Design update

[Robo]

Mechanical design update

[TheCunningFellow]

Robo,

Can you show me the red part in the first photo by itself.

I am currently trying to work out a way to attach the belts to the carriage.

tnx

On Sunday, April 9, 2017 at 2:14:11 PM UTC+10, Robo wrote:

Mechanical design update

[Robo]

Just m working on it and want to add some more functionality to tight belt by screw.  i ll update soon

[TheCunningFellow]

I was contemplating having one of the pulleys at the non drive end movable for tension.  This would keep the carriage bracket smaller.

On Sunday, April 9, 2017 at 2:35:23 PM UTC+10, Robo wrote:

[Robo]

Yes can do by 3d printed bearing based pulley

[Trampas Stern]

For the Y axis I ran a 5/16 (8mm) bar across the back side and had one plate with a bearing. Then by using a double shaft stepper I only had one stepper motor.  This will be a lot better especially when you start trying to keep the X and Y axis perpendicular. 

On the base plate I did like you initially and had my MDF cover the entire bottom of the machine. However this left no room for feeders. So I am working on redesigning my machine to have room for feeders. 

If you plan on using Yamaha feeders the stock mounting plate, is ~250mm from the bottom of mounting plate to the pick location. Therefore to make it the same height as your machine you will want the build height to be 250mm from the table top machine sits on. 

Additionally plan out your build height that you place PCB should be the same height as the strip feeders and any that needs head camera as the head camera will be focused at one height. 

I have also changed the Y/X carriage with the loop belt holder as well as Peter's head design:

https://groups.google.com/forum/#!searchin/openpnp/trampas$20head%7Csort:relevance/openpnp/1hjPDobNIpk/FvsSZEq5BAAJ

Also I have found that the 20 tooth idler pulley are not very good. Specifically, the inner race diameter is so thin that if you tighten a socket head screw against idler it will bind up the idler, hence you have to leave the pulley floating on the screw.   Additionally in order to get belt centered you will need spacers between plate and pulley, this places large moment on the screw and has caused my 3D printed plates to bow.  I am considering making new plates from aluminum or machining a plate when the material is left for spacing.  I am also considering changing idlers to use larger ones with real bearings. 

Trampas

www.misifitech.net

[TheCunningFellow]

> For the Y axis I ran a 5/16 (8mm) bar across the back side and had one plate with a

> bearing. Then by using a double shaft stepper I only had one stepper motor.  This will

> be a lot better especially when you start trying to keep the X and Y axis perpendicular. 

I have started with 2x Y motors thinking 2x the power would be good.  Will the steppers

really get out of sync and cause the machine to become a parallelogram?

> Additionally in order to get belt centered you will need spacers between plate and pulley,

> this places large moment on the screw and has caused my 3D printed plates to bow

I decided to put a plate on each side of the ally rail for the moment (pun intended)

https://groups.google.com/forum/#!topic/openpnp/6PQQ0OcrdWg

so that I had more options with the types of styles of pulleys and/or tension devices.

BTW - like the look of your machine.  I hope mine can end up looking that good.

[Bernd Walter]

On Sunday, April 9, 2017 at 11:16:47 PM UTC+2, TheCunningFellow wrote:

> For the Y axis I ran a 5/16 (8mm) bar across the back side and had one plate with a

> bearing. Then by using a double shaft stepper I only had one stepper motor.  This will

> be a lot better especially when you start trying to keep the X and Y axis perpendicular. 

I have started with 2x Y motors thinking 2x the power would be good.  Will the steppers

really get out of sync and cause the machine to become a parallelogram?

 Short answer: yes
A stepper has 2 coild building 4 main positions (a few times repeated per revolution).
When the machine starts the position of the motors are unknown, so the driver starts
with a specific coil and polarity.
If both steppers were left with the same coil in the oposite polarity the motors might turn
left or right to catch on the position creating a possible 4 step offset between them.
It doesn't happen very often in practice, but can happen.

Loosing steps is another thing to consider.
If you use 2 separate drivers to run them one motor might stall, while the other won't.
If you run 2 motors in parallel on a single driver one stalling motor usually stalls the other as
well, because of back EMF, but requires more current from the driver and the current isn't
perfectly equally  shared between the motors, which not just creates different torque, but also
negatively influences microstep precision.
The best way to avoid loss in microstep precision is running the motors in serial, but this
increases the inductivity and therefor reduces torque at higher speed.

