Recently I purchased the H2D Cutting Upgrade Kit for my H2D combo. I started experimenting with the Pen Module, which I planned to use for marking workpieces and simple PCBs. However, I noticed a very unpleasant issue that makes this impossible: the Pen Module doesn’t seem to be firmly fixed (in the XY direction) inside the cutting module. I understand that it should be floating vertically, since it appears to use a load cell and a solenoid, or something similar. But in the X-Y direction it has noticeable backlash - a few degrees relative to the shaft. This becomes especially obvious when using thin 0.3 mm lines and multiple passes. The lines turn out doubled and blurry, especially on small details. I would like to get a response from support and the community - is this behavior intentional, or is it a problem?
I don’t have the module yet but that is definitely going to be a problem. Have you watched the install video? It looks kind of complicated. Are you sure it is in right?
Of course, it won’t be possible to install it any other way. Apparently, the part tolerances are too large.
I almost submitted a support ticket before I saw you post ;). OK so that’s normal :(, I have the same issue when using ultra fine tip pens, the way it it designed is that as you noticed there is play between the holder and the module. If you use the large tip pens supplied, it is not an issue as it will overlap the lines and it will be hidden. Of course this only works for artistic drawing, not blueprints.
I am designing a spacer to fix it 
I don’t think this is “normal” — it’s clearly a design flaw, and in a premium product at that. Even in the pen settings in BambuSuite there’s an option to select a 0.3 mm pen (and it even seems to be the default), which implies the equipment is intended for precise work.
As for the spacer, I’m not sure it would help without affecting the module’s vertical movement. Right now I’m considering how to eliminate the backlash using a rubber band or a spring.
I had 3 ideas and I’m currently designing the third which I think is the best way (until I find a 4th option…).
- A very thin spacer to go between module head and holder. It works but it’s a pain to install and as you say, when installed the pen holder cannot move up and down
- A sleeve on the bottom of the pen holder with a screw on the side to push the pen holder to the module head and eliminate the clearance, this works well but a little bulky and not very mechanical.
- A sleeve that goes under and over the module that incorporates a keyway because strangely the pen holder has a key strip on the back that seems to have been designed to lock it in X/Y but not used. I’m working on that one because I think it’s very promising
NEW EDIT: This time it works!
Option #3 is the best. It works great and can be left installed for the cutter as it does not interfere with anything and keep the led visible.
Here are my 3 working options:
and the 3mf of option #3 if you want to test it:
Cutting module insert for pen holder.3mf (43.5 KB)
Note that due to the very low clearance between the module and pen holder, the back of the key strip of the pen holder will have to be (very) slighly filed until the pen holder can move freely up and down. When it’s done, the homing of the pen has no error and the wobble is gone
Result:
And BTW, if you’re like me and use small tip pens from sharpie which are just 10.5mm in diameter and don’t really grip well in the holder to use a small o’ring below the gripping tabs like this, you can tighten the pen better.
interesting. I’m still learning the program and waiting for my cutter to be shipped
I significantly reduced the backlash by wrapping 1.5 turns of Kapton tape (because it was at hand). Teflon sticky tape would obviously be better.
Often, the simplest way is the best
Probably should have been mounted to a vertical linear rail.
Did you try “just wrap tape around the part” to make it fit?
I know we have a robot that can make custom platsic parts but sometimes the simplest way works.
Obviously this is an issue that bambu should resolve, but the above might be a possible workaround.
Originally, the brass shaft of the quick-change head (cutter and pen holder) should have been made with a locking slot. There was no point in making it rotatable. The cutter blade rotates on its own bearing, and the pen holder doesn’t need any rotation at all.
I designed some adapters that let me use a variety of smaller diameter 3rd party pens, here:
When using a 0.1mm pen, the wobble problem was even more noticiable. So I designed a simple part that takes out about 90% of the X wobble (backlash) while not inhibiting the Z motion of the pen.
It snaps onto the Cutting Module, and slides over the pen holder to prevent the wobble. I have several hours of pen time on it and it is working well.
In the figure below the adapter rests on a ‘box’ on the bottom of the print head, and the white ring above it is my Adapter for a 0.1mm Copic pen. I will be posting it soon.
And this is the difference beween using my Pen Guide, and not. The arrow points to the line drawn with the Guide installed. The line comes down and flares out to the bottom of the letter. Besides the shadows, the non-guided line starts to move to the right (crossing over the guided line), but has a break in the middle of it, where slop is finally taken up and the non-guided pen movement becomes parallel with the guided (straight) pen line but at an offset to the left of the guided line.
Lugamodder, could you provide a link for the SVG of the Bambu print head that you used above. I would like to see the difference that my Pen Guide might make. Thanks!
Lugamodder, Thanks for the link! I will try to print it tomorrow.
And I just published my Pen Guide here:
It may be worth trying to print this model entirely in TPU or with a TPU insert, slightly reducing the overall dimensions. This would create an interference fit and eliminate the remaining backlash.
The trick will be minimizing the x motion while not impeding the Z motion of the pen holder in the Cutting Module. But there is not a lot of z motion. It is hard to see when it is drawing. Certainly no more than than a mm. My guide can easily rock up and down that much. But if you do try TPU, please let me know how it works.
Check out the latest version of my Pen Guide.
I think that I’ve completely sovled the problem. Rather than using TPU (which is always sort of a pain), I added printed spring clips to the Guide, which basically reduce the X backlash to zero.
In my post I use your Hotend SVG example to show the difference between with and without the guide.
I’ve achieved an almost perfect result using PTFE adhesive tape.
You’ll need PTFE self-adhesive tape with a thickness of 0.08 mm (I used 19 mm wide tape) and a sharp knife. The tape should be wrapped in a single layer, but in such a way that the front flat surface of the module has two layers of tape.After that, the protruding tape needs to be trimmed flush with the bottom edge.
