uneven blank causing overcut and undercut - vinyl recorder

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tragwag
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uneven blank causing overcut and undercut - vinyl recorder

Post: # 36087Unread post tragwag
Fri Jul 17, 2015 5:04 pm

I believe I'm having a problem with overcut and undercut at the same time due to an uneven blank.
unfortunately with the plastic, this is to be expected, and these aren't in the worst shape.

I'm cutting on the vinyl recorder, a stereo track, fairly bass present, though I've tamed it with a multiband and EQ.
And turned down the whole cut about 1.5 dB since test cuts.

In some areas it looks as if I severely over-cutting, and other areas it looks as if the grooves approach the too thin realm.

The resulting record usually skips my 1200 once or twice a side, just sort of jostling forward one grooves worth.

Is there a way to tell which is causing the skipping?
(my microscope is only 40x so it's not the best picture of what's going on)
making lathe cuts on a Presto 6N, HIFI stereo cuts on vinylrecorder
at Audio Geography Studios, Providence, RI USA
http://www.audiogeography.com

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ROLANDJAYS
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36089Unread post ROLANDJAYS
Fri Jul 17, 2015 6:08 pm

Can you measure how much the blank is warped?

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tragwag
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36155Unread post tragwag
Wed Jul 22, 2015 10:58 am

on a 12" blank, it measures around 1/16"-1/8" from flat at the worst spots.
it seems to get LESS even with the center hold down on there.

the oddest thing, is one side will be uneven, waving up and down about 1/16"
and the B side of that blank, will be nearly flat.

I haven't been able to figure out a good way to flatten them either.
any help is super appreciated, I'm wasting a few a day (usually after cutting one good side too!)
making lathe cuts on a Presto 6N, HIFI stereo cuts on vinylrecorder
at Audio Geography Studios, Providence, RI USA
http://www.audiogeography.com

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ROLANDJAYS
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36157Unread post ROLANDJAYS
Wed Jul 22, 2015 11:35 am

If one side is flat and the other is warped then the material thickness is not consistent. The whole group of parts from that sheet are probably bad .
Return items or throw away......
Tell me no ?

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tragwag
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36158Unread post tragwag
Wed Jul 22, 2015 12:21 pm

aw man, that's a bummer.
I think you're right, but I want to keep trying on these.

I've heard of people putting them out in the sun under two sheets of glass, but that could take hours :(

I keep thinking about something with slight pressure and heat - almost like a shirt press, to flatten plastic blanks.
just would have to not melt the plastic. no idea if that would be feasible
making lathe cuts on a Presto 6N, HIFI stereo cuts on vinylrecorder
at Audio Geography Studios, Providence, RI USA
http://www.audiogeography.com

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handcut
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36176Unread post handcut
Thu Jul 23, 2015 5:31 pm

Do you know any t-shirt printers? They usually have some kind of thermostat-controlled heat press in their set-up, that may be worth a shot... If the thickness is out though, I imagine the blanks will just distort again when heated for cutting.

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tragwag
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36194Unread post tragwag
Fri Jul 24, 2015 3:22 pm

handcut wrote:Do you know any t-shirt printers? They usually have some kind of thermostat-controlled heat press in their set-up, that may be worth a shot... If the thickness is out though, I imagine the blanks will just distort again when heated for cutting.
Oh yeah! that is true... I didn't think of that, and I live above a Tshirt printing shop!
I'll definitely ask them
making lathe cuts on a Presto 6N, HIFI stereo cuts on vinylrecorder
at Audio Geography Studios, Providence, RI USA
http://www.audiogeography.com

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Bahndahn
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36205Unread post Bahndahn
Sat Jul 25, 2015 1:40 am

If your into building stuff you may be able to alleviate these problems entirely by fitting the cutterhead with an advance ball apparatus. There isn't too much talk about them around here and perhaps there is a good reason for that, but the concept seems promising. I am currently designing one for my home-built lathe because I am experiencing a similar problem.

