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questions about making tongues


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11 hours ago, lucayala said:

the idea is that the plates are printed. 

Lucayala, I looked at the information in the link and find it most interesting that the slots in which the tongue vibrates are formed directly in the accordion-style reed blocks.  How is this done?

 

Does the 3-D printer form only a rough slot, and afterwards there's a necessary filing step to make the final shape?  It's my understanding that the tongue should fit within 0.001 inch on either side within the slot, and I'd be surprised if the 3-D printing process allows such accuracy.  Does it?  

 

In addition, with all the slots being an integral part of the reed block, if you make filing errors in finishing the slot, there's no simple way to fix just that one slot.  I realize that many bandoneons contain metal plates that have many slots, presenting the same kind of issue, and nevertheless, makers do go in that direction.  

 

I guess the bottom line is how well these 3-D printed instruments sound and play.  Have you ever played one of them?

 

Regards,

Tom

 

 

 

 

 

 

 

 

 

 

 

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2 hours ago, Pistachio Dreamer said:

Interesting to see this project. I briefly experimented with plastic 3d printed reed plates as a prototype, before I found a supplier that could print them in stainless steel for a similar cost for bulk orders - https://www.hitch3dprint.com

 

Unfortunately my reed tongue making was not consistent enough at that stage (and still isn't) in order to make a suitable sound comparison, what tests I made did not sound great, with a distinct lack of dynamic and tonal range.

 

I experimented with reed shoes laser-cut from delrin holding spring steel tongues. I only made one that worked before deciding I was better off just ordering from harmonikas.cz. It didn't work well, but a big part of that was certainly my poor job of profiling and fitting the tongue. It would be interesting to see what a more experienced reed maker would get from these materials and processes. But I'm pretty sure everyone making a significant number of reeds has already mostly automated the production of the shoes/plates, so there would be very little cost savings.

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4 hours ago, Pistachio Dreamer said:

So I expect there are good reasons for using metal, for example the gradual cold weld that forms between the tongue and the plate and how that may affect the performance.

Hi Pistachio, why do you say a "cold weld" forms between tongue and plate?  Such does not occur between dissimilar metals, and most reeds have steel tongues and aluminum plates.  I doubt even with brass tongues on brass plates cold welds occur because the mating surfaces probably cannot be cleaned well enough of the metal salts that form on them, but I could be mistaken.  I also don't see how any such weld would affect performance, since riveting and screwing work so well.

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1 hour ago, ttonon said:

Hi Pistachio, why do you say a "cold weld" forms between tongue and plate?  Such does not occur between dissimilar metals, and most reeds have steel tongues and aluminum plates.  I doubt even with brass tongues on brass plates cold welds occur because the mating surfaces probably cannot be cleaned well enough of the metal salts that form on them, but I could be mistaken.  I also don't see how any such weld would affect performance, since riveting and screwing work so well.

You may well be right, cold welding could be describing the wrong process. I recall reading on here or elsewhere of this being one explanation for reeds playing in and sounding better after a period of time, in that the shoe, clamp and the reed tongue become more like a monolithic piece rather than an assemblage of parts. Chance of me finding the discussion on this now is pretty slim, but i'll see what I can find.

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13 hours ago, alex_holden said:

Interesting photo. I would guess they are using an SLA resin printer for the reed blocks?

Some detail can be seen in photo #8 showing a diagonal extrusion pattern typical of an FDM printer.  As someone familiar with FDM printing I'd tell them to increase their wall count to smooth out the perimeter around the reed.

  

8 hours ago, ttonon said:

 I guess the bottom line is how well these 3-D printed instruments sound and play.  Have you ever played one of them?

I found this video of the instrument being played.  Lucayala, is this the version with the printed reed plates?

Edited by dabbler
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Quote

I looked at the information in the link and find it most interesting that the slots in which the tongue vibrates are formed directly in the accordion-style reed blocks.  How is this done?

sorry, Tom. I didn't understand the question. the plates and reed blocks are 2 separate things. the plates that contain several tongues (not individual notes like in the accordion or concertinas) are bolted to the blocks

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Posted (edited)
Quote

How many reeds does a bandoneon have? 

 

a professional bandoneon has 14 reed plates (6 big in the left keyboard, 6 big in the right and 2 small for the highest notes also in the right), with 284 tongues in total. a study level bandoneon cuts that in half, because eliminates the high octave tongues. on a professional instrument, when a note is pressed 2 tongues sound one octave apart. yeah, a lot of work...

Edited by lucayala
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3 hours ago, lucayala said:

sorry, Tom. I didn't understand the question. the plates and reed blocks are 2 separate things. the plates that contain several tongues (not individual notes like in the accordion or concertinas) are bolted to the blocks

Okay, but there are still outstanding unanswered questions. 

Quote

How are the slots machined to the typical accuracy demanded by traditional concertina reed making standards"

  (Are you familiar with these standards?)  

 

From the pictures, I don't see the separate "Plate" assembly, consisting of many tongues mounted above slots carved in their own plate portion of the assemble, as with the traditional bandoneon.  But I'll take your word for it.  But again, how is the necessary accuracy accomplished?