All in all there are many 2 motor systems out there, which seem to do their job.
I'm running 4 3D printers with 2 Z-Motors in serial connection myself, but since I'm
using autoleveling I wouldn't notice a new 4 step offset.
It in fact is a problem, but maybe happens rarely enough.

[Bernd Walter]

On Sunday, April 9, 2017 at 12:57:42 PM UTC+2, Trampas Stern wrote:

Also I have found that the 20 tooth idler pulley are not very good. Specifically, the inner race diameter is so thin that if you tighten a socket head screw against idler it will bind up the idler, hence you have to leave the pulley floating on the screw.   Additionally in order to get belt centered you will need spacers between plate and pulley, this places large moment on the screw and has caused my 3D printed plates to bow.  I am considering making new plates from aluminum or machining a plate when the material is left for spacing.  I am also considering changing idlers to use larger ones with real bearings. 

Yes - they use 2 bearings in them, so applying pressure is a no go.
You must to use them in a loose fit.
Another big problem I've faced is that many of them, especially teethed ones, have
a super small diameter difference between the rings and it is a real challenge to get
matching washers - in other words: super expensive special parts.

E.g. for a 16 teeth with 3mm hole an M3 washer is too big, but will work fine for the toothless versions.
I've bought the 20 teeth and toothless with 5mm hole, which both have the same problem.
3mm should work I assume, maybe 4mm as well.

[TheCunningFellow]

OK - sounds like a problem I am willing to live with.

I imagine the "Direction at startup" thing to be self leveling.  As you go too trapezoidal the

tendency to pull to the median will be higher.

I eventually want to install servos and may to a single motor then, but I will

leave it as is for now.

[Robo]

So 2 motors for Y axis is not a good idea right?.
Today i ll change my design for single motor.

[Paul Kelly]

2 motors for Y is fine.
Many many machines use this configuration, it allows you to use the same motors for X and Y because Y needs more torque to accelerate at the same rate as X.

A stepper motor will either never lose steps, or lose steps every time. As long as you set them up correctly and home both motors at start up, it will work well.

PK

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[Arie Lashansky]

Hi Robo

Can  you please send me or post the 3d model for the part.


Thanks Arie

[Makwana Chetan R.]

Sure,

Once i complete design i ll update

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[Arie Lashansky]

Thanks Robo

Your part looks good. My build  is only now taking shape  with all the parts sourced

Arie

On Monday, 10 April 2017 13:38:38 UTC+3, Robo wrote:

Sure,

Once i complete design i ll update

On Apr 10, 2017 4:07 PM, "Arie Lashansky" <ariela...@gmail.com> wrote:

Hi Robo

Can  you please send me or post the 3d model for the part.


Thanks Arie



On Sunday, 9 April 2017 07:33:26 UTC+3, Robo wrote:

Just m working on it and want to add some more functionality to tight belt by screw.  i ll update soon

On Sunday, April 9, 2017 at 9:44:11 AM UTC+5:30, Robo wrote:

Mechanical design update

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[Robo]

so if i use single motor than how much Kg-cm torque need ?

[Paul Kelly]

It depends on the mass of the belt, the mass of the thing attached to the belt, the diameter (and mass) of the pulleys, and how quickly you want to accelerate that mass.

 

It’s actually not too hard to work out for a belt driven system. See http://www.leadshine.com/Pdf/Calculation.pdf

 

PK

 

 

From: ope...@googlegroups.com [mailto:ope...@googlegroups.com] On Behalf Of Robo
Sent: Tuesday, 11 April 2017 1:27 AM
To: OpenPnP <ope...@googlegroups.com>
Subject: [OpenPnP] Re: Design update

 

so if i use single motor than how much Kg-cm torque need ?

On Sunday, April 9, 2017 at 9:44:11 AM UTC+5:30, Robo wrote:

Mechanical design update

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[Robo]

Finally arrived..

[Trampas Stern]

In order to get the Yamaha feeders working with PnP I had to change up the mechanical design a bit. I had to raise up the PnP to get it where the reel feeders were at the nozzle height. 

