View Full Version : Karbunkles 1st Gantry Machine

01-01-2006, 03:57 PM
After spending my time researching, since joining in Aug. 2005, I've started construction.

Mind you I'm using the vast knowledge of this group, so I'm not going into this blind, It's more like I have been poked in one eye.
My figurative "poked eye" is the electronics hook up.

I have moved right along building the machine base x axis and z axis. I am now about to fill in the middle y axis.
I have the great fortune of working for a company that has a great deal of "stuff" at it's disposal. Anything I need for construction comes from the scraps from another job.

I am a Prototype Modelmaker and this machine will be used for both 2D and 3D work. Anything from routing Sintra signs to vacuum-form patterns.
I work for a Display Company.

I'll be posting pictures of the progress. I have a few already but, as of this writing they are on the harddrive at work.

Currently, I have this dilemma: How do I make the electronics work?
Let me tell you what I have and please give me advice and links to the information. As noted previously, I've used this forum to get this far, it is my hope that you can help finish it.

Here's what I have:
1. 3 pcs. 640oz/in Model #RHT34-640 Bipolar Steppers from www.homeshopcnc.com
2. 3 pcs. Gecko 201 Drives
3. 1 pc. Magnetek MG1 MODULAR POWER SUPPLY 48vdc 15a regulated (www2.magnetekpower.com/cps/CPS_MG_DS.pdf)

As I understand it here's what I'll need yet:
1. A parallel port interface card (to talk to the Geckos)
2. a 5vdc power source for the Geckos
3. A capacitor (10000uf?) for the feedback EMF from the steppers to the Geckos since the power supply is regulated.
4. A fuse block to protect each Gecko
5. Maybe a Safety Charge Pump (but I'm not sure how that all works)
6. Mach3

Please feel free to direct me (kick in the butt, I'm an apprentice) to the proper vendors.

The capacitor part is confusing me at present.
If I buy one large Capacitor, Can all three Geckos be connected to it?
If so, are they isolated in any way? What voltage Capacitor do I use?

I know from reading the "Stepper Basics" PDF on the Gecko page there is supposed to be at 470uf 100v Cap on each Gecko. But I've seen examples on this forum where just one large Cap is used.

01-01-2006, 04:21 PM
1) www.campbelldesigns.com www.cnc4pc.com www.pmdx.com
2) I **think** you can pull this from the PC.
3) I think there is a formula in the Gecko paper on power supply design, which will give you the cap size.
4) Haven't used Geckos, but this is in the manual, right. Mariss (Gecko owner) is on vacation. Give him a call later in the week and he'll tell you everything you need to know to hook up your Geckos correctly.
5) Works with Mach3, and certain breakout boards (possibly all the above, CNC4PC is an add-on card) to keep motors from moving when Mach3 doen't have control of the system.
6) www.artofcnc.ca Also, watch all the videos at www.machsupport.com

01-01-2006, 07:14 PM
Thanks Gerry,
It's the whole feedback emf issue that has me a little worried.
According to the Gecko page, if I used an unregulated power supply the feedback wouldn't be an issue since it would be absorbed by the capacitors in the power source. But since I got a deal...$35.00 on this surplus regulated "powerhouse" powersupply... I'd like to use it. (Cooling fans already part of the power supply case!)
I hope Mariss can fill in the Cap question.

01-01-2006, 08:04 PM
What I meant, was, to use the formula for the cap as if you were building a comparable size supply as shown in the Gecko white paper, and just hook that up to the output of your supply.

01-03-2006, 09:12 PM
Here is the progress.
I started with whatever I could scrounge from around the plant.
The framework is made from straight pallet rack rails.
The Rails are 2 inch EMT conduit
The Rails are sitting on Unistrut
The Bearings are Skate bearings sandwiched in Machined Aluminum.
All dimensions are completely made up. I'm Drafting this thing on Cadkey98 as I go along.
That's why I started with the x axis then went to the z axis. It'll be easier to meet in the middle with the Y axis Gantry construction.

01-03-2006, 09:16 PM
I laid out how the bearings would touch the rails at 60 degree angles.
Then milled the 1 inch stock so in could all be sandwiched together.

This whole works is very Bridgeport intensive.

It's been slow at work so I keep myself busy on this project. It will be used for low volume production.

01-03-2006, 10:25 PM
I think I'm going to like this thread. Any thread that has the word "scrounge" in it is allright by me. I like the idea of using the EMT and Unistrut, makes it simple. Not to worry you but in time the galvanized coating on the EMT will begin to flake off where the bearings ride.

