A few questions to start a DIY mini CNC

[irving2008]

Rob,

Don't forget if you order something from outside EU you will probably have to pay VAT and import tax (8% on electronics I think) so that puts the price up (even if you think you've got away with it they find you months later as I found out once :( )

"Cheap and small" and CNC in the same sentence is an oxymoron! So far my 250 x 250 build has cost me £40 in MDF, £55 for the steppers, £180 for the rails & screws, £65 for the electronics and power supply (parts only, I'll make the PCBs), £20 for a box for the electronics, £40 for a 500W Dewalt die-grinder as a milling spindle, £30 for couplers and bearings and £20 for screws, bolts, etc. Add another £50-odd for tools and petrol... so I'm on the wrong side of £500 already...

Parts from a printer might do for milling PCBs or balsa wood but aren't robust for anything heavier... the milling spindle I have is 1.7kg and the likely cutting force I've designed for is 20N using a single flute 3mm cutter at 20,000rpm and a cutting speed of 1m/min. To get close to 0.05mm accuracy needs 20mm rails on the Y axis to avoid excessive deflection and 16mm rails on the X axis to support a maximum 4kg work piece. That's based on a 18mm MDF design with some additional steel angle reinforcement on the fixed gantry sides.

Again, think about what you plan to machine the resin with and what sort of accuracy you want. Hard materials need cutting power. A simple 130W Dremel or Proxxon hand-held rotary tool has a lot of run-out and so accuracy is poor and doesn't have the grunt for hard plastic or ali. A full-size 1500W router is robust but heavy. The 1000W Kress-type milling spindles are great but pricey.

An alloy tube with v-mounted skate bearings could work as a cheap linear motion rail, the bearings are cheap enough at £3 for 8, and heavier alloy tube as structural parts would do although box section is easier to work with.

hope that helps a little more...

[proddy]

hi rob, like you im gonna start a mini build of my own, i have a good sense of what my m/c will look like but i aint got a clue about the hardware or software side of it, (pretty sad when i've been a cnc miller for 8yrs now).

i was watchin youtube an seen the cnc router carving a tigers head an that was it, i was hooked on 3d cutting, its been my life long dream for the last 2 weeks now lol

anyways, wish you all the best an make sure you let us know your progress

[Swarfing]

Rob

In between doing my main build i started another the whole footprint of the machine is 400 x 400 x 350. Just need to finish off the Z, its using old printer steppers and will be controlled by DIY drivers. Its all steel frame 25 x 50 box section. As soon as i get a chance i will put some picks and details up on a log. Shame is i will have this finished before the main. The reason i did it was to try things out, its the best way to learn and it cost me almost nowt. Sometimes you need to just jump in - but before this comment bites me back as i did say on a previous thread to plan first???? sometimes it is acceptable. Join freecycle for your area and pick up a few old plotters and printers (steppers, 8,10 and 12mm spindles) you will be surprised how far you can go. Steel rule and a sharp pencil is your best friend. Remember to clamp everything before drilling and you won't go far wrong.......Mine may never right but i will never be right without experience and that has to cost somewhere. Good luck