What governs print quality

As a self employed CNC machinist/programmer (mills mainly) I am aware the quality and accuracy of a part is based on the accuracy of the axis', rigidity of the setup and correct use of the cutter via the appropriate settings during programming and operation. Being new to printing I am interested in what governs quality and accuracy with 3D printing. I can assume that there are similarities to "subtractive" machining like some of the ones mentioned above. When machining metals, for example I would start with certain base settings, analyze the result and make adjustments (tune) to achieve the level of quality and accuracy desired. Is it the same process with printing? If so is it safe to assume that any 3D printer can be tuned to produce quality prints if the machine is mechanically/electronically sound, the filament feed assembly/extruder/nozzle is of good quality and functioning correctly, the software has the adjustability to optimize all settings and the operator (me) has the analytical capacity to determine those optimum settings? Thanks

In a word, everything.

In a few more. It is safe to assume that a sound machine that is used for cnc will work for 3d printing. The basics are the same but there are a few differences. In a subtractive setup the Z axis does not as large of an effect on the finished quality. In a 3d printer the Z axis is key to getting a good print. With a 3D printer, once the motion is tuned, it is tuned. You don't have to return motion for each print. You do have to change the tuning on the print head depending on material. There have been a few guys who have put 3d print heads on their cnc setups and had good results, it is definitely worth trying. Honestly it is a learning process that you can only start by trying. With your background I am sure you can be making great prints in no time.

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From my experience i have to say yes. If the machine is in good working condition it is a matter of determining the correct parameters to get an optimal print. I have no experience with CNC machining metal, but from what i know i would say that the material properties have a higher impact on the quality of the print then they have with milling etc.
Don't be fooled though, the number of possible parameters that need adjustment per material can be incredibly high. Thankfully often enough things translate between materials and with a bit of experience you can start printing new materials at good quality in very short time.

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... in short - the basic parameters are the positioning accuracy (=machine) and the uniformity (dimensional quality) of the extruded filament.

But this 'uniformity' depends on all possible factors from material quality, ambient temperature, thermal properties (->warping), humidity/moisture in the filament and surrounding air, ... and much, much more ...

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Viktor
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the level of precision is greater with cnc because the part size/precision is controlled by the radius of the cutting tool, and the direction of the cut.

It is just a fact that we trade up precision for the ability to simplify design structures and speed up part manufacture, such as multisize objects and holes as well as curves.


there are some advantages with 3d printing that do not exist easily with cnc, and that is the ability to print curves and angles with high detail, but accuracy is sometimes +/- 100th of an inch.

many people still think that this is not accurate enough. but if you view this in the same way a casting is viewed as the overall part is consistent, just it evenly shrinks or expands (based on wall thickness), then designs become better and more interesting that cnc parts.

lines and flat walls usually will look flat, they just will be off in position +/- 0.01inch over time and do to temp and wall thickness variations. but this will likely not change during the course of a print.

by using beveled edges, and pressure contact fitting allow some give, but allow for parts to snap together. also you can build in leaf springs, and other structures to increase precision or allow for adjustment.

design parts to be built together and in such a way that it is an advantage, such as the top and bottom part of a box. printed around the same time all the edges should line up on the 4 sides,

design with curved surfaces, this improves appeal of part, and makes it harder for the eye to pick up small and slight variation,

from part to part built around the same time the tolerance is +/- 0.001 inch, but with temp change, and wall thickness variations over all it is about designing for swell and shrinkage. then there also is part swell and moisture level of the air. for example abs can absorb 1% of its weight in water from the surrounding air within 24hrs!


some people result to machining after additive manufacturing, others still use laser, but laser is just as inaccurate if you include the kurf and curve variations around the corner.

this all being said a few things to keep i mind

it is low contact, not non contact, their always is drag on a nozzle when it lays down filament.
frame structure is important, but it is more important to minimize the effects of motion as the nozzle is always extruding
xcarriage and nozzle need to have no slop to improve quality of part.
temp stability is critical.
part variation also comes from outside temp factors. some people take this as to design all parts enclosed inside of a Chambers that is heated.
quality of part comes from strength and appearance. print the outside shell of the part slower, and the inside of the part fast, so with less time you have more internal structure for strength, and detailed outside look for appearance.

many people will have comments....

Edited 1 time(s). Last edit at 01/21/2014 06:40AM by jamesdanielv.

In the end, the user is the biggest factor of all.

