jhertzberg

I think that a delta configuration might be better than a sliding bed. The abrupt accelerations of a bed changing direction would likely collapse any delicate wet clay walls. Nevertheless, clay extrusion with my UM1 is a back burner project for me. I started out with a moineau pump printed in PLA, but I'm now thinking that filling a big syringe, then gearing a motor to slowly press the plunger will be simpler. I want to avoid dragging the weight of the clay and a motor around, so I picked up some cheap 100cc syringes a while back and some tubing with the intent of seeing if there are any clays that would have low enough viscosity to impel through ~50cm of 3-4mm ID tubing, but would not buckle upon being extruded. I don't have the workspace for using an air compressor, so that approach is out for me.

Welcome back. You have confused some of best mods and contributors this board has to offer.

You have those wide arms on the wood arms at the front, but you attached your two front bed points to the springboard. Why not to the arms?

The three z-axis screws was part of the discussion here because JonnyBischof was trying to come up with a rock steady self leveling bed as part of his dream mod.

I was getting that feeling too. OP, declare yourself! :-) (But seriously, six garbled posts, then silence. And, the googles show no other hits of that username.)

Since a clay extruder is cold, know that you will need to either rebuild Marlin to ignore MINTEMP errors, or add a resistor to supply a constant temp reading in the proper range.

There are probably a couple of issues to overcome, either with the strain gauge at the drive end, or the hot end. With the gauge at the drive end, you might have to compensate for variations in bowden friction, as the bend radius varies with the x/y position of the head. This would also be filament dependent; stiffer filaments would cause a greater effect. A solution would be to calculate the bowden bend radius based on the head position, and to have some sort of stiffness factor for each filament type, with which to calculate a modifier for the measured force. With the gauge at the hot end, there are fewer factors, but the lateral acceleration on rapid x/y movement will probably introduce some noise. Some sort of clipping filter applied to the data and/or a deep set probe housing to minimise lateral slip across the force sensor might work. With either design, any gap in the bowden path would have to be the minimum necessary, or else very soft filaments could bend or deform in the gap.

That thing is a remix from http://www.thingiverse.com/thing:112718 There are a bunch of remixes at different pitches, so you may be able to find or design one that has a pitch that will match the 1" per turn. If you are thinking of using this to emulate a 3 ball screw z-axis arrangement, you may want to run some tests to make sure you can print well matched copies.

I think with that design, one would have to carefully isolate the strain gauge portion of the filament path from bowden movement further downstream, as the hot end moves about.

George, how would that open design work with nylon or flex PLA?

That is what I was envisioning, the sheet set on top of an aluminum bed. Downward facing tabs on all four sides of the sheet could be used to hold the sheet firm to clamps or clips on the bed that don't impinge on the print area.

Well that is a fantasy z-stage! As long as we are spending buckets of cash. - To get around the issue of tension between the straight rods and the ball screws, how about a mechanism that releases the linear bearings to float in their housing (like the stock z nut capture) on the x and y axis during leveling, then clamps them in place from above and below to hold the new location. A couple of solenoids would do nicely if you want to completely automate it.

If you decide to add a leadscrew, then why not add two? Place the new ones in the front corners. Tie them all together with a timing belt. Add a release mechanism so that you can turn them separately, and you could do your bed leveling right at the leadscrew.

I have printed a few things with the Makergeeks Flex EcoPLA. I also tried (unsuccessfully) to print with 3mm Eagle Blue 80 EC Polyurethane Belting. The issue with the bowden is that you are essentially trying to push a string uphill. If the filament is too soft and its diameter isn't a perfect match to the inner diameter (ID) of your bowden, it will either kink up or bind in the bowden. If it kinks up (gets waves), you may still get it to feed all the way to the hot end, but flow rate control will be unreliable, and retraction won't do anything to remove head pressure. There are a few things you can try to get it to work. Print very slowly, 20mm/s or less. Oil the inside of the bowden. It sounds crazy, but if you put a drop or two of machine oil on a regular piece of PLA and run it back and forth through the bowden you will get a little less friction and the oil won't damage the print. If that does not work, see if you can obtain a couple of spare bowdens with slightly different IDs. Measure your filament diameter and use the bowden that is the best match. Beyond that, you would have to heavily mod your UM to run without a bowden. There are a couple of threads on this board discussing that: http://umforum.ultimaker.com/index.php?/topic/2544-small-steppermotor-for-direct-extruder/ http://umforum.ultimaker.com/index.php?/topic/3199-crazy-idea-about-feeder/

Patient: Doctor, Doctor, it hurts when I do this! Doctor: Then don't do this! Because you used too much glue stick, you are trading a simple, (relatively) inexpensive print bed material for something complex, expensive and sharp-edged. I can imagine several failure scenarios including head crashes at the wrong spot chipping a panel edge, sliced open palms, concave bed along one axis from warp forces bending the hinge, loose and broken hinges, etc. Instead, perhaps a 1:3 dilution of PVA based glue (wood glue, school glue) instead of pritt stick, and a sharp edged spatula instead of a knife. To flex the bed to pop the print off, perhaps there is a thin flexible plastic sheet material bonds only poorly with PLA, ABS, etc., will hold tight to a rigid, flat bed substrate when hot, but release for flexing when cooled.

I use one of my wife's old crochet hooks to remove the stray bits of blobbing and stringing that might ruin a print while still printing. I suppose a button hook would work too.

For getting a large print off the bed without stressing any delicate parts, I recommend a strong but thin edged spatula like this.

I understand your point, but my original UM bowden is long gone, and the replacements are of various ID ranging from true 3mm, up to 4mm. I use the 3mm one for good 2.85mm filament, and the 4mm for stuff like nylon. I suppose a further refinement that would address your concern would be to tap a blind rivet of sufficient ID into the end of the bowden.

Regarding 3-point leveling, I get very good results with Murat's design http://www.thingiverse.com/thing:84754, plus adding thumbwheels to the screw heads. I just superglue washers to the right spots on the bottoms to my various print beds; acrylic, glass, plywood, Garolite. The magnets hold very well, but make it a breeze to pop the beds out for removing prints, painting with PVA glue slurry, etc. I also strongly recommend Owen's hot end bowden clamp http://www.thingiverse.com/thing:11864.You get a positive grip on the tube, but can remove it easily if you have to get to a clog from above, or if you sometimes swap in an oversized ID bowden for oversized PLA or swollen Nylon. I made the slight mod of cutting a short section of bowden that runs the length of the wooden hot end cage. I hold it in place with a M4 washer captured between the top of the wood cage and the bottom of the base-and-riser part. You may also want to pick up some lights (eg. Ikea Dioder) and hang them, with printed clips, pointing at the bed. It may sound like eye candy, but late at night it makes it easier to see minor print problems before they become a big mess. This is extra good if you also intend to mount a camera.

I got one with a D-shaped shaft and 55N.cm holding torque from Lulzbot: https://www.lulzbot.com/?q=products/nema-17-stepper-motors It's a little longer that the Ultimaker motor. You will have to solder on your own connector. I got mine here: http://www.ebay.com/itm/1-JST-JST-XH-3S-Balance-Wire-Extension-Adapter-30CM-12-long-/350678187003?ssPageName=ADME:L:OC:US:3160

Hmmm, When I click your YouMagine link, I get "You are not authorized to access this page." and I am even logged in there.

How rigid are the flexible couplers along the axis? Do they expand, compress or bounce when torque is suddenly applied? It looks like a great idea, but I don't want to trade off z-height accuracy.

I assume you would anchor the fulcrum to the top-rear of the case and the tracer to the original head mount, right? I played around a bit with adding an articulating arm to hold tensioned belts between the head and a second extruder motor. You will need to keep the arms supported so they don't sag as the z-stage drops, but also you need to keep the assembly light enough for the old head assembly to drag the tracer about. If you try building this, I suggest that you pick up some 623ZZ bearings for the pivot points on all the arms. You may also want a fixed height stage below the full travel area of the long arm pivot and then support the pivot on a ball caster.

Thanks MadOverlord, that makes much more sense. How about using a miniature solenoid valve between the heat chamber and the nozzle? I know they make them small enough, I just don't know if the little ones can take the heat.

I don't know if I understand your use of the solenoid for retraction correctly. I don't think that the oozing problem is solved by retracting the head. I think that the retraction of the filament creates a negative pressure in the heating chamber, and that slows the flow.