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artyman
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OK... for Hawkeye, and anyone else that is interested... a brief synopsis of the parts used :-

 

Z-axis - 8mm stainless steel rails + linear bearings, NEMA17 48 Oz-in stepper

Y-axis (Gantry) - 12mm rails + linear bearings, NEMA17 48 Oz-in stepper

X-axis (Base) - 20mm rails + linear bearings, NEMA17 78 Oz-in stepper

 

all lead screws are standard M6, 1mm pitch threaded bar, with thrust bearings on each end.

 

The fabric of the machine is reclaimed 12mm MDF for the Y & Z axes, new 18mm MDF for the base.

 

Control electronics are a generic 3 axis TB6560 stepper driver board - combined breakout board and 3x stepper drivers

 

All of this is controlled through Mach3 software.

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  • 3 weeks later...

Found one problem with the build... machining a long cut from front to back, the cut gradually got shallower until the tool came out of the workpiece.. NOT GOOD!!!

 

after some investigation, I found that the endpiece at the back was about 1mm shorter than the front, so the table had a slight slant on it.

 

THE SOLUTION:- machine some shims to place betwen the table and the endpiece.

 

Now the back is slightly proud by 0.2mm (I can live with that), which should settle down as the MDF shims compress under the bolts.

 

As far as cutting goes, I started out very conservatively at 2mm/sec and a fast spindle speed. but found that while cutting well, it was also prone to burning the wood. So... I decided to slow the tool down a bit to half speed (about 12000RPM) and gradually ramp up the feedrate, now I can cut at a whopping 6mm/sec, almost as fast as it's rapid rate (which is the fastest it goes).

 

@Johey - Thank you, It was a long build, but SO satisfying to see it working.

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Can you drill and engrave aluminium panels with this?

 

...and/or acrylic LCD windows - though I'm owning a CNC myself I never was able to get good results while cutting acrylics though this was probably a result of using no fancy (i.e. expensive) cutting bits. I used Cut2D program to create the tool path for Mach3, in case you're interested in giving it a try...

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My first foray into machining Aluminium has met with partial success:-

 

Engraving, using a 0.1mm 10deg engraving bit came out perfect (see photos..). This was 3mm high text, engraved to a depth of 0.3mm.

 

Milling, however, threw up it's own problems.... The 3mm endmill I was using kept getting pushed up into the collet, no matter what spindle speed and feedrate I used. Also, at some point, both the X and Y axes missed steps and threw the whole cut out of line.

 

To address these problems, I now have a proper milling spindle on it's way, and, starting with the X-axis, moving the whole gantry, a much heftier NEMA23 stepper. If the new stepper proves to give me much more accuracy (without missed steps) and a higher feedrate, I'll replace the Y-axis as well. The Z-axis can have the stepper that is currently on the X-axis, which has slightly more torque than it's existing one.

 

 

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  • 2 weeks later...

New upgrade parts have now arrived.... hopefully this should make a difference to the speed of the machine, and stop the cutting bit getting pushed back up into the tool.

 

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now making the new mountings for them... if a bit slowly !!

Edited by artyman
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Thank you for your support and interest... It was a daunting prospect at first, but then, so is building your own synth from scratch. The processes involved are very similar, break it down to small sections... design, build, test.... add on the next section... etc..

 

Anyway, got the new mount for the spindle done. I had to recess the T-nuts due to the clearance between the tool mount and the Z-axis frame being so tight. The holes and the pockets machined very well with the original tool, but it was having difficulty with the cutout, so I had to cheat a bit and stop the cut, then using the slot I already had as a guide, jigsaw it out completely and file the edges flush. Overall I'm pleased, as the most important parts were machined properly before the problems.

 

Photos show:-

 

- New spindle and mount

 

- Underside of the above, highlighting the recessed T-nuts

 

- New mount in place on the Z-axis

 

- New spindle mounted in place

 

- Despite inaccuracies in my jigsaw work, the CNC work was perfect, leaving the new spindle perfectly vertical

 

 

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  • 2 weeks later...

UPDATE:-

 

Now the spindle upgrade is done, It's so quiet that now I can hear all the other rattles and rumbles that the frame is making.

 

So... in addition to the motor upgrades, and re-designing the X-axis transmission, a bit more bracing is needed on the gantry. The most worrying is some lateral play along the X-axis which is causing a slight 'twist' around the centre.

I believe this can be solved with an arrangement of wire rope and pulleys to keep the gantry in a fixed orientation, in a similar manner to the rulers on a draughtsman's drawing board.

 

On the positive side... my first project made with the aid of the CNC is now built, fitted and working - the power 'pods' on my workbench.

note.. I had to chamfer the edges by hand, because I didn't have a suitable tool for the CNC to do that.