The user reads, the user experiments, the user calibrates. If calibration is done badly, prints will come out horrific. If the user decides to use the cheapest and lowest quality electronics and vitamins, this will be also visible. If the user doesn't have affinity with perfectionism, it's hard to build a printer and commission it after.

If you are the kind of person that likes to read up on forum posts, knows how to use the search option and if you are dedicated to your goal of building and finishing the machine to the smallest detail, then I think you can't go wrong.

But most of all, don't be afraid to ask questions (after using the search of course hehe )

First I'd like to say welcome I like you come from machining background I used to be a prototype technician for a large Pro audio company. I wanted to let you know it you can use programs like Mach 3 or EMC to run printers which in turn will let you build with larger motors and more torque. Speed of the print especially with ABS seems to have a lot to do with quality one thing to remember is you need quick acceleration to get good square corners. Extruder accuracy I think is probably the most important thing and with that being said filament changes slightly even from same manufacturer and sometimes on the same spool. Here Is a picture of the one I built they don't like me to post pictures here but your new you might want to look at this

Edited 1 time(s). Last edit at 01/21/2014 10:06AM by cnc dick.

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cnc dick
they don't like me to post pictures here

Are you joking ? We all love seeing pictures of machines and parts !

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Most of my technical comments should be correct, but is THIS one ?
Anyway, as a rule of thumb, always double check what people write.

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DeuxVis

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cnc dick
they don't like me to post pictures here

Are you joking ? We all love seeing pictures of machines and parts !

I should have said some people that post here don't like me to post pictures have received quite a few negative replies. But again since he seems to be new here and he comes from machining background I thought I'd post those pictures. And let him know that Mach 3 or EMC 2 could be used

Edited 2 time(s). Last edit at 01/21/2014 10:49AM by cnc dick.

Hi cnc_dick,

AFAIK this 'picture-antipathy' comes from your repetition of the specific picture series in many threads, so it comes out like spamming.

Most users browse only through the new marked threads in the forums and grumble when finding 5 to 6 times the same (image-heavy) post in different forums ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

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VDX
Hi cnc_dick,

AFAIK this 'picture-antipathy' comes from your repetition of the specific picture series in many threads, so it comes out like spamming.

Most users browse only through the new marked threads in the forums and grumble when finding 5 to 6 times the same (image-heavy) post in different forums ...

I don't know why I've seen thousands of the same pics of kits and hot ends that are out there. Why is it when I show a couple pics I get all this negativity yes they are the the same pics. And the reason I posted them and I stated is because Bill seems to be new here I think it was his first post and thought he might like to see them. It's was his post it was to benefit him not everybody else

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cnc dick

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VDX
Hi cnc_dick,

AFAIK this 'picture-antipathy' comes from your repetition of the specific picture series in many threads, so it comes out like spamming.

Most users browse only through the new marked threads in the forums and grumble when finding 5 to 6 times the same (image-heavy) post in different forums ...

I don't know why I've seen thousands of the same pics of kits and hot ends that are out there. Why is it when I show a couple pics I get all this negativity yes they are the the same pics. And the reason I posted them and I stated is because Bill seems to be new here I think it was his first post and thought he might like to see them. It's was his post it was to benefit him not everybody else

So are you going to upload the contents of your photo album for every new user? You know, just in case they might want to see your printer. Can you think what happens if *everyone* does that?

I've said before, the proper place for stock pictures is on a blog, and you can post a link to them.

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Bob I notice you didn't give any replies to this man's post just complaints about me. Maybe I'm wrong but this man was interested in 3-D printing and had some questions I thought that helping him was the idea here

Gentlemen, I sincerely appreciate you taking your valuable time to offer some very informative responses. I truly mean that. I wasn't expecting this much information and I will continue to study those replies. What my plan is at this point (and steer me if you think I'm going in the wrong direction) is to by a assembled, lower priced machine to get my feet wet and make improvements to it as needed. I would love to start from scratch but knowing how I am it would take many months and end up being this billet monstrosity. I really want to get printing (learning) now and take that experience and build a machine. The thought of fitting my Haas or Miltronics with a print head sounds tempting but those are at the shop and I want to tinker with printing in my home shop (got to get away from work even though my vocation and avocation overlap).
I attached a couple pics of a component I want to make once I gain some experience (don't laugh ). The part (a control linkage pulley) is very small and detailed. The outer diameter is about 1" and the total thickness is .12". Would something like this need small filament and nozzles to produce. I do have some larger, less involved parts I want to make but these are the ones I dream of. Even if I could get close and then 2nd op in the Mill to finish that would be fine but this is indicative of the size/detail I am interested in.
I don't want to ruffle any feathers and I can understand where regular users are coming from but CNC Dick that is an impressive unit. I can see why you like to show it off. Does the fact that it isn't enclosed (or maybe the cover is not on?) effect your printing. I will assume if your shop is at a constant temp an enclosure isn't required?
BTW this is the machine I was looking at [www.robo3dprinter.com]. Its probably a POS but it has produced decent pints, uses popular software, etc. I'm sure I would be reworking the mechanics in short order but atleast I could get going for a small investment. Certainly open for suggestions for a better option (for future growth too) under $1K. Thanks again guys.

