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Dockable Probe


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As a mechanical engineer I spend countless hours working out the mathematics, testing both the theoretical and practical aspects behind the many many ideas that pop into my head.


He is a Video of a test of one version of my probe


Dockable Probe


I was driven to look for a suitable (to me) solution due to other units on offer (in my view) having multiple different issues, with the “popular” magnetic probe in my opinion being stupidly expensive compared to the sum of its parts, or with the likes of the Duet IR sensor which is very particular about reading (or not reading) the data produced by certain print surfaces, then the likes of a BL touch which shits the bed in a decently heated chamber 9anything above 50c), or inductive sensors providing huge reading variances due to reacting badly to temps.

This led me into initially designing my own magnetic version of a collectable probe, but I encountered a problem after installing this type of probe in that the hot end and part cooling fan performance was compromised which led to prints failing, I tracked the issue down to a negative interaction between the magnetic field being produced by the fan motor windings being affected by the strength of the rare earth magnets used to hold the two parts of probe together.

So that ruled out direct contact magnetic probes which led me on to a simplified version of what I have today.

My design criteria were as follows

The design must exceed the performance of other products on the market

It needs to be inexpensive for the user to put together.

It needs to employ readily available components of the same dimensions and standard across the world

Its needs to operate in a manner where its presence does not negatively impact the performance of the machine in which it has been installed

Parts count needs to be low; I am a great believer in the K.I.S.S methodology


So on to the current iteration of my design

There are three main printed parts, of a design that can be easily manipulated to allow simple mounting on almost any printer, there are other versions which are designed to fit specific printers such as the voron 2.4 with the stealth burner head.

Those parts are printed in PC (ASA would be a suitable alternative) there are the two dock holders and the actuator switch holder.

Then there is a simple switch which I modelled using the standard 3d printer end stop switch, with direct actuation on the contactor the switch is more than accurate

There are two standard “smooth” idler pulleys used with 6mm belts and have bearing with an I/D of 5mm

The actuator shaft can be a shouldered bolt or as my latest version uses a classic American car door hinge pin with is precision ground of a 5mm O/D and has a machined groove that allows a circlip to be attached (this retains the spring)

And lastly an easily available 30mm long compression spring with an I/D of 6mm.


On to the design


If you look at the two idler pulleys, they are both the same and have specific sizes, THE O/D of the main inner surface is 12.15mm and the O/D of the Shoulder section is 17.85mm, the distance between the shoulders is 6.45mm so if you design (and print) the holders for the actuator to a specific tolerance you can achieve the desired goal.

The main circular holder part of the dock is printed to be 0.10mm larger in diameter than the pulleys and the fingers of each dock partially encircles back around the pulley and  those dimples are 0.10mm smaller in diameter than the pulley, the fingers are designed in such a way that they act like springs, upon entry to the dock the diameter of the pulley spreads these two dimples open allowing the pulley to enter the dock, once fully home the fingers spring to their normal shape and this spring action makes the fingers encircle the pully effectively adding a positive lock retaining action, that design is on both the head portion of the dock and on the storage portion.

With regards stability and repeatability, the pulleys diameter and shoulders provide the stability holding the actuator very firmly in place, after the actuator has been “grabbed” and snapped in place, it does NOT matter if there is a minimal amount of lateral movement along the X/Y planes as that is not is what is going to be measured by the probe.

Once the actuator has been collected and snapped into place the actuator shaft is forced to move upwards (as either the tool head lowers itself on the print surface in the manner cartesian and delta printers do or in the case of corexy the bed raises and lowers instead) this movement occurs as the actuator contacts the print surface, the actuator shafts O/D is a precision diameter which matches the I/D of the bearing inside the pulley which in this case is 5mm, the very close clearance tolerance between the shaft and the bearing means that things do not tilt on the Z axis plane enough to cause any measurement issue.

The actuator is held in tension by its return spring and that tension is held against the precision machined surface of the upper bearing holding everything in a fully vertical position, the whole setup has been designed in such a way so that the distance between the base of the actuator which touches the print surface and physically actuates the end-stop switch means it travels LESS than HALF the distance between the top and bottom bearings, this has been a carefully calculated distance which ensures that the actuator shaft stays vertical throughout its travel during operation.

The fact that pulleys have two shoulders which are of a larger diameter than the main retaining diameter means that further stability is ensured and as the distance between those shoulders is 6.45mm and that thickness of the dock itself is 6.35mm there is only a chance of the free play amount being 0.1mm but that is not being measured by the switch so it doesn’t matter,  the length of the actuator rod is constant no matter what, and one the trigger height and offset has been calibrated repeatability stays pretty constant to a point of being almost imperceptible with a dial indicator.










