How "hard/tough" are the supposed hard resins for desktop SLS printers?

[sfriedberg]

Aaron, I'll be very interested to hear how well these hold up in use, once you've make all the appropriate "thickenings".

 

[aarongough]

Aaron, I'll be very interested to hear how well these hold up in use, once you've make all the appropriate "thickenings".

I was able to break the test part last night... I have basically been using it as a stress ball whenever I'm at home watching TV or whatever. A couple of days of that treatment and it suddenly cracked across one of the 'thinner' walls (0.080" thick).

I think the resins vary dramatically in their strength and behaviour under load. I have heard a lot of good things about the 'BLU' resin from Siraya Tech so I have some on the way. They also make another resin called 'Tenacious' which is less hard but far more resilient to impact. They advocate mixing a percentage of 'Tenacious' into other resins to tweak the properties and I have heard from other sources that even a 5% - 10% addition can dramatically improve the impact performance of resins.

I will be trying BLU by itself as well as formulations with 5% and 10% of Tenacious added. We'll see how it goes! I will report back when I have the test parts printed. Will likely be a week or two as I'm waiting on the resins to ship.

-Aaron

 

[Mike1974]

Labor for post-processing[/COLOR]
4) Amortized cost of machine and post-processing equipment
SNIP
Total cost for 10 parts: $14.33
Cost per part: $1.43

Even at double that I think it would still be a bargain! Especially given that it's not a specialized process. I can print a mix of parts simultaneously or in series, and use the machine for short-turn prototyping as well!

-Aaron

No experience with resin. I use PLA for making toys essentially. The finishing is ALL the work. I can download a file, extract it, open it in my software and position and scale it, slice (prepare G code more or less), and be printing in less than 10 minutes most of the time. I have my material cost and size/weight all set up so after slicing I get a "cost" of the part and how material will be used. It is surprising how cheap it is (material), most of my prints are sub 25 cents. I have probably printed 100's of parts now since Christmas and I am just now finishing my second spool of material.

 

[aarongough]

Yeah agreed, the finishing can be a lot of work!

I do think that extra time spent in the prep process (or even the design process) can help to minimize it though...

For the sheaths that I was FDM printing for instance the slicer-generated supports were an absolute nightmare. No way to cleanly get them off as they would break apart and they would leave marks all over the print when removed. So instead I modelled a monolithic support in CAD like this:



You can see the 'support base' at the bottom. It's printed as one piece with a 0.4mm gap between it and the part. The part sticks to it, but just well enough to stay in place. After printing a quick twist with a pair of pliers and the whole base comes off cleanly in one piece, no further work needed.

The round holes in that print are another thing I've since optimized away. The top of round holes forms an ever-steepening overhang which inevitably causes finish problems (at the least) so now I have modified the holes to be hexagonal instead. The constant 45º overhang makes the print more reliable and improves the appearance.

The finishing with resin printing is actually much faster than I thought it would be. Quick dunk in IPA to clean off the uncured resin, some time in the curing station and they're largely done... Support removal is again one of the biggest issues. On resin prints the supports lave little dimples on the part after removal...

My approach to fixing this is actually going to be to make the dimples an aesthetic part of the model. I'll be altering the layout of the supports to form a regular pattern, and then deliberately replicate that pattern on the underside of the part as well so it looks more deliberate. That should mean that no post finishing is needed at all. We'll see how it works out.

 

[LOTT]

So, detailed total cost for a batch of 10 parts:
Resin: $8.60
Alcohol: $0.30
Printer amortization (@ 2.5 hrs): $0.266
Post-processing amortization (@2.5 hrs): $0.155
Electricity (2.5 hrs @ 40W @ $.21/kwh): $0.021
Labor (5 mins @ $60/hr): $5.00

Total cost for 10 parts: $14.33
Cost per part: $1.43

Even at double that I think it would still be a bargain! Especially given that it's not a specialized process. I can print a mix of parts simultaneously or in series, and use the machine for short-turn prototyping as well!

-Aaron

Aaron, I suspect your numbers are a bit optimistic.

4,000 hours of printer life time would be great, but maybe count on a quarter of that for an entry level printer. Still, not a deal breaker on it's own.

Expect quite a bit of resin waste, by the time you dump resin back and forth between bottles and tank and mixing containers. Again, not a deal breaker but will add up.

Labor is what I think will bite you. Grab a stop watch and time all your labor for a complete cycle, to include resin prep and cleanup of the tank afterwards, and it will probably be 20+.

