DIY machining a compression screw

I built a powered milling attachment to replace my toolpost and added CNC control to the spindle of my lathe (carriage was already CNC'd) so that I could machine a compression screw for an extruder. The screw is 25mm diameter, 25mm pitch and the threaded section is 500mm long. It was very slow going, the motor I used on the milling attachment was only 1/4HP, would get very hot after 10 minutes and needed frequent breaks. The channel in the screw is 6mm deep in the feed section, reducing to 2mm in the metering section giving a compression ratio of 2.5:1

[@crunchworks22]

I would love to see more videos about the making of this screw and about your CNC lathe in general. It looks like you do very interesting work.

[@antongyrt4814]

Браво! Грамотное использование станка.

[@creast56]

I am seriously impressed!!!

[@HeaanLasai]

Amazing work, dude!

[@OneArmyVideos]

wow impressive job! Looks amazing

[@AndysMachines]

Thanks! It was a bit of a challenge!

[@ernestasus8053]

@@AndysMachines ן⁷

[@user-pg5xs9qj9s]

@@ernestasus8053 贊分享，現在能在處看到眼福阿們

[@Madeinoz1967]

Herculean effort. Well done

[@alitn588]

Love everything specifically countdown music !😉😂 Well-done mate 🌺

[@peterfitzpatrick7032]

Carol & Richard would approve... 😂 So, the pitch is fixed, I thought a variable pitch was used in these moulding machine spindles ... living & learning ..🤔 😎👍☘️🍺

[@juancarruyotrainer5128]

Great Job. Congrats..!

[@motoca660]

Very good your work! could you pass the details of the electronics and programming code?

[@damienmiller]

Would love to see how you CNC converted your lathe - I have a similar one and was toying with doing it myself.

[@AndysMachines]

Maybe I'll do a video on that one day. I use it mostly as a manual lathe, so I didn't want the CNC conversion to affect normal use, but also be able to quickly put it in 'CNC mode'.

[@damienmiller]

@@AndysMachines I'm even more interested now!

[@gordon6029]

Very cool!

[@ReneJurack]

Impressive :)

[@user-sm1xz4go6d]

good job

[@mrwolsy3696]

Using a centre lathe as a 4 axis mill, frugal and intelligent.

[@svin3819]

I really like this. Great job. Any reason you didn't just turn it with turning tools if its cnc?

[@AndysMachines]

Because the pitch of the screw is quite large (25mm) to turn it with the correct surface speed the carriage would have to move extremely fast.

[@mufaddalsogiawala1857]

which material did you use for workpiece?

[@felixdietzCGN]

awesome!

[@Frank-bh3cm]

Just WOW!

[@Deetalks87]

how do you figure out the tilt angle (of the saw)? P.S: the final result looks very pro, also what kind of steel did you use, and finally any videos of the screw in action ?

[@AndysMachines]

The tilt (helix angle) is equal to the inverse tangent of the pitch of the screw divided by the circumference. Imagine wrapping a piece of paper around the screw, drawing on the shape of the thread, and then unrolling the paper. You will have a straight line at the helix angle. This screw was just cold rolled mild steel, you can't see it but it went into this machine: kzbin.info/www/bejne/qZ-tp4CphadoqKs I later built a better machine without this screw, but I still have it and may repurpose it one day.

[@showcase-me]

3:05 i need this music in My workshop 😅

[@shimmerite_ua]

Definitely went creative on sound design of the vid!

[@BradleyDWoods-pz8rv]

How are you controlling the horizontal feed? Are you geared for something like .75 TPI ?

[@AndysMachines]

More like 1TPI (25mm). It's not geared, the lathe's leadscrew is driven by a motor controlled by CNC

[@RCDinsmore]

This is cool, but to me the most important part of this video is between 1:02 and 1:29. Please post more about your adjustable saw and your CNC Spindle drive!

[@AndysMachines]

These were both custom things I built in order to make this screw. The CNC spindle drive is just a stepper motor geared down with a high reduction ratio and driving the gear on the back of the lathe spindle (the one that normally drives the changewheels). It's controlled by Mach 3. The toolpost milling attachment is a motor from an old drill press with an appropriate gear reduction for driving HSS milling cutters of around 60-75mm diameter, it has a short spindle that I can mount different cutters to and the whole thing can tilt, the motor was really a bit underpowered, it would get hot and was very slow going.

