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Topic: Kit for Calibrating X and Y with a Dial Gauge

This is a kind of a rail that slides on to the printbed, and a piece that fits into the rail with a hole for the dial gauge.   

For X, push the gauge holder back against the stop and hold it steady.  Give the nozzle a head start and move it toward the plunger until it barely moves it.  Zero the gauge and then move the nozzle against the plunger 10 or 20mm.  Record the actual movement vs the commanded movement.

For Y, turn the gauge 90 and set it in the rail, holding it down with your finger while doing the same test in the Y direction.

Print both of the pieces with support.  Support is needed under the triangle parts and under the tab of the gauge holder.  In Advanced settings in Slic3r you can set a separate extrusion width for support material.  I used .7 which means 70% of the width used for the rest of the print, and made the supports thin enough to pull off.

http://solidoodletips.files.wordpress.com/2012/08/x-calibrate.jpg

http://solidoodletips.files.wordpress.com/2012/08/y-calibrate.jpg

Post's attachments

XY Dial Gauge Slide2.stl 20.77 kb, 99 downloads since 2012-08-19 

XY Dial Guage Hole v2.stl 60.2 kb, 86 downloads since 2012-08-19 

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Re: Kit for Calibrating X and Y with a Dial Gauge

Are you going to do a post in your blog on how to adjust motor steps if axis are over/under travelling?

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Re: Kit for Calibrating X and Y with a Dial Gauge

I'll try to get one up tonight or tomorrow. 

The steps/mm are set to 88 by default, and since I told it to move 10mm, it turned 880 steps.  It actually moved 9.83 in those 880 steps so it is actually 880/9.83 = 89.52 steps/mm.

On  Y is moved 9.75mm, so that would be 880/9.75 = 90.25 steps.mm.

I still need to make those tweaks in firmware and see if it works out.  It's better to calibrate this way by movement, rather than measuring prints.  With printed models, slicing and the physical extrusion of plastic comes into play and you might be chasing around values that are affected by flow or toolpath generation and not just the mechanics of the printer itself.

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Re: Kit for Calibrating X and Y with a Dial Gauge

That will be great, thanks.

Im a big believer in calibration.
Id rather spend 2 days calibrating, printing, measuring...making sure everything is 100% than trying to print 1000's of things and having constant problems with print quality etc

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Re: Kit for Calibrating X and Y with a Dial Gauge

Ian:
Some of our customers may be interested in the exact model of digital gauge. Can you tell us about it?

Former Solidoodle employee, no longer associated with the company.

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Re: Kit for Calibrating X and Y with a Dial Gauge

He has an amazon link to it on his blog.

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Re: Kit for Calibrating X and Y with a Dial Gauge

I made a friction fit dial gauge holder. The scad file contains test pieces that allow you to iterate a good friction fit for both the extruder and the gauge. My gauge has a fixture on the back that can slide into a slot.

I put three slots on the gauge holder so you can measure in the three axis directions.

Post's attachments

ExtruderConnector.scad 5.92 kb, 41 downloads since 2012-09-10 

ExtruderConnector.stl 60.98 kb, 1096 downloads since 2012-09-10 

gauge1.jpg 528.95 kb, 11 downloads since 2012-09-10 

gauge2.jpg 531.89 kb, 7 downloads since 2012-09-10 

gauge3.jpg 466.06 kb, 10 downloads since 2012-09-10 

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Re: Kit for Calibrating X and Y with a Dial Gauge

Jinja, I like it.  This morning I printed a new back to my dial gauge since I didn't want that mount sticking out of the back, that way I could use Ian's mount...  I'll be putting it back on and using yours I think.

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Re: Kit for Calibrating X and Y with a Dial Gauge

Can you post an STL of just the mounting plate?  I like that one better than mine, because mine won't work with most of the S2s that shipped after mine, which have the lower bolts sticking out from the extruder.  Once you have the base plate, you can add whatever you want to it

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Re: Kit for Calibrating X and Y with a Dial Gauge

Sure, here are a few of different thicknesses. I strongly recommend installing OpenSCAD and generating your own STL files. That way you can fine tune the positions of the bolts and the size of the holes. The generated files are made specifically for my solidoodle, which doesn't seem to have perfectly aligned bolts. You don't have to be a coder to change the files. It's just editing numbers within a text file.

I've attached three different thicknesses, 3, 6, and 9mm. Also, I've added one with a blank face to give you more gluing space.

Post's attachments

ExtruderConnector_3mm.stl 46.92 kb, 71 downloads since 2012-09-10 

ExtruderConnector_6mm.stl 44.6 kb, 52 downloads since 2012-09-10 

ExtruderConnector_9mm.stl 44.6 kb, 55 downloads since 2012-09-10 

ExtruderConnector_block.stl 53.96 kb, 78 downloads since 2012-09-10 

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Re: Kit for Calibrating X and Y with a Dial Gauge

IanJohnson wrote:

Can you post an STL of just the mounting plate?  I like that one better than mine, because mine won't work with most of the S2s that shipped after mine, which have the lower bolts sticking out from the extruder.  Once you have the base plate, you can add whatever you want to it

Your plate did fit (mine has the lower screws reversed with the nut facing out), with a little bit of reaming out the bottom holes, and pressing it on.  It was a very tight fit without the magnets.

I still like this design better though.

12 (edited by IanJohnson 2012-09-10 18:43:45)

Re: Kit for Calibrating X and Y with a Dial Gauge

I just remembered that my indicator comes with an additional back with the tab on it.  I'll definitely be switching it out and using this mount.  Mine has just enough wiggle to it to change the reading a bit as it drags across the bed.  If the slot fits tight enough, this one should be more stable. 

Neil, have you used this to measure your Y backlash yet?


Now we need an electronics cover with a fan mount.  It's getting so that I can't print without occasional squished layers if I don't keep the board cool.

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Re: Kit for Calibrating X and Y with a Dial Gauge

Not my Y backlash yet. I've done X and it travels 0.996 to 1.02mm when I request 1mm. There's no backlash in the X, or at least it's smaller than my error in measurement. I'm surprised by this considering my oval holes. Perhaps my backlash is all in the Y?

I'm going to do a lot more measurements today.

I wanted a super tight fit on the mount so it didn't wobble at all. That's why I put little gaps near the bolt holes so you can pry it off with a screw driver.

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Re: Kit for Calibrating X and Y with a Dial Gauge

I suppose I could code up a graph plotter that reads gcode. Then I could add hysteresis to it to see how it affects the plot. If I can add faults to the plotter such that it gets the results I see on my printer then maybe I can compensate for the faults.

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Re: Kit for Calibrating X and Y with a Dial Gauge

Did you check the backlash in Z?  I would expect that to be consistent between printers, since that depends on the fit between the threads of the rod and the nut. 

I didn't have any measurable backlash in X either.  It's just one belt, and shorter.  There seems to be more that can go wrong in the Y axis.

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Re: Kit for Calibrating X and Y with a Dial Gauge

By the way, if anyone is reading any my posts and thinking that there's something wrong with the Solidoodle, that's incorrect. The Solidoodle is frikkin' great and I've printed awesome things on it. Right out of the box it was calibrated spot on. I've printed a load of prusa mendel parts that came out just great. After 50 or so prints I think I've managed to jostle the bed enough that it is no longer level, which is why I now have a cheap gauge I'm playing with. The fine calibrations that we talk about on this forum and others is talk of improving something that already works great, not fixing something that is broken. We're talking about raising the quality of the prints from 95% to 96%.

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Re: Kit for Calibrating X and Y with a Dial Gauge

I haven't checked Z yet either, but I'll be leveling the bed today as well. I'll let you know the results when I have them.

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Re: Kit for Calibrating X and Y with a Dial Gauge

My Y (and I assume everyones) has two belts between the motor and extruder. That is, motor -> pulley -> belt -> pulley -> belt -> extruder Y. So it has two pulley/belt interface backlashes. I would expect it to have a larger backlash.

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Re: Kit for Calibrating X and Y with a Dial Gauge

I can't count, that's 3 belt/pulley interfaces for the Y axis.

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Re: Kit for Calibrating X and Y with a Dial Gauge

IanJohnson wrote:

Now we need an electronics cover with a fan mount.  It's getting so that I can't print without occasional squished layers if I don't keep the board cool.

I was getting squished layers on most prints... so I added a fan.  I was going to build a box for it.  If you look at my workspace post here, you'll see I started to print a box.  There is one on thingiverse that almost worked.

At some point I'm sure I'll design a cover for the box and a fan mount, but I was having the chicken or egg problem.  I couldn't get good prints without the fan, and couldn't print the fan cover with out the squishes... or y step misses.  So I was focusing on fixing that first.

The antec fan I have seems to be doing the trick easily.

I've seen so many of these boards with aluminum head sinks, I think I'll try and find some of those too.

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Re: Kit for Calibrating X and Y with a Dial Gauge

My Y axis motion is 0.988 to 1.0029mm for a 1mm request. The backlash is 0.147mm!! I haven't done enough measurements yet but it's obviously there.

I tried M99 Y13, but M99 Y12 gave me better results. The backlash appears to have gone. Later on I'll try printing that pulley again to see if it fixes the teeth.

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Re: Kit for Calibrating X and Y with a Dial Gauge

My Z backlash is 0.068mm, and M99 Z154 seems to fix it. So I'm going to add this to my start code...

M99 X0 Y12 Z154 E0

Ian, what did you get for your Y backlash?

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Re: Kit for Calibrating X and Y with a Dial Gauge

My Y backlash was running about .14.  I uploaded the marlin.pde and planning files you attached.  M99 seems to have worked, enough though it didn't return anything to the log in Pronterface.  I was using my jig on the hot bed, and after awhile it started to get loose and wiggle a bit, so the measurements started to get dicey.  After I print your mount I'll run it again.  Having the M99 command makes it easier to dial a setting in.  Can you do the same with the steps/mm?  It would be cool to be able to change them from the host, and then plug them permanently into the configuration.h when you get them to a point that you like.

Can you have a default value in there that can be overridden by an M command?

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Re: Kit for Calibrating X and Y with a Dial Gauge

I believe the M92 command does what you want. It will set the steps per mm for each axis. The defaults are set from the configuration.h. There is also some code in there for reading the values from an EEPROM. Do we have EEPROM storage on the Solidoodle board?

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Re: Kit for Calibrating X and Y with a Dial Gauge

Sure do. We can use Repetier-Host to save values directly to the EEPROM. The Panelolu can also do it from the screen.