We tried SLA printing for limited production like your situation, and it didn't work out for us. Not trying to be a Debbie Downer, just sharing the bitter taste of defeat... The printer is great for prototypes and fixtures, it wasn't a total waste.

What has been working for us and may work for you is a small injection molding machine. We got a Morgan, there are a few out there with similar specs. You already have the Fadal and knowledge to make your own dies. An afternoon of molding could make enough belt clips for six months of knife making. And the skys the limit for mechanical properties.

 

[aarongough]

@LOTT:

I have a lot of pride in being able to call myself an 'ok' machinist, but I think it would take a lot of time for me to get to the point where making an injection mold would be a quick and 'one shot' task...

Also the part in question would require a somewhat complicated mold to make it, it would need at least one slide to form the 'tunnel' that goes through the part I believe. Unless it were molded 'end on' in which case the geometry of the mold would be very deep and I'd probably have to use a sinker EDM to make it, or make a mold out of stacked plates or something, which would likely preclude any possibility of texturing the part unless I added a lot of draft, which in turn would make the part look a bit weird.

While I would LOVE to count injection molding amongst my skills I think it would be a bad choice for this part. Quantity would be 500/year MAX, and the investment in learning to make the mold, the mold itself plus molding equipment would account for probably several hundred hours of work, plus thousands and thousands of dollars of capital investment. Not what I would consider to be a reasonable investment for what is probably 500x a $5 part each year.

Additionally each mold would very much be a 'one trick pony'. If a customer comes to me with an idea for improving the part, or I find an issue then I'm back at square one and have to re-invest in a new mold.

The part in question would already ideally come in two flavors, one designed for casual 'dress' belts that you'd wear with jeans or whatever, and another designed for active service personnel (military & police) who would need a larger version for use with a gun belt. So that's two molds right out of the gate...

Additionally molding only really works if I want to do a large run of parts and then keep inventory, but again I've found in the past that doing that usually bites me as it precludes making improvements or changes 'on the fly' and can also eat up a lot of storage space.

3D printing, if I can make the materials properties work, is kind of a unicorn technology for my business I think. I get the flexibility to make changes whenever I need/want, I can make parts 'just in time' to eliminate the need for storage, I can more easily accommodate customer requests for custom changes or improvements, and the space and investment is fairly minimal for the machinery involved.

If the labor turns out to be the sticking point then I think at that point I'd look at what investments could be made to minimize it. For instance a small automated cleaning line where you mount the build plate straight onto it and then it goes through cleaning tanks and a curing station would speed things up quite a bit.

One question: how come you're cleaning your resin tank after each print? I have been cleaning mine about once a week and simply topping it up between parts with good results so far!

All of this assumes that I can find a resin with acceptable material properties for the use case, which is still something I'm working on! If that doesn't happen then honestly the answer will likely be that this part is simply not worth making, given that it's basically meant to be a 'value add' rather than an essential component of my basic design...

-Aaron

 

[Mike1974]

@Aaron - I like your idea of creating the part to be more support friendly. I just make toys, so filing and sanding isn't a big deal, but no way I would want to do it on tens or hundreds of the same parts. Question, what software do you use to model, and do you export as an stl or xmf file type afterwards? Is that part free form to be aesthetically acceptable/pleasing, or is it done by creating arcs and lines and trimming them together?

 

[aarongough]

@Aaron - I like your idea of creating the part to be more support friendly. I just make toys, so filing and sanding isn't a big deal, but no way I would want to do it on tens or hundreds of the same parts. Question, what software do you use to model, and do you export as an stl or xmf file type afterwards? Is that part free form to be aesthetically acceptable/pleasing, or is it done by creating arcs and lines and trimming them together?

Hey mate!
I model everything in Fusion and export as STLs currently. For slicing I use PrusaSlicer for FDM and Lychee for resin prints.

The sheath model is shaped the way it is largely for functional reasons, it basically forms a 0.080" shell around the form of the knife with some extra clearance to prevent binding, and some places where the shape acts as a 'spring' to retain the knife... Honestly it may not look it, but that sheath model is easily the model difficult 3D model I've ever had to make!

I have found that altering the model/orientation with 3D printing in mind really makes a big difference. I asked a 3rd party to print some of those sheaths in a resin printer for testing and they did a dog of a job because the part was oriented to minimize print time, rather than to minimize supports! I printed the same part and it looks miles better... Shame the resin I have on hand is too brittle!

Still waiting for the resins from Siraya Tech to arrive unfortunately...

-A

 

[Mike1974]

Hey mate!
I model everything in Fusion and export as STLs currently. For slicing I use PrusaSlicer for FDM and Lychee for resin prints.

