Tangential cutter in development

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This topic contains 160 replies, has 10 voices, and was last updated by  geodave 1 month, 2 weeks ago.

Viewing 30 posts - 121 through 150 (of 161 total)
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  • #48837

    geodave
    Participant

    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:

    http://bit.ly/2zH0TnW

     

    Attachments:
    #48892

    geodave
    Participant

    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.

    #48915

    James Donnelly
    Participant
    I have to put this fun project aside for a little bit and  finish making my Christmas cards

    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.

    #48916

    James Donnelly
    Participant

    Wow.  This Openscad stuff is COOL.

    #49070

    geodave
    Participant

    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.

    #49281

    geodave
    Participant

    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?

    #49282

    James Donnelly
    Participant

    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.

    #49341

    geodave
    Participant

    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.

    #49391

    geodave
    Participant

    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.

    https://www.primeline.net/sp-9728-

    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.

    #49394

    James Donnelly
    Participant
    Can you give a good estimate in how much z travel to expect with the spring?

    It depends on the spring tension, but I guess the most would be 3mm or so.

    How does that sound?

    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.

    Sorry I’m  not much more help.

    #49406

    geodave
    Participant

    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.

    #49437

    geodave
    Participant

    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.

    1 user thanked author for this post.
    #49440

    Ryan
    Keymaster

    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!

    #49445

    James Donnelly
    Participant
    What is the best stuff to lubricate those metal bushings

    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.

    Here is my 1st assembly of the parts.

    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.

     

    #49446

    Jeffeb3
    Participant

    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.

    #49461

    geodave
    Participant

    Did I already mention that somewhere?

    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.

    #49469

    geodave
    Participant

    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.

     

    #49575

    geodave
    Participant

    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.

    #49583

    Jeffeb3
    Participant

    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.

    #49603

    James Donnelly
    Participant

    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.

    cutting-head

    blademount

    #49787

    geodave
    Participant

    After changing the design of the cutter holder to match the Husky utility blade profile, I was starting to think about a better way to hold the blade in place & be able to change it without taking 1 or 2 screws out. In the middle of the night I realized a binder clip might work for this.  If I make some recesses in the plastic on the bottom & the top cover this might work well.  Here is a photo of what I had in mind.  I will have to adjust the cover & holder to match the clip better.  This clip is 1.5″ wide.  Looks like I will have to clip it to the side or along the top sharp edge of the blade instead of the top as I don’t have enough clearance on top.  I might be able to design a plastic clip, but would not be as strong as the metal binder clips.

    #49886

    geodave
    Participant

    I came up with a clip clamp along this idea which looks like it will work.  I need to make the diameter a little bigger to get more strength, but 1st test seemed pretty good.  I made it 8 sided so it would print well. Here are 2 pictures & a dimensioned part.  I made the design with 5 customizable dimensions.  I have not put it on thingiverse yet.  I am going to use this idea for something else also, which is why I made the 2 sides individual variable lengths.

    #49927

    geodave
    Participant

    I got a little sidetracked & went a little overboard with customizing variables for this little clip clamp.  Hope I did not get too far off topic here.  I am not sure it will be strong enough to replace the screws in this design, but should have some other uses.  Here is an example image showing most of the possible variations in the design.  The part can be found thingiverse & also opened in the customizer: https://www.thingiverse.com/thing:2726864

     

    #50343

    maong
    Participant
    Un piccolo passo in avanti, in grado di tagliare 7mm di carte a doppia parete in un singolo passaggio ora, quindi di nuovo in pista. Risulta molto preciso il tracciamento dell’angolo della lama per tagliare a quelle profondità. Gcodetools è stato modificato per opzionalmente i gradi di output nel gcode. Avevo sperato in una soluzione in cui non fossero richieste modifiche al firmware, ma purtroppo non sembra possibile. Hai bisogno della precisione di andare in gradi (solo valori di magnitudine più alti, ma i gradi hanno senso). Ma questo innesca la lunga prevenzione dell’estrusione. Quindi ho dovuto commentare quanto segue: configuration.h:

    #define PREVENT_LENGTHY_EXTRUDE
    
    #define EXTRUDE_MAXLENGTH 200

    james ..

    thank you very much for the work you have done…

    I want to try your project but I have a problem ..I commented on the two lines of the firmware

    //#define PREVENT_LENGTHY_EXTRUDE

    //#define EXTRUDE_MAXLENGTH 200

    I can not make 1 full turn at the cutter..

    I entered the order 103.xx steps per mm for E ..I’m using the basic firmware with a 1 degree temperature..

    when I try the g1 e3600 command (10 full turns) and checking that 10 turns happen and the final angle matches the initial angle,

    it always runs without stopping….

    you can give me some more information??

    thank you so much james

     

    #50348

    Jeffeb3
    Participant

    I guess you hit the quote button on a google-translated page? I didn’t know it would do that.

    I think you’re saying: G1 E3600: It continues forever, and doesn’t stop. Is that right?

    Can you try something smaller?

    G1 E4

    or

    G1 E360

    I think the steps/mm is way off. It really should be steps/unit, and in this case unit is degrees. If you have the drv8825 driver, and all three jumpers installed, then it should be 200 * 32 / 360 = 17.777 steps/degree. If you have the a4988 driver, or some other jumper configuration, then it should be even smaller (with 1/16 steps, it would be half that). This is also assuming you have a 200 steps/revolution stepper.

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    #50378

    maong
    Participant
    I guess you hit the quote button on a google-translated page? I didn’t know it would do that. I think you’re saying: G1 E3600: It continues forever, and doesn’t stop. Is that right? Can you try something smaller? G1 E4 or G1 E360 I think the steps/mm is way off. It really should be steps/unit, and in this case unit is degrees. If you have the drv8825 driver, and all three jumpers installed, then it should be 200 * 32 / 360 = 17.777 steps/degree. If you have the a4988 driver, or some other jumper configuration, then it should be even smaller (with 1/16 steps, it would be half that). This is also assuming you have a 200 steps/revolution stepper.

    thank you so much…

    the problem was in the formula to calculate the engine steps

    forgive me for the scandalous English

    #50380

    Jeffeb3
    Participant
    forgive me for the scandalous English

    No problem. I’m an engineer. I work with many native English speakers who have a hard time with English. 🙂

    #50442

    maong
    Participant

    Hello
    I can not get the firmware to work in degrees….

    use as step dvr 8825 I worked with step 0 to 32 step with the same result!  I used the formula 200 * step/360 = ……

    when I try to give the command G1 E360 the knife always turns!!

    I followed the tutorial from the site: https://www.thingiverse.com/thing:2624654

    I can not understand how you can have 103.XX steps …..I followed everything in step by step his tutorial…

    thanks to those who can explain me..

     

    #50458

    Jeffeb3
    Participant

    Can you try something smaller until it actually stops?

    G1 E1.0

    #50529

    maong
    Participant

    my configuration  is: nema 17 1.8 degrees 200 steps/revolution stepper jumpers 1/16 steps..

    I inserted in the firmware :#define DEFAULT_AXIS_STEPS_PER_UNIT { 200, 200, 800, 8.8888888889 } //MPCNC

    200 * 16 / 360 = 8.8888888889

    I try to give the command G1 E1.0 always runs more than 1 turn…

    I have to be able to take a ride with the command G1 E360

    (james)which configuration can have him to have 103.xx steps

    maybe he modified something in the unspecified firmware….

    thank you

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