KNOP lathe DIY build

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KNOP
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KNOP lathe DIY build

Post: # 45111Unread post KNOP
Thu Dec 08, 2016 6:46 am

Hello everyone!

I am in progress of developing an overhead lathe using only standard parts and 3D printed parts, as I do not have easy access to a machine shop. Nor do I have a 3D printer, but as of now I am using the materialise 3D printing service. I started looking around on ebay, and bough myself a THK 140mm linear slide, and a sigma koki Z axis slide. Then ordered adaptor plates in a material called Alumide, looks nice and shiny :), and fitted them to a bridge made out of Maytec aluminium extrusion profiles. As I found out stupidly yesterday, I had the slide mounted on the wrong side of the lathe, but thats an easy fix.
IMG-20161121-WA0002.jpg
A couple of days ago I received the parts for the suspension assembly, and a 3D printed suction tube (I tried and failed a couple of times making a nice looking suction tube the manual way)
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But It seems I had made a couple of mistakes in my STL files, as a couple of smaller parts were not printed, and the lever for the cutterhead drop movement was fused with the main body. Luckily the crucial parts were printed OK, and a dremel severed the lever from the rest. One small note is that the dye of these parts was not as nicely finished as the adapter plates, because of the box containing the components. The better was was probably to connect all the pieces using rods, and cutting them when received.
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I used some metal plates as a quick makeshift counterweight, used some small RC bearings which were press fitted into the 3D print, and attached a Airpot Dashpot.
WP_20161207_11_38_28_Pro.jpg
Since I was quite excited to get up and running, I did a fast assembly of everything, not really measuring and aligning thing etc. and got some quick and dirty test cuts. The head is an 500 Ohm Fairchild 541A overhead. The stylus holder was originally bent, but opened it up and bent it back to straight. I was pretty scared to open the thing up, but the process of disassembly and assembly was actually pretty straightforward. Only the gap alignment was a bit fiddly. I wired a nice 70V toroidal transformer and a fuse between the amp and the head, and fused it with a 100mA F glass fuse on the secondary side. I now came to the conclusion that the assembly was mounted on the wrong side of the record player. I just installed a steel needle and tried some embossing (since the needle is backwards when mounted "correctly"), with mediocre results. Audio level was very good, frequency response not bad but a lot of distortion, and my lesser turntables have difficulty tracking the grooves. On the plus side, when cutting silent grooves I found no evidence of noise from the stepper motor, and under a 100X microscope I could not detect any 'stepping'. I used a Trinamic TMC2100 based stepper driver controlled by an arduino. This driver has 256x microstepping, and more importantly a mode mode called StealthChop. This makes the steppers motors very silent, but at the cost of most of the torque. But the torque is still more than enough to move the carriage. There is also a inline rubber coupler to the slide axis, and a viscous damper, which should be good for the faster lead out moves. I will do some more proper testing when I have some time, and decide later to maybe upgrade to a belt driven setup with DC / Brushless / Whatever motor.


I hope to free up some time this weekend to start building a floor plate, control panel, ...
In the meantime I'm still waiting for a stereo cutterhead print. I ordered the body in Polyamide as well as Alumide, and the torque tube will be 3D printed in aluminium.
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KNOP
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Re: KNOP lathe DIY build

Post: # 45112Unread post KNOP
Thu Dec 08, 2016 6:50 am

WP_20161207_15_55_15_Pro.jpg
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CUTTERHEAD V4.jpg
I am still debating on the platter problem. I could get a SP10/SP15 and be done with it. Or make something of my own.
Anyone knows if these kind of acrylic hifi platters are worth investigating?

http://www.acrylteller.com/ACRYLIC-PLATTER-for-Pro-Ject-RPM-51-RPM-5-RPM-4-35mm

Also I have no spring at the suspension, but have provided some space for it, next to the dashpot. Is there any benefit to attaching a spring there?
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fredbissnette
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Re: KNOP lathe DIY build

Post: # 45113Unread post fredbissnette
Thu Dec 08, 2016 8:16 am

nice build
Instagram @styluspressurerecords

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Casanova
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Re: KNOP lathe DIY build

Post: # 45129Unread post Casanova
Fri Dec 09, 2016 11:32 am

Hello KNOP, nice and very clean work!