01-04-2006, 12:39 PM
I really like those bearing blocks you made! And with the pipes mounted down, they won't flex at all. Can't wait to see the rest.


01-07-2006, 11:17 PM
How did you adjust the bearing block to fit tightly on the EMT?

01-07-2006, 11:31 PM
How did you attach the pipe to the unistrut?

01-13-2006, 09:40 PM
After I welded up the whole frame, I took a large piece of corrugated cardboard and laid out my hole placement for the unistrut mounting screws. That way I could make sure the holes at least laid out square and parallel to one another. I also laid out holes that would go through and through my welded frame rails.

Now, mind you this is a one of a kind deal. After doing this once I wouldn't build another one the same way. This machine is basically using everyone else's various techniques. I'm just building with the materials I have and adapting on the fly. Back to the story....

The unitsrut is then bolted down to the top of the frame. I drilled and tapped the conduit and installed threaded rod. I bottomed out the threaded rod in the conduit. I added a jam nut up the threaded rod against the conduit. I then dropped the conduit/threaded rod assembly onto the unistrut/frame.

Then it was a matter of using my 48" calipers and working up and down, tippy tapping the conduit left and right until the while works was parallel.

I tightened the nuts onto the threaded rod, continually checking to make sure it wasn't pulling too hard in one area making a big steel banana.

When I'm all finished I may go back and tack weld in areas so the unistrut always stays put.

Check an end view you can see the threaded rod going all the way through.

01-13-2006, 09:45 PM
Great, none of the pictures I have so far show how the blocks snug up to the rail.

Here's the theory....The bearings on both sides are attached to the aluminum the same way on the same 60 degree angle. One side is actually made up of two pieces bolted together so the entire assembly can be tapped to the correct distance.

I'll get a better photo on Monday.

01-13-2006, 09:53 PM
Using a little of this and that, I made up a mongrel Y Gantry of 1.5" pipe, birch ply and extrusion.

The pipe is screwed down to the wood and sits in little saddles like the other torsion box designs on this site. That keeps it all lined up true and parallel.

The square extrusion is bolted to the wood.

If you're wondering how it's attached...it's not yet, I just have it laying on the x axis.

01-13-2006, 10:31 PM
I went to the Axeman, A local surplus place. They have everything.

I picked up a 48v 15a power supply. It's a Magnetek. $35.00 It has a bunch of pins to use on the back.
I'll attach a drawing.

Please give me your Ideas on firing it up.

I say on the output module I have to put a SPST switch between pins 3 and 4.
But what are the rest of the pins for?

On the Input module I say I have to put a SPST switch between 8 and 9.
But what are 1 and 10 for?

Mouser had all the proper connections. I just have to wire it up correctly.

I do understand it is a regulated power supply. I guess that means Ill have to use large capacitors to take up the excess emf from decelerating motors.

I'll be asking about that in further writings/ramblings

Please advise.

01-14-2006, 03:36 AM
As I understand it here's what I'll need yet:

1. A parallel port interface card (to talk to the Geckos)
2. a 5vdc power source for the Geckos
3. A capacitor (10000uf?) for the feedback EMF from the steppers to the Geckos since the power supply is regulated.
4. A fuse block to protect each Gecko
5. Maybe a Safety Charge Pump (but I'm not sure how that all works)
6. Mach3

The capacitor part is confusing me at present.
If I buy one large Capacitor, Can all three Geckos be connected to it?
If so, are they isolated in any way? What voltage Capacitor do I use?

I know from reading the "Stepper Basics" PDF on the Gecko page there is supposed to be at 470uf 100v Cap on each Gecko. But I've seen examples on this forum where just one large Cap is used.

First of all, You will need 3 each 470 uF 100 VDC capacitors. These capacitors will be installed across terminals 1 (Gnd) and terminal 2 (+48V) on each of the Gecko 201's.

Additionally you will need a filter capacitor (Some may say you don't, but you do) across the regulated output of your power supply. I would recommend a 10,000 uF (or larger) rated at 100 Volts DC. This is not based on a formula, just experience. The reason for the filter capacitor is that the majority of these supplies are switching supplies and can have some switching noise or ripple in the output voltage when supplying high currents. The filter capacitor will kill ALL the noise and almost all the ripple.

You will need an external 5 Volt DC supply. A 500 ma. (1/2 Amp) will be more than sufficient. Some people use the wall wart type. They work just fine.

I think that the charge pump is built into the Campbell breakout board. The charge pump is only required if using Mach 3. It disables the electronic signals from the parallel port to the Gecko's during the computer operating system boot-up process. The charge pump is a safety device for Mach 3 software.