The sheath model is shaped the way it is largely for functional reasons, it basically forms a 0.080" shell around the form of the knife with some extra clearance to prevent binding, and some places where the shape acts as a 'spring' to retain the knife... Honestly it may not look it, but that sheath model is easily the model difficult 3D model I've ever had to make!

I have found that altering the model/orientation with 3D printing in mind really makes a big difference. I asked a 3rd party to print some of those sheaths in a resin printer for testing and they did a dog of a job because the part was oriented to minimize print time, rather than to minimize supports! I printed the same part and it looks miles better... Shame the resin I have on hand is too brittle!

Still waiting for the resins from Siraya Tech to arrive unfortunately...

-A

I've found about half the stuff I download to print is unusable, at best less than ideal. Talked with a couple friends and same story, big hollow openings, things with different heights for no reason

 

[LOTT]

Aaron, I've seen a couple of your knife making videos and the finishing you do. You are a mold maker at heart.

Check out the "mill" this guy uses: https://youtu.be/T1b6pkQG-rc. Granted his injection molding machine is an actual industrial unit, not a table top, and he knows a whole lot more than we do, but his molds are very rudimentary.

Here's another example: https://youtu.be/UmpG57VRa9c.

The barriers to entry and minimum numbers for BASIC parts are lower than you might think. Everything we want to do falls into short run/prototype range, so some blocks of 6061 will do the trick. We're not talking 10's of thousands to make a mold, we're talking 10's of dollars.

"Additionally molding only really works if I want to do a large run of parts and then keep inventory,"

Not neccessarily. 500/12, you need about 42 a month? They might have a two-three minute cycle, spend two hours a month knocking them out. They'll fit in a small bin, if you make a change they get tossed.

Regarding the slide, being a short run mold you might get away with a bar you lay into the B side before closing mold, then manually remove from the part. Maybe?

We got lucky, in that we had one part that justified the purchase of the machine on it's own, but now I'm working through making molds for all the parts we had been milling from delrin.

We've been cleaning the tank out because the SLA printer only gets intermittent use, so perhaps with constant use you can discount that time.

 

[aarongough]

Ok, so I finally have something to report regarding the new resin - Siraya Tech "BLU" resin.

Printed the first parts with it last night. I messed up the support settings so the parts came out UGLY, but some of them were intact enough for testing.

I would say overall they feel a lot like Polycarbonate. Hard surfaces that a fingernail will skate over, but somewhat flexible in thin sections. A piece that is 0.080" in thickness can be bent almost 180º before sudden failure.

The only issue is that it does seem somewhat 'notch sensitive'. Some of the parts I printed got chipped when removing the supports before curing, and the parts with those small chips/cracks failed easily after curing with cracks starting at those same places.

Also the material is definitely sensitive to the rate of loading. Bending it by hand slowly and it will flex quite a long way, however hold the part in both hands and strike it on the corner of a bench and it shows brittle failure and will break easily.

That is just the pure resin with none of the 'Tenacious' material mixed in which is supposed to be a lot more durable/flexible. I will be doing some more testing and will report back... If the material ends up with roughly the same properties but a little bit more flexible and without the sensitivity to shock then I think it would be a winner!

-A

 

[aarongough]

A little bit more quick experimentation with the two Siraya resins, 'Blu' and 'Tenacious'.

I poured a little bit of each into the bottom of some plastic cups, and then cured it using the cup as a mold. Ended up with 2 little pucks about 1.5" in diameter and 1/8" thick.

When placed on my concrete floor and struck with the rounded end of a ball-peen hammer the puck made from 'Blu' shattered like glass, small shards went everywhere. When I did the same with the puck made from 'Tenacious' the hammer just bounced. Couple of dozen more strikes with the hammer and the 'Tenacious' puck shows no sign of injury at all, not even dimples from the hammer.

The 'Tenacious' material feels a lot more like a hard Urethane rubber. Thin sections of it around the edges of the puck will dent/roll with pressure from a fingernail and then slowly creep back to their original shape.

I am doing a test print now with a mix of 80% Blu and 20% Tenacious, we'll see how it turns out. Ideally I'm looking for behaviour fairly similar to Kydex or Polypropylene. Moderately stiff, fairly hard surface, but will deform or yield under stress rather than shattering, leading to parts that are practically indestructible.

 

[mkd]

@LOTT:

I have a lot of pride in being able to call myself an 'ok' machinist, but I think it would take a lot of time for me to get to the point where making an injection mold would be a quick and 'one shot' task...

