KNOP lathe DIY build

[KNOP]

Got the swarf suction kind of working. The swarf is sucked away consistently, but my poor vacuum cleaner overheats every two minutes or so.

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Good enough to some test cuts now, but am looking into a vacuum pump.

https://polyestershoppen.nl/vacuummaterialen/olieloze-vacuumpomp-364.html

This one is oilless, supposedly silent and has a 68l/min capacity. Would that be enough?

The recordings are getting better. I aligned the diamand tip a lot better then before, resulting in less background noise. Started using a heating lamp for disc heating and played around with the fabfilter eq.
here is a sample: https://clyp.it/0paivkza

There is however still a harsh sound in the high frequencies I cannot seem to get rid of. I am however still using a 25W RMS per channel amp, perhaps a beefier amp will help there.

Any tips also as on how to improve the dynamic cutterhead? I'm not planning to upgrade to a feedback setup.
I'll try the metal printed torque tube with a plastic V spring perhaps.
I can shave off a gram or so off the moving mass using carbon fibre tubes as pushrods and a setscrew instead of the m3 bolt for setting the shank. Perhaps a little more. But what is an ideal moving mass for a dynamic cutterhead?
I'll play around with the V spring stiffness but have no idea if it should be stiffer or less stiff.

Best Regards,

Wim

[Ritter]

Hoi Wim,

Great project - I'm inspired by your success... keep going!

Couple of questions for you:

- why did you pick the Grampian style stylus for your head?
- do you have any kind of counter-weight on the cutting head?

Cheers!

[KNOP]

Hey ,

I used a grampian style needle because I had one lying around. Could make a neumann style hole as well in the torque tube, but I'm not sure if the stylus would clear the cutterhead body.
The counterweight are the metal plates on the backside of the hinge.

I seem to have issues with one channel being noticable louder than the other one. Could this be the result of not having the stylus at a perfect 90° angle sideways, or does this imply a difference in the drivers, or both? I didn't measure any angles when setting up the head, just adjusting it by eye.

My recording chain somewhere still sums all signals to mono somewhere as it seems, so again I was mislead by the recordings on my PC for analysing. Maybe I'm doing something wrong on my Allen & Heath Zed panel (never really used the build in soundcard before). I need a decent soundcard anyhow, as I am using the built in soundcard in my Lenovo laptop as of now.

[KNOP]

Ok I did a quick test and seems that one of my ortofon cartridges is responsible for the left/right volume difference. There are however slight tonal differences in the left and right channel. I will try to work with left and right seperate EQ's for the next recordings. I ordered a vacuum pump, some cute heatsinks to put on the back off the drivers (don't know if that will actually help), a nice box for building a control panel and some DB9 connectors, for easy swapping of cutterheads. I hope the vacuum pump system will go as planned, as I'm tired of my vacuum overheating every minute or two. Also waiting on some new blanks and an extra cutting stylus. In the meantime i'm working on a V2 body for the cutterhead, which should get rid of the driver clearance issue, remove the need for dremeling excess plastic in the driver mounting holes, and get the right dimensions for the cutterhead mount. As of now it is only attached to the overhead mechanism using 1 bolt, since I got the mounting hole dimensions wrong.

Best Regards,

Wim

[woodrat123]

Mate this looks the absolute nuts, my mind is racing now how much does a 3D part like that cutterhead cost? Is it pounds or tens of pounds?


Sent from my iPhone using Tapatalk

[KNOP]

The prices for the 3D prints are quite reasonable in costs I think (for small parts). The cutterhead body + 2 torque tubes was about 30 euro without shipping costs. An alumium printed torque tube was about the same.

[KNOP]

Hi!

I've been working on the machine a bit. I've broke a torque tube by using to much force to set the needle. I've rebuilt the head and added DB9 connectors on top. I switched the setscrew of the shank to a real setscrew, saved almost 0,7gram.

I bended a new tube for suction, this time 6mm OD instead of 5. This got me cursing more than a few times.

The vac pomp didnt work out, not enough airflow I guess. Pretty bummed about that.
Bought a small shop vac today, noisey but reliably pulls in the string without overheating.

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[fredbissnette]

awesome work

[KNOP]

Here's another testcut, this time about 10db hotter than the previous ones. Still recorded in mono, I feel like an idiot as to why I cant get stereo recorded on my allen & heath ZED mixer.

https://clyp.it/b5dnrmuh

and the original song for comparing:

https://www.youtube.com/watch?v=4wfSIsAnUzg

[Fabougino]

Amazing job.


Envoyé de mon iPhone en utilisant Tapatalk

[KNOP]

Hey everyone !

I've been busy finishing my lathe. I made a nice table for it, plus got a higher powered amp from NAD and an external soundcard.
I am still finishing up the electrical parts of the control panel.

lathe.png

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Got new 3D prints for 3 new cutterheads in mail, this time solving a few issues like having to cut out the surround for clearance issues, and put the mounting holes of the cutterhead in the correct position for mono type cutterheads. Using a few optimalisations for the cutterhead the moving mass will go down to 3,7 grams from 5 grams. I'm hoping to finish up everything by next week.

A bit off topic, but my friend and I are also experimenting with low quantity printed covers, and finally got a solution that is affordable and good looking.