The power wiring for the Gecko's should be in this order:

The filter capacitor should be across the outputs of the power supply. You should also have a bleeder resistor (a 5000 ohm 5 watt from Radio Shack works great) across this capacitor to bleed off the voltage when the power is off. Otherwise you will have +48 Volts on the Gecko's and could mess up a drive by removing a motor lead etc.These two wires should then go to some type terminal block(s). From the 48 volt common (some people say Gnd or -48 Volts) run a wire to terminal #1 on each Gecko. From the +48 Volt stud or block, you should have 3 each 5 Amp fuses. After passing thru the fuse the +48 Volts should be wired to Terminal #2 on each Gecko. Remember that the 470 uF Cap. also goes across these terminals when you are wiring these.

Hope this helps answer some of your questions. I have built a few (about 6) systems and wired them as above without ANY problems.

01-14-2006, 04:06 AM
I say on the output module I have to put a SPST switch between pins 3 and 4.
But what are the rest of the pins for?

On the Input module I say I have to put a SPST switch between 8 and 9.
But what are 1 and 10 for?

Please advise.

The ONLY connections you need to make are the utility power connections as follows:

On Jl
Power cord GND (Green in the US) to terminal #1
Neutral (White) to Terminal #2
120 Volts AC (Black) to Terminal #3

Connections to the 10 pin connector are not required in normal operation.

The inhibit inputs are to shut down the outputs of the power supply.

The sense pins are designed to be used in a special wiring arrangement and compensate for voltage drop in long runs of cable.

I only wrote down the important pin #'s which I have addressed above. Special care MUST be taken in wiring anything to the 10 pin terminal.

Hope this helps.

01-16-2006, 09:36 PM
I decided to mill a couple of pockets at 45 degree angle to make the carriages for the z axis.

01-16-2006, 09:46 PM
I built the uprights from 1/2" birch and filled it with 2" urethane 10 pound sculpting board.

Drilled all the holes then milled off the bottom of both pieces at the same time with a killer end mill.

01-16-2006, 11:22 PM

I really do like your ideas and methods.

Looks good.

Should give you a nice system.


Mike F
01-20-2006, 09:20 AM

I like your ideas of the birch ply either side of the polyurethane foam - it will give a really rigid yet reasonably lightweight structure. This is also the thinking behind my composite machine where I will use carbon fibre where you use the birch ply.

One thing to be aware of though is localised areas of stress where you may be bolting things together. These areas need reinforcing with something a little more resistant than the polyurethane foam. I did notice in your photos that there is a central spine but no other areas of reinforcement. Are you sure there will be no give in the ply when it is all bolted together?


01-20-2006, 09:24 AM
Very cool so far! Gotta watch this one, looks like you will have a really nice machine.

I love the pockets you made, they came out great.

01-21-2006, 10:46 AM
Here's the deal....You are correct, There will be stress on the sides as I bolt and crush this together. I see that now.
Now whether or not it makes a difference? I'll have to wait and see. I didn't lay this out before starting so I wasn't sure where all the holes were exactly.

This would be a good example of went you have the machine all completed you go back and remake parts on the CNC that you built on manual tools.

Right now as I'm assembling the gantry parts together I'm finding all the little points of error adding up. A little out of square here and there.

It's labor intensive. If I were to buy a machine I found these guys...http://www.tigertec.us/products.html...I will have about $2000.00 in materials and software and about $5000.00 in labor. These guys are selling a 4x8 chinese unit for US $7,595.00 with mach 3 software. Just do a search for ebay user ID "tigercnc". The Z axis is a little short for me at 4.7 in.

02-11-2006, 07:21 PM
I haven't been able to get back to the machine. Layoffs threatened at work so I have been laying low on building "government jobs".

03-30-2006, 11:33 PM
Here's my progress so to date. I have the steppers mounted and the acme screws and anti backlash nuts attached.
This is one custom piece of work. I measure and cut and weld as the machine evolves. So far everthing seems to be working out. If something isn't quite aligned....I just machine a new piece at lunchtime or after work.

I've begun on my power source. I picked up a surplus Magnetek power supply as described earlier in the thread. I got it to pump out 48V but I'm still not sure of all the "INHIBIT-Logic high or open" and "ENABLE- logic low". I wrote Magnetek several times but they never answered my questions as to which pins to jumper. So I jumpered the "INHIBIT LOW" to the "V1 - SENSE" pins and the green LED came on and the outputs read 48V.