 

Regards,

Tom 

 

 

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I'm familiar with the those standards. the precision/tolerances for the slots are easily obtained with a simple test. if I need, for example, a 3mm wide slot, I can design in 5 minutes a sample plate with 5 or 6 slots with little gradual different width sizes, like 4.92, 4.95, 4.97, 4.99... print it and see what is the correct number to obtain a 3mm wide 3d printed slot

 

here is a picture of the printed blocks, the printed plates and the plates bolted to the blocks:
 

plates-blocks.png

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51 minutes ago, lucayala said:

if I need, for example, a 3mm wide slot, I can design in 5 minutes a sample plate with 5 or 6 slots with little gradual different width sizes, like 4.92, 4.95, 4.97, 4.99... print it and see what is the correct number to obtain a 3mm wide 3d printed slot

 

Lucayala, yes, I can now see that the blocks and reed plate are two different components. 

 

I don't mean to belabor this, but have you tried 3-D printing of tongue slots?  Your statement doesn't acknowledge the tolerance that is present in all fabrication.  For instance, what is the tolerance of variation WITHIN a given slot?  It would be something like 4.97 +/- x1 for the AVERAGE width - an issue that you can overcome by your trial-and-error approach.  But there will also be a tolerance on how much different parts of the the actual slot differ from the average, or something like 4.97 +/- x2.  And also, the printing machine might change the "average" value over time. 

 

Maybe you understand all that, and I mention it only because you didn't.

 

Regards,

Tom 

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23 minutes ago, ttonon said:

Maybe you understand all that, and I mention it only because you didn't.

yes, I understand. my printers are very well calibrated and print evenly. after all, I printed all the other parts of the bandoneon with great precision. and I understand that if a tongue is wider than the slots because a bad printing, I can file the tongue or the slot to the right size. and the project that used the printed plates worked good. so I have hope

 

I did print some little plates. IMG_20220423_143053_119.thumb.jpg.8a661b547c14cb3912a2eee0411f8f3b.jpgthe borders are completely straight and flawless
 

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25 minutes ago, lucayala said:

the borders are completely straight and flawless
 

Can you measure the slot width at 5 - 6 places with an inside Vernier caliper and tell me what the measurements are?  I'm interested in this for my own projects.  Thanks.

 

Regards,

Tom

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5 hours ago, lucayala said:

sorry, I don't have a digital caliper. it's impossible to tell if there are some very subtle differences in the width

As you know, you can verify an acceptable fit with your eyes, by looking at the gap between the tongue and slot through a bright light.  

 

But it's another issue to measure and provide quantitative data that others can evaluate.  So, too bad you don't have a way to do that.  

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If it helps, I dug out the plastic plates I had printed back in 2014, I got 3 identical prints, each with a non tapering slot of 27mm by 2.5mm on the stl file. I opted for an ABS print in 250 micron layers. They had a 30 micron service but this was prohibitively expensive. Results of my measurements (MIB digital caliper) as follows, width taken in 5 increments from base to tip.

 

1.

26.84

2.75, 2.69, 2.63, 2.69, 2.66

 

2.

26.87

2.76, 2.70, 2.68, 2.61, 2.59

 

3.

26.90

2.72, 2.71, 2.65, 2.61, 2.57

 

This does suggest that whilst the dimensions are not calibrated well to the model, the parts are at least fairly consistent between themselves as Lucalaya suggests.

 

I'm interested if makers attempt to hit a precise dimension for the slot, or cut and fit the reed tongue to match the slot, at whatever exact dimension it turns out at after fettling?

 

Paul.

DSC_0723.jpg

shoe2ascii.stl

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3 hours ago, Pistachio Dreamer said:

If it helps, I dug out the plastic plates I had printed back in 2014, I got 3 identical prints, each with a non tapering slot of 27mm by 2.5mm on the stl file. I opted for an ABS print in 250 micron layers. They had a 30 micron service but this was prohibitively expensive. Results of my measurements (MIB digital caliper) as follows, width taken in 5 increments from base to tip.

 

This does suggest that whilst the dimensions are not calibrated well to the model, the parts are at least fairly consistent between themselves as Lucalaya suggests.

 

I'm interested if makers attempt to hit a precise dimension for the slot, or cut and fit the reed tongue to match the slot, at whatever exact dimension it turns out at after fettling?

 

 

Hi Paul, if they are ABS presumably they were made on an FDM printer? My (limited) understanding of 3D printing is that the SLA process produces more accurate parts and finer details but is slower and more expensive.

 

A slide caliper tends not to be a very reliable way to take accurate internal measurements, but if your numbers are good it sounds like you got a width variation of about +/- 0.1mm or +/- 4 thousandths of an inch. That is probably good enough if you are individually hand fitting the reed tongues to the slots (i.e. making the tongues oversized and then filing each one narrower until it is a tight fit in a specific slot, or conversely filing the slot wider). It wouldn't be good enough if you were buying mass-produced tongues that are an accurate width and hoping to calibrate the print to make the tongues fit without individually adjusting them.

 

The way I make mine is to cut the slots on a CNC mill, then use hand files to make the corners sharp, add the back bevel, and try to get the edges as straight and smooth as I can. The result is probably more accurate than your 3D prints but not perfectly consistent. I then shear the tongues oversize, and file them down to a tight fit in each slot. There is enough variation from slot to slot that if I fit two tongues of the same pitch and then swap them around, they will usually be a poor fit in the other frame. Then I profile the tongues. Annoyingly this sometimes causes tongues (particularly long bass ones) to go slightly banana-shaped due to some weird stress relief effect and they no longer fit as well as they did before profiling. Then I do a 'second fit' where I carefully refine the width of the tongues to get a consistent very small gap around each tongue. There always has to be a gap between the two or it will buzz and stick, but you want it to be as small as you can practically make it for reasons of efficiency, response, and tone.

 

Other makers may do things differently. I imagine a CNC wire EDM machine would be a big time-saver, but they are very expensive.

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