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Upgrades are in progress now... and now that I have a milling bit capable, I thought I'd try cutting something a bit thicker... 18mm MDF.

 

The results were excellent !!!

 

 

 

.. and HOW much quieter is this spindle than the old tool??

 

...and a few stills...

 

 

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Cool!  I just finished building mine, its a shapeoko.  I'll be connecting the electronics tonight.  have you noticed any performance loss with the new spindle.  I've heard that the quieter spindles have less cutting power.  I'll be fitting mine with dewalt dw600 after I adjust the runout.

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Hi, actually, the new spindle is more powerful than the tool I was using, I've not had any problems with it's performance, even using an underrated power supply (currently using 12V... waiting for the 48V one to arrive).

 

I'm more than pleased with the cutting performance, both in thickness of cuts achieved - 18mm MDF,... and speed, though the speed of cut is more limited with the type of bit being used.

 

I'm guessing yours is slightly larger than mine, having a full router as the spindle. Once you get started, you'll be having loads of fun, but it's quite a learning curve to get used to spindle speeds and feedrates... be prepared for broken bits !!

 

on another note, I've just finished a prototype for some front panel bling..... very unobtrusive until power-on....

 

 

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  • 2 weeks later...

The rest of the upgrades have now finally started... beginning with the new drive mechanism for the X-axis, and the cable arrangement to stabilise the gantry and reduce the lateral play.

 

The 2 cables are arranged so that when under tension, each one is trying to twist the gantry in opposite directions, so that in equilibrium, it is unable to twist either way, and any slack movement is eliminated.

 

 

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  • 3 weeks later...

OK, slightly late addition to the upgrades... new leadscrews on the X and Y axes.

 

These are now in place, with much more robust bearing supports.

 

The gantry (my Y-axis) has a TR10x2 trapezoidal screw - 10mm dia. and 2mm pitch. The base (my X-axis) has a TR12x3.

 

This should see a significant improvement in speed over the original M6x1 allthread screws.

 

Still waiting on the new couplers before I can re-fit the motors.

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Couplers have now arrived, and the CNC is back in motion.

 

Initial testing shows mixed results...

 

X-axis (TR12x3 leadscrew) - marginal increase in speed. This was slightly disappointing, but investigation showed there is a slight wobble on the leadscrew which causes it to jam above 650mm/min.

Y-axis (TR10x2 leadscrew) - 66% increase in speed. Much better, This axis now moves at 1000mm/min. attempts to get it faster gave the same result as with the X-axis, the screw would jam.

Z-axis (original M6x1 leadscrew) - The only change on this axis was fitting the larger motor which originally drove the x-axis. Now the Z-axis moves 100% faster.

 

Although the speed tests were not as good as hoped for, the increase in acceleration is much more pronounced. Both the X & Y axes now accelerate 5x faster than before, and the Z-axis is 10x faster.

This results in near-instant motion at full speed, so that now it looks like a proper CNC motion.

 

pics and video to follow

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As I already know the machine performs well on wood, I decided to try the first test of the upgraded motors and leadscrews on aluminium!!

 

At first I had both the spindle speed and the feedrate a bit too fast, and the bit wandered off course, prompting an Estop from me, but after slowing them both down somewhat, I tried again and got a nice clean, even slot cut!! :smile: :smile:

 

I'm extremely pleased... the upgrades were worth the expense and effort.

 

http://youtu.be/SZkmMECG09A

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  • 2 months later...

Time to revisit this thread... The upgrades I made to the X & Y axes are working well. I can now get rapid moves of 1200 and 1300 mm/min respectively, which I think is quite a respectable pace. However, since I started trying some v-carving, I have been having issues with the Z-axis sticking on upward moves, so that the next downstroke would plunge the tool deep into the workpiece and ruin it. The tool mount was also showing some flexing during cutting, which was introducing inaccuracies in the final product.

 

Time now to re-design and rebuild the Z-axis, while sorting out a few small irritations with my first design.

 

- make the stroke longer so that the new spindle with my longest mill can clear the working area.

 

- lift the whole axis so the base is level with the bottom of the gantry to maximise working height.

 

- eliminate the leadscrew and nut protruding from the bottom of the axis, again maximising working height.

 

The new axis will now be built around a TR10x2 leadscrew (the same as the Y-axis), with a longer tool mount, and all structural parts made from 18mm MDF instead of 12mm to improve the stiffness of the tool mount.

 

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I had to slow the Z-axis right down to a crawl to stop the sticking on the upstroke, so cutting the parts for the new axis took some time, but this is now all done, and ready for assembly.

 

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