Calibration vs cut area

![CNC1|666x500](upload://cIlFJ9dN 14conxdXGusEQSDF7d3.jpeg)

Hi All, My first post. I wont apologize for my questions as I’m in the “no judgment zone”, but would like to say BIG thanks to everyone who contributes to the forum. With family & work commitments, its taken me about 6 months to get to this point of a finished, adjusted frame, balanced motors, chains and a smooth working temp sled. For sure a lot of frustrating days (and nights), steps forward, steps back etc but finally feeling pretty good about where I am at with the project. The forum has been very helpful getting to this point. I added some pics but im not sure if they are visible?.

some project notes:

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    I adjusted my metal frame several (many) times in different places to get a VERY flat work surface. Im now at almost a zero depth difference anywhere on the back support. (+/- .25mm) This was a critical step in getting repeatable smooth calibration cuts on my test OSB sheet.

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    I added lengths of rubber feet onto the bottom of the unistrutt legs (using pieces of an old rubber cable trough) and added cinderblocks - for less vibration and more weight at the base of the unit.

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    I had to rethink my chain support and chain runners on this project. For some reason this was a big sticking point for me as I could not get my chains and cogs to run smoothly using the suggested (one end of the chain fixed to the frame method). I was always getting too much (or not enough) tension and as a result the chain was always being unevenly guided on and off of the cogs. resulting in random snagging and jumping of teeth. After some experimenting I came up with a floating system using 2 bungee cords that provide the correct tension at all times on the chain no matter where the sled is on the work surface. This100% got me past the snagging issues and actually added an increased smoothness to the machines operation. I also lightly re oiled the chain after handling it so many times.

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    I used carriage bolts to attach my router to the temp sled and countersunk the carriage bolt heads to the underside of the sled with approx. 1mm or so of the bolt head sticking out. This helped glide the sled over the worksurface in a smoother manner as opposed to the friction of wood on wood. I realize I may or may not need this when I cut the actual sled from smooth MDF and use a smoother finished wood sheet for my project pieces.

My question relates to the work surface and the calibration cuts - Im using mostly the default settings and using the motors to calibrate the chain length. So using the following measurement’s:

Chain length 2978.4mm
Default work surfaces 4x8’
Motor offset 374.65mm
Default sled measurement’s of 310 / 139 / 79mm

(with the router turned off but the bit following in the channel)
I an getting repeatable precise calibration movements of:

OE of Cut 1 to cut 2 1930.4mm (6ft 4")
OE of Cut 3 to cut 4 1930.4mm (6ft 4")
OE of work surface to OE of cut 5 346.075mm (13 5/8")

Do I need to calibrate the test cut area to reach to the same area I want to cut within on the 4x8 sheet?
When I use the manual control arrows of launch control, I am able to take the sled to all 4 corners and along the edges of the 4 x 8 sheet. (as close as i can without the sled falling off) but the calibration cut will only cut to the dimensions mentioned above. Should the calibration cuts cover the same area as the area I want to cut within? or is the calibration test cut unrelated to any sizing a g.code file might have at this point.?

Testing the calibration size without a router bit - If I increase my chain distance in the maslow settings (ie from 2978.4 to 3678.4 and manually reset my router to center, the router WILL cut within a larger area L to R but I loose the cut height.?. Am I overthinking this?. Its taken me so long to get to this point, I’m worried about damaging the machine or that I’m now still missing some steps?. Hope this is making sense. Thanks in advance for any input.

There’s no specific calibration for certain areas. The calibration cut you did is designed to cover the entire board. There’s lots of posts on this forum regarding accuracy of the calibration. Look for holey calibration posts as well because it describes a new calibration routine we hope will produce better results.

Also, looking at your picture, make sure the chain does not hit your bars holding your top beam otherwise your cuts will be off.

I’m not sure what you are trying to describe, but ‘manually reset my router to center’ isn’t going to be a good thing.

Very likely :slight_smile:

MADGRIZZLE Thanks for the input. I did make some adjustments to the top bar as you mention. I was experimenting a while back and when i increased my chain distance in maslow settings this offset the router from the center point to the left. So I manually removed the chains and sled and re-centered the router onto my 4x 8 surface, adjusting any slack in the chains so the sled was re-centered again. when i re-ran the test calibration again this visually showed me showed me the actual L/R distance increase of the calibration, rather that the sled just shifting to the left during the calibration cut. Probably not something I needed to do and of course in hindsight I could have split this measurement to see the increase L & R from center but at the time iwas trying to understand the software and the machines adjustments to different settings. Im going to cut my actual round sled and see what happens!.

I’m really concerned about what I’m reading and maybe I don’t really understand what you are saying.

When you say:

specifically what are you doing? when you refer to chain distance, are you referring to how far the motors are separated?

I don’t think this works as you hope it will.

You are correct and heres why. I was assuming up until now that my calibration cut should match the example given in the calibration test picture where it shows the calibration test cuts very close to the edge of the work area. I was expecting my calibration cut to go as close to the edge of my 4x8 sheet as show in the image and when it didn’t I assumed I needed to increase the distance between motors to create a larger area to work within. Does that make sense?

Ok, I follow what you are saying, but no… that’s not how it works. :slight_smile:

Only under one specific condition should you ever remove and reinstall your chains:

Beyond that, don’t ever adjust your chains. The controller keeps track of how much chain is between the motor and the sled and if this value is ever wrong, your calibration will be off and square cuts won’t be square, round cuts won’t be round, etc.

Maybe its just me :crazy_face: that i was expecting such a literal translation from the calibration image show to the actual calibration cut. ( cut distance from the edges)

Yeah, I get it… perfectly reasonable assumption.