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Author Topic: Getting 2 different size cuts on each side of machine  (Read 7370 times)

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Re: Getting 2 different size cuts on each side of machine
« Reply #10 on: December 31, 2015, 12:03:24 AM »
Update. More info toward all responses.

I was hoping to post a picture here ...... I imagine it can be done but i dont see the option atm.

Anyway this is the test i ran.
I cut a series of rectangles from top y+ to bottom y-
Rectangles are all 3" in y direction.
1rect)44 x 3
This rect is the Correct size
3)14" x 3"
The Left 2 rects were correct the right rect was bigger
8)4" x 3"
1&2 correct 3rd small 4th correct 5&6 small 7th correct 8 large
2) 20" x 3"
Left side correct right side small

I really think this points to a broken or worn tooth on the gears 3 gears interlock each other mathematically its the only explaination i can figure for why the box sizes vary so when i cut 8 of them.   

For arguement sake lets say 1 wheel had a brroken tooth and as it turned the broken tooth hit some boxes 0 times some boxes once and some boxes 2 times. It would make sense .....no?

I just emailed the manufacturer for pricing. If u guys thinkt can be something else before i purchase the parts and spend my time please weigh on .
Thanks so much!

Offline Tweakie.CNC

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Re: Getting 2 different size cuts on each side of machine
« Reply #11 on: December 31, 2015, 01:56:13 AM »
Quote
I was hoping to post a picture here ...... I imagine it can be done but i dont see the option atm.

Click on the Reply tab  (rather than using Quick Reply)  then use Additional Options... to attach the pictures (size images to about 800 pix. wide).

Tweakie.
KEEP SAFE !
Re: Getting 2 different size cuts on each side of machine
« Reply #12 on: December 31, 2015, 10:14:10 AM »
Thanks!
I see it.
It wont let me post pics from ipad .
Ill have it transfer, change file type and upload later.
Its really just pictures to show what im looking at but sometimes pictures really do speak a thousand words.
Re: Getting 2 different size cuts on each side of machine
« Reply #13 on: March 11, 2016, 06:52:15 PM »
Changed pinion.
Problem still persists.
1 side cuts 1/32 bigger then other.

Offline RICH

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Re: Getting 2 different size cuts on each side of machine
« Reply #14 on: March 12, 2016, 06:01:13 AM »
So you now have no bad gears after changing the pinion.
Great!

So here is what I would do:

A. I would manually calculate the steps per unit including what a step per unit is in linear movement. Make note of the calculated value.
    The calculated value is theoretically correct if all was mechanically aligned properly. Any actual movement should be close to the calculated
    value. You will need to assume something as a standard when using the calibration feature so lets assume the left side is adjusted correctly.
    If the steps per unit is correct you should be able to  machine accurately.

    When using the calibration feature of Mach make sure you always remove any backlash and move in the  same direct for what follows.

1. Use the calibrate feature  for the left side. Note the steps per unit value. And set the steps per unit for the left side.
2.  "                             "              right    . Note the steps per unit value. DO NOT set the steps per unit!
3. Now calibrate across the spit of the rack, 1/2 of the pinion diameter rotation for  each side of the split. Make note of the steps per unit.

B. Compare the steps per unit in terms of distance values of 1 &2.

1. Adjust / tweak the right side rack. Make a calibration check and see if the steps per unit are closer to the left side.
   You are making a small mechanical adjustment to the right side to see if you can duplicate the left side rack.
   Ideally the steps / per unit should be the same for the left and right side, BUT, a small difference may be of no concern if
   the difference is small.

   With the right side rack adjusted correctly you can then check what affect the spit does and if it is acceptable.
   Note that that a rack may nay not linear and you can check portions of them to see the amount of increase / decrease / or variance.

Know what you have before you adjust and such that you have a basis as you adjust.
Remember that one rotation of the pinion would be a good linear reference to use.
There are easier ways to do this but unfortunately you do not have the equipment to do it.

RICH

Offline ger21

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Re: Getting 2 different size cuts on each side of machine
« Reply #15 on: March 12, 2016, 08:02:51 AM »
The rack is in 3 pieces?

Is the pinion spring loaded into the rack,or fixed location.

My guess is one of two things.
One, you have a bad section of rack.

Or, if the pinion position if fixed, perhaps the pinion height is not parallel to the rack, getting looser on the right side?
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Getting 2 different size cuts on each side of machine
« Reply #16 on: March 12, 2016, 12:04:49 PM »
At gerry
2questions below


The rack is in 2 pieces.
Its along the x axis driven by 1 motor.
Pinion is at a fixed location(not spring, belt , chain or pulley )

I thought it was the rack but replaced it with 2 brand new racks with the same result.

