Luthier CNC

[Clive S]

I also used Alum see this post #11 http://www.mycncuk.com/threads/8903-...highlight=alum I am not sure if there are different strengths of Alum

[Voicecoil]

The best taps I've found for through holes in ali are the blue ring spiral point types like this:

They're made specially for aluninium, the interrupted thread higher up seems to help with binding. Typically I've found you can tap a hole in 12mm plate in 3...4 seconds with one of these in a cordless drill with some cutting fluid. For blind holes as Mekanik said you need to use a spiral flute tap (to get the chips out), again I've found the blue ring types are marginally the best.

[mekanik]

This might be of interest
http://www.europatool.co.uk/threading/application-taps
Regards
Mike

[MikeyC38]

Hi Bluesking

Just seen your post here. Well done for joining the forum, doing a design and taking advice!. I wish I had seen this earlier because I would have told you to get the parts water-jet cut which also would have done some of the bigger holes for you and spotted the rest. This is the approach I took on my build and saved me a lot of grief (see build here http://www.mycncuk.com/threads/8206-...Axis-CNC-Build post #10 ) All I had to do was counterbore and thread the extrusions using a spiral tap. I then used a finishing tap to clean the threads or a plug tap where the hole is stopped.

Regards
Michael

[bluesking]

Hi guys,
Have not been on for a while as have been busy sorting out my new workspace and stocking up on parts. Thanks for everyone's various messages - don't have time at the mo to answer everyone individually.

Its all go on the CNC front now my space is sorted and I have all my parts, so I wanted to post an update.

Today I built a table for the CNC. 18mm MDF & C16 CLS timber from B&Q. About £30 worth of materials:

1 Cutting to size


2 Table top is 900mm x 1220mm; Supported by a timber frame:


3 700mm legs screwed on to table top:


4 timber base frame for support and shelf:


5 MDF shelf for base frame, and a few corner supports for increased rigidity (may need more of these in the short-dimension in future)
Table finished, ready to start assembling the machine itself:

[Doddy]

Looking good. Just a thought - is MDF the best, most appropriate worktop for something that could end up working with water (if only a failure-case for the spindle coolant, for example). My point - I have a sacrificial MDF layer on my "electronics" bench - and that's suffered some small water damage from an ultrasonic bath - and the surface is now perpetually feathering and impossible to flatten. My personal preference atm is ply, but most of the shops are stocking cheap eastern boards with large filled voids. The bench I've used for the mill is steel framed with ply top, sheathed in 1.2mm steel sheet (I had a bit lying around) - that's tough as boots.

I'm assuming that the bench is entirely separate from the machine? (it doesn't form part of the machine build?)

[bluesking]

Hi Bluesking
Broken drills/taps in non ferous materials can be dissolved using Alum solution.
https://www.google.com/url?sa=t&rct=...9aX0rtzdbxJhZP
Also when tapping go with the recommended size from your Zeus book ie 4.2mm but use a solid(no flute's) spiral tap.
Regards
Mike

Nifty solution, thank you.

I used a 3 flute straight M5 tap with some cutting oil. Did about 50 holes with no problems at all (once I’d drilled everything to 4.2). What would be the advantage of solid spiral tap?

[Scustom]

Hi bluesking
Any progress lately?
What gear ratios did you use for x,y and z axis?I assume 2:1 on x,y and 3:1 on z?
Thanks

[bluesking]

Hi bluesking
Any progress lately?
What gear ratios did you use for x,y and z axis?I assume 2:1 on x,y and 3:1 on z?
Thanks

Hi,
I've almost finished the machine. Just about to post a progress update. Gearing is 2:1 on XY and 4:1 on Z.

[bluesking]

Been a little while since I last posted but progress has been made. Almost finished and very pleased - things all worked pretty much to plan, even the electronics and software.

1) Made a simple 400x400mm MDF enclosure for the control box. 3D printed some connection panels so I can change the interface in future if necessary. Bit of spare clear acrylic for the top.


2) Spent about 50 hours of bench time to wire the control box. Surprised at how long this took - thought it would be simpler but I was testing individual functions as I went to make sure it all integrated OK.


3) A lot of the bench time was spent preparing cables and connectors. Here's all of the prepared cable ready to go into the workshop:


4) Back in the workshop, attaching the drag chain to some 3d printed mounts:


5) Attaching various homing and limit switches, once again on 3d printed mounts. Laying cable in the drag chain.


6) Here is the basically complete machine!


Heres a quick vid of the machine doing some initial rapids. Spindle yet to go on, but I'm getting 9000mm/min on the X & Y axes before servos stall. Thats setup for a theoretical precision of around 1/1000th of a mm with the encoders I have and running the UC400ETH at 200kHz. Obviously that precision is pretty goofy, I was just erring on the side of caution - still there is plenty reason to think I can squeeze a bit more speed and torque from this setup after a bit of experimentation and tuning.

https://streamable.com/orect

There is still spindle mounting and some tuning to do for precise axis scaling and servo PID controller tuning. After that I'll be moving on to spoil board, jigs and dust extraction.