Also the part in question would require a somewhat complicated mold to make it, it would need at least one slide to form the 'tunnel' that goes through the part I believe. Unless it were molded 'end on' in which case the geometry of the mold would be very deep and I'd probably have to use a sinker EDM to make it, or make a mold out of stacked plates or something, which would likely preclude any possibility of texturing the part unless I added a lot of draft, which in turn would make the part look a bit weird.

While I would LOVE to count injection molding amongst my skills I think it would be a bad choice for this part. Quantity would be 500/year MAX, and the investment in learning to make the mold, the mold itself plus molding equipment would account for probably several hundred hours of work, plus thousands and thousands of dollars of capital investment. Not what I would consider to be a reasonable investment for what is probably 500x a $5 part each year.

Additionally each mold would very much be a 'one trick pony'. If a customer comes to me with an idea for improving the part, or I find an issue then I'm back at square one and have to re-invest in a new mold.

The part in question would already ideally come in two flavors, one designed for casual 'dress' belts that you'd wear with jeans or whatever, and another designed for active service personnel (military & police) who would need a larger version for use with a gun belt. So that's two molds right out of the gate...

Additionally molding only really works if I want to do a large run of parts and then keep inventory, but again I've found in the past that doing that usually bites me as it precludes making improvements or changes 'on the fly' and can also eat up a lot of storage space.

3D printing, if I can make the materials properties work, is kind of a unicorn technology for my business I think. I get the flexibility to make changes whenever I need/want, I can make parts 'just in time' to eliminate the need for storage, I can more easily accommodate customer requests for custom changes or improvements, and the space and investment is fairly minimal for the machinery involved.

If the labor turns out to be the sticking point then I think at that point I'd look at what investments could be made to minimize it. For instance a small automated cleaning line where you mount the build plate straight onto it and then it goes through cleaning tanks and a curing station would speed things up quite a bit.

One question: how come you're cleaning your resin tank after each print? I have been cleaning mine about once a week and simply topping it up between parts with good results so far!

All of this assumes that I can find a resin with acceptable material properties for the use case, which is still something I'm working on! If that doesn't happen then honestly the answer will likely be that this part is simply not worth making, given that it's basically meant to be a 'value add' rather than an essential component of my basic design...

-Aaron

molding in two halves is a possibility? For lower production, don't forget about compression molding. Certainly an easier point of entry compared to a full blown slide injection mold. Bonding the two halves via ultrasonics would be the first choice for low labor costs AND low initial investment..

 

[bryan_machine]

1. There are a variety of FDM materials (which is not SLA of course) - some of which I've found useful for things like "buffers" on an FP1 (a kind of rubber spring to keep students from jamming it by bottoming the travels) and the making of other useful things (a basket for fetching tennis balls out of the lake...) Is this true of SLA as well? Seems like a much narrower range of materials? (PLA seems most widely used and least interesting. Does SLA suffer from this as well?)

2. There are FDM materials I have not tried (yet) that are "metallic" - but they require some relatively elaborate oven treatment (sintering, or just baking.) Anybody tried any of these? Surely no similar thing (aluminum or copper material) for SLA?

3. In addition to the observation above about injection molding is maybe not as hard as we think for simple parts, it seems that some FDM materials are suited well-enough to investment casting. I wonder if SLA works for this? (Mold "investment" around it, "burn" it out, then cast aluminum, say???)

4. Aaron - do you think any of the SLA materials would be "real world good enough" - assuming correct design to avoid notch issues and so forth? I can say that for *some* tasks *some* FDM materials are actually really hard to beat. So far, aside from the sideways belt device mentioned above, SLA seems to be about non-functional parts (models, mock-ups, etc.)

 

[aarongough]

1. There are a variety of FDM materials (which is not SLA of course) - some of which I've found useful for things like "buffers" on an FP1 (a kind of rubber spring to keep students from jamming it by bottoming the travels) and the making of other useful things (a basket for fetching tennis balls out of the lake...) Is this true of SLA as well? Seems like a much narrower range of materials? (PLA seems most widely used and least interesting. Does SLA suffer from this as well?)

2. There are FDM materials I have not tried (yet) that are "metallic" - but they require some relatively elaborate oven treatment (sintering, or just baking.) Anybody tried any of these? Surely no similar thing (aluminum or copper material) for SLA?

3. In addition to the observation above about injection molding is maybe not as hard as we think for simple parts, it seems that some FDM materials are suited well-enough to investment casting. I wonder if SLA works for this? (Mold "investment" around it, "burn" it out, then cast aluminum, say???)

