There is a solution of chemicals and hormones that is commonly refered to as "cell divider" that could heal a wound much quicker than normal. Basically it makes cells divide and reproduce at about 4 times the normal rate. It's great for doing some baseline cellular tests. I wouldn't put it on a human or any living animal though, due to an increased risk of cancer.by criswilson10 - Tissue Engineering
You can also make your own mini gear puller using a flat steel bar, a tap, and a screw or bolt, a hammer, and a file. Start with a piece of 1/8 inch thick steel, 1 inch wide, and 3 or more inches long (3 inches will let you pull a 1 inch diameter gear). Bend the steel bar into a box that is 1 inch long and 1/2 high, with the plate ends touching in the center of one of the 1 inch long sides. Fileby criswilson10 - Mechanics
I have this strange feeling that Viktor has a spy camera mounted in my research lab...that is almost dead on correct with some of the research I'm doing. That was just a creepy response. :-) Of course, most home users don't have access to gold plating equipment that won't kill the cells. Or they can't afford to do the gold plating. And I think we are going to move away from using metals asby criswilson10 - Tissue Engineering
Milling and printing are definitely to different things when it comes to machine designs. To mill with a mendel I would increase the bar diameters to at least 12 mm, but probably more like 25 mm (those are non calculated off the cuff guesses). One important thing from this is that you learned how to do a theoretical beam deflection and you got the correct answer. And if you want to go with Aluby criswilson10 - General
I'll go on and warn you now, beware of using plastic in the design. Plastics have/develop a static charge that makes cells move around when printed. Also, the chemicals used for cell binding react with anything carbon based. And as I said in a previous thread somewhere, the reprap base is a great place to start, you just need a different tool head to handle biological liquids.by criswilson10 - Tissue Engineering
Could it be done with just a PC? Sure. The Parallel Port may only have about 14 usable pins for I/O but you can multiplex them to get however many you need. Or you could even build your own IDE card to plug into your PC to do the control. That's how we did things in the 1970s, 1980s, and a bit into the 1990s. It is easier to just use a microcontroller and it's a lot cheaper to replace a blown miby criswilson10 - General
The calculations are roughly correct give or take a few microns (I'm a mech. engineer), but the simple bending equation doesn't take the real world into account and can have an error of +/- 30% which in this case is about +/- 0.1 mm. And your elastic modulus of the steel is a bit high, it should be around 200 GPa. So in theory you are looking at a bar deflection of about 0.5 mm as the worst caseby criswilson10 - General
xoid I'm just guessing about the design, but my guess is he needