which is a geared extruder where the original was a direct drive, Will go into the why I did this in a later post when I start crunching numbers.

Personally I prefer the open source printers as you are in total control of how your printer is and what it can do,
fix any short comings, change anything at will.

As far as performance goes with today's generation of printers there is not much difference between the 2 types when properly set up with the same settings.

Next time will recap some bits from earlier posts before I start throwing numbers around

Timbologist

P.S And If I don't explain something clearly enough please ask for clarification of what I have said.
FLASHFORGE-CREATOR.jpeg
ORIGINAL FLASHFORGE
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FLASHFORGE IN CURRENT STATE OVERALL
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WADES EXTRUDER
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P2230047.JPG
ARDUINO RAMPS CONTROLLER
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Re: CAD 3D PRINTING MODEL MAKING

Postby End2end » Thu Feb 23, 2017 10:51 pm

Watching with interest Timbologist but can I "be a real pain in the bit you sit on" :lol: and ask If you could add any links you think would be useful for your preferred items for us to look at.
Thanks
End2end
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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Fri Feb 24, 2017 4:03 am

End2end wrote:and ask If you could add any links you think would be useful for your preferred items for us to look at.
Thanks
End2end


Not sure what you want to look at, but will put some links I think could help a bit and backup some of the things I have and will mention.
The fine print is that I don't have any association with these sites and I am not approving or disapproving the products on these links

In the previous post I mentioned a friend with a proprietary printer this is the link to there range of printers The one I have used have 4 years old.
http://www.up3dusa.com/

This Link is about the mechanical side of the Ordbot Hadron that I use for fine work. There is also about the electronics here as well, I use the Arduino Ramps on my 3 printers
http://www.buildlog.net/wiki/doku.php?id=ord_bot:the_ord_bot

A bit about the wades extruder.
http://www.reprap.org/wiki/Wade%27s_Geared_Extruder

The different open source 3D printers you can make< plus a wealth of information on 3D printing.
http://www.reprap.org/wiki/RepRap_Machines

And this will be my next printer if I decide to build another one, is multifunctional which would be ideal for me :)
http://www.reprap.org/wiki/Cartesio

Hope this is useful to you, and does not confuse the issue.

Timbologist

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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Fri Feb 24, 2017 6:52 am

So recapping from a previous post. ( had to plagiarise my own work :) )

I will try to explain a bit about what is going on as the model is printed.
In earlier posts I explained the basic parts of the printer head, cold end and hot end.
extrusions.jpg
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Now looking at what is happening at the nozzle the above Pic shows roughly what you would get if I set the printer with extrusion width of 0.2 mm ( nozzle dia ) and layer heights of left 0.2 mm, middle 0.1 mm and right first 5 layers at 0.1mm and the last 5 at 0.05 mm. The blue section is the infill which can be set at various angle but is the same height as the outer layer. you can also change the extrusion width to be wider or narrower than the nozzle dia but there are limits on going narrower as its like stretching chewing gum gets to a point and you have no control as to what happens.

There is a limit of the minimum layer height, which is a ratio of the thickness of the extrusion x the layer height to the diameter of the filament that is being used. This is also influenced by the number of steps/mm of the extruder.

So even with the finest settings depending on what the item is to be used for you may have to manually clean up the item. Treating the surface with Acetone smooths the outer surface, but at the cost of detail and sizes.

One thing that needs to be taken into consideration when printing items that have to have some mechanical strength is how you slice the model and the direction of the layers.

It ends up a bit like a phone book, you can't tear across the pages but you can force the pages open. 3D printing
is the same, if the forces are high enough the item will separate between layers. This is because the current layer is at 220 deg C and the previous layer is down to 90 deg C ( this is in my case with bed at 90 and filament at 220). This can be minimised by printing at slower speeds so the previous layer has a longer time to melt and combine with the new layer, So comes down to time vs quality which means cost.

Different materials will give different results as will different settings so good records need to be kept, so you can get repeatability, so you need to experiment to get the desired results.

Next time will do some number crunching so get your crash hats ready :wink: .

This shall do for now

Timbologist

And If I don't explain something clearly enough please ask for clarification of what I have said.