IMG-20170209-WA0001.jpg

And we also made a gold record using spray paint just for giggles

IMG-20170210-WA0001.jpg

Best Regards,

Wim

[Gus]

Congrats looks really nice !

[Ritter]

Beautiful work... shame my own build isn't progressing this fast!

[sifis1983]

Hi Wim,

Amazing work! Congratulations! Very inspiring job!

Well, I have some queries...

1st. Where do you find the airpot dashpot? Is there any specific characteristic to choose it? Is it matters the weight of the cutterhead?
How you attach it in the whole mechanism, for pulling up and lower down you cutterhead?

2nd. Why you choose Visaton BF 32 for drivers? What material are the push rods are made? How you attach them in the center of the driver? Did you just open a center hole and glue them? Did you try the carbon fiber push rods?

3rd. Is this sound example, that you upload, has enough power, compared with industry records?

Regards,
Sifis

[KNOP]

1st. Where do you find the airpot dashpot? Is there any specific characteristic to choose it? Is it matters the weight of the cutterhead?
How you attach it in the whole mechanism, for pulling up and lower down you cutterhead?

The airpot is a model 2K160, and has a very wide range of resistance. I use near the minimum amount of resistance, so heavier cutterheads will probably work ok. I use this model because I got a free sample, but would choose a smaller model in the future.
The lever to lower the cutterhead is attached to a fishing wire which pulls up the rotating assembly of the cutterhead.


2nd. Why you choose Visaton BF 32 for drivers? What material are the push rods are made? How you attach them in the center of the driver? Did you just open a center hole and glue them? Did you try the carbon fiber push rods?

The visaton drivers are chosen because of the decent power handling, easy availability in europe and the concave cone. The pushrods are actually M2x20 bolts. Due to magnetism they stick to the driver cone, and you can adjust them to 90° easily. Then I poured epoxy in the concave shape up to the point where the cone meets the coil. I did not try the carbon push rods, but am going to use them in the next version of the cutterhead.


3rd. Is this sound example, that you upload, has enough power, compared with industry records?

The upload has about the same level as an LP with about 18" min a side. Not very scientific but I did not try to cut louder as of yet.

[sifis1983]

Perfect! Thank you for the information.

I can't find to buy this kind of airpot dashpot in europe. However, I will search in local shops here.

Also, I can't unsterstand why this concave cone of your driver is a benefit.

Anyway, keep us uptaded in your project. I would like to see if carbon push rods act better.

Regards,
Sifis

[KNOP]

A little update: got the lathe control and heat control up and running. Note to self: stop using tight fit enclosures.

IMG_20170224_150917.jpg

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It all fits inside, but barely.
The whole thing took about 5 days to build, made a lot of errors on the way.

It has LPI and rpm adjustment, lead in and lead out, manual left/right movement and adjustable heating from 1 to 5v. I added no inside out cutting feature, but you can reverse the 4 motor cables to cut inside out. Anyone interested in the source code(c arduino) you can always pm me. Im far from a pro programmer, but may be useful for people just starting out with programming.

I'll start building some more cutterheads tonight, pretty excited about it.

[crowesBR]

Wow. Impressive work man.

[KNOP]

Ok made a new cutterhead yesterday, and finished up the vacuum solution. Going to do some testcuts later this day.

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I made some jigs to align the pushrods, this tiblme 2mmcarbon fibre rods.

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V2 head next to the v1. Tip: aluminium tubes are way easier to bend.... Added clamps for needle heating as well. Unfortuately the built in heating only goes up to 3v under load, should have tested this before. Anyway there is an extra input for an external variable ps, so I will use that in the meantime.

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The vacuum box with an external cooling fan. Makes all the difference for vacuum noise.


Best regards,

Wim

[KNOP]

Hello everyone

I've recorded a sample in stereo this time, using a scarlett 2i2 interface.
https://clyp.it/k2ynhwho

Recorded with a broken tip, at 75LPI and loud to cover up the background noise. I still make too many operator errors to try out the brand new stylus from myshank. The song were recorded at 33RPM, and too much weight on the stylus (Forgot to check beforehand), resulting in more wow issues than my previous recordings, which were at 12gram and 45rpm.

w=1khz sine stereo.png

stereo sine wave recorded at about 1000Hz

white noise right channel.png

white noise left channel.png

White noise cut no filters left and right channel

freq response head 2.png

White noise response after filtering

I've used fabfilter again to flatten out a white noise cut, and while the white noise recorded with the EQ correct sounds and looks pretty flat, when recording real sound it does not always follow through. It seems especially the two resonant peaks at 700Hz and 10KHz do not scale linearly with volume increases, so when compensating in Eq it tends to overcompensate.
While a perfect cut will be impossible on a cutterhead built with drivers and no feedback, I hope to get it as pleasing sounding as possible in the future.

Other issues are the lead in and lead out motion, you here a distinct motor noise, which is luckily (almost) absent while at recording speed. I will try out a smaller stepper like ciuens use on a ZEZ cutter, in combination with a rubber belt to reduce the motor noise.
The other issue I have is that about one time in ten the swarf does not get removed at first, but on the plus side the swarf does get sucked to the inside of the platter so you can use a brush to save the cut.

Still got a lot of work to do, but hoping to resolve the issues one by one.