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DIY CNC Machines

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Schietwedder
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Re: DIY CNC Machines

Postby Schietwedder » Wed Dec 01, 2021 6:21 pm

A lot of valuable information, glad that I posted it here before ordering the mechanical drive units.

What is the origin of creep, is it purely related to the quality and lets say electronics and design of the drivers or does a high force/velocity (Heavy milling/a fast plotter) enhance those problems?


BR Niklas

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Re: DIY CNC Machines

Postby BalsaMichel » Wed Dec 01, 2021 8:23 pm

Schietwedder wrote:
Wed Dec 01, 2021 6:21 pm
A lot of valuable information, glad that I posted it here before ordering the mechanical drive units.

What is the origin of creep, is it purely related to the quality and lets say electronics and design of the drivers or does a high force/velocity (Heavy milling/a fast plotter) enhance those problems?


BR Niklas
...To simplify it a bit (I am absolutely no expert here anyway): The windings of the stepper-motor are feeded with a wafe pattern that makes them move. If the wafe pattern does not fit to the motor characteristics or if it´s unclean (cheap driver circuit) creeping could occur. Normally the motor creeps more in one direction than to the other. The vertical Z-axis more often downwards. The mean thing about this is that this could happen very slowly. Mills are breaking, milled surfaces are not even...you´re starting to search loose screws... :D

Micha

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Schietwedder
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Re: DIY CNC Machines

Postby Schietwedder » Thu Dec 02, 2021 11:26 am

Hi Micha,
Sounds logic!
I'll see how it goes.
Just by interest do you have some pictures of your machine(s)?

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Re: DIY CNC Machines

Postby Jan:) » Thu Dec 02, 2021 5:24 pm

fluidity wrote:
Wed Dec 01, 2021 6:31 am
Very tedious but I now have a pretty radical hydrofoil to ride. I'm not sure what the answer is for the Z axis other than trying to sort a solution just for that axis with positional feedback?
Habe you tried to limit acceleration, rather than speed.
Aside from mechanical problems, like binding, that is the most likely problem.

Z-axis often has significant weight, so accelerations in the up direction, can create pretty high forces. So the motor is missing steps before you even reach your speed limit.

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Re: DIY CNC Machines

Postby BalsaMichel » Thu Dec 02, 2021 5:58 pm

Schietwedder wrote:
Thu Dec 02, 2021 11:26 am
Hi Micha,
Sounds logic!
I'll see how it goes.
Just by interest do you have some pictures of your machine(s)?
...This is how it looks like. 800x500x140mm workspace, so quite small. I use it mainly for milling splitboards and since a few months also for commercial surf stuff (but wasn´t built for this). Can take the side panels out for full lenght board milling in two steps. Suction hose is integrated in the e-chains (3D-printed with PLA, 1.6kg only the two chains :D ). Vacuum plate integrated into the main frame.

Control system is ESTLcam (on a Microsoft Surface Go 2) and an Arduino, so quite the same that fluidity uses for his milling system.

Micha
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SBX5.jpg

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Schietwedder
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Re: DIY CNC Machines

Postby Schietwedder » Thu Dec 02, 2021 11:24 pm

Nice one Micha, looks very tidy and neatly built!
Hehe mine will be a lot more pragmatic approach because of the size and resources :D very nice with the dust collection and housing+controls

First thought about making a large vacuum table as well with a steel flooring to be able to laser cut the sailcloth, but then I would have had to install a smoke collecting hose as well as it's located in my office room at home. Maybe I will upgrade to this but rather unlikely as I won't have so much to cut that it's worth the large investment compared to a pair of scissors and some beers.
Plotting the nested patterns onto the cloth is already 60-70% timesave of the kite making process.

BR Niklas

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Re: DIY CNC Machines

Postby nemoz » Fri Dec 03, 2021 12:05 pm

I have a cnc machine home made and i'm using it to build foils, wingfoil and surf boards, fins and other stuff.. I'm using the DMXX drivers and nema 23 motors, In the past I used an Arduino UNo and universal gcode sender, then I mooved to GRBLESP32 and now I'm using Fluidnc that have a web interface so you can use the machine with a pc-tablet-smartphone... https://github.com/bdring/FluidNC/tree/main/FluidNC it is still under development and there is a new release every 4 weeks, you can update firmware via wifi, a very great project in my opinion.
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fluidity
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Re: DIY CNC Machines

Postby fluidity » Thu Dec 09, 2021 10:04 am

BalsaMichel wrote:
Wed Dec 01, 2021 2:12 pm
fluidity wrote:
Wed Dec 01, 2021 6:31 am
...The moulds I did with straight cuts and it's here that I discovered Z axis creep. Severe enough to make my first set of moulds worthless. for my second set, I put in a stronger Nema 23 motor, limited my Z speed but i still had to do a Z axis reset about every 100mm on the X axis of y axis cuts...
Hi fluidity,

I would bet you´re having trouble with the stepper motor / stepper driver combination. There are still some really cheap, bad drivers on the market. Unfortunately you can´t see without opening them. Many of them look just the same from the outside (DMxxx). Try to use a DM542T from stepperonline for example. Don´t know if it´s available in your country. Option would be a driver with a Toshiba driver chip. They´re a bit more expensive but will normally work more reliable than cheap ones.

Two years ago I´ve switched to the stepperonline DM542T and NEMA23 motors with low inductivity. This has solved my creeping problems and has increased my XY-max. axis speed from 3.000mm/min to 12.000 mm/min without loss of steps (spindle with 10mm pitch thread). Even too much for my nerves so I went back to 7.500 :D

Micha
Thanks!
I've just put on order an integrated stepper/encoder/driver yesterday:
Integrated Stepper Servo Motor 2Nm(283 oz-in) 24-50VDC NEMA 23 Closed Loop
from stepperonlin who I've used before, good company.

Meanwhile I'm experimenting wih metal casting from pure PLA (after burnout of the plaster in BBQ) and my new swept delta hydrofoil. Getting a little better at it and also enjoying the practical rapid creativity, turnaround I'm getting with a large 3D printer and metal furnace etc.

I think my effort at the moment to do a hydrofoil is less with 3D printing and resin infusion than with mould making. Ideally though, it needs thickness removed from the model before printing, from leading edge to permit rounding without wearing through seam and a double wall cubic infill for sealed flotation inside.

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fluidity
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Re: DIY CNC Machines

Postby fluidity » Thu Dec 09, 2021 10:08 am

Jan:) wrote:
Thu Dec 02, 2021 5:24 pm
fluidity wrote:
Wed Dec 01, 2021 6:31 am
Very tedious but I now have a pretty radical hydrofoil to ride. I'm not sure what the answer is for the Z axis other than trying to sort a solution just for that axis with positional feedback?
Habe you tried to limit acceleration, rather than speed.
Aside from mechanical problems, like binding, that is the most likely problem.

Z-axis often has significant weight, so accelerations in the up direction, can create pretty high forces. So the motor is missing steps before you even reach your speed limit.
I have acceleration set almost to lowest, I put bigger lifting Z axis Nema 23 on it, got slightly better but still not good enough. I'm assuming it's not missing steps from the Arduino and it does progressively get lower so I'm of the same opinion as you. Motor combo on order should fix it hopefully...

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Re: DIY CNC Machines

Postby Schietwedder » Fri Dec 17, 2021 9:13 pm

Progressing with a lot of provisionally wooden parts which I will later replace by more sophisticated metal/3d printed parts.
For testing and doing a few dry runs it should be sufficient.

I let the belts a bit longer and did not cut them yet so I can use fresh belt when I have more sophisticated mounts available.
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