K40 Conversion to LightObject XLE 900 x 600 Gantry

Machine: K40 with Cohesion3D Mini being converted to LightObject XLE 900x600
Board: Cohesion3D Mini
Firmware: Cluster from (Improved Raster Speed Firmware Update for Cohesion3D Boards!)

Here are the other specifics of the new hardware, stepper motor, stepper driver, etc.

Gantry: XLE-900-x-600-XY-Stage

2:1 reduction gear box for X & Y
Belt: 3Mx15  (Pitch 3mm)
Speed: X: 900mm/s, Y: 500mm/s (if driver set to 1/32)

Stepper Motors (Both X and Y are identical - ignore LO product page saying 2 different motors for X/Y - my kit came with 2 identical motors)
Model: 573S15
Step angle: 1.2 deg
Step per revolution: 300
Phases: 3
No. wires: 3
Current: 5.8A
Holding Torque: 1.3 NM (184ozin) - MFG Spec
Single shaft (dia./length): 8.0mm/19mm
Inductance: 1.35 mH
Phase resistance: 0.9 ohms
Detente torque: 480 g.cm2
Rotor Inertia: 480 g-cm

Stepper Drivers
Model: 3DM580

Driver Power: 36V 15A Switching Regulated Power Supply

Problem/ Question:
Need help determining the new config settings for the hardware conversion. And need help in confirming/determining the proper driver setting.
I’m taking the C3D Mini to the new XLE gantry.

On my K40, everything was crystal clear and made sense for what knowledge I have. i.e. 1:1 gear, 1.8 degree motor with 200 steps per revolution for X/Y and Z with driver was set to 1/16 - 3200 pulses per revolution. the steps_per_mm was 157.575

With the new motors, drivers, gearing the math is not coming out (for what I know) to come up with a proper number for C3D config.
i.e.: Steps per Revolution × Microstep × Reduction) / 360 = Steps per Degree

IF I set the drivers to 1/16 or 1/32, I come up with this:
(300 * 16 * 2) / 360 = 26.6667 steps_per_mm
(300 * 32 * 2) / 360 = 53.3333 steps_per_mm

BUT the other issue, is the pulse/rev table (will attach a photo) doesn’t match an exact 1/16 or 1/32 for the motors like the K40 did.
Pulses per Rev / Motor Step per Revoltion = Microstep
If I set the driver to 5000 it comes out to 5000/300 = 16.6666 or 10000 is 10000/300 = 33.3333 or 6400 is 6400/300 = 21.3333

Please help me understand where I am going wrong ‘if possible’ as I would like to understand how to determine the configuration properly. Otherwise, I would like to at least just know what I should be setting the drivers to and the C3D configuration for.

Once I know the proper steps_per_mm settings, I’m hoping I can take that witht he motor specs and figure out the rest of the configs like _axis_max_sped, _max_rate, etc.

Please be kind, this is my first post. If there is more info needed, just ask. I tried to include as much as I thought was relevant.

The math is a bit more complicated than that. The steps per mm value is going to rely on some angular math and is dependent on the size of the final drive pulley.

Ignore the microstepping ratio - LO has some weird shit on their product descriptions that doesn’t make any sense and this seems to be one of them. Set your driver to 6400/rev. With a 2:1 pulley drive that’s 12800 real steps per revolution (resulting in .028125° per step). Here’s where the angular math comes in. The formula for arc length is (mAB / 360)(2πr) so you’ll need to know the radius of your final drive pulley as accurately as possible. mAB is the arc measure in degrees. Say it’s a 10mm pulley - (0.28125/360)(2π5) ~= .00245 mm/step. To derive steps per mm from this take its inverse 1/.00245 ~= 407.43 steps per mm.

Fortunately there’s an easier way. The gantry looks from the pictures on the product spec like it has a 10mm GT2 belt driving it. It will probably be written on the belt somewhere what it is. In any case, GT2 is pretty much the de-facto belt for small drive mechanisms like this so we’ll assume that’s what it is. Count the number of teeth on your drive pulley. Each tooth corresponds to 2mm on a GT2 belt. It looks like it might be a 16 tooth pulley (just a guess - I can’t see it in the pics), so that’s 32mm/revolution. I’ll do some example math for you here :slight_smile:

(12800 * (1/32)) = 400 steps per mm.