[Robo]

All parts are 3d printed, Now on the way to design head for 3d print

[DAniel Dumitru]

Congratulations ! Nice setup.

If I may, I have a comment here : I don't like that big pulley that you are using in order to return belt trough middle of alu extrusion.

Big pulley means reduced precision + correlated with wide spread of 8825 drivers ..

Br,
Daniel

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[Robo]

Thanks for comments.. yap.. i got that point after completing this design and print. but in next update i ll replace with small pulley like 16 or 20 teethes. but with small pulley m worried for speed. will 16 or 20 teeth of pulley give enough speed ?

[Robo]

Some update on 3D printed head.. yap need to do some modification on design,..

[Arie Lashansky]

Hi Robo 

 Endstops and belt Tension. 

My head looks the same missing endstop  and the tension slack taken up with the x movement or the  z slide rails 

I use the Spring loaded Juki mounts it will let me do easy head change 

[Arie Lashansky]

Here is My first Update 
https://www.youtube.com/results?sp=EgIIAQ%253D%253D&q=openpnp

lots of work still to do not square and still needs lots of more support but it
moves x y z and theta  1 top camera mounted.

No Lighting for camera
Joints for theta axis. 360 degree movement 
I am using abs to glue the theta motor mounts to z slides
z belt also has issues of the screw falling out ( printed in PLA but ABS molten abs put into the screw hole) ( acetone abs used as glue)

My aim is get working then redesign the parts like the z sled that I have issues with.

improve the the supports and square the design. base plate 
Next steps are to install endstops.
move to getting the electronics working   http://www.instructables.com/id/Configuring-MKS-Sbase-V12-32-bit-Controller-Basics/  

I am sure more will follow after that

[Robo]

Could you please upload the photos ?

[Arie Lashansky]

I will make better photo's as the build gets on this is still very early days.
here are some views I advise to use the spring loaded Juki changer not the one I got from China In my hand on the photo

Z stage is from Trampas Stern
the the Z base is from Peter Betz  design  with a hole drilled in the bottom. I know need to rework the design to have optical endstop


https://drive.google.com/file/d/0B6KVfqVSGwUATmd0RjFuWmVqV3c/view?usp=sharing
https://drive.google.com/file/d/0B6KVfqVSGwUAdEJEd1NVeDVNMlk/view?usp=sharing
https://drive.google.com/file/d/0B6KVfqVSGwUAOFJCZDF4ZU1CRHc/view?usp=sharing
https://drive.google.com/file/d/0B6KVfqVSGwUAdmlEWGRla0xjaFk/view?usp=sharing
https://drive.google.com/file/d/0B6KVfqVSGwUAQnRlV1BQQk1FN3c/view?usp=sharing
https://drive.google.com/file/d/0B6KVfqVSGwUAajBKcHZ0RXRoRE0/view?usp=sharing
https://drive.google.com/file/d/0B6KVfqVSGwUASFF0N1VyNFB3ODQ/view?usp=sharing
https://drive.google.com/file/d/0B6KVfqVSGwUAN2NDN0llR25XMTA/view?usp=sharing
https://drive.google.com/file/d/0B6KVfqVSGwUAOXFjbTJKT3VMQmc/view?usp=sharing

[Robo]

Hello,

Here is the my first machine test for X and Y axis,

https://youtu.be/d5_LHcNdrEQ

Thanks

[Robo]

Almost ready except

1. Z axis end stop(Even after triggering end stop motor trying to push more) :(

2. Pneumatic connection

3. Software setup

[Paul Jones]

Have you tested the stepper motors running on the ribbon cable? I tried that but I had trouble with missing steps and no torque. I ended up replacing the ribbon cable with flexible Cat5 from network patch cables which worked much better.

 

Paul.

 

From: ope...@googlegroups.com [mailto:ope...@googlegroups.com] On Behalf Of Robo
Sent: Monday, 5 June 2017 1:40 AM
To: OpenPnP <ope...@googlegroups.com>
Subject: [OpenPnP] Re: Design update

 

Almost ready except

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[Robo]

Till now i haven't seen any issue with this cable.

Let's see. If any issue,i ll change with Network cable.
Thanks

[Robo]

Hey,

Anyone help me to setup Z axis end stop with mks board?