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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Sat Feb 25, 2017 7:38 am

Hi all

Ready for some number crunching, got those helmets on :)

For all the calculations I'll use my second printer The Ordbot Hadron which I currently use for my fine work.

So I'll start with the easy numbers X,Y,Z positioning and accuracy

AXIS STEPS PER UNIT
The stepper motor receives step by step moving command from the controller. The controller needs to know the steps/mm ratio to send the appropriate steps to reach the required distance. How many steps are needed to move an axis by 1 mm?

X AND Y AXIS BELTS AND PULLEYS

steps_per_mm = (motor_steps_per_rev * driver_microstep) /(belt_pitch * pulley_number_of_teeth)
On the OrdBot X and Y movement is by a Nema 17 Stepper motor with 200 steps/revolution or 1.8 deg/step, this drives a GT2 toothed belt 2 means the tooth pitch is 2mm, the driver is set for 16 microsteps
therefore
steps_per_mm = ((360/1.8 ) * (16) / ( 2 * 18 )) * 0.90183505855403442555576411741336
(200 * 16 / 36) * 0.90183505855403442555576411741336
(3200/36) * 0.90183505855403442555576411741336
88.888888889 * 0.90183505855403442555576411741336
steps_per_mm = 80.163116316
so 1/80.163116316
0.012474565
therefore the resolution in the X and Y axis is 0.012474565 mm per step or 0.000491125 inches per step
I can live with that

Z AXIS LEAD SCREW

steps_per_mm = (motor_steps_per_rev * driver_microstep) / thread_pitch
On the OrdBot Z movement is by a pair of Nema 17 Stepper motors with 200 steps/revolution or 1.8 deg/step, this drives a 1.25mm pitch lead screw the driver is set for 16 microsteps

steps_per_mm = ((360/1.8 ) * (16) / 1.25)
(200 * 16 / 1.25)
(3200/36)
steps_per_mm = 2560
so 1/2560
=0.000390625

therefore the resolution in the Z axis is 0.000390625 mm per step or 0.000015379 inches per step
I can live with that.

Depending on the brand and style of printer these values will vary up or down.
As far as repeatability goes if the printer is set up correctly with the slides nice and free and the stepper drivers set properly the printer should always maintain its repeatability and accuracy. The main cause of this not happening is missing steps caused by the before mentioned problems.

That's enough brain food for today.

Timbologist

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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Sun Feb 26, 2017 12:05 am

A short addition to last post.
In the area of positioning and accuracy there is probably not much difference between the open source and the proprietary printers as they are virtually all using the same mechanical components to drive the printer.

To achieve more accuracy on the open source printers you can change the stepper motors from a 200/1.8 degree to a 400/0.9 degree which would give you twice the steps and twice the accuracy.

Or you can change the stepper driver from a A4988 which has 16 microsteps to a DRV8825 which has 32 microsteps so again you double the accuracy.

if you combine both you get 4 times the accuracy, which is a bit insane really :shock:

Timbologist

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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Sun Feb 26, 2017 7:06 am

Hi all you still with me

Today we shall look at the extruder, this is where it can all go pear shaped and you don't know why!

The amount of plastic out is a ratio of the plastic in 1:1 pretty basic isn't it, BUT!!!!

The filament in in my case is a nominal diameter of 1.75mm so for ease of explanation shall use 1.75mm.
The area of the filament is pi x r squared
therefore
area = 3.14159 x (1.75/2)x(1.75/2)
3.14159 x 0.875x 0.875
3.14159 x 0.765625
2.405281875 square mm

My nozzle is 0.2mm diameter.
Most printers have a nozzle of 0.5mm diameter some have 0.4mm diameter.
So I will work out the area's of the 3 nozzles, so we can later compare actual extrusion figures.

Firstly the 0.2mm nozzle.
area = 3.14159 x (0.2/2)x(0.2/2)
3.14159 x 0.1x 0.1
3.14159 x 0.01
0.031415927 square mm

Now the 0.4mm nozzle.
area = 3.14159 x (0.4/2)x(0.4/2)
3.14159 x 0.1x 0.1
3.14159 x 0.04
0.125663706 square mm

Now the 0.5mm nozzle.
area = 3.14159 x (0.5/2)x(0.5/2)
3.14159 x 0.25x 0.25
3.14159 x 0.0625
0.196349541 square mm

So what does this all mean you are probably wondering.