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EpicenterBryan
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36255Unread post EpicenterBryan
Sun Jul 26, 2015 6:20 pm

Bahndahn wrote:If your into building stuff you may be able to alleviate these problems entirely by fitting the cutterhead with an advance ball apparatus. There isn't too much talk about them around here and perhaps there is a good reason for that, but the concept seems promising. I am currently designing one for my home-built lathe because I am experiencing a similar problem.
Here is my idea for a simple advance ball add-on...
It's a Ruby probe attached to a micrometer. The micrometer would attach to the cutting head. This version has a printed plastic adapter. The final one might be metal.

I'm not thrilled with this version. I thought the small knob on the micrometer head was a lock. It is not. It's also a bit more bulky than I wanted so I'm looking for a smaller micrometer head.

Alan Graves mentioned that having lateral adjustment would also be nice since you could adjust the ball so any traces of riding on the disc could be cut over by the stylus. He said they do that on the Westrex 3D head.

Bryan
IMG_3849.JPG
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Gus
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36258Unread post Gus
Sun Jul 26, 2015 8:06 pm

EpicenterBryan wrote:
Bahndahn wrote:If your into building stuff you may be able to alleviate these problems entirely by fitting the cutterhead with an advance ball apparatus. There isn't too much talk about them around here and perhaps there is a good reason for that, but the concept seems promising. I am currently designing one for my home-built lathe because I am experiencing a similar problem.
Here is my idea for a simple advance ball add-on...
It's a Ruby probe attached to a micrometer. The micrometer would attach to the cutting head. This version has a printed plastic adapter. The final one might be metal.

I'm not thrilled with this version. I thought the small knob on the micrometer head was a lock. It is not. It's also a bit more bulky than I wanted so I'm looking for a smaller micrometer head.

Alan Graves mentioned that having lateral adjustment would also be nice since you could adjust the ball so any traces of riding on the disc could be cut over by the stylus. He said they do that on the Westrex 3D head.

Bryan
IMG_3849.JPG
Advance ball works well on soft materials like wax or laquers , i don't think it will work for PVC or PC. Just a thought!

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Bahndahn
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36291Unread post Bahndahn
Mon Jul 27, 2015 10:53 pm

Gus wrote:
EpicenterBryan wrote:
Bahndahn wrote:If your into building stuff...
Here is my idea for a simple advance ball add-on...
Advance ballworks well on...
Interesting!

Nice design, Bryan. A little bulky, yes, but if it was integrated into the overall design of the cutterhead, it could be mounted atop the head like an antenna of a remote-control car or something.

I'm suprised that the advance ball works better on softer materials, I don't understand the cause of that - my initial thoughts are the opposite: softer materials would 'intent' more from its pressure therefor increasing the resistance via increased surface contact.

Perhaps the harder materials are more prone to oscillation?

I'm working on a design for one this week, I will post some updates soon.

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tragwag
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36318Unread post tragwag
Wed Jul 29, 2015 10:45 am

ah! I hadn't thought of an advance ball, because I've honestly never seen one in a working setup.
that's a great idea, definitely let me know if the implementation works out for you.
making lathe cuts on a Presto 6N, HIFI stereo cuts on vinylrecorder
at Audio Geography Studios, Providence, RI USA
http://www.audiogeography.com

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rsimms3
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Re: uneven blank causing overcut and undercut - vinyl record

Post: # 36320Unread post rsimms3
Wed Jul 29, 2015 11:01 am

You could mimic the setup on a Fairchild cutterhead carriage. The knob on top adjusts the depth of the stylus relative to the advance ball and the advance ball can be swiveled for inside>out or outside>in cutting along with adjusting the amount of advance. This particular carriage does not include the angle adjustment parts that attach to the cutterhead. I have a complete carriage minus the cutterhead at home if you'd like more pics.

Image
Image

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