will resonance be an issue?

[Raj Quest]

Hello!

I'm working on building Alexander's 3axis PIC (Because, that's the easiest for me to build!) for two separate Home made CNCs.
Will be using a desktop PC-printer port. Details mentioned below.
Since there is no microstepping, will resonance be an issue and result in messed-up results?
If yes, Is there a mechanical solution? (because I cannot write my own program for micro stepping)

CNC-1: First Project
Purpose: PCB Routing (for SMD),
[Doubt if PCB will ever exceed 4” x 6”]

• Construction material –MDF & some aluminium
• Table size 12” x 12”
• X table mobile, Fixed Gantry Design
• Home made LM system (Bearings on alu angle rails)
• Lead Screw - Acme - (5/16 general purpose)
• Unipolar Stepper: NEMA 17s for all three axes
• Ready available dremel tool – for spindle
• Controller: Alexander’s 3axis PIC, (with Current Limiter)
• Using IRL504N, PIC12F508 (programming using ICProg)
• MACH3 Trial Version – (500 Lines of GCode)



CNC-2: second project:
Purpose: MDF Routing (for engraving MDF, art pieces, wall décor items),
[Expected max size 6’ x 3’]

• Construction material –MDF & Aluminium, Steel
• Table size 6’ x 3’
• Fixed Table and Mobile Gantry Design
• THK LM system with ball screw OR
• Lead Screw ACME ½” (* *)
• Unipolar Stepper: NEMA 23s for all three axes
• Ready available router tool – for spindle
• Controller: Alexander’s 3axis PIC, (with Current Limiter)
• Using IRL504N, PIC12F508 (programming using ICProg)
• MACH3 Trial Version (initially – for test runs)

Thanks,
Raj

[PMinMO]

The 3 axis pic is a full step controller, resonance is an issue with full step controllers as you go up in rpm's.

[Raj Quest]

Thanks Phil,

If I use MACH3 to set a max-motor-speed which is fairly low, then,
1) will this take care of resonance and missing steps?
2) Just that the job will take longer to complete. is that right?

I want to assess if the 3axisPIC will be suitable for my purpose, or I should go with Linistepper or SLA7062.
Any help, links, URLs in this regard?

Thanks,
Raj

[Raj Quest]

Phil,
Went through the following post.....
So lower speed is the only solution afterall?
Thanks,
Raj
viewtopic.php?f=27&t=415&start=15

Well pminmo,
I GOT IT WORKING!!!! I had to go from 4000 steps per mm to 10 per mm! Now it works ok.
At fast speeds (over 100mm a min) i get missed steps around 50 seams good.
How can i improve my accuracy at speed? New Steppers?
Can wait to get my machine finished now!
Thanks for all your help!!!

Speed is a problem with full step controllers because of stepper resonance. Full step is strong, but not fast in it's simplest form.

[Raj Quest]

Hi again,


http://www.solsylva.com/cnc/dampers.shtml
The simple solution mentioned in this link will take care of the resonance (due to full step controller)?
There are some other sites also mentioning the use of 'dampers' - in its simplest form like an additional weight fixed onto motor shaft

Could this be a simple homwbrew solution to the resonance and missing steps when using 3axispic (full step controller)

Thanks,
Raj

[PMinMO]

Yes mechanical dampers can help considerably. The SLA7062 is a better solution if you can get those parts. Linstepper would depend on the amount of current your motors draw.

[Raj Quest]

Thanks Phil,

The DIY Driver comparison page http://pminmo.com/driver-comparison
mentions "Chopper 46V" against SLA7062.
Any place where I can get schematics and DIY build information for "chopper 46V"?

Thx,
Raj

[PMinMO]

Thats how the SLA limits current, it's in the IC.

[Raj Quest]

OK! Thx!
Time to do some more reading! ..... will hunt for the datasheets..
Raj

[Raj Quest]

Phil,
Regarding 3axisPIC:

PIC12F508 has memory=512 whereas,
PIC12F509 has memory=1204

So, using the same circuit, using 12F509, will it be too difficult to add half stepping?
(will it eliminate resonance?)
OR is it not worth working in that direction?

Thanks,
raj

[PMinMO]

It's not difficult to add the code for half step.

[Raj Quest]

Phil,

Thanks,
Raj