Based on this, 6400 might be a bit too high a microstepping setting if you want to get any real speed out of the gantry, so you might have to fiddle with this setting a bit and re-do the math as necessary.

With those motors and that 2:1 reducing belt, this gantry has some serious torque capability, btw. Stay out of its way when it’s moving! :slight_smile:

Report back how this goes …

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Just saw your post. Thank you for the explination which is very much what I wanted/needed.

I’ll measure the final drive pully and count the teeth and report back what I come up with in the morning.

To make sure I understand what the final drive pully is. Are you talking about the pully in the 2:1 box not on the motor or the pully on the belt connected to the laser head?
I think I know what a Gt2 is (on my K40) and these on the new gantry are huge. The 2:1 box is even bigger. The smallest pully is bigger than 10mm. All pullies are the same size except for one in the 2:1 box.

The pitch is 3mm not 2 as the belts are 3Mx15’s.

Oh, those are huge belts. If the pitch is 3mm, then multiply the number of teeth on the pulley by 3 to get the mm/revolution value. I’m talking about the pulley that actually drives the gantry/shuttle on the long belt(s). That’s the only one that really matters here as we know the ratio of the reduction belt (2:1) and it’s normalized out in the 12800 steps/rev value.

The pulleys on the belts that drive the shuttle and crossbar are 20mm 20 Tooth. So let me see if I understood what your math was about:

Driver Config: 6400 Steps with 2:1 gearing = 6400 * 2 = 12800 steps per rotation
(mAB / 360)(2πr) where
mAB = 0.028125 = (360 / (Steps Per rotation * Reduction)) = 360 / (6400 * 2) = 360 / 12800
r=radius (10 = 10mm for a 20mm pulley)
(0.028125/360) * (2 * π * 10) = 0.00490873852123405
1 / 0.00490873852123405 = 203.718327157626 step/mm


3 mm pitch with 20 teeth (pitch * teeth) = (3 * 20) = 60 mm/rev
(12800 * (1/60) = 213.3333 step/mm

Did I understand your math correctly? and if I come up with 203.718 or 213.333 for a _steps_per_mm value. Does it matter which I use? Which is more accurate for C3D? Does a difference of ~10 matter?
Since it comes out in the low 200’s I’m assuming this is not a problem for speed with C3D correct? Should I lower or raise the steps/rev on the driver to get higher speed if desired?

I’m waiting for about 100+ pounds of 8020.net (30-3030) extrusions to be delivered this wed/thur for the frame I’m building for the new machine.
I figured while I was waiting for delivery I would start building the new config file for C3D, along with some other modifications to the XY stage that I wanted to do like better limit switch mounts.
I prefer to have Min and Max switches and I was able to squeeze another 30+ mm out of the X and Y working area by doing different mounts and switches. It is a small increase from the listed 900mm x 600mm working area, but I figured why not.
(Yes, for reference, that is a yellow 36" inch yard stick | 915 mm stick) This should also give you an idea of the size of this (dare I say?) beast. Compared to the K40 size, this is a massive upgrade to working area.

Here is a model of the frame I am putting together:

Since LO doesn’t sell the frame kits anymore, I designed my own and based it off of these frames (I have some very minor alterations):

That’s quite the project and I look forward to seeing pictures of the completed unit!

You understand the math well, here. I’d use the second of the two calculations to start, as those values are generally better for belt-driven machines. It takes the belt itself into consideration.

To verify it, command the laser to cut e.g. a 30mm x 30mm square then use a caliper to as accurately as possible measure the resultant cut. You may need to scale that factor by a small percentage if it’s off. I used 30mm here because it’s an even multiple of steps - 640. A difference of ~10 bewteen the two factors is pretty significant - when you think about it, that’s almost 5%.

The speeds will be good - if it doesn’t move fast enough try moving down to 4000 steps per rev, which will result in a 133.3bar steps per mm value which is right around where the K40’s calculated steps per mm (157.575) is :slight_smile: The trade-off here is precision - the longer the translated step is, the less precise the machine will be overall. Keep in mind with a step size this small you’re at sub-thousandth precision already, but inevitable mechanical slop in a machine that large will probably be higher than that, affecting the machine’s overall accuracy.

