Monday, 4 June 2012

Mantis-a-like CNC miller, build part 1

I'm going from fuzzy ideas and sketchup models to actual hardware now... After sourcing silver steel from these chaps in Wales (and most of the bolts, leadscrews, nuts and a few washers...) I grabbed a lump of MDF from Wickes and started building on Saturday...

The mutt is for appreciation of scale.

So far I've got X and Y sides match cut to try to ensure parallel accuracy between the steel bars. The process basically went like:
  • Cut two similar sized rectangles from MDF board
  • Mark up on one where all your cuts/drill holes will go. This will be the 'master' for all cuts
  • Screw the two boards together in at least 3 places (taking care not to go near where you'll be cutting!)
  • Drill away!
I wanted to make sure the board edges where as close to flat and square as possible. To do this I used a jigsaw (not the best tool for straight cuts!) and clamped a metal straight edge (my set square) to the board as a 'fence' to guide the side of the jig's shoe. This seems to work OK for MDF as the lack of grain direction means it machines nicely... The downside is that, like Gremlins, you must never get MDF wet lest it turneth into papier mache.

The silver steel and leadscrews were uncut on arrival, so I grabbed a 30cm hacksaw with a standard blade and, well, 'hacked' the rods to the right length. A quick bit of deburring of the sharp edges with a multi tool made them look nice again. The multitool was bought with the hacksaw, just in case the saw couldn't work through tool steel, and also as a potential spindle motor for the CNC machine :D

Now I'm waiting on the oilite bearings (from these guys) to arrive sometime next week before I can assemble the X and Y axis systems. In the mean time, I've sketched-up the dimensions of what I've built and designed a z-axis sled and tool mounting plate. Unlike the Mantis, this design should let me upgrade the spindle or put different tools on for different jobs (3D printing anyone? :-]  )

Z and Y axis sleds with z-axis stepper motor on top (z axis leadscrew not shown)
As above, side view

Second build update here

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