Building a Kronos Robotics KRMx01 CNC Router

KRMx01 Book 1The Kronos Robotics KRMx01 CNC machine is mostly a steel and aluminum machine driven by lead screws.  The selection of this machine and some potential modifications done to it were made after some discussion with the designer, Michael Simpson of Kronos Robotics.

My current machine is a JGRO CNC Router that I originally built in 2006.  It sat in the basement of my workshop for a number of years because of other commitments and was water damaged.  In November 2011 I dug the machine out and put it in the basement of my house, surmised the damage and repaired it.  While using it in a semi production manner I started seeing problems.  First with the long x-axis pipes.  I could not get enough adjustment and could not get all four bearings to ride on the pipe the whole length.  This led to a modification exchanging the pipes for a box like slide I seen on  The second problem was rigidity in general.  Cutting slow and multiple pass depths I can manage to cut whatever I like.  However, when your cutting lots of pieces for wooden puzzles the cut time takes too long.  This is what led me to build a new machine.

 I looked at a few different designs of CNC machines trying to decide which would be a good fit for me.  I eventually got to either a MechMate or a Kronos Robotics KRMx01 or KRMx02.  I ruled out the MechMate because I do not have the capacity of experience to work metal at the level required for the machine.  This left my decision to either a KRMx01 or KRMx02 from Kronos Robotics.  Both of these machines would suite my needs very nice and these are pros and cons with both designs.  The KRMx02 is a super rigid machine built with rack and pinion for speed.  As a result the costs are more and there is somewhat less precision than you would get with a machine driven with leadscrews.  The KRMx01 is still a fairly rigid machine, but built with components that will be consumed over time.  Notedly that would be the plastic anti-backlash nuts and the aluminum angle used to make the vee ways for the carriages.  Also, because it is driven with leadscrews, you have a maximum size that you can make the screw before whipping causes a degradation in performance.  Simply put, it means that the machine can only be so large.  Any larger and you would have to run at slower speeds to compensate for the screw length.

Armed with the above information, I decided to go with the KRMx01.  My decision was driven by the fact that I originally built a CNC router to help make complex patterns for sand casting.  These parts need a specific taper, shrink and machining additions.  So precision was my driving factor and rigidity second.  An attempt will be made if money and time are both available to make some modifications to the machine.  These will include exchanging the aluminum angles that are used for the Vee ways with hardened steel Vee ways.  Second, use the KRMx02 style Z-Axis.  The KRMx02 design is more rigid and this would provide more support for the spindle (read router in my case).

Now, about this build log.

Building anything takes a lot of time and energy and as time goes by you seem to forget what all went into it.  Then you are graciously reminded some time later when you get that email from some guy who is trying to do the same thing.  You want to help, but your not sure what you done.  It is amazing what you can forget when you get a nights sleep or two.  So this log will show (in painful detail in some places) what I done to get this project made.  Additionally, I plan on using motors and electronics that are different than what are specified in the book.  The reason being that I already have them and it is a money saver.  I also plan to use LinuxCNC as my controller rather than Mach3.  I have nothing against Mach3 and am sure it is a great controller, but I have already been using LinuxCNC and it is getting to be like a comfortable fitting slipper to me.  I am getting older and a new machine is enough change for me at the moment.  I hope that the changes in motors, electronics and controller does not take away from the design but rather enhances and gives potential builders more choices in their project.

The build log will be laid out like the book.  I will break it down by chapter.  As a final note, you can get the PDF of the book for free from the Kronos website.  But, if you are serious about building one, I would bite the bullet and spend a few dollars at Amazon and get the printed version.  You can read the illustrations in it and it supports the guy who spent all the hours, money, blood, sweat and tears developing it.

OKAY, enough of that stuff, lets get building