A First OpenFab Print for me.

[John Sullivan]

Dear All, I just printed this great fiddle!  I used a random function on a Mosaic Palette 2 filament to have a multi-colored body.  The fiddle sounds incredibly good (compared to the Hovalin that I printed a few years earlier).

However, the Open D String sounds a little off.  It is in tune, and if I play an E, F, G, etc on the D-string, those pitches are fine.  But the open D seem 'dead'.  Any ideas?

Thanks,

John

Multi-colored OpenFab Design Fiddle (front)

Multi-colored OpenFab Design Fiddle (side view)

[David Perry]

Hi John,

Welcome! Wow, a beautiful fiddle! I have not seen one printed like this, thank you for the pictures. 

Ah yes, I believe I know exactly what you mean with regards to the D string. I have a similar effect in my bodies, all of which are printed in ProtoPasta's CFPLA these days. What I notice in mine is that the open D seems to have a strong echoing sound that I can feel in the instrument. It sounds a little hollow and soft and I have this sense that something is out of control. By which I mean that the sound reverberates more than it should, I think...

I believe that this is some sort of a wolf tone. This video provides a good example of wolf tones on a violin. I have fought wolf tones since my very first bodies, and it seems that I am trying to balance wolf tones with the plastic box tone that comes from an overly stiff and/or massive plate. 

My (uninformed) take on this D string effect is that the instrument has a natural resonance in the volume of the instrument that is about the frequency of that pitch. Thus, when you play it, there is an amplification of the wrong kind of vibration in the instrument. We want just the right vibration and resonance in the plates of the violin, not as much in the air volume inside it. 

This type of effect is common on a cello, where wolf tones are almost unavoidable. The Modular Fiddle body has a volume to plate area ratio more similar to a cello than a traditional violin, and I believe this is a contributing factor.

That said, I would love to talk with a luthier about it! So, what to do about it. I would recommend trying to add stiffness to the plates. Did they print solid? Try using a stiffer material, like a carbon fiber filled PLA. Are you using the recommended strings? You could experiment with lighter and or heavier strings to see what impact they have, or you could try just changing that D string. 

In the end, more design iteration is needed on the body!

-David

[allen...@gmail.com]

I've been playing fiddle for 30 years, and I've had several fiddles that had a wolf tone on the open D.  I haven't noticed it too much on my modular fiddle, though.  I suspect it may have something to do with having just gotten in a habit of setting things up in a certain way for my particular playing style.  I like to bow aggressively, and prefer my bows to have a lot of bite, so I use dark horse hair.  My style is similar to what you might see called "chop fiddle", like Darol Anger or Casey Driessen.  I also like deep round tones on my strings and very much dislike the strings that tend more toward screechy higher tones.  I've always used Tomastik Dominant medium strings, because they usually have a nice round tone, but I did change things up a bit this time and went for D'Addario Ascenté medium strings; they are far less expensive and I'm very happy with the sound.  Finally, my bridge, tailpiece, and neck are all printed in Matterhackers RYNO filament, which is basically a formulation of PETG.  The body and pegbox are both Hatchbox PLA.  I think the PETG on the tailpiece and bridge may be having the greatest effect on dampening the wolf tone.  

The RYNO filament is a bit expensive, but it is very easy to print, much moreso than typical PETG in my experience.  Its a lot like printing PLA and doesn't seem to have the tendency to be all stringy like typical PETG.

Allen

[allen...@gmail.com]

OH, and by the way, that fiddle you've made looks awsome!

[John Sullivan]

Thanks very much David and Allen,

A) I had not heard of wolf tones previously, but I understand what you mean - and I do think I might have some on the low G string - and maybe so on the open D too (interesting).  My fiddle playing is virtually nonexistent. I play Irish flute, but the sessions that I might join outdoors, etc, don't want singers or woodwind instruments with Covid.  Hence, I said - time to finally learn the fiddle!

B) The multiple colored filaments were PLA.  My guess is that the PLA would have better tone than a PETG or ABS due to the increased rigidity of the PLA.  I've never used Carbon-Fiber Reinforced PLA, but I'm willing to give it a whirl (just won't look as pretty).  David?  Do you believe the carbon reinforced filament will give a stronger/louder tone?

C) I used the build posted by Mark Doberenz with the support for David's main body.  I didn't realize (thanks Allen) that the f-hole was filled with support and should be removed.  I'll look into that first.

Appreciate your comments.  Thank you.  John

[Mark Doberenz]

John,

  I'm glad to see someone used the tweak I made. I didn't see the f-hole was plugged still when I looked at the pics, or I'd have mentioned it.

  Good catch Allen!

  I've done a few prints using PETG and been pretty happy with them. I donated a couple to my church's youth fundraisers so I can't try them out anymore and my latest one is in PLA. I'd never noticed any fatigue in the PETG versions but I also don't know if the rigidity difference caused any other sound issues.

Mark

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[David Perry]

@Allen -- I'll have to get some Rhyno and give that a go. I usually don't like PETG much, but a lot can vary with a change in formula...

John,

Yes, the carbon fiber PLA absolutely gives the instrument better tone. Use it for the bridge at the very least, and ideally use it for both bridge and body. I remember when I first made a body from the CFPLA. I took it in to my local classy violin shop -- they had been testing variations over the months for me. When they tried the CFPLA body the player instantly looked up and said "now, this one has tone!" 

-David

[Mark Doberenz]

Really? It's that much of a difference?

I've got a hardened steel nozzle but I haven't installed it yet. I also haven't bought any CFPLA as I'm cheap and don't like the price. I guess I'll have to bite the bullet. My son wants to try the new 3/4 one you designed so that would be a good test case. He'd get  kick out of playing a carbon fiber violin I think.

Mark

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[Allen Irvan]

I spent a whole spool of ProtoPasta Carbon Fiber PLA before I realized that I needed a 0.6mm nozzle rather than my 0.4mm to keep the carbon fiber PLA from clogging.  Has anyone here had any luck printing CFPLA with a 0.4mm?

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Allen Irvan

[David Perry]

Mark, I would totally say go for it. It's a big difference in sound! 

Allen, I have printed CFPLA with a 0.35mm nozzle and haven't had a problem. That said I can't print any of ProtoPasta's HTPLA, including the HTPLA-CF, reliably with a 0.35mm nozzle. Now I use a 0.5mm nozzle for pretty much all my fiddle prints.  

-David

[Chris DeLeon]

David, do you use their htpla fiber as well or just their cfpla?

[David Perry]

Thanks for your input, Michael! Good to hear from you. 

Chris, I use CFPLA and HTPLA-cf. I have tried a bit of their matte fiber HTPLA and found that it had a tendency to absorb loads of moisture and overextrude. 

I have not had any issues with the CFPLA or HTPLA-cf, and I’ve had spools open for years that still printed like new. 

David 

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[Chris DeLeon]

David, gonna give their cfpla a shot. how are you printing your bridges? parameters and infill to be exact.

[David Perry]

Hi Chris,

I just published a blog post with some specific settings, troubleshooting, and materials info. You can check that out here. I think I need to update with some more specific info about the bridge settings, though, so here's the low down:

For the bridge, I like to print with thinner layers, about 0.15 to 0.20 thick. I print with a 0.5mm nozzle set to 0.6mm extrusion width. I use three perimeters, and grid infill at about 30%. Print with enough bottom and top solid layers to make at least .6mm thickness.

-David 

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[Chris DeLeon]

Perfect, almost completed the body, after several attempts and getting clogs ive dialed in the settings. Attaching a photo of the almost completed body, I've printed one already out with PETG but the sound sounds muffled. 

[Carlos Mendez]

Looking good Chris, is that CF you are printing on?, What are the temperature settings you are using? You can hardly see any layer lines, looks really good.

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[Chris DeLeon]

Yes protopasta cfpla. Printing it at 240c.