Bill I think you going to need support material on that little part which means you need a printer with two heads. And yes I have a temporary enclosure that I place over to printer when printing large parts I never got to totally complete the enclosure

Why would you need two heads for support material?...

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Ohmarinus
Why would you need two heads for support material?...

Support is usually a different material than your part material I've never had good luck with same material support I think different material is better so it doesn't bond very well and it can be broken away easily or depending on what material may be dissolved. So you need a different head loaded with different material for support and a head loaded with your part material. I think the printer he is looking at has only a single print head part could be made with a single head if he split it and then printed it and glued together afterwards. Or try same material support but I think it would stick way too much because it's a total right angle shelf

Edited 5 time(s). Last edit at 01/21/2014 09:04PM by cnc dick.

So the channel could just be completely filled with support material? PVA or ? there is a guy on the Robo forum fitting a Bowden dual extruder to his machine so apparently it can be configured as such. Word is the extruder will be the first upgrade on that machine anyway so I planed on buying that pretty quick. Who are some of the top quality extruder manufacturers? I have a sinking feeling I will soon become consumed in this 3D printing stuff

Bill I think you just going to have to look at all the popular ones out there and make a choice it's like the difference between Ford Chevy Chrysler. I personally can't help much there because I built my own and don't have much experience with purchased ones. You can try it with the same support material but with anything flat like that I've never had good results on an angle it works pretty good Maybe start another post just inquiring about hot ends

Edited 1 time(s). Last edit at 01/21/2014 10:29PM by cnc dick.

There is another factor
CNC uses much mode G-codes.
Like the difference between bimap and postscript in printing.

Currently 3D printers use move to X, Y, Z and extrude.
Does not utilize Center, Radius, arc type functions.

The controllers just don't do it.

CNC Dick do you have a writeup on the details of your machine (what controllers, software, etc.) you are using? I would also love to see a video of your printer printing.

Cozmicray AFAIK marlin is able to handle arc movements, there just aren't any slicers that output arc data.

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jzatopa
CNC Dick do you have a writeup on the details of your machine (what controllers, software, etc.) you are using? I would also love to see a video of your printer printing.

Cozmicray AFAIK marlin is able to handle arc movements, there just aren't any slicers that output arc data.

if you Google large scale repstrap you should come up with a couple things. You should be able to find a post I had at the cnczone forum or the Mach 3 forum. I use Mach 3 for the machine operating system which is a CNC based program here is a quick small video[www.facebook.com]

Edited 1 time(s). Last edit at 01/22/2014 03:19PM by cnc dick.

Richard,
I'm putting an extruder head on my CNC. Since printers tend to move faster than mills I was wondering how fast your machine can move reliably? I currently have my motors all tuned for 100ipm rapids in Mach 3. However I did some experimenting the other day and I don't seem to have any problems at 350ipm. My machine is a little bit unusual configuration. Stationary table, moving head, 18" x 18" x 18" travels, 12" x 12" heated bed for printing. I can turn the head and operate as a horizontal mill. I have a lathe tool post behind the spindle for use with a Harbor Freight lathe bed, headstock and tailstock. The 3D extruder mounts behind that and I don't need to remove anything but the tool to use one of he three devices.

[s811.photobucket.com]

... I'm actually reworking a servo-driven CNC-mill as basis for my laser-works.

My old Isel-gantry with halfstep-drivers and 16/5 lead-screws (12.5 microns per step) can move with up to 50mm/s, but I'm laser-engraving only with max. 20mm/s to avoid resonancies

The other mill with servos (I'm now modifying) has the same 16/5 lead screws -- but when tested yesterday some special servo-drivers, that are controlled similar to steppers with DIR+STEP, I've managed to drive the axes without acceleration ramps with 40kHz and 100mm/s positiong speed (@2.5 microns encoder-step resolution), what can be maxed with higher voltage (tested with 24V, got today a 48V-PS) and proper acceleration to 750mm/s @300kHz stepping rate !!!

