I picked up a box of 200 Husky heavy duty utility knife blades from Home Depot for $10 & a box of 10 mini utility blades for $1.59 at harbor freight. The heavy duty blades measure .65mm thick which is about .05mm thicker than the Stanley blades I have & it does fit into this blade holder mount. The notch side measures 1.6mm longer than the Stanley, but the cut side seems to be the same length. The width is the same. I might look at tweaking the design to fit these blades better, but might be good enough. These 200 blades might be a lifetime supply for me unless I start cutting up a storm.
The mini blades seemed like they might be a good blade to use for this also, but more expensive. I will make a version for those to see how it looks. It will definitely but the blade tip a lot closer to the 8mm rod.
I can not find the Husky blades on Home Depot site, but they were in the special Christmas sale items. I saw them last Friday & they still had some today.
Here is a link to the mini blades at harborfreight:
Replaced Olfa blade holder with MPCNC_TN_OlfaBladeHolder_Rev73.scad to add recessed M3 nut traps for cover. Also added a version for mini utility blades MPCNC_TN_MiniUtilityBladeHolder_Rev14.scad. I kind of like these mini utility blades, but least expensive place seems to be harborfreight in packs of 10. The long side of the blade measurers 28.3mm. I printed this one up yesterday to test fit. The center hole in the blade makes it a nice way to tighten it down. Think I have holders for 4 different types of blades so far. I need to edit the x-acto blade version a little more & upload that.
I have to put this fun project aside for a little bit and finish making my Christmas cards. Most of the parts I need for making this should be in on Monday, so maybe I can start printing the machine & motor mount next week.
Well that seems fair. Thanks for moving things along. Once I get small lettering working great I’ll probably back off a bit and go back to making things. Right now there is work to be done before results are consistent. My first attempt was beginners luck.
Having tried to consistently get acceptable centre axis blade tip alignment with your mount, I now recognise the need for your new design with side screws. What’s great about this approach is I’ll be able to align the tip precisely after mounting it. Box cutter/Stanley blades actually have a tip that is shy of the angled back edge of the blade, so along with the fact the mounting design (inherited largely from the original) it’s been difficult to get the blade centred. The one of yours I’m using has been an improvement for the thick material, but I’ll be trying out the latest idea next.
I did receive my 30 degree Olfa blades, and they are smaller than I thought, but will still cut thick material. I will probably have go at reworking your design to accommodate their dimensions. I really like the acute tip. Once we have the pointy tip, rigid design and precise tip positioning, I do believe it will be job done.
I am constantly amazed at what can be done in openscad. Most of my parts came in on Saturday, so I will test print some parts for fit today with the bearings. I am planning to use 4 of the drylin Igus bearings, 2 on the main shaft & one each on side M8 rods and a 608ZZ skate bearing on the bottom end of the side shafts.
I have all my plastic parts printed out now & test fit the mount in the quick release & looks like it should work. I will have to wait for a warm day before trying it on my MPCNC in the shed. It is snowing here today. I still have to get a spring & cut the rod.
A couple of questions occurred to me yesterday & maybe you mentioned this somewhere. Which direction should the cutting edge of the knife blade be initially, along the positive x-axis? What are you using as a spoiler surface under your cardboard or foam core?
Yes initial blade direction is positive x with this system.
And yes cardboard is working well as a spoil board for cutting card, and foam. Foam would work equally well.
For vinyl I’m using my a0 cutting mat. You need something firmer to get the blade depth precision, or the blade presses the material into the spoil board instead of cutting.
I’ve had some time away, but currently designing a new cutting head for the little 30 degree blades based on your ideas and designs. I should be able to print and test tomorrow.
I am going to look at getting a spring tomorrow. Can you give a good estimate in how much z travel to expect with the spring? You mentioned earlier that it was not much. I might have to lengthen my rod a few mm’s to clear the bottom of quick release. I would just like to have a better idea of what it would be, so I can avoid a clearance problem & I don’t cut the M8 rod too short.
I found this 9/16"(14.3mm) x 1"(25.4mm)x .054"(1.4mm) at my local Ace Hardware store and planning to compress it to about 22mm. How does that sound? I would have liked to find a shorter spring, but that was the closest match I could find.
My center M8 shaft is currently at 120mm & the side M8 shafts should be between 75 & 80mm. In the screen shot, I have the middle parts blue & green as separate parts with aM8 bushing in the center of each & a bushing in the blue part for the side M8 rods. On the side M8 rods, I am only putting the M8 rod thru the top part as it does not seem like they need to go all the way down. I have the center parts & side part held together with 4 - M3x50mm stainless screws and locknuts. With those screws & the quick clamp around it seems like it should be held in place pretty good. I was starting to think this was looking a little too complicated, but it does go together easily.
It depends on the spring tension, but I guess the most would be 3mm or so.
It’s difficult to say, but I would say your system would be stiffer than mine with that guage of spring and starting with 3mms of compression. I don’t know if that’s better or worse to be honest. I haven’t found the optimum in a scientific way, but set mine up with little to no initial compression so it has some give. Of course the mass of the assembly above the knife exerts a downward force through gravity too. I still haven’t got into much vinyl cutting as I’m still working on the prototyping/design, but I expect to need a bit more tension. I will add tension by placing extra washers above the mount assembly to provide initial compression.
You were lots of help. Some of it is just going to have to be trial & error. I did notice something I did not expect with the purchased drylin Igus bearings. With the tighten gap I left in the middle bushings tightened a little too much for a smooth movement of the rod, but the side ones work good. The difference was in orientation of that slot gap. I might make the diameter of that middle opening slightly bigger to see if that fixes it. I did not really want to use metal ones, but I have some now.
What is the best stuff to lubricate those metal bushings? I have not used those before.