Can you tell me the sizes of the aluminium profiles you used for your lathe?
Another question... I know that the kind of THK slider you used has a kind of rod that comes out from the back of the stepper motor. Can you attach some kind of wheel knob to it to manually move the cutter head?

Thanks.

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KNOP
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Re: KNOP lathe DIY build

Post: # 45130Unread post KNOP
Fri Dec 09, 2016 12:04 pm

Hey. The profiles are 40x40 mm, ordered them at www.damencnc.nl.

You could attach a wheel knob, but I don't think that it would produce a smooth motion.

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Casanova
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Re: KNOP lathe DIY build

Post: # 45131Unread post Casanova
Fri Dec 09, 2016 12:38 pm

A smooth motion would not be a big issue for me since I would just use the knob to position the cutter head at the beginning of the record.

I keeped an eye on THK sliders for some time I'm thinking to buy on, but first I'd like to know if the carriage movement is really smooth and precise.
Is the stepper motor noticeable in cutted grooves or the steps are so small that you can't hear them?

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KNOP
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Re: KNOP lathe DIY build

Post: # 45145Unread post KNOP
Sat Dec 10, 2016 6:18 am

I'll do some test cuts tonight at different LPI settings, for checking the stepper noise. I have this 15€ USB crap microscope, I will upload some pictures of the grooves.

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KNOP
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Re: KNOP lathe DIY build

Post: # 45148Unread post KNOP
Sat Dec 10, 2016 9:42 am

Got the lathe setup properly and cut some silent grooves and test music. I did not hear stepper motor noise on the groove, it is below the background noise.
WIN_20161210_15_02_23_Pro.jpg
WIN_20161210_15_03_04_Pro.jpg
And some grooves with audio:
WIN_20161210_15_19_51_Pro.jpg
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Casanova
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Re: KNOP lathe DIY build

Post: # 45155Unread post Casanova
Sat Dec 10, 2016 3:23 pm

Nice! So your project looks promising.
Thanks for the info.

Keep us updated. :wink:

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KNOP
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Re: KNOP lathe DIY build

Post: # 45176Unread post KNOP
Tue Dec 13, 2016 11:04 am

I've just got parts for 2 stereo cutterheads today. One printed in alumide(the shiny one), which is noticably stiffer material than other, printed in regular polyamide.
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I've 3D printed the torque tube as well, with an integrated V spring. It is designed for a grampian style shank, it fits snugly. I'm curious to know if the V spring will work, would be an easy solution. The torque tube + V spring combo weighs 0,94 grams.

Seems like I have got some clearance issues where the V spring and the rubber surround are, but I think I can just clear it by cutting off some plastic. Will have to set the drivers a couple of mm further out or deeper in future prints. I'll have to finish the head another day, as work is piling up at my desk!
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markrob
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Re: KNOP lathe DIY build

Post: # 45178Unread post markrob
Tue Dec 13, 2016 4:29 pm

Hi,

Nice looking job. One problem I see is that you are coupling to the push rod using the driver diaphragm. I think that will cause issues at higher frequencies due to mechanical decoupling. At this point, its worth a try to see if the performance is acceptable. The best bet is to try to couple as directly as possible to the voice coil via some sort of cone. Its all part of the fun and everything you do will be a good learning experience. Keep us up to date on the project.

Regards,

Mark

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Sillitoe
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Re: KNOP lathe DIY build

Post: # 45181Unread post Sillitoe
Tue Dec 13, 2016 10:44 pm

Cool build KNOP!

Definitely give the directly coupled pushrod-cone design a go.
You may also want to experiment with a second spring at another point along the pushrod, these can compress the diaphragm giving a higher mechanical resonance.
Metal dome drivers with same sort of specs may give you better results than those plastic domes.
No problems with high frequencies with that kind of design in my experience, but there are trade offs with every design. :wink:

Totally agree Mark! Fun First!!!

Cheers
James

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KNOP
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Re: KNOP lathe DIY build

Post: # 45239Unread post KNOP
Mon Dec 19, 2016 12:32 pm

About the mechanical decoupling of HF, I did not think of this issue before, but I guess I will find out if is an issue. If the first prototype actually cuts any audio into a blank, I will be more than happy.
And James, are you talking about a pretensioning of some sorts on the pushrod? I'm not really sure what you mean with the spring.

So I assembled the cutterhead. Quite a tedious work, i'm not used to working at such small scale.
I managed to knock a magnet of one of the drivers out of alignment, but quickly got a third speaker up and running.
Also got an aluminium 3D printed torque tube in the mailbox, really quite amazing what they can 3D print these days.
I hooked the cutterhead up to a amp for a quick test, there is sound and no obvious unwanted noises. No time to get it up and running on the lathe today,

I hope I can get to testing this week.


IMG-20161219-WA0001.jpg
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EpicenterBryan
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Re: KNOP lathe DIY build

Post: # 45240Unread post EpicenterBryan
Mon Dec 19, 2016 1:00 pm

KNOP wrote:Also got an aluminium 3D printed torque tube in the mailbox, really quite amazing what they can 3D print these days.
I'm thinking the V spring may not flex as needed. You might end up cutting that off and make it with either plastic or shim stock. A feeler gauge will do in a pinch.

Bryan

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Sillitoe
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Re: KNOP lathe DIY build

Post: # 45241Unread post Sillitoe
Mon Dec 19, 2016 1:01 pm

Hi KNOP!

Yes, I was talking about a pretentious spring on the pushrod. :lol: jokes

Looks like you're on the right track mate, keep up the experimentation! :D

Cheers
James

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KNOP
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Re: KNOP lathe DIY build

Post: # 45258Unread post KNOP
Wed Dec 21, 2016 2:25 am

I did some test cuts of audio, but especially the vocals sound distorted. Then i recorded a white noise + inverse RIAA back into the pc, but forgot that my dj mixer was set on sum to mono. got this result:
grafiek 2.png
But then the (biggest) issue became clear: the two drivers have a very different tonal character, noticable when playing in free air or when playing back cut grooves. When played back on a turntable and setting the amp to only one side, one side sounds quite a lot duller, boxier and resonant then the other. I think possibly a alignment issue or the fact that I tore the M2 bolt + the epoxy of the drivers with the misaligned magnet and glued it on top of another driver. So I will get this issue adressed first, then get a suction tube going.
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KNOP
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Re: KNOP lathe DIY build

Post: # 45297Unread post KNOP
Fri Dec 23, 2016 6:43 am

Ok so I rebuilt the head, made a swarf tube but did not test it as of yet.
Did a weighting of all the moving mass, it sums up to 5,5 grams.

Here is the head response using IRIAA and white noise, now just 3 resonance peaks (the 100hz also appeared in a silent groove, so I guess some 50hz mains harmonic).
cutterhead V2 response left.png
cutterhead V2 response right.png
I looked up fabfilter pro, it really is a very handy plugin for EQ.
And did a quick test cut, sounded a lot better than before. Still a lot of background noise, but thats not related to the cutterhead. You can listen to the link below:

https://sndt.gl/Q6hYT8BkKJHvj/r/bz4341wRrOKNcKWGqL1a?utm_source=sendit&utm_medium=email&utm_campaign=sendit-recipient&utm_content=web
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Gus
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Re: KNOP lathe DIY build

Post: # 45301Unread post Gus
Fri Dec 23, 2016 10:40 am

Nice Keep it up!
do you cut with diamond on pvc or sapphire on lacquer?

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KNOP
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Re: KNOP lathe DIY build

Post: # 45308Unread post KNOP
Sat Dec 24, 2016 10:25 am

Diamond + Blanks from Myshank. I would like to cut a lacquer someday but not really comfortable with the flammable swarf thing.

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Gridlock
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Re: KNOP lathe DIY build

Post: # 45309Unread post Gridlock
Sat Dec 24, 2016 1:49 pm

Come on dude FIRE rules! Explosions! Mel Gibson! Just take it outside to light it on fire. I should really take more pics and video and post here except I don't know anything about computers and y'all think I'm joana for some reason! I'm a punk rocker with a super ghetto fabulous presto. Mono and fire. Reeeaaally wasted this Chris mas
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Recordette Sr.......Presto K-8

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