This is backwards to what actually happens we will look at what we put in and see what we get out, in all cases I will feed into the extruder a length of 10mm of filament. The volume of this 10mm of filament is area x length

volume = 2.405281875 square mm x 10mm
24.05281875 cubic mm

Firstly the 0.2mm nozzle.

Length = volume / area ( volume of filament feed into extruder by area of the nozzle )
24.05281875 cubic mm / 0.031415927 square mm
= 765.624988561mm long so we end up with this length of 0.2mm string.

Now the 0.4mm nozzle.

Length = volume / area ( volume of filament feed into extruder by area of the nozzle )
24.05281875 cubic mm / 0.125663706 square mm
= 191.406250187mm long so we end up with this length of 0.4mm string.

Now the 0.5mm nozzle.

Length = volume / area ( volume of filament feed into extruder by area of the nozzle )
24.05281875 cubic mm / 0.196349541 square mm
= 122.499999885mm long so we end up with this length of 0.5mm string.

Summary of above.

So 10mm of 1.75mm filament gives
0.2 nozzle = 765.624988561mm long
0.4 nozzle = 191.406250187mm long
0.5 nozzle = 122.499999885mm long

You are probably still wondering what is he going on about, but to understand what is really going on I needed to explain it this way.

But this is all I shall write this time, next time will get right into the extruder and squirting plastic.

Good to see everybody is understanding me so far as I have had no questions.

Timbologist

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Re: CAD 3D PRINTING MODEL MAKING

Postby TimberSurf » Sun Feb 26, 2017 8:33 am

You have Elsie's undivided attention!

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Please continue, we are listening for each instalment avidly!
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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Sun Feb 26, 2017 9:55 am

At least I know there are 2 people out there scratching there heads over what I am writing. :wink:

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Re: CAD 3D PRINTING MODEL MAKING

Postby ElDavo » Sun Feb 26, 2017 4:15 pm

Lots of interesting numbers but why would anyone want to know this level of detail. I would have thought it was largely irrelevant unless you are building a printer. Using a particular printer you only need the specs of that printer surely?

Cheers
Dave

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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Mon Feb 27, 2017 7:23 am

ElDavo wrote:Lots of interesting numbers but why would anyone want to know this level of detail. I would have thought it was largely irrelevant unless you are building a printer. Using a particular printer you only need the specs of that printer surely?

Cheers
Dave

Interesting point, A lot of people no nothing about 3D printing, and want to know the differences between them, Sales people will spin you a yarn on what is the best in there opinion, may throw some numbers at you. And all sorts of other guff.
At least with what I have written here,it may give you a better understanding of what is actually happening, and a better decision on a printer purchase whether it be build your own or proprietary can be made.
If you know there limitations you won't buy something then find it can't do what you want, and you are stuck with a boat anchor :!:

Timbologist

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Re: CAD 3D PRINTING MODEL MAKING

Postby timbologist » Mon Feb 27, 2017 7:28 am

sorry but a bit of a long one today, did not want to spit it up.

We are gradually getting there for today's calculations I will use the original FlashForge, Ordbot Hadron, and the baby ToyRep .

The original FlashForge uses a direct drive extruder, which means the filament drive is on the end of the stepper motor shaft i.e. ration of 1:1. Most proprietary printers are this way.

The Ordbot Hadron uses a wades type extruder which has a gear set between the stepper motor and the filament drive and have a gear ratio of 47/9 = 5.222222222:1.

Both the above use a Nema 17 stepper motor with 200/1.8 deg steps.