What tube are you putting into this?

I want/plan to put a reci 80 watt at some point, but since I just spent a decent amount of money on the new gantry and frame material (damn 8020.net is proud of their stuff) and supporting upgrades in preparation for a new tube, but a new tube and tube power supply will have to wait a few weeks.

I have a K40 that works very well right now with a LO powered Z table. I figured that I would transfer what I need to the new frame/gantry get it all setup (with the thought of a new tube in the near future) and be ahead of the game with only having to switch out the tube and power supply. I have a lot of equipment already in my K40 like dedicated 5v, 12v, 24v switching power supplies (stock power supply is purely for the tube now) for all supporting drivers, lights, C3D, electronic cooling fans, water pump, meters, switches, displays, etc.
I am adding a 36v switching power supply, water chiller, 730cfm 6" fan for exhaust, air purifier/dryer for the air assist and more work area intake fans to control air flow across the work area and prevent dead air zones. I’m also building a new z table for the massive Honeycomb that is also in transit so I’ve also got new leads screws for the frame to be mounted. I’ll have to wait for the belt as I’m not sure what size to order yet until the z table is built in the frame. There is also the cost for all new acrylic to completely enclose the frame also.
Im sure you already understand the massive project I’m undertaking and in the end, basically have a fully new machine as the tube and tube power supply is technically the only stock K40 stuff left.

Got the shipment in of the 8020 stuff on Thursday and as I’m building the frame this weekend, I realized that I’m one hell of a lazy bastard. I forgot that the C3D Mini was a pain to install in the K40 since I did it so long ago (not the C3D Mini’s fault but the chassis). The panel I mounted the C3D Mini to was a pain to get out of the chassis which was required to actually mount the Mini.
So, I just broke down and bought a new C3D Laserboard. Figured I’d have time to finish the frame and mount everything else while it ships to me.

At this point I’m wondering if this is really a conversion anymore… :stuck_out_tongue: As it is turning out to almost be a new build now.
I guess I have until I finish the frame, z table, and start wiring/mounting equipment to decide if I’m going to be able to buy the new tube and LPSU before I’m done. Now that I got a new C3D Laserboard on the way, the only thing that is going to come out of the K40 is the tube and LPSU now.

I would buy a high quality tube (and get a 60 or 80W). As well, get a good quality matching PSU. You have so much invested now, why skimp on the heart of the machine?


Your right. I’m not going to skimp. But, it’s all about the money. With what I have spent on the new gantry and frame and extra materials for it all. I have to wait a little longer. The 80w reci I want and lpsu is another chunk of change that I have to wait on. At least with the old 40w tube I can get by with a bigger working area until I save the money for a new tube and lpsu. I set the time back with the purchase of a new laserboard too. The money I was saving got a little smaller with that new laserboard.

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Yeah, but in the end you’ll have a more workable machine - and the K40 to put back together when you do eventually purchase the new tube/psu. I think using the K40’s tube in the meantime, to get you started, is a great idea. You’ll be able to tune the motion control and get all the kinks out before putting the stronger tube in it.

Finally got the shipping info for the new Laserboard. I’m hoping it’ll be here sometime in the next few days (probably not before the weekend though :frowning: ) . Just wanted to keep this thread alive while I wait for some other items to finish the frame (had to order more 8020 profiles to mount the Z-Table the way that I wanted).

Not sure if I should post all the little items that I’m doing, but as I was thinking about it in researching things, not a lot of people post some of the little details one might like to see or know about. If this is too much, just let me know and I’ll not post the extra stuff.

With that, here is my make shift version of my end-stop mounts for the gantry and the crossbar carrier mount. I still have to design the left and right side cable carrier mounts to transition from the gantry to the frame itself, but that’ll have wait until I’m done with the Z-Table so I can mount the gantry in the frame. The way I’m mounting the Z-Table I didn’t want the gantry to get in my way until the Z-Table mounting is completed.

