Author Topic: It's CNC Jim, but not as we know it...  (Read 632 times)

Offline Joules

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It's CNC Jim, but not as we know it...
« on: January 30, 2020, 08:54:57 AM »
Ahhhh, after years of procrastination and frustration I have finally got CNC for the little SU1 mill.

OK, OK  it's "Carefully Nudged Cutter" machining.  After years of making Delrin parts and using what ever router bits I could find as form tools, I was talked into this being a really good idea....  Cheers Rob, and as it turns out    :med:

I bought one of Eccentric Engineering Turnado full kits with the intention of fitting to my 12x36 lathe, but whilst machining the tool post block on the SU1, it struck me that this was what I wanted to CNC the SU1 for.   Profile work and ganged tooling, due to lots of issues it never happened and the SU1 was really needing to justify its place in the workshop.  I changed it over to permanent horizontal use a while back and for small stuff it has been good, this bit of kit has assured it's place in my workshop.  The Tornado kit isn't cheap, unless you factor in my years of wasted effort and time trying to figure out automating the SU1, in which case the Turnado is very cheap based on those hours wasted.  It operates like a little graver, you can move the tool holder around by hand, or use guide rails for rounded components, or the parallelagram arm to trace a profile.  Hmmm a laser cutter would be good for cutting profiles out of thin perspex, might need a bit of rubbing smooth, but easy to build up a collection of profiles and engrave what they are at the same time.   Cor...  You would have thought I planned this.

The examples below show the dome on a bar being hand turned, the geometry of the cutter doesn't allow it to be pulled into the work, and the load is very light so easy to control.   Some good magnifiers are a must for us Old Gits.

I only have a limited number of ER11 collets, so part of this brass rod needed turning, on the lathe, to fit.  The little ER11 chuck is great for small work and being able to change out for the ER32 makes for a large range of material sizes.

For larger work I can use the overarm on the mill and set up a live centre to support longer work.   I am writing a list of tools and accesories to make for the Turnado, the grid pattern plate offers lots of scope for adding stops for doing repeat parts.  Lets see where we are with it later in the year.   A big thanks to "Gary" at Eccentric Engineering for making a real quality tool, lots of attention to detail and well thought out.

Honour your mentors and pay it forward.

Offline Brass_Machine

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Re: It's CNC Jim, but not as we know it...
« Reply #1 on: January 30, 2020, 11:21:43 AM »
That's a nifty tool!

Eric
Science is fun.

We're all mad here. I'm mad. You're mad.

Offline Joules

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Re: It's CNC Jim, but not as we know it...
« Reply #2 on: January 30, 2020, 02:56:59 PM »
The first of many Mad Mods....    I need to be able to tram my stock and the profile mount for reasonably accurate work, within 0.02mm.  Now the arm does have some play in the joints, but once you load it up in one direction it stays accurate.  Not a great example here as the stock isn't great, or that long, but you get the idea.   3D printed arm puts the DTI ball at centre height and a piece of 1/4" stock is used to mount the arm in the tool post.  This print is out by about 3mm top to bottom, so revision 2 is printing now.
Honour your mentors and pay it forward.

Offline Joules

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Re: It's CNC Jim, but not as we know it...
« Reply #3 on: February 04, 2020, 03:20:27 PM »
First test with a template, 3D printed rather than laser cut as I still don't have any thin Perspex, and expect the laser to not leave a clean edge.  Bearing in mind this material had quite a bit of stick out, I turned the small end first and worked back.  My material wasn't long enough to clear the ER32 collet nut so a bit of juggling at the large end meant I had to reposition things and line them up best I could.  That resulted in the ring on the rear of the centre ball, and not able to clean the large ball.   Lesson learnt from this, you need a live centre and leave stubs each end to clean off after.  Even with the flexing the result isn't bad for an unsupported first try.   It was a lot of material to hog out in the first place.  I may try again, but remove the bulk on the lathe first that would also prepare the stubs for mounting at each end and they could allow the ER11 collet to be used, with much better clearance.   The 3D printed profile looks like it might work, the little notches in the template indicate the centre line.  The tool I used rubbed at the small end, so could do with a deeper grind to give more clearance.
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Offline slowcoach

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Re: It's CNC Jim, but not as we know it...
« Reply #4 on: February 05, 2020, 08:20:39 AM »
Looks brill that does. I bet there's not many people who turn on an horizontal mill :clap:

Rob :thumbup:

Offline Joules

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Re: It's CNC Jim, but not as we know it...
« Reply #5 on: February 11, 2020, 12:57:26 PM »
I put an order into ArcEuro yesterday and it turned up this afternoon, great service.   Part of the order was for the mill, the rest of the ER11 collets I don't have, a new ball raced collet nut and a mini live centre, it just wasn't worth making for the price.  I shall be making a fitting for the overarm support to take the centre.   The new collet nut is quite a bit smaller than the old one, with the added advantage that you can pretty much tighten them up enough to use with just your fingers.  The extra clearance round the nut was worth the cost alone.

Further mods are on going, including adding an old DRO.  The wire sensors are causing some issues as they are quite big and I would rather fabricate brackets that pick up on existing fasteners, than drill and tap new holes.  The mounting plate for the read head is laser cut from perspex and mounts where the vertical head used to go.  I need to find a new location for the switch panel as a 25mm digital dial gauge is due to mount there for my Z indication.
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Offline Joules

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Re: It's CNC Jim, but not as we know it...
« Reply #6 on: February 12, 2020, 03:01:01 PM »
This afternoons work, getting the little centre drilled and tapped M4.  The centre has a spigot size of 10mm, the bearing in the over arm support is 10.5mm.  I didn't want to sleeve the centre or risk contacting the support bearing.  A Delrin spacer was made to pick up the front of the support and offer a snug fit to the centre, it is then all pulled together with a small drawbar.   The drawbar was cobbled together with a thumb wheel I had in my bits box a stub of brass and an M4 socket head screw, cut down.  Pictures below show the parts and fitted to the overarm support.   I end up with a maximum of 140mm between centres, but don't expect to make components over 100mm in length with this setup.  I haven't checked alignment yet, but as I only have about 0.25mm clearance in the supports brass bearing, pretty much what I have is what I got.   The profiles can be adjusted to run true to the stock even if the mill centres are not true to the arm.   I will see how the Delrin part works out, if it flexes (not expected) I will machine an alloy version, the actual loading on the live centre should be very low.   
Honour your mentors and pay it forward.