Tool Head Dock.png


Edited by Calvinx
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I love the idea that the switch is actually on the toolhead and that you can "assure" decent vertical alignment of the actuator rod with a simple design.

I have an Euclid probe on my Voron Trident and although it is more stable than a Klicky probe (don't get me started on the wire wrapping contacts on KlickyNG and Unklicky) the magnets are pretty hard to get, you have to get the PCB made, so the best bet is buying the $25 kit + shipping from a handful of stores (mostly out of stock). It's expensive.

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I like some aspects of this design. I like the double spool idea and having the switch located on the toolhead as opposed to the probe itself.

Klicky probe... You need a switch, a handful of magnets, a dab of glue, a length or wire, a connector and some time and filament to print up the parts.

I don't really see where this idea is more cost effective, but let's compare.

CalvinX Probe... You need all of the same stuff the Klicky needs (except for the magnets) and additionally, a spring, a nut and two pulleys.

You're probably a dollar or two over the Klicky by now, maybe not depends on cost of magnets.

Let's look at effort required to make and implement the designs.

Klicky... You need to print parts, attach wires, switch and glue in the magnets. Tools are just a screwdriver, allen key and a pair of pliers

CalvinX Probe... Same deal as with this probe sans magnets and glue but it looks to me like the probe is a SHCS with the head ground down or perhaps turned on a lathe... that might be a bit of a challenge for some. Not impossible but definitely some extra work.

So in the end it's kind of a wash, neither is really that much more or less than the other and FWIW... if someone is complaining about 25 bucks expense for your 3D printer hobby... you might have the wrong hobby. LOL

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ok lets compare


Currently the actuator shaft is using a hinge pin (which was actually mentioned above) so i will quote myself



The actuator shaft can be a shouldered bolt or as my latest version uses a classic American car door hinge pin with is precision ground of a 5mm O/D and has a machined groove that allows a circlip to be attached (this retains the spring)

With regards the popular rip off purchased by sheep, I will quote myself again


with the “popular” magnetic probe in my opinion being stupidly expensive compared to the sum of its parts

as for the cost of a single unit I have shown

Total component cost (per unit) equates to €2.24 (INCLUDING SHIPPING) plus x3 printed parts

parts  from aliexpress 





The current popular rip off unit is available to me is the EU for the following price of €33.12 (PLUS SHIPPING) at €6.05 bringing the total to €38.17 from the following official reseller

rip off magnetic unit


Which by my rudimentary mathematic skills means that the popular rip off probe is SEVENTEEN times more expensive...   Factually i could make TEN units and still have spent LESS than the cost of a SINGLE rip off unit. 

Facts are facts, facts which can be verified by anyone with half a brain.



Edited by Calvinx
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1 hour ago, RopusLongus said:

Verry cool.

Did you do some tests for repeatability of the measure of the hight error?

 I have carried out repeatability tests using both a dial indicator and as I only run Duet Hardware, 6HC control boards (luckily I can afford it and I dont mind paying for my 3d printing hobby when the item is value for money, I do however taker exception when some idiot tries to bend me over and roger me dry by selling an item that is terrible value for money) so with the conditional G code that the Duet can employ i set the printer into a conditional probe loop of a 1000 cycles overnight and the deviation was averaged and was not worth bothering about, and more than good enough no matter what

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1. Firstly... Dude... Why so angry? Please don't be offended by a little constructive criticism. If you read my bio in the introduction section... you'll see that I am ME as well and over the past 40 years give or take... I haven't had one of my designs not go thru the rigors of objective analysis, i.e. the scrutiny of my peers. So don't get bent. No one here is trying to belittle you or take anything away from what you've created. It's a good design and no one is stating anything to the contrary. A good objective analysis by some of the very knowledgeable people on this forum would net you some valuable information that you could use to make what you have even better. 

2. I didn't compare your design with the Euclid probe... I compared it to the klicky so not the same comparison. Klicky would still be cheaper and you'd have a better Omron limit switch.

3. Sadly... your 2.24 Euro price is not what someone would have to pay to implement your design. it's more along the lines of 10 Euro's because you just can't buy those items as single components and... at the very least the Euclid probe is using an Omron switch as opposed to "rip-off" Chinese switches which historically have been mediocre at best so... Euclid gets a point for higher quality components.

Lastly... Have a nice day, hope you have a great weekend and... thank you for sharing your design. 