03-30-2006, 11:41 PM
I'm posting another shot of the trucks that the gantry rides on.
This machine is based on japoni's design. http://spaces.msn.com/members/japoni87
Credit where credit is certainly due. :cheers:

I changed the bearings on the z axis. The nylon .750 dia bushings from McMaster Carr were too loose.

So then I turned four of my own out of Delrin...Way too tight. I then went to VXB Bearing and bought 4 linear ball bearings for $27.00 total. But they are 20mm.
Now its back to MSC for 20mm shafting.... It's back ordered.
Finally, I settled on 20mm OD hydraulic annealed tubing. It has a little give, I guess I'll see if it comes to bite me in the rear once I start cutting.

03-30-2006, 11:49 PM
You'll notice a lot of the material has a, shall we say, patina.
That's the color variations you get when you work out of the scrap barrel. The design takes twists and turns depending on what I find that day.

That is why the cross member for the x axis is extruded aluminum that had a couple of odd milled features from a obsolete machine setup. And the brackets that hold the motor mount are bits of steel cutoffs that were to small to use or were cutoffs found on the horizontal bandsaw chip pan. :rolleyes:

03-30-2006, 11:58 PM
I like the looks of the machine, I have been designing a simular Linear Rail system only with Hex Shafting. Now that you have the gantry mounted have you noticed any shifting back and forth due to the amount of distance you have between bearing surfaces, it just doesn't look that far apart between centers? Keep up the good work, can't wait to see how it turns out.


03-31-2006, 08:58 PM
You can get a nice 5 by 12 volt power supply board from


You can get a nice parallel port breakout board from


The capacitor is used as a huge storage sink to smooth out the pulsed output from the bridge rectifier. The bridge changes AC to DC. The capacitor can be almost any size. I used a 56,000 uF at 50 VDC with a surge rating of 65VDC for my 360 in-oz servos. My voltage to the servo motors is 36 Vdc giving a normal safety factor of 50/36 = 1.39 and a surge rating of 65/36 = 1.8. So I would choose an approximately 60,000 uF electrolytic CAP with a voltage rating of 1.5*48 = 75VDC with a surge rating of approximately 100VDC because you have larger motors than mine. Having too large a capacitor will not be detrimental and the voltage from your bridge at the capacitor will be approximately 1.5 times your transformer output rating. So the transformer will need to be approximately 30 volts. Probably not hard to find that rating. I chose a torroidal transformer with two output windings rated for 10 amps per winding. See source below.

As the voltages of the capacitors goes up the size remains the same but the capacitor capacity goes down. I would choose two of the following (37,000 uF at 75Vdc) and wire then in parallel. (www.mouser.com part number 539-CGS75v37000) The link below might work. You will also need two of 539-VR12 capacitor brackets. (www.mouser.com part number 539-VR12)


Some on the forum may disagree with my selections but why save 40 bucks by buying one capacitor when it is better to have a lot of surge capacity to absorb sudden movements of the axis. I guess my conservatism comes from being an engineer.


Available from www.avellindberg.com part number Y236851. That transformer is a 30 volt unit that will give approximately 45 Vdc for the GECKOs to drive the steppers. My transformer cost approximately $75 shipped to Seattle. Since this is a somewhat bigger transformer, it may cost $100. Why use a Torroidal? Quiet, and less hum. Again some will take issue with the cost but it is better to buy it once rather than twice.

You should also have a bleed resistor across each capacitor's terminals. They are availabe from www.mouser.com. I suggest a larger wattage than I used. I suggest part number 280-CR10-1.2K-RC. Although the wattage drop is about 2, again the difference in cost is pennies.

Good luck with you project.


03-31-2006, 09:19 PM
Wow, didn't realize till now how well I really did with my parts scrounging for my PS. Will have $20 into it and get a 60V, 20A(guess) PS. Depends on what I sell the extra 60K uF caps for, but should be at least free...maybe make a few $.

Noise? Trannie hum? lol. It's a CNC router! Minimum motors, router and dust collector running at the same time. Probably at least another stationary tool if not another handheld router running at the same time. Not gonna be baby's nap time! Trannie hum?

04-02-2006, 09:56 PM
I gutted a computer for the case and fans.

I've got the Magnetek DC Supply for the steppers.
3 Gecko 201's
a 10000uf cap
a PMDX 122 breakout board
3 5A fuses
A 12VDC 1.5A Walwart power supply for the fans and breakout board.
A switch for main power
A switch to cut off 48VDC power to the steppers. Since I had to jumper the ttl low side I figured I'd put a switch in.

Next big job is to attach limit switches and wire the motors.
I'm using 4 conductor 18Ga shielded.