[@milestone821]

😳😳😳😳😳 unbelievable 👌👌

[@impactodelsurenterprise2440]

Does the lathe have a gearbox? Can't imagine how the spindle would generate enough torque at that low of an rpm

[@AndysMachines]

I'm not using the lathe's motor at all, the spindle is turned by a Nema 23 stepper motor which has plenty of torque via a gear reduction.

[@doctorpc1531]

What's the circular cutting bit called? I'm facing extreme trouble trying to identify it.

[@AndysMachines]

It's a 'slitting saw' they are available in many diameters and thicknesses and usually used on a milling machine.

[@doctorpc1531]

@@AndysMachines Ahhhh, thank you so much!

[@alcsvamakinasaypek4452]

hayranlık verici

[@thomasmica2856]

Это супер !

[@marcinose]

How is that a 2.5:1 compression, and not 3:1?

[@AndysMachines]

It's just the difference in volume of plastic that can fit in the root of the threads of the start and end sections of the screw. ie. the amount of metal removed from the feed section is 2.5x that of the metering section.

[@dans5595]

what is this *for*? i google compression screw, and all i get are links for repairing bone fractures.

[@AndysMachines]

It's for an injection moulding machine. You can see the machine I built with it in one of my other videos (still a work in progress).

[@trapezoidalthread7052]

Super. You would have a bigger machine.

[@prom368]

Tell me the post processor for the manufacture of such screws?

[@AndysMachines]

No post processor, just done with G-code and Mach 3. G-code written manually.

[@prom368]

@@AndysMachines Can you send us the G code? Surprisingly such a complex process was written, commendable)

[@AndysMachines]

@@prom368 I don't have the file anymore, this was over 3 years ago, but it's very simple. I cut the screw with multiple passes, each pass is a Y move to the cutting depth, then a simultaneous A and Z move to cut the thread. For the tapered section it's a simultaneous move in all three axes with Y starting and ending at the required depth. Each pass would look something like: G00 A0.000 Y15.000 Z0.000 G01 Y8.000 G01 A360.000 Y9.000 Z25.000

[@joaopizza93]

What's the external diameter and length of this screw?

[@AndysMachines]

It was 25mm diameter and I think it was around 500mm long.

[@evildrome]

Any reason you didn't rough it out with a single point tool & finish with the milling head (or a TP grinder) ?

[@AndysMachines]

The pitch of the screw is to high to screw-cut on my lathe, and there would be a lot of flex. I don't have a toolpost grinder so I built the milling attachment which is faster and less messy than a grinder.

[@evildrome]

​ @AndysMachines You built an ELS so that you could machine the screw. Could you have used the ELS with a single point tool? TBF you'd need to have driven it around a lot faster. The flex only matters on the last pass. You don't really care about it when you're roughing something. The milling attachment is really nice BTW but TP milling is always very limited because you need to transmit the cutting force into the bed and that has to happen through the tool post. I often wondered about making a bridge from the rear of the slide to the toolpost and mounting a milling cutter in the middle of the bridge.

[@AndysMachines]

The lead screw is the original one on the lathe and only has a pitch of 3mm, to turn the thread at any reasonable spindle speed it would have to rotate extremely fast, as you say. The leadscrew is only driven by a size 23 stepper motor, it wouldn't have enough torque at high speed and would just stall.

[@edvaldog.ferreira2499]

Boa noite amigo: Qual o RPM ( rotação) da fresa de corte e ela é de aço rápido ( HSS )

[@AndysMachines]

Yes, HSS cutters and it was geared down to around 120rpm I think.

[@edvaldog.ferreira2499]

@@AndysMachines Obrigado meu amigo Deus te abencoe e te ilumine.

[@hyperhektor7733]

impressive but i would have used a grinder instead

[@AndysMachines]

I did consider that but grinding this much material off would be extremely slow. On the plus side, grinding can produce a better finish and with less cutting force so longer screws could be made without extra support.

[@adamodeh7068]

How come its diy video

[@AndysMachines]

Because I did it all myself at home.

[@user-pg5xs9qj9s]

👍🙏👌🤫

[@tonycstech]

Me when video started: LIKE LIKE LIKE ! Me when he attached milling saw: 😒

[@ddsolihtea998]

Oke

[@jouhaed841]

Ok

[@jayare8448]

Very cool!