Chester Model B 3-in-1 conversion

[klonx]

Well, after many years of lurking on here in the background I thought I'd finally get down to the business of converting my lathe/mill, she's the Chester Model B 3-in-1 machine available over here in the UK, but very similar to the Smithy machines in the US as well as several others...



I'm going to start with just converting the Lathe part of the machine, the reason for doing this is that I plan to buy a seperate mill at some point and convert that to cnc too, the mill head on the chester understandably isn't that great but if you take small cuts and clamp everything rigid then it's possible to get some very good results, the lathe itself is capable of good results though the backlash present in the cross slide needs to be taken into account!

All the parts will be added using exisiting mounting points where possible, I want to ensure that the machine can be returned to its original state should I decide to change machines at a later date.

Steppers/drives: I'm currently in possession of some 12nm steppers and MCP/Leadshine 2278 drives (with internal power supply) both of which where purchased from MCP in the UK. The drives give me peak amps of 7.8 which should be plenty for quick rapids

One problem I've identified already is that there is little room beneath the cross slide to mount a ball nut, so this will need to be mounted to the right instead...



So this will mean drilling new mounting holes in the ends of the milling table, this in itself could be fun as I need to do this on the machine itself!

I have a couple of ballscrews to hand that can be used for the x axis, both are THK precision ground, C1 and C3 accuracy, so should be up to the job

as for teh Y axis I don't have a clue at the moment, it may be that I have to go down the route of buying a rolled one for this unless I can find an alternative on ebay somewhere.

Well that's it for now, I'm hoping to have the wiring sorted soon for the drives & motors, I have a steel electrical cabinet already that will be used to house everything. More pics coming soon

Kev

[klonx]

It's all going very slow at the minute, waiting to receive ballscrews and things so that I can measure things up and get building! Just started drawing up a few of the bits, here's one of my front mounts for the x-axis:



If only I had a cnc mill to make them it'd be much easier Looks like I'm stuck with making them all by hand, so I doubt it'll come out as nice as that

Just need to work out how to wire up these drivers now, got my mach licence through today so I'm itching to give it all a go

[klonx]

well, slowly getting a bit closer, these arrived today





The big one is a meter long

Picking up some ali plate today too so I can make a start on the mounts!

[klonx]

I finally managed to find a couple of hours at the weekend to make a start on the mountings, I managed to get the ballscrew mount done for the x-axis, including drilling and threading the crossslide to accept it, so we now have threaded holes front and rear:



Also started work on the front stepper/bearing mount as shown in a previous post, tough going though as the piece of alu is far too big to chop down on my bandsaw so having to millout the profile first and then clean it up once it will fit in the vice!



I've also ordered a breakout board from cnc4pc (c11) so I have a much better range of options when it comes to putting it all together, hopefully it'll turn up soon so I can start wiring!

[klonx]

ok, quick question!

I'm going for direct drive with the steppers, what sort of coupling do you all recommend to allow for zero backlash, I was reading the catalogue and there's so many different types out there!

Best bet seems to be the bellows type, followed by the slit type, I really don't have any idea what to go for though any recommendations?

[klonx]

managed a few more bits this weekend...



namely the rear ballscrew mount components (x-axis), also got my breakout board setup running one of the steppers, just waiting for the touch screen to arrive now so i can start to construct the control panel/enclosure, at the moment it's a bit of a mess



Everything will be built into the wall mounted enclosure that I have, pc included.

[mung]

I have a chester model B, and am just considering doing a cnc conversion. I have to say I think the model B is a load of crap (though I am a lathe newbie so maybe my expectations were too high?). They are cheap and probably value for money but there were so many problems when I first got it, and still loads of annoying things about the lathe design.

I wonder whether it will be worth spending loads on conversion and what the finished machine will be like.

I am on a real budget so am not going to use expensive or new stuff, probably no ball screws and cheapest steppers I can get from ebay. I will try to botch together as much as possible from my scrap box.

I will probably be starting the build in the next week or two with what I have available (I am going to work on the PC and power supply first as I have that stuff in the junk box) so may post some pics. Will workout the steppers and stepper drivers hopefully in a month and mountings and installation after that.

Any suggestions or info about budget cnc conversion of the model B?

Regards


Will

[klonx]

Hi Will,

The lathe element is actually pretty good if well set up, but as per your observation, the mill element isn't the greatest apart from when doing very light cuts.

From my pespective when starting the conversion the most important change for me that I felt was essential was adding the ballscrews, there's a lot of backslash in my model B that can't be tuned out so very early on I decided that the current screws had to go if I wanted any sort of accuracy. Software like Mach will account for some backlash but it all depends how bad it is on your machine really. I managed to get some good quality ballscrews off ebay for very little cash in the end which was the driver for actually starting my conversion.

My conversion is on hold at the moment whilst I await delivery of a new mill, I found that the model B mill feature whilst ok for building the parts above was beginning to get infuriating when trying to produce any parts that required more accuracy to the point where I gave up.

My conversion will continue in september so I'll keep updating. Let me know how you get on with yours if you decide to go ahead.

Kev

[mung]

Will post some more pics this evening, and maybe a test video.

http://www.cnczone.com/forums/showthread.php?t=60541

[klonx]

ok, as my new mill has now arrived and is all set up I thought I'd get back on to this little project...

I've got teh x-axis pretty much sorted bar mounting the stepper, and I have the z-axis ballscrew and all bearing ready to be mounted... question is what sort of mounting should be used for the angular contact end of the ballscrew?