Amadeal CJ18A Mini Lathe CNC Conversion

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29 Sep 2022 17:08 #253037 by Nosveratau
Hi All

Just new here and to CNC in general so my plans may be a little ambitious.

I bought an Amadeal CJ18A Mini Lathe a few years ago and its been a good little machine for me, now I know this is a Chinese Clone machine and they dont have a great reputation but for what I use it for, making small aluminium and steel parts for Robotics projects it works well enough.

However one thing I have always struggled with is my own ability and would like to create more complex parts and want to convert the lathe to CNC.

So my idea is to change the lead screw to a ball screw and use a Nema 23 420 Oz Stepper Motor for this axis.

However on the compound slide I am not sure what to do as the space is really constrained so not sure I could get a ballscrew to replace the current screw or do you think attaching a Nema23 420 Oz to the existing screw is advisable?

Due to the noise it makes I would like to remove all the different gears and be able to index the spindle, have better speed control and still be able to cut threads so was thinking about either changing the motor to a servo motor or a closed loop stepper motor, but I have really no clue on this. Is this even possible?

Finally, how to control, my old MPCNC was basic using ESTLCAM and a RAMPS 1.4 Board with Arduino but as that basically a step by step build i was basically hand held doing that build, so this lathe is a bit of a challenge for me.

Any help or advice would be great, especially if someone has already converted one of these machines. 

Cheers DJ
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29 Sep 2022 18:23 #253041 by andypugh
My first CNC conversion was an Amadeal 8 x 20.

Space is, indeed, pretty tight in the cross slide, but it can be done, I think.

You might as well get rid of the top slide / swivel slide / compound slide. It just reduces rigidity on a CNC lathe.

I have lost the photos of that conversion (they were on Picasa) but there are some later ones here. photos.app.goo.gl/nwM9Ze59j3zi5TB77
The machine was a lathe/mill combo, and wasn't a good mill at all, but was an OK lathe.

My cross slide was converted using an 8mm ball screw. The problem is not the screw, but the nut. I ended up having to cut away some of the cross-slide dovetail to make space for the nut, but that was largely because I wanted to copy a feature of my dad's Smart and Brown where the screw is protected by a steel shim cover that passes through a "tunnel" over the ballscrew. The album above shows the same arrangement being set up for the Z slide of the mill attachment.

One thing that did help my conversion was moving the thrust control ourboard into the handwheel area. Cunningly none of the photos really show this, but there was a pair of angular contact bearings mounted in the handwheel area, then a needle roller bearing where the belt drives the ballscrew pulley. This pulley (T2.5 belt) was just small enough to fit under the cross slide as it came back.

The Z axis is very easy.

You probably can get away with using the original screw, as software backlash comp can cope better on a lathe than a mill. You would just have to write the G-code such that tapers are always cut large-to-small so that only one side of the backlash is used

My subsequent conversions spent a lot more money, and look a lot better. If you have a 3D printer then I would suggest printing foundry patterns and making parts that actually look like they belong on a lathe. Reckon on paying £10/kg for castings from AJD and you will find that it starts to look tempting.

(Much bigger than your lathe, but this is the set of castings I made for my second lathe conversion, a whole new gearbox, saddle apron, toolpost riser and covr for the X axis drive chain: photos.app.goo.gl/F5CtJY9Fed1Cruk2A )
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30 Sep 2022 15:07 #253104 by arvidb

Due to the noise it makes I would like to remove all the different gears and be able to index the spindle, have better speed control and still be able to cut threads so was thinking about either changing the motor to a servo motor or a closed loop stepper motor, but I have really no clue on this. Is this even possible?

I have pretty much the same idea. I'm going to try using a HTD pulley with a 28 mm taperlock bushing to drive the spindle:

It's just loosely fitted for measuring in the image: some steel rings/sleeves will be needed to preload the spindle bearings through the bushing.

As a waypoint on the road to full CNC I plan to drive the original Z leadscrew with a servo slaved to the spindle to start with. (Kind of an advanced electronic leadscrew if you will.)

You've seen RotarySMP:s CNC conversion? He's a member here and made a very nice conversion of a CJ18A: www.youtube.com/playlist?list=PLHRtJd1bD...-A-CPBwys-tTM3wKMOGW
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30 Sep 2022 15:22 #253105 by andypugh

It's just loosely fitted for measuring in the image: some steel rings/sleeves will be needed to preload the spindle bearings through the bushing.


I didn't bother, I just preloaded the spindle before final tightening of the taperlock and it worked fine for years.
As long as contact on both sides is only with the taperlock and not with the pulley you can treat the taperlock bush as a solid sleeve.

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30 Sep 2022 18:20 - 30 Sep 2022 18:21 #253118 by arvidb
That's what I'm planning to do as well. Nice to hear that it works! But surely you needed some kind of sleeve to take up the axial distance between the bearing race and the taperlock bushing? The bearing race is about 10 mm below/inside the surface of the headstock, at least on my machine...
Last edit: 30 Sep 2022 18:21 by arvidb.

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30 Sep 2022 22:12 #253128 by andypugh
It's been a while, but probably. I have a vague memory that perhaps I replaced a bit of plastic pipe (Mine was _not_ a quality lathe from the factory)

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30 Sep 2022 23:14 #253132 by arvidb
Haha, yeah, mine had the plastic tube too. The quality of the Amadeal CJ18A really is awful, but the size (and the price) is right! Biggest issue with mine was that the paint was literally falling off of it - it hadn't been cleaned/prepped before painting so lots of oily grinding dust under the paint. That took some effort to sort out.



I replaced the plastic tube with a steel one a while ago to be able to properly preload the spindle bearings (which I had changed earlier to angular contact ones so they really needed the preload), but a shorter tube will be needed to accomodate the taperlock bushing.
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01 Oct 2022 10:45 #253162 by Nosveratau
Hey

Thanks for the posts @arvidb

I am still reading up on all of this, to be honest I thought it was going to be a simple as just sticking a couple of stepper motors on the axis, haha.

Thanks for the link to the youtube series, will give that a look.

I have just been given a little Performance Power PP2505BD Pillar Drill and a Stahlwerk CT520P Welding machine, both look like Chinese knockoffs too. The Pillar drill chuck is damaged and the last owner for whatever reason as welded the chuck to the taper, so I need to find a new quill for this, and never use a welding machine before so no idea about this, so if you dont hear from me, things went wrong, haha.

DJ

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