4. Aaron - do you think any of the SLA materials would be "real world good enough" - assuming correct design to avoid notch issues and so forth? I can say that for *some* tasks *some* FDM materials are actually really hard to beat. So far, aside from the sideways belt device mentioned above, SLA seems to be about non-functional parts (models, mock-ups, etc.)

Hey Bryan!
1) I think most SLA resins that are easily available are aimed at modelling and decorative parts and seem to be quite brittle and notch sensitive. However I am much more familiar with the range of FDM materials as opposed to SLA materials in practice. There are lots of great videos online of people testing materials though and overall they seem to come to the same conclusion.

2) The metal filled materials (thevirtualfoundry.com is a well known source) seem really interesting. For metal parts where the geometry is impossible on a 3 axis mill they might be compelling if the tolerances can be held close enough. I have also heard that if you can get your hands on the feedstock pellets used in Metal Injection Molding then you can use those to extrude your own filament for use in an FDM printer. More complicated but probably a lot cheaper than buying pre-extruded filament!

There are also a few places that sell metal filled filament along with 'tickets' that cover sending the resulting parts away for post-processing and sintering: BASF Ultrafuse 316L Metal 3D Printing Filament - 1.75mm (3kg) | MatterHackers

3) There are actually a wide variety of SLA resins specifically designed for producing investment castings! They are used pretty widely in jewelry and dentistry I believe. They are available for the inexpensive printers as well:
- WaxCast - Direct Investment Casting Resin – MakerJuice Labs
- BURN Jewelry Casting 3D Printer Resin - 100% Ash Free Burnout Casting – powerresins

4) Yes I think that the tougher resins like the one I recently tested "Siraya Tech BLU" are probably fine for functional parts assuming minimal shock loading and relatively thick sections. For machinery parts I wouldn't want to go thinner than 1/4" or so I think, for simple instrument jigs and so on you can probably go thinner than that.

I have also found lots of uses for FDM in the shop! I have been printing organizers using red PLA, it's cheap and easy to print and means I can cheaply produce bins to divide small drawers and so on in exactly the size I need...

-A

 

[marissaadrianna8]

Hi, My employer is looking into buying and I know they'll buy one heck of a lot better than me, so I'm kind of holding on to them, but I can just buy one to play with. ... I still think it's too expensive, but I think it's worth buying

 

[marissaadrianna8]

Hi, My employer is looking into buying and I know they'll buy one heck of a lot better than me, so I'm kind of holding on to them, but I can just buy one to play with. ... I still think it's too expensive, but I think it's worth buying worktime

I think that the tougher resins like the one I recently tested "Siraya Tech BLU" are probably fine for functional parts assuming minimal shock loading and relatively thick sections. For machinery parts I wouldn't want to go thinner than 1/4" or so I think, for simple instrument jigs and so on you can probably go thinner than that.

 

[BugRobotics]

I've been using a 50/50 mix of Siraya Tech BLU and Siraya Tech Tenacious for about 7 months now for various prototypes. Pretty tough material for a 3D print. Thinnest wall with that mix probably around 0.03in. I wouldn't ever use it in a high loading scenario or even in Aaron's knife sheath but for low risk stuff/testing fits it works great and has excellent detail.

 

[Leif820]

I have an Elegoo mars and have printed the ABS like material with great success. I have made electronic enclosures for test fits and they held up well enough to be used for prototypes. I bought this specifically for prototyping.

 

[crickets]

SLA printer resins vary in their properties quite a bit. Most are quite brittle for making engineering parts, like for tapping or driving screws through. Like some pointed out there are specialty resins available that can take some torture, so it very much depends. I would add that while the printers can produce the details quite well, there are many caveats specific to the process. Couple of things I ran into :

1) Parts warp during curing.
Not sure how to mitigate that, but basically if you print a box (like electronics enclosure), can expect that the walls will be crooked.

2) Parts bleed.
If it's not 100% fill, there is a chance of uncured resin being trapped in the hollows that will later find a way to drip out of the part.

And of course parts aren't dimensionally stable, still need to account for shrinkage post-curing.

Having both FDM and SLA, FDM is basically go-to for most stuff... SLA being messy and peculiar is only for specialty parts.

I mostly design the parts I print, but I was recently getting a used Bridgeport into operation and it was missing the finefeed wheel and Thingiverse had one. Came out quite okay, and seems plenty strong. Resin is RICH-OPTO black, general purpose. I tested other prints for strength before, and it does have some elasticity before breaking.