Pinion is fixed and parallel throughout..
When motor is removed and i push the spindle assembly back and forth along the x axis it used to get tight at the far right.
I modified the rack slighly so it requires even pressure throughout the x axis.
1)Also note then when i change direction there is Zero play in the pinion,which in my understanding, this rules out backlash as being an issue?
2)is there supposed to be an extremely slight angle to the racks? Like 1 degree or less?
Re: Getting 2 different size cuts on each side of machine
« Reply #17 on: March 12, 2016, 12:37:24 PM »
At rich.

Im going to follow your response step by step explaining as i go just to make sure i am understanding correctly but before i do that i do want to mention i dont see the fix.
Woukdnt Calibrating 3 different locations on the x axis just change the entire x axis all 3 times or is it possible to actually calculate each section of rack?
Because if i can calibrate each section that will solve all my problems.

So....
Yes i ruled out a bad pinion so that is good.

A) calculate steps i did cut a series of rectangles for this problem.
I dont remember exact numbers but for explaination ourposes this should suffice.
(Replace the following word box with" rectangle")
10 boxes 4" wide
4 boxes 10" wide
3 boxes 14" wide
2 boxes 20" wide
1 box 40" wide
From this above information i get the following numbers as answers to your next suggestions.

using the 3 box test from above
A1) 14"
A2)14 1/32" (i did nothing to calibrateas you suggest)
A3) 14" although im not following the math you are asking for here? "1/2 pinion diameter"? If diameter is 6" you want me to travel 3" on wither side? Or 1/2 the circumference? In other words have the pinion make a half of turn on one side and then a half a turn on the other side of rack? I think thats what u r suggesting but not entirely sure.

B) 1/32or slightly greater
B1) how? How do i adjust or tweak a solid 1 piece rack that has groves into the steel? What small mechanical adjustments can i make? Are there things i can do like shim on an angle or something to that effect? This could also solve my problem but not sure how to go about doing this. Yeah i dont mind if steps per unit are different from one side to the other but can i set it that way? If so where? The only steps per unit i have found adjust for the entire axis unless i am mistaken.

I follow you regarding rotation and remainder of your response.

Last thing.......you mentioned easier ways but i dont have the tools.
Can you mention some of those tools ?
If they r inexpensive enough i have no problem spending sone money to resolve this.
Or if someone has the name of a local tech here in ny thatd be  great. I dont mind paying i just want this to cut properly.

As always iappreciate your and everyone taking the time to help me try to resolve this.
It means alot!


Offline RICH

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Re: Getting 2 different size cuts on each side of machine
« Reply #18 on: March 12, 2016, 08:42:01 PM »
First let me say that what you find by machining a piece of wood and measuring is just not the way I test.
Using measurements just eliminates any thing to do with possible code or actual cutting.
Simply put, steps / unit from pc = a linear distance of travel movement.

You calibrate the axis for  only one section, say the left, and then test  / check what the error is across the joint and also the right section.
Now you know  comparative error amounts. For the joint, you position to the left of the joint by approx  180 degrees of the pinion travel, and then move another 180 deg of pinion travel, which puts you on the right side rack.

SO,
You can compare the two different racks separately for linearity of movement and after that you can check across the joint.

How would I do it with my equipment?
I place a 48" calibrated scale, which is accurate to within 0.001" at each 0.1" division and can measure to within  .0002" in between the divisions.
An optical alignment scope with measuring capability ( optical micrometer ),is used to read the scale.
The axis is moved and readings of movement are taken and the linearity is plotted. I have even checked the reverse movement as sometimes the reverse movement is
different than the forward movement. So one easily and quickly  profile the movement.

One can accomplish the  same thing with long calipers or a known reference but it is cumbersome to do for long distances.

BTW,
If one has a nice 48" Starrett scale graduated in 0.010" and calibrated you can use that along with a cross haired optical magnifier.

Also make note of what Jerry said as the pinion contact on the rack may be different along the rack and would affect travel.

RICH



« Last Edit: March 12, 2016, 08:45:27 PM by RICH »
Re: Getting 2 different size cuts on each side of machine
« Reply #19 on: March 12, 2016, 10:45:30 PM »


Yep, googled some of those tools you mentioned......some expensive stuff there.
I think its time i start researching a quality machinist and let a pro handle it.(it would cost far less then just one of those tools)
It seems i am in over my head.

I have dealt with manufacturer tech support and they were unable to diagnose and resolve the isdue, ive also dealt with a more local cnc shop and they too were unable to help but i will look for someone with the right tools, knowledge and know how to work on machine and check back here when it gets resolved.
Thanks again to all for your input and assistance!