'New' to the forum, although I have been browsing for over 4 years.
Eventually starting to CNC build process... MKI
I've done a LOT of reading, and calculations from several members (too many to mention)
- To mostly cut 6mm MDF, plywood etc.
- Also to cut 20-25mm woods (mixing from soft to hardish(oak))
- Aluminium cutting (3mm) - maybe somewhere down the line...
I want to have the ability to cut A2 size (i.e. 420mm x 594mm ) - So with cut size, clamps etc:
Cutting size: 480 mm x 640 mm
For hardware I was thinking:
Nema 23 (3.1Nm) - Drivers [ Was thinking some 50v Drivers from CNC4You - powered by 36v ? ]
SBS20 rails + Support blocks
RM1605 Ball Screws and nut (Above 2 items from Chai - I've made contact and he said he is still shipping to UK and ready to take my order)
Aluminium Profiles (40x80 heavy duty, Ix: 26.87cm4, Iy: 101.19cm4) - The Support Rails will be bolted on top of them, so extra stability...
Router/Spindle: Looking at the Makita RT0700CX for now.
The Z Axis has the ability to move 140mm, but will initially only us ~40-60 of that - unless I drop the table/raise the machine.
The entire machine will be bolted down on a bakelite(?) top (super flat strong surface) with steel support under the top.
(Will see if I need to weld a movable table one day...)
Software, I've played around with bCNC and got a Arduino with grbl running on two Nem17's with a CNC Shield (Drivers DRV8825 - Will not use these on final machine)
Below is my design so far: [Version 4 mind you, but at a stage where I feel confident to post to ask for further assistance and advice from experienced people ;) ]
(Some final adaptions from JoeHarris, but really, the credit goes to the entire MyCNCUK Forum member builds!)
Your input and thoughts on the design would be most helpful!
HI Jacques Welcome to the forum. CNC4you do some very good 3.1Nm motors and are a good buy but you are limiting yourself with the drives AM882 or EM806 are much better and can be run them at a higher voltage 68V would be about OK. If you are mainly cutting MDF etc then 10mm screws for X and Y and 5mm on the Z.
Think about the router as the Chinese 1.5kw or 2.2kw water cooled with VFD are a much better bet.
Don't be temped to buy a kit of electronics as they are never matched as you will know if you have been reading the forum for the past 4 years.
Start a build log so all the questions etc will be in one place.. Good luck with the build..Clive
Spindle: http://www.ebay.co.uk/itm/170745857956 ??
It has a ER11 Collet - are you limited to the cutters? (What Collet size do people recommend ?)
[ Any recommendations on spindles + water cooling systems anyone? ]
My thinking for the Makita RT0700CX was I could use it on the CNC & Other project. But in reality, a dedicated spindle is more realistic.
Thanks about the reminder about buying the Kit's... Originally I was thinking 4Nm Nema's. It is only a slight increase to got from 3.1Nm to 4Nm, but I'm not sure if the 3.1's are an overkill already...
About 10mm for XY & 5 for Z - I want to keep my options open to eventually cut small Aluminium parts (for toy cars etc - so 4mm) later down the line - but as stated, not essential.
The 3Nm motors are more than big enough if you can go with belt drive all the better as then you can use a 1:2 reduction if you need to.
I think you might have to beef the frame up as well...Clive
Clives suggestion to use 10mm screws is correct and it mostly do everything you want, even small stuff. But if you really want flexabilty then connect motors to screws using Timing belt and pulleys with 1:1 ratio then you have option to change up or down if required. Also and much better reason to use Timing belts considering the drives your thinking to use is to lessen resonance which affects motor performance/smoothness.
I'd also urge you to use Profiled linear rails rather than cheap Round rail Chai sells. While Round rail does work ok the slight extra cost of profiled rails makes huge difference to machine stiffness and reliabilty. It will also increase sellabilty and value much more than the extra cost difference.
Also with Motors you'll notice No Difference between 3.1Nm and 4Nm motors. The important thing to look for is inductance you want Lowest inductance possible. This will allow higher RPM and more torque for same voltage compared to High inductance motor.
Again Clives advice of AM/EM drives and 60-70Vdc is sound advice you'd do well to take up. Esp when using Slaved motors.!
For Components contact Fred Lee here and get a quote. He's good to deal with and his stuff tends to be slightly better quality than Chai's. Esp the End bearings for the screws.
It's not very clear on the design, but the intent is to use a belt with pulleys, 1:1 timing. (Very similar to JoeHaris' design) - as I've read, it helps with resonance and gives me the ability to do 1:2, or 2:1, or other rations if I allow a variable positioning of the Nema (which is the intent)
I looked at Profiled Linear rails - just seems to cost a tad more... although, would be easier to fit to the Aluminium profile... Will see what pennies I can get out the couch :)
Thanks for the 3.1Nm vs 4Nm motor advise - I think that's one tick I can put next to - "Buy Nema 23, 3.1Nm motors" :D
Once I have all the input and design tweaks, I'll know what length ball screws to get - So recommendation so far is RM1610 (with the end an extra 15mm for the pully) [This should give a resolution of 0.05mm (at full step) and 0.00625mm at 1/8 step - that actually pretty decent! ]
As for Slaved motors, should I go with 3 Nema's (One belt connecting both Y Axis to one Nema ?) - this will save on buying one driver and Nema, but worth it ?
Last edited by JAZZCNC; 26-01-2016 at 07:40 PM.
I am looking into the HIWIN Rails - and many people on the forum suggests 20mm because of grease, access to bearings etc. So I take it 20 is good,15mm bad ?
The motors I am looking at can be 3mH if you couple them in series, 12mH in Parallel configuration.
Those drivers are nice, £100 nice - will have to save up for them....
Busy re-designing for the Linear Rails... will post new design within the next week.
Zapp motor are a good buy http://www.zappautomation.co.uk/elec...tor-48577.html
or CNC4you as I suggested before https://www.cnc4you.co.uk/Stepper-Mo...s/Nema23-3.1Nm
Drive about £53 http://www.aliexpress.com/store/prod...570168083.html or similar..Clive
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