You will be able to tell if you look at the roller bearings that I truly attempted to maximize all possible travel distance of the carriage. For reference, I gave about 4-5mm as a buffer for deceleration stop movement once the switch was triggered. Of course this can all be changed quite easily by just cutting new mounts if needed.

I mentioned before that I prefer min/max switches (not just min) and there are multiple reason for it, but my main reason was to be able to adjust where the ‘home’ location is at. I didn’t like that the stock home location was going to be back right and I personally prefer back left home location like my K40 had. Don’t know really why I like it that way, but with mounting Min-Max it give me the flexibility to change it at will. The other obvious reason is to not have the axis’ bounce around if they should be told to move where they can’t.

Here is the left side crossbar limit switch (when facing the gantry from the ‘front’ where you would be typically looking at the gantry when using the machine).

And the alignment of the left side limit switch mount:
There is room for wiring under the carrier and that will exit to the left side cable carrier, along with other wiring for crossbar lighting that I will placed under the crossbar to help light up the working area but stay out of eye line of sight.

Here is the right side crossbar mounts:

Cable carrier mount on the carriage:
The way I designed the interlocking supports this acrylic (cast acrylic) and the acrylic adhesive I use make this plenty strong enough for the carrier, air assist hose and any other wiring I might want to run to this point. If it ever breaks, I can always cut a new one in a matter of minutes and either up the acrylic size or keep the same size. I do not expect it to break though as a prototype piece I made before I tested and stressed to the breaking point and it took a lot of energy to snap the acrylic.

Right side limit switches for Y axis travel:

Interesting thing about this location is the there are two holes right where the switch lever is at that you can mount a M3 screw that would could be used to adjust the actual location where the switch would activate at. Probably becasue this was the stock location for a limit switch, but I wanted to use mine and not the basic ‘switch’ that came with the gantry.

Other updates: Well, I’m not sure if I’m unique about this, I’m impatient. I typically like to work with cash as much as possible, but I broke down and dusted of an old credit card I havn’t used for years and decided to buy a few more items…

I got:

  • LightObject Water Chiller LO-Q600W
  • LightObject Pro 25mm Beam Combiner Mount with Laser Pointer
  • LightObject 60W PWM CO2 Laser Power Supply
  • SPT 60W CO2 Laser Tube (from LightObject)

I’m a Master Scuba Diver, Divemaster, and Tech Diver and I now have to go looking for a sharks to bring home… Why?

Dr. Evil's sharks

I know I wanted the RECI 80, but they were out of stock and very pricey compared to the SPT 60W. I had to err of the side of compromise (money compromise). I don’t want to say I skimped becasue now that the tube is here, I am super surprised at the quality of the tube!!! This thing looks like it’s going to rock!! High-quality glass and water inlet/outlet and a massive plus of high-quality pre-wiring on both positive and negative sides (not the cheap crap on a Chinese laser you have to always redo).

This SPT 60W has specification of 60W at 22mA current max.
LightObject evidently tests each tube before it goes out as it came with a test report of the tube dated 7.13.2020.
The test report says it does 60W output at 12mA current. That is about half of the specified max current which means there is lots of overhead room before hitting max current. I know the test was at 7 inches and I’ll probably have to move up the current to get 60W at the table after going though a beam combiner, mirrors, and a lens. BUT, it’s not going to need a another 12mA’s to get to 60W at the table, so lot’s of headroom for usage of the tube before it drops below 60W at 22mA.

The most important thing for me was I current feel it is money well spent (currently have no buyers remorse at any level). I’m sure you know that when you spend a lot of money and the items comes in you sometimes feel like it wasn’t worth the money or at least not the price that was paid. The tube feels great and already had high quality pre-wiring and that was actually a massive bonus not expected. Of course time will tell once I fire this beast up and dial it in to really see if it was worth the money.

This thing is long, 1250mm

This now officially makes this a new build and not a conversion. Nothing is coming out of the K40 anymore.

Easy fix - topic auto-close timer removed :slight_smile:

By all means, please continue. Show and tell is great, I have moved this topic to that category.

You are among friends… Welcome to the dark side. Err, the light side?

