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Discussion in 'CNC Mills/Routers' started by Colin Russon, Mar 14, 2016.
Z axes 1605 ballscrew, a comparative design proposal.
Colin Russon published a new build:
Read more about this build...
An M8 eccentric spacer is definitely something that would be useful in a lot of situations.
Agreed, this is just one example...
I like the idea, so how much would you charge in comparison to the linear actuators sold on Openbuilds?
using bigger wheels/spacers along a bigger distance and a 1605 ballscrew is problably 98 % of improvement on this setup.
The 2 rond alu and their receiving blocks account to the 2 missing percent at max. Actually i would call them dead weight and counter productive to be honest.
Here is why:
First off they "up" the partcount and thus to complexity and "up" the cost without a real contribution to the system.
secondly the parts needing perfect aligning is upped from 6 ( 4 wheels and a 1605 screw) to 8 which is not only a 30% raise but mainly a physical problem: even the slightest misaligning will cause somewhat binding and thus wear or lost steps etc. all effort to improve might be rendered useless by that.
KISS does aply to all designing simply because it is true.
third: You do not belive that two 8mm alu will stiffen the system? For the forces they withstand only the outer dimension (8mm) counts and thus they have like a 5th of the stiffness of the c-beam and thus the c-beam will take all forces while the round alu setup will only ride along...
fourth: using round unsupported alu is the worst and weakest possiblility of all. If you had at least incorporated those "supported round rails" (look at e-bay) it would have made at least a (slight) difference cause it would have been screwed to the c-beam and thus makeing the part bigger in (square)area and thus would have stiffened it up at least some...
simply using a single 30 mm type square rail, the rail attached to your spindle plate and the long wagon screwed to your x-plate would have solved all your desires to upgrade the z axis for all eternity and beeing a 10th off effort....
Just me thinking..
@Florian Bauereisen , any link on the KISS? I know others but KISS is new to me, would like to see how that can be applied, thank you.
@Colin Russon , make sure you use a larger diameter shim/washer on the opposite side of the plate where the eccentric spacer is placed. That would help a lot. I agree with most of what Flo said, sorry, but don't give up .
Bear in mind this design uses a 6020 profile as the 'mount' so the design is based around that. The two rods are there to act as stiffening rods to counteract the 'flexing' forces applied to the front of the rod plates when cutting. Without the rods the entire force from the cutting would be applied to the rod plates and the profile retaining bolts, this puts excessive force on the plates.
The rods pass through the 4020 profile, they don't use bearings to hold them in place so they don't need perfect alignment.
Can this design be used without the rods? Yes of course like all V-Slot Rod Plates it can, but the design is diminished because the rods act as simple load bearers between the upper and lower plates for very little extra cost.
a: The rods do act to stiffen the system and to counteract flexing off the plates
b: No alignment of the rods is necessary and the cost for the rods is less than 2% of the overall design
c: This design utilises 6020 V-Slot, not C-Beam. Certainly C-Beam could be used as an alternative (see picture below) and then the supporting rods would not be needed, however a 1605 ball nut cannot fit into the internal section of a C-Beam so the C-Beam would need to be mounted inversely. This would make the design another 20mm wider than it is now.
e: Supported rails would not fit onto a 6020 profile or allow the use of wheel motion, they would in fact make wheel motion pointless, this is a wheel motion design.
happy to receive these comments!
KISS is a saying used in design circles (don't take offence please I am just the messenger) the saying is 'Keep It Simple Stupid', meaning keep any design as simple as possible.
No need to be sorry, all critique is taken and absorbed!
I have to finalise the supply chain to reach a point where the costs have been fully realised, and of course build the design to test it. Once that happens I will be able to supply pricing, however the cost for the parts will be on a comparison to the OB actuators.
Hello Colin, learned something new today, now I know what KISS is. I thought is was something like a risk assessment for design, and to keep it simple, it is .
The rods indeed don't need adjustments if there is no flexing in the wheels and plates.
Hi Colin. Any word about when I could purchase some of the M8 eccentrics? I have a build that is in the planning stage that can benifit from these. I'd sure rather buy them than make them.
BTW - I really digging your modeling skills. After seeing them I think I'll stick to crayons and newsprint.
I have them available now Larry, how many do you need?
If you need help with modelling let me know, it takes a lot of the stress out of building and ordering the wrong size stuff!
I'm, interested, how much for 30 of them?
Brian. Take note of the last entry date.
ah crap... thanks.