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Really no idea why you’d over-complicate this compared to just making an Unklicky NG BFP. Total build cost is 5 6x3 magnets and a few screws, plus about 50g of filament. I’d be stunned if it cost more than £1, holds up flawlessly in a 2.4 at 80C where a microswitch won’t, and even has more than an order of magnitude better standard deviation than any of the commercial offerings. In all of your writing I couldn’t see a single reason to have gone to this length?


With that said, plenty a wonderful project happens without good reason - you’ve put an impressive amount of effort into this and got a cool output. Nice work. 

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Fascinating read. Good on you for putting your expertise into a good functional design. People are going to be curious and ask a lot of questions. Comments made will not be criticism but the purpose will be to stimulate debate, which helps all that are interested. Cost is all relative. Whether one probe is better than another is up to individual opinion.

Great effort and thanks for sharing

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It is an interesting design and you should continue to develop new ideas. You have a good future as a tinkerer... 😉

the only problem now... you couldn't have known. .. .is that Voron Design just developed TAP and it will be released in the next days..  Official video of the presentation available on YT today.... 

This makes all probes obsolete. Bad timing... sorry.. 😕


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8 hours ago, Meishu said:


This makes all probes obsolete. Bad timing... sorry.. 😕

Thank you for posting 

No need to be sorry, this highlights numerous questions that we should ask ourselves with regards to how we as humans think.

From a personal perspective I come up with ideas test theories and create designs from those ideas because I want to learn for MYSELF, I want to  expand my knowledge, I want to understand what works (and what doesn't) I want to design and create items that carry out their purpose to the best of my ability, in the age old way of design, test, prototype.

I want to create and design things that are financially economical for myself, I am an engineer and luckily financially stable but that doesn't mean that I am prepared to spend money indiscriminately, if I can simplify and create an item that is value for money then everyone  would be able to make and use it too.

I think such an outlook of not doing something purely for personal gain is similar to the ethos of what the Voron community and core values of what Voron development team stand for.

Which is why when I see a commercial product that has been (Over)priced in such a way that it is obvious that the seller place profit first, I become somewhat animated at such narrow minded ideology, and I become very animated when some incorrectly attempt to support or lend credence to such products through ignorance or avarice.

You listed that showing one of my designs is  "Bad timing" why do you think that ?

Is there a perception that the reason for presenting any idea is to advertise it for commercial or financial gain? 

I only ever publish anything I create to encourage others to create and expand their personal knowledge too.

If I see a design that is technically superior, that is fit for purpose and has not been created to be deployed as a closed source proprietary product then I wouldn't be upset or jealous, I commend and support such innovation without ego.

With regards the system you pointed to I will reserve any actual discussion or comment for a thread which relates to it specifically


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i rarely if ever post comments due to the visceral negativity everyone brings, but in this case i feel like a couple point need to be brought up. to the gentleman who said that individual parts (hinge pins, etc) can not be purchased individually. one can be said about the magnets for a klicky. sure if you want to pay 10 of your moneys in shipping plus the cost of the 8ish magnets sure, but anything in bulk is going to add up. i have the same issue with cooking as well when someone says only "$3 dollar meal!". i promise you can not buy .35 cents of dijon mustard or cardamom pods, or whatever "micro" ingredient you add. if you're going to use that as a knock against someone else, at least be honest and take your own argument into consideration. 

regarding the "tap" probe, i started watching the video and was intrigued because i'm actually in the market to swap probes and have been looking at all the different options, and as everyone knows "new" ALWAYS equals "better". but as soon as i saw them take it a part and show an mgn9 carriage and rail i had to go get up, go to my kitchen, open my cabinet, pull down a glass, go fill it with water, take a sip and subsequently spit take it out. i'm honestly half surprised they didn't opt for an mgn12 rail just to add even more unnecessary weight to the mix. i'm all for creative solutions but this is just a moving backwards from a speed and weight savings perspective. i feel this could have easily been archived with something like the original 2.4 plastic spring din mounts. i'm 100% confident others will improve upon this and lighten the carriage up 10 fold by the time they release the .stl files. i am surprised this is they path they chose given the other options. on my non voron printer i had the idea to stick force sensors under the bed to use the nozzle tip as a probe. ended up costing around $10 in parts and made me laugh to see a couple years later the bambu x1 uses this same approach. 

overall i think op's design is pretty clever, and as soon  as  i cad out an mgn9 carrier mount, i'll piece one together and see how it goes. this might actually be a good candidate for using an optical sensor as opposed to a mechanical switch. 