I have over 30 3D Printers, 4 Lasers, 2 CNCs, a lot of rock climbing gear, played multiple instruments, and most recently started learning how to make cocktails and signed up for a motorcycle course.

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Wow! Yeah, this is really coming together! Don’t worry about posting too much. The more information the better, really. You’re doing great work with this and it looks fantastic so far.

I agree with the dual limit switches. I want them to be hard endstops, always.

I’m glad you’re happy with the purchases so far! This thing is going to turn out to be a monster. And please, if you can somehow get a shark inside your machine and get a picture it’d be internet famous. At least on this forum :slight_smile:

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I started this thread for a serious support question and had my original questions answered (thanks very much for that), switched to progress updates (show and tell), and now also want to add an R&D side to it.

Some background: this beast all started because I’m a diver. (indirectly using this as an excuse to make a bigger better machine than a K40). I have a 25’ Pontoon that I converted to a Tri-toon (because I’m a diver - needed more bouyancy to carry more gear/divers). Last June I had a full achellies tendon rupture that for that reason turned into me needing surgery on both ankles over the last year. Basically couldn’t walk on both feet for the last year. Had nothing better to do than sit around and surf Amazon, ebays, etc for items I wanted on my boat or new dive gear (I really needed to start walking again to save money - or so I thought). Now I’m able to walk again I set into working on the boat to install all the new sonar (real-time side scan, forward view, down view) and associated/other gadgets. Turns out I didn’t have enough room on my helm to mount everything. So I started building a new helm. I designed the new helm to be modular in the sense that all the equipment mount points was going to use acrylic panels so I could create a glass helm look and if anything was every changed I could cut new acrylic as needed. This is the point I realized I needed a bigger laser cutter/engraver. So I could cut acrylic panels for the boat that were up to 28 inches long…

Here’s the R&D part:
Now that this beast is almost alive I’m thinking forward to the future.
I’ve been researching rotary attachments and nothing exists that will allow me to etch scuba tanks. Scuba tanks/cylinders come in all different sizes but typical 80 cuft tanks are 7.25" x 25" (31.9 lbs) or 120 cuft are 7.25" x 30" (39.2 lbs). So you can see where I’m going with this… Building a rotary that can handle this kind of weight and size.
Rotarys are pretty basic in what I can tell and in essence have basic components I. E. Drive motor, gears, drive wheels, and idler wheels. All adustible to meet various widths, lengths and sizes.
BUT, for small light weight (compared to scuba tanks).

Where and how would I start with calculating the motor size and gearing and if drive wheel size matters (outside of just a basic size to hold the cylinders properly) to handle scuba cylinders and more importantly, if it is even possible?

I already assume a stepper driver is required since ‘if’ it is possible the current required is going to be big.
I also do not have any machining capability so it has to be in the realm of design that can be created without much or any machining.

I’m sure I could design a rotary that could handle that kind of weight. Honestly, it probably wouldn’t even require anything more than a NEMA 23 if geared right - a NEMA 34 at the absolute worst. You don’t have to lift the cylinder - all you have to do is overcome the arm moment needed to rotate the cylinder in place, which is a much smaller amount of force.

A bigger question is’t so much how we can make it work - it’s all math and gear ratios and circumference/diameters - basically the same stuff we went through earlier - it’s whether or not we should (at least for this particular purpose). When you engrave on the surface of a metal object you change the crystalline lattice structure of the underlying metal and create internal metallurgical stress with the intense laser heat (this is exactly why you can burn off anodization on aluminum and use something like cermark/moly lube spray on steel). Normally this wouldn’t be a big deal for a nonstructural part - (warning: gross oversimplification) internal stresses in the metal don’t typically matter until you put that metal under an outside stress. But, that’s exactly what we’re doing: HP tanks can reach ~3500 psi (as you well know), and get repeatedly charged and discharged. That’s a lot of stress to put metal through (and the reason they make us hydrostatically test the cylinders every few years). I weld (among other things) and have a lot of high pressure cylinders around. Now, I’ve never had one fail, but i’ve seen photos and videos of it happening (and the resulting aftermath), and I can assure you I would not want one of these strapped to my back - or anywhere near me - when it happened. So, I’d take this piece very seriously before attempting it and take extra precautions if you do decide to go down that route. e.g. send a cylinder off to hydro to get the initial expansion data, engrave that cylinder, then immediately send it off for hydro again and see how the expansion data changes. Work with the shop that does your testing and tell them what you’re trying to do.

