Initial design advise wanted

[fifa]

No, every ball-nut allow
angular misalignment, and ballnut is not designed to support radial loads.

You shall not drive screw up to critical speed, 70% limit is recommended, this is due straightness tolerances (screw is not ideally straight)...

2010 robust, however, I would say for such type of machine too big. You will not be able to work with high speeds. Frame is too flexible.

I am assuming you are from Netherlands, threrefore German language shall not be an issue:

Check this site:


Search for Minerlaguss...

kr

[driftspin]

No, every ball-nut allow
angular misalignment, and ballnut is not designed to support radial loads.

You shall not drive screw up to critical speed, 70% limit is recommended, this is due straightness tolerances (screw is not ideally straight)...

2010 robust, however, I would say for such type of machine too big. You will not be able to work with high speeds. Frame is too flexible.

I am assuming you are from Netherlands, threrefore German language shall not be an issue:

Check this site:


Search for Minerlaguss...

kr

Dear fifa,

Thanx for taking interest in my project.


"2010 robust, however, I would say for such type of machine too big. You will not be able to work with high speeds. Frame is too flexible."

I have actually selected the 20mm over 1610 ballscrew based on lenght and critical rpm vs speed, based on the zapp automation calculator.
And some other docs i found to verify outcome.

1610 screw looked a bit thin on a 1500mm + span.

Thanx for clearing things up on using the balnutt for a virtual span reduction.


Since i am unsure about max speeds i need... i designed towards >5m/min speeds. Did i mis something here?

Although i might only need that speed for rapids?

2010 will be harder to get moving though..
but is more rigid.
trade offs..

You might be right on maybe not being able to take advantage of 2010 over 1610 on my machine.
Do you feel it is over the top?

Will i lose much speed on small movements?

1610 screw looked a bit thin on a 1500mm + span

Or will i need more powerful motors: step up to servo's.

Now working towards diy 68v psu /80volts digital drivers using 4 x nema 23's 2:1 belt reduction 3.1 / 4nm... probably zapps. not final on this.

Or will better motors be ott compared to "flexible" frame design?
Is 120/80 x80x4mm box section considered flexible? 🤤

About my design.. there will be additional diagonal bracing towards the legs.

I am starting to think i need a 50ton battle tank chassis to get a " rigid enough " base. :-)



Please specify.
Don't be gentle.


The whole idea was to skip a typical mk1 and mk2 build and go straight for a mk3 quality and size machine.



Grtz Bert.








Verstuurd vanaf mijn SM-A320FL met Tapatalk

[fifa]

It is your design, your money.

5m/min with 10mm pitch is 500rpm.

It is better to choose 2020 screw...

I do not understand why you need "rapid" speed. It is hobby machine, and it is CNC. You do not need to be with machine to do the work...

It is relative very easy to "limit" the spindle "wobbling" - 2 nylon bushes do the job (bushes must be splitted axially and loaded with spring to omit radial clearance...

Check the motor torque curve - steppers are not good at high speeds, therefore belt pulley reduction does not work....

For whatever reason link do not works. I am suggesting to do the "bed" form cheap "cast" (epoxy concrete - cheaper than welded structure), gantry must be designed to be torsional stiff, however it is better that laterally it is flexible - to reduce loads caused by rail misalignment...

regards

martin

[driftspin]

It is your design, your money.

5m/min with 10mm pitch is 500rpm.

It is better to choose 2020 screw...

I do not understand why you need "rapid" speed. It is hobby machine, and it is CNC. You do not need to be with machine to do the work...

It is relative very easy to "limit" the spindle "wobbling" - 2 nylon bushes do the job (bushes must be splitted axially and loaded with spring to omit radial clearance...

Check the motor torque curve - steppers are not good at high speeds, therefore belt pulley reduction does not work....

For whatever reason link do not works. I am suggesting to do the "bed" form cheap "cast" (epoxy concrete - cheaper than welded structure), gantry must be designed to be torsional stiff, however it is better that laterally it is flexible - to reduce loads caused by rail misalignment...

regards

martin

Dear martin.

It is as always a trade of isnt it?

stepper : ballscrew pully's 1:2 results in 400 steps per 10 mm right .. so... resolution would be 10/400=0.025 mm per full step right...

Microstepping does not count for repeatability or precision right?

I did actually think 1:2 reduced 1610 and 2010 was generally accepted as the better solution here for alu and hard wood machines diy builds on this forum.
Or am i wrong here?

When one would use 20mm pitch ballscrews... what would you suggest the reduction should be like and keep some resolution?

If i would not need speed i better go for 1605? low rpm and low speed high resolution.


Using 2010 ballscrew on a 1500mm span looked like the best trade of to me. speed vs critical speed vs inertia price.

And yes... it is gonna be expensive

For controls it looks like uccnc 300eth has the affordable price quality i like... not decided on this though...

The most amount of money is not in C7 ballscrews anyway.. it is in linearguides and and bearings ... shipping and tax...


Do you feel i should make a radical move / design change?


Scrap the frame buy an used tank chassis?


And if yes... can you suggest what you would change at this point in the build.



I am open to any suggestions...
The build of the machine is part of the hobby right :-)



Grtz Bert.





Verstuurd vanaf mijn SM-A320FL met Tapatalk

[driftspin]

Epoxy 105 209 questions



What would be a sufficient epoxy thickness and width mounting surface for hiwin type 20mm rail?

My box section is 120x80mm so the flat surface width of the 80mm side
is about 60 mm wide... would 50mm wide and 5 mm thick be enough?

After welding the overall flatness of the frame will be in the +/- 1.5 mm range... so 3.5 to 6.5 mm epoxy thickness after optimum leveling by spirit level..

I am planning to do a single epoxy pouring of the x rail mounting surface and bed supports.. this will give me a good start for a level bed vs x rail

Total needed epoxy amount will be in the 3.0 dm3 range at 5 mm thickness

Verstuurd vanaf mijn SM-A320FL met Tapatalk

[Boyan Silyavski]

Epoxy 105 209 questions



What would be a sufficient epoxy thickness and width mounting surface for hiwin type 20mm rail?

My box section is 120x80mm so the flat surface width of the 80mm side
is about 60 mm wide... would 50mm wide and 5 mm thick be enough?

After welding the overall flatness of the frame will be in the +/- 1.5 mm range... so 3.5 to 6.5 mm epoxy thickness after optimum leveling by spirit level..

I am planning to do a single epoxy pouring of the x rail mounting surface and bed supports.. this will give me a good start for a level bed vs x rail

Total needed epoxy amount will be in the 3.0 dm3 range at 5 mm thickness

Verstuurd vanaf mijn SM-A320FL met Tapatalk

40mm width and 3mm thickness of the epoxy are the minimum for 20 size Hiwin rails. 5mm thickness as all around is ok. 6x6 or 8x8 steel bar welded to frame will provide nice strong cheap channel for pouring in the epoxy. If not a continuous weld, then prime all well to check for leaks. Then pour on second step.