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OP ...oh man. .. you really get angry quickly... 🙂

No one on this Forum is making fun of you or of your work... You see a problem, think about some ideas and more important... you do the job to make it a reality. This is a highly respectable set of skills that serve you well in your live and job too. You have at last my respect for this. I am designing stuff myself. I know how much time you need for a "simple" thing sometimes. And if I have something that the Voron Community can use, then i am glad to publish the design, or other stuff, for free. On the other hand I have no problem, if someone offers me a superior solution for a problem and I have to pay something for it. Especially if I am convinced of it.

And I don't understand why you so quickly speaks about a commercial side of things. When I said  "bad timing", the last thing that was in my mind, was commercial gain. Even if... full disclosure.. I am a reseller of Voron kits. This was the best way for me to get a kit in my country... I just badly wanted to build a voron. ..:) but I digress. .. With "bad timing" I mean that you have spend a lot of time and effort to create something new, that works good and fulfill many other of your criterias. And practically on the day you present your work to the world, there is a new shinny solution, that basically does the same as yours, is an official one and does the job perhaps a little bit better.. (obviously i cannot tell if this is the case because I haven't got either of the solutions in my hand for now) ... This is a "oh.. really now?!" moment that can be really frustrating. This is the way humanity goes forward... can you imagine if only one person at a given time would have a solution for a problem? we would probably still live in caves today.... 

Speaking about the financial aspect of your solution... On the costs side... your solution is a little bit more expensive then Klicky and - relatively spoken - far less expensive than TAP. (that will cost round about $20 as kit and less if you can provide the linear rail and the optical sensor somehow cheaper) I am using Klicky now and it works great... but Tap should deliver a new level of accuracy .. and quicker. (don't need to attach a probe) I suppose your solution will be better then klicky,  but you will probably not reach the accuracy of Tap ... Basically you can get the quality you want to pay for. 

One of the main purposes of Voron Design, is to give users access to a high-speed, high-quality printer, but that has still a low price tag, compared to other commercial machines. This is even true today.. You pay it partly with your work to build the printer yourself... But either way...  a voron..  especially a v2 or Trident,  is more expensive than many printers..  If you just wanted to have a 3d printer,  then you could buy an Ender and be happy with it. But no...  we ...  the voron  builders...  IMHO  ... are willing to spend more on our passion...  If you are willing to spend 1000-1500 $  for a printer, then you will probably be ok to spend 10-20 $ on some improvements....  This is not only a cold, rational raison... we love to thinker.. it is emotional.  (and yes...  i understand, that sometimes,  20$ are a lot of money...)

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Trust me when i try to advise you that im chilled, if i was angry as anyone who knows me could attest, they wouldn't raise an eyebrow at any recipient of my ire being straight up told to go fornicate themselves and to do that fornicating elsewhere.... 

A vast number of my designs have been around in one form or another for years and years, many never see the light of day outside my workshop, the release of this idea came about by pure chance at the request for more information from a forum user who happened to view the original concept video on you tube. 



Edited by Calvinx
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With regards using an optical switch, i travelled that route already. 

A number of factors came into play with trying to employ an optical switch. 

I couldnt actually locate a reasonably priced optical switch with a wide enough "air gap" spacing between the emitter and the collector to retain the 5mm O/D actuator shaft. 

I did have success using a standard optical switch with a 3mm steel shaft as the actuator, but that required me to turn a custom oilite bronze bush reamed to 3mm then those bushes were pressed into the pulleys to retain accuracy when the actuator was travelling through its stroke, and i had to hand grind a tool steel groove cutter so i could make custom 3mm O/D grooves so i could place the circlip grooves in the desired location to allow the shaft to protrude far enough up from the upper circlip to enable the shaft to be retained properly and still activate the switch without interference between the actuator shaft and the optical switch. 

Easy to do and fully operational as long as you have access to the correct equipment, but i was also trying to think of how the average user who might not have access to a lathe might be able to put one together. 

Which is why i went the route i did 

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This is an interesting design and it's great to have another option. I also had the unfortunate timing thought with the Voron Tap being announced right after this thread started. Largely because it being an official team mod and announced with a Voron Live stream, it's going to take all the oxygen in the room for a while; I remember when Stealthburner was announced. The team made it clear that Tap is not for everyone, so there's room for other solutions like what @Calvinx is presenting.

I currently use KlickyNG, so this mod does much the same thing. For me Tap presents a solution I've been wanting so I'll go that route. The $20 or so in parts and reported 40g extra weight is fine for me--That's not a lot of cost compared to the rest I've sunk in and I'm not chasing grams on the tool head--I'm not playing in the speed boat races.

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