The ToyRep uses a wades type extruder which has a gear set between the stepper motor and the filament drive and have a gear ratio of 47/9 = 5.222222222:1. But uses a 28BYJ-48 stepper motor (with Bi-polar hack)
steps= (360°/5.625°)*64"Gear ratio" = 64 * 64 =4096 ( has in built 64:1 gearbox )

The extruder movement is defined as E steps and is the number of steps per mm filament, which is found by

E steps/mm = ((motor_steps_per_rev * driver_microstep) * (big_gear_teeth / small_gear_teeth) / (hob_effective_diameter * pi))

So the FlashForge

E steps/mm = ((360/1.8 ) *16) * (1 /1) ) / (10.89 * pi)
(200 *16) /34.211943998
3200/34.211943998
93.534585471 steps/mm

So the Ordbot Hadron

E steps/mm = ((360/1.8 ) *16 * (47 /9)) / ( 8.712 * pi)
(200 *16 * 5.222222222) /27.369555198
16711.1111104/27.369555198
610.572988472 steps/mm

And the ToyRep

E steps/mm = (((360°/5.625°)*64 ) *16 * (47 /9)) / ( 8.712 * pi)
(64 * 64 * 16 * 5.222222222)/27.369555198
342243.555540992/27.369555198
12504.534803912 steps/mm

As you can see there is a fair bit of difference between the different types of extruder.

These step values are stored in the printers memory so are independent of the slicing software, so the same model can be printed on any printer just as long as the nozzle diameter is the same and the model will fit inside the limits of the printable area.
So how does this all relate to what comes out of the extruder and how it is controlled.
We need to look at the actual code that controls the printer to see this.

The slicer was set with a nozzle of 0.2mm with an extrusion width of 0.24mm and a layer height of 0.2mm
( the reason for the 0.24 width is that this is the first layer and the ratio of height to width is recommended to be no less than 1.2 times)

Line 1 G1 X12.083 Y19.356 E2.2806
Line 2 G1 X12.083 Y12.076 E0.1453

Line 1 G1 is the Gcode for a straight move, X and Y the co-ordinates we are moving to and E is the amount of filament to extrude during this move.
For our calculations we do not need to worry about the actual movement, only the amount of filament.
But will do the maths for the movement just to show it
We use the X and Y position in Line 1 as our starting position of our next extrusion, and we ignore the E value as that was for the last move.
Line 2 contains the X and Y position of where the end of the extrusion is, and E is the amount of filament that needs to be fed into the extruder for this movement.
P2260052.JPG
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So the FlashForge we have 93.534585471 steps/mm and we need 0.1453mm of filament

93.534585471*0.1453 = 13.590575269 steps

So the Ordbot Hadron we have 610.572988472 steps/mm and we need 0.1453mm of filament

610.572988472*0.1453 = 88.716255225 steps

So the ToyRep we have 12504.534803912 steps/mm and we need 0.1453mm of filament

12504.534803912*0.1453 = 1816.908907008 steps
so all printers handled that move ok.

Now I will go to a another line where the slicer was set with a nozzle of 0.2mm and an extrusion width of 0.2mm and a layer height of 0.1mm

G1 X10.923 Y26.621 E0.0030
G1 X10.277 Y27.267 E0.0097

So the FlashForge we have 93.534585471 steps/mm and we need 0.0097mm of filament

93.534585471*0.0097 = 0.907285479 steps !!!!!!!!!!!!!!!

So the Ordbot Hadron we have 610.572988472 steps/mm and we need 0.0097mm of filament

610.572988472*0.0097 = 5.922557988 steps

So the ToyRep we have 12504.534803912 steps/mm and we need 0.0097mm of filament

12504.534803912*0.0097= 121.293987598 steps

So the FlashForge with the direct drive extruder has fallen over.

Now I will go to a another line where the slicer was set with a nozzle of 0.2mm and an extrusion width of 0.2mm and a layer height of 0.1mm

G1 X10.277 Y28.737 E0.0024
G1 X10.277 Y28.681 E0.0006

So the FlashForge we have 93.534585471 steps/mm and we need 0.0006mm of filament

93.534585471*0.0006 = 0.056120751 steps !!!!!!!!!!!!!!!

So the Ordbot Hadron we have 610.572988472 steps/mm and we need 0.0006mm of filament

610.572988472*0.0006 = 0.366343793 steps

So the ToyRep we have 12504.534803912 steps/mm and we need 0.0006mm of filament

12504.534803912*0.0006= 7.502720882 steps

So the only one left is the ToyRep.

That's the end of all the maths then, hope you all survived, and you understood what I was talking about.
Next post will give a summary and what it all means when looking at printers, and those glossy pamphlets, and listening to the sales blurb.

Timbologist


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