Received one of our new 4-axis stepper-controllers with 100kHz max. stepping frequency too, what would result in max. moving speeds of (only) 250mm/s ... now I have to test, what's possible with the complete machine running and engraving without resonancies ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

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garyhlucas
Richard,
I'm putting an extruder head on my CNC. Since printers tend to move faster than mills I was wondering how fast your machine can move reliably? I currently have my motors all tuned for 100ipm rapids in Mach 3. However I did some experimenting the other day and I don't seem to have any problems at 350ipm. My machine is a little bit unusual configuration. Stationary table, moving head, 18" x 18" x 18" travels, 12" x 12" heated bed for printing. I can turn the head and operate as a horizontal mill. I have a lathe tool post behind the spindle for use with a Harbor Freight lathe bed, headstock and tailstock. The 3D extruder mounts behind that and I don't need to remove anything but the tool to use one of he three devices.

[s811.photobucket.com]

if I remember correctly I think I set it that 200 mm a second Rapids or Max speed. The main thing with 3-D printing is you need fast acceleration and deceleration to get good quality prints with nice corners.

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VDX
... I'm actually reworking a servo-driven CNC-mill as basis for my laser-works.

My old Isel-gantry with halfstep-drivers and 16/5 lead-screws (12.5 microns per step) can move with up to 50mm/s, but I'm laser-engraving only with max. 20mm/s to avoid resonancies

The other mill with servos (I'm now modifying) has the same 16/5 lead screws -- but when tested yesterday some special servo-drivers, that are controlled similar to steppers with DIR+STEP, I've managed to drive the axes without acceleration ramps with 40kHz and 100mm/s positiong speed (@2.5 microns encoder-step resolution), what can be maxed with higher voltage (tested with 24V, got today a 48V-PS) and proper acceleration to 750mm/s @300kHz stepping rate !!!

Received one of our new 4-axis stepper-controllers with 100kHz max. stepping frequency too, what would result in max. moving speeds of (only) 250mm/s ... now I have to test, what's possible with the complete machine running and engraving without resonancies ...

Sounds good 250 mm a second with 5 mm pitch with 16mm dia screw of course depending on length you could end up with screw wip

Edited 1 time(s). Last edit at 01/22/2014 09:42PM by cnc dick.

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bobc
So are you going to upload the contents of your photo album for every new user? You know, just in case they might want to see your printer. Can you think what happens if *everyone* does that?

I've said before, the proper place for stock pictures is on a blog, and you can post a link to them.

You do know how this forum works right?

He's not uploading anything...

He is linking to the pictures....

Thank you ShadowRam

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cnc dick

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VDX
... I'm actually reworking a servo-driven CNC-mill as basis for my laser-works.

My old Isel-gantry with halfstep-drivers and 16/5 lead-screws (12.5 microns per step) can move with up to 50mm/s, but I'm laser-engraving only with max. 20mm/s to avoid resonancies

The other mill with servos (I'm now modifying) has the same 16/5 lead screws -- but when tested yesterday some special servo-drivers, that are controlled similar to steppers with DIR+STEP, I've managed to drive the axes without acceleration ramps with 40kHz and 100mm/s positiong speed (@2.5 microns encoder-step resolution), what can be maxed with higher voltage (tested with 24V, got today a 48V-PS) and proper acceleration to 750mm/s @300kHz stepping rate !!!

Received one of our new 4-axis stepper-controllers with 100kHz max. stepping frequency too, what would result in max. moving speeds of (only) 250mm/s ... now I have to test, what's possible with the complete machine running and engraving without resonancies ...

Sounds good 250 mm a second with 5 mm pitch with 16mm dia screw of course depending on length you could end up with screw wip

... completed the reassignment of the CNC-machine and the controller - first tests runs really good with 150mm/s ... have to wait until the developer of the controller gives me some timing/PID-values related infos -- then I'll try to tune the machine for higher speeds and accelerations ... and I have to source a much heavier/sturdier table, as the machine is 'tilting' on the actual one

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

... I've uploaded a short video where the machine is positioning with 50mm/s and 'running' with 150mm/s:

[vimeo.com]

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]