FWIW, I’d be looking at vinyl-cut decals instead :slight_smile:

If you still want to consider building a large rotary after this, I’d go with a roller-type instead of chuck. You could build a frame out of yet even more 8020, and do all the “machining” of the end plates on the laser out of sandwiched pieces of 1/4" acrylic polywelded with methylene chloride (as it’s hard to cut 1/2" acrylic without a special lens, even on really high-powered machines). Affix your wheels, rollers, stepper, etc. to that. 1/4" would probably hold it by itself, but I’d suggest going to 1/2" for the added rigidity. You can do fun things like embed bearing races in one half of the sandwich, too.

Jeez - did I forget to ask about yet another one of your past lives when we met?

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I have a lot of hobbies and pastimes - welding, metalworking, forging, and metallurgy among them! I never really did get into diving (inner ear problems), however, and I feel like I missed out.

Anyways, if you want to go down a fascinating rabbit hole, look up how high pressure cylinders are manufactured. I never would have thought to do it this way!

Also, I should point out that all this stuff for a laser engraver/cutter is a hobby for me. My passion is diving. And I’m an excentric diver. All equipment I have (boat, compressor, mixing sticks, 27 tanks, etc) is about diving or enhacment of diving where I can be self sufficient without relying on someone else for basic needs. Even the up sizing of the engraver was becuse of the boat (there are other benefits but it started because of diving). FYI, I am a network/systems/electronic engineer by trade. Sounds like you guys might be doing the laser stuff for business/commercial reason (maybe?)…

You are absolutely right about the cylinders. I am PSI certified for cylinder inspections and eddy testing. I’m even gas blender certified for tri-mix.
Vinyl is the way most common divers go but they find out real quick it’s expensive as the wrap has to be taken off every year to properly pass the tank for VIP inspection and it gets ruined every 5 years when they do the hydros. Basicly costs money every year for new wraps.
But, I’m think about etching my tanks for myself because for the wow factor of my exentricness (is that even a word… :stuck_out_tongue:) and the fact I’ve personalized my tanks in a one-of-a-kind type of way…
The type of etching I’m thinking about doing is basic marking with spray. Nothing like a wrap at all as that would be to much etching on a cylinder and really expensive with spray cost to cover that much surface.
I was thinking just small personalization of my tanks.
The impact on the metal is less than the stamping done for hydro every 5 years which really digs into the metal and affects the tank.
BUT, you are right about the hydro testing before and after. I even have a cylinder that’s 25+ years old that I could test against (has like 5 or 6 hydro stamps on it). This particular cylinder is the worst case test scenario for tank impact for etching with all the abuse it has been through over the years and just in hydros alone. Can’t even comprehend how many times it has been filled in the last 25+ years. I inspect my tanks every ~50 dives (not once a year like normal divers do) so my tanks are down to 0 psi quit often (i do about 5-10 dives a weekend). This is just info to convey that my tanks go through A LOT of pressure changes quite often.

But, it would be a lot of work to build the rotary to possibly find out it was all for nothing if the tank does fail hydro… Just as I was typing this and thinking about trying to salvage the rotary (if needed) and I just had an idea. It wouldn’t be a waste as I have been wanting to build a tumbler for cylinders and guess what a rotary is… Just a very slow tumbler. Pull the stepper off and attach a regular 120v motor to it with a speed control and I have my tumbler…

I like your idea of the acrylic as the machining (I’m guessing you probably figured that would be OK to me since I basically did that for my limit switch mounts or my reference to a glass helm look which is done through layering of acrylic or glass). You basically confirm a question in my mind before I asked it is that would be enough for a big rotary.

Had a question come up as I was working on the frame and starting to mount stuff.

While I was mounting the tube I realized I don’t know the proper material to use to place on the tube mounts. I figured it needs to be something non-compressible so it doesn’t change the alignment over time.

Is this alright? I used a silicone gasket material like this: