Grunblau Platform CNC Groupbuy - RC Groups
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Sep 23, 2012, 11:17 PM
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Grunblau Platform CNC Groupbuy

I wanted to finally make a post to describe the status of offering kits for the Platform CNC. I decided to post this separate from the build thread as I am hoping for a conversation and to gauge interest based on these numbers.

I went back through everything to see what I ended up spending for the prototype. You remember that when I started out, I wanted to build the machine close to the specs of the Rockler Shark Pro. Since I started this build, the HD version has also come out.

The basic specs of these machines from Rockler's site are:

Rockler Shark Pro Plus

$3,799.99 (current price plus shipping)

High-density Poly-ethylene and Aluminum Construction
25” X 25” X 5” (Routing Area)
120 IPM (Maximum Travel Speed)
Bosch Colt 1 HP (Suggested Spindle)
Precision lead screws on all axes
Single drive gantry with 269 oz/in steppers
24V Power supply
USB interface with on controller memory storage.
CNC Shark Control Interface (common upgrade is to dump this for Mach3)

Rockler Shark Pro Plus HD

$3,999.99 (current price plus shipping)

High-density Poly-ethylene and Aluminum Construction
25” X 25” X 7” (Routing Area)
200 IPM (Maximum Travel Speed)
Reinforced for 2.25 HP Router
Precision modified stainless lead screws with backlash reducing nuts on all axes
Single drive gantry with 269 oz/in steppers
24V power supply
USB interface with on controller memory storage
CNC Shark Control Interface

Current specs for the Platform CNC

Laser cut and CNC bent steel and Aluminum Construction
30” X 48” X 6” (Routing Area) + adjustable spindle clamp location
300 IPM Travel Speed (Combined axes speed is around 450 IPM @ 25kHz kernel speed)
Currently using my Bosch 1617 (planning for a spindle)
1/2”-10 5 start precision Acme lead screws with CNCRP Dumpster CNC anti-backlash nuts
Dual Drive gantry with 380 oz/in stepper motors on all axes
48V 12.5A power supply
Gecko G540 4-Axis stepper controller
Mach 3 Control Interface

As you can see, I abandoned the Rockler specs for a more useful footprint, more powerful drive system, faster rapids, all metal construction and to use the venerable Gecko G540 and Mach3 for the driver and interface.

Bigger, Better, Faster

What did this machine cost me to put together?

Without considering the parts that I remade in the process (ouch), my cost was approximately $4800. Keep in mind that this was for a one-off machine. Fabrication companies really like to charge for one-off parts. My hopes for this kit would to be for people to be able to put this machine together for right around $4k. Amazingly, this can be accomplished by doing multiples, so if there is interest, I would need to do a run of 5+ machines.

I already have 2 people interested locally and I wanted to put this feeler out into the online community.

The costs per machine breaks down like this based on the quotes I have received...

$1200 for the laser cut and bent steel fabrication
$ 300 for the powder coating, painting, finishing, etc...
$ 300 for the waterjet cut aluminum (still waiting for quotes from new company)

This is $1800 for the parts that I would have fabricated and represents all of the 'smart' components. This includes the integral 45 degree linear rails, structural legs, uprights and bolt together steel structure. I have decided to try to do this initial run as close to my costs as possible. Future runs (if any) might cost a little more.

The costs per machine breaks down like this for the other parts I sourced...

~$1000 for parts at
~$ 550 for fasteners, leadscrews etc from McMaster
~$ 390 for the T-slot extrusions and nuts
~$ 210 for 16 V-Groove bearings and bushings
~$ 50 for misc electronics (E-stop, fans, power switch, etc...)

This is $2200 worth of parts to be sourced from other suppliers.

This is a total of $4000 to have a complete dual drive machine based on these numbers.

How could this get even less expensive?

It makes very little sense for me to pay to have 100's of pounds of stuff shipped to me only to pay to have it shipped elsewhere. I will look into the options for the V-groove wheels and the McMaster stuff as the companies that make them are about an hour drive from me.

Ahren @ CNCRouterparts has been incredibly helpful and depending on some new stuff he has on the horizon, there might be some more savings from what I paid based on packaging and/or quantity.

The total from McMaster is what is required based on their per box quantities. One solution could be to buy these in bulk and split up the boxes as this could save a few nickels. Not buying these from McMaster might also save some cash.

The t-slot extrusions seem to be pretty much a locked-in price. Short of setting up shop and cutting and tapping these myself, this is what 80/20 charges for 5 sets of cut-to-length parts with tapped holes. There are a couple other suppliers for extrusions but none as well known to the DIY community. Parco, for example, was $50 cheaper for 5 sets, but with a bigger volume, 80/20 has been known to cut a deal on pricing.

The V-groove wheels and bushings work out to about $13/set and seem to be pretty inexpensive to me. These include eccentric and concentric bushings allowing for fine adjustment of the axes.

The misc electronics are sourced mainly from Digikey.

All of these prices do not include shipping.

In summary, for about $4K I believe anyone could build this incredibly rigid, dual drive, bench top machine.

The features that are most useful to me is the ability to R&D additional functions based on the flexible structure and drive system (unless someone else beats me to it). The most exciting modes for me to explore currently are Plasma and Tangential knife with the plan of adding a rotary axis in the future. Of course, If a laser fell into my lap, I would be ordering some aluminum honey comb and designing a downdraft table. I really see this as a Platform for making, prototyping and the development of ideas for personal manufacturing.

It has taken me 2+ years to get to this point and I have had a lot of fun along the way and I expect to enjoy my machine for a very long time. I am finally getting back to designing projects instead of a machine capable of producing them.

How I am currently planning to structure an initial run of 5 machines.

Step 1
I am currently gauging interest. Please email me or post here if you are interested. There is no obligation, I will not spam you etc... I just want to see if this is feasible now that the numbers are getting solidified. This would be for the 'smart' steel and aluminum parts.

Step 2
If there is interest enough to do a run, I would require a non-refundable deposit before we got the party started. This is just locking in those people that are signing up for the groupbuy. If there ended up not being 5+ people, you would be refunded your deposit.

Step 3
Once the fabrication and powder coating had begun, I would require that the remaining balance be paid before shipping.

Expected delivery time would be conservatively 4-6 weeks from placing the order.

If you are at all interested, please email me or post in this thread!!!

That's it for now!

Brian Oltrogge
Grünblau Design Studio
Last edited by Grunblau; Sep 25, 2012 at 02:33 PM.
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Sep 27, 2012, 01:30 AM
Registered User
Please put me down for one.

Oct 04, 2012, 03:25 AM
dougmontgomery's Avatar
Brian, What software are you using after your part is modeled.

Oct 05, 2012, 05:52 PM
Registered User
Originally Posted by dougmontgomery
Brian, What software are you using after your part is modeled.

I generally do all of my modeling in Rhino3D, and then I use RhinoCAM within Rhino to generate the gcode. I have used MasterCAM, but sometimes things get lost in the translation. RhinoCAM is basically a VisualMILL plugin for Rhino.

This file is then transferred to Mach3 via USB.

Hope this helps!

Oct 05, 2012, 05:57 PM
Registered User
Originally Posted by Radiokai
Please put me down for one.

Noted I am working on getting a couple locals to commit. Hoping one of them wants a RTR machine, so that I can do some assembly videos. I will post when I know more. Currently fixing my roof, water heater, boiler and painting the entire house before the snow flies...


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