Here is my 1st assembly of the parts. I am using the metal bushings. I will test fit it on the machine tomorrow, but should fit as I test fit the main parts before. I see a couple of things I still want to change, but feels pretty sturdy. I do not have any tension on the spring and the plastic coupling is resting on the top bushing. I realized the collar I was originally going to use did not seem to be needed. I made the coupling 38mm high with 20mm to grab the M8 rod & 16mm to grab the 5mm Motor shaft. I bought a metal coupling, but I did not like that it only has around 8mm to grab the 5mm shaft.
That looks so crazy! You guys are killing it on this thing, I have had some questions about stencil material recently and I showed them this thread. Perfect!
The metal ones I tried lithium grease, but it was too thick. Perhaps a lithium grease spray? As a side note, I watched a test on a few different lubrication choices for the plastic bushings and silicone came out best. Did I already mention that somewhere? I’m getting old.
Great to see! Looks very cool. Like a speeder bike from Return of the Jedi…
I also never used the collar, as the coupling did the job. Does your plastic coupling have really good grip? I could never match the grip of a metal one. Have you replaced the skate bearings with a linear bearing for the centre rod? When I did that, the blade was turning really true and it solved all the slop problems.
I really must move away from red, white and black filament. Hmm, just bought new rolls of each.
There is some dry lubricant made by the wd40 people that I use on my miter saw. On the part that slides on the big tubes (Sorry, not a mechanic mind here). I used wax with graphite powder in it, that was easy to make, and makes metal on metal pretty smooth.
Seeing it on the carpet, and 3D printed really makes it cooler. I think someone needs to add some 3D printing marks to openscad. While at it, they should add in some standard textures, like carpet, kitchen counters, and workbenches. Just to make the photo realistic renderings more realistic.
You probably did. I read thru this thread a while back, but was not considering some things until running into them recently. I probably should read thru this thread again now that I understand it better.
Seeing it on the carpet, and 3D printed really makes it cooler.
I could overlay a different background on it in photoshop. I usually put the parts on a surface without all that texture, but the lighting was better there at the time. The jpg files are usually larger when using all that varying texture.
Thanks for the various ideas on lubricant. I will look into it further when I am ready to actually try it out. Cold weather came here early this year in Western NC, but should have a warm day or two in the next month to test it.
I attached a better photo of all the parts separated. I might make those middle 2 parts one part & just extend the center linear bearing hole for 2x 24mm high bearings.
The lip on the outer part is only 2mm thick which is sufficient once it is all together, but am planning on increasing that to 4mm & add another 3 to 4mm high weld around it.
I will add tension by placing extra washers above the mount assembly to provide initial compression.
I also had an idea for your washer shims to change the spring compression. I call it a horse shoe washer which seemed like an appropriate name. It is a washer which is cut a little off center to allow it to stay in place. I included an image and the customizable openscad file zipped to check out. You can vary all the dimensions for best fit. It certainly will not take very long to make a test print of it to see if it works for you.
Thought I would also mention that I use eSun PLA PRO (PLA+) plastic which gives me a little bit more flex than regular PLA. It is the only plastic I print in now except for the occasional PETG. I usually pick whatever color amazon has the best price at the time unless their is a particular color I want. I have seen their prices on different colors vary from $18 to $25 a roll. Currently they are $23 to $25.
I played around with these washers today. Since my spring’s inside diameter is a little over 3mm more than the M8 rod, I made a version for the spring to rest in the washer by making a donut cutout in the top of the washer. I don’t know if that is really needed, but it does make the spring stay symmetrically around the M8 rod. Here is a photo & an updated openscad file.
I was not happy with not being able to use those drylin bearings, so I redesigned the middle section so it is split in half instead of 2 parts vertically. My test prints show that this way does not compress the plastic bearings. This will work for either style bearing also. I am reprinting the middle parts & lip mount today. I seem to have lost one of my drylin bearings, so I will have to order some spares from ebay if it does not show up in the next few days.
I found some openscad code to generate a spring sized to what I am using to make the openscad assembly look better. I might try printing a plastic spring to see if that will work. I will make it less coils to get a better print angle & make it thicker gauge. I can not get more than about 15 degree angle, so it probably won’t print well.
A 3D printed spring could really be useful, and the typical spring design is really not well suited. There’s definitely some room for some good ideas there.
For one thing, printing these layer by layer in z doesn’t make sense. I could see this being a good place for a more custom slicer. Something that would move along the spring, up and down, adding a little height each time. That would be neat.
Another thing is that shape is really meant for bending a spring. There must be a shape that is easier to print (and cooler). Even taking a few springs and super imposing them in the same place, mirroring half of them, would make something with a lattice of sorts. Another good alternative would be to have horizontal layers every 5mm or so, and have pillars to support in between, but with different locations for the supports in each layer.
Sorry, I think CAD would be a better way to explain these, but I’m on my phone ATM.
I’m still chipping away, but Christmas slowly swallowing me.
I love the 2 part middle section. And all the discussion about printed / plastic springs seems like the right direction too. I can visualise the lattice spring idea, sounds cool. I have some flexible PLA sitting here waiting for a project too.
I’ve got my new cutting head printed and installed. Working on some calibration gcode files to help me get the point within 1/10th mm or so within centre axis. I think this is needed to do really small lettering, because with any ‘tabs’ left in the work due to misalignment, weeding becomes impossible.
I decided to go with lots of captive nuts and set screws, as inspired by one of geodave’s designs. Looks promising so far. Blade extension is controlled by top left screw on sides, bottom left and right screws fix the position in the plane of the blade and there are 2 screws (top and bottom) to control the lateral position of the blade. I’m calibrating with a cross and a square. It’s printed for the 30 degree olfa blades right now, but it’s fully parametric, so can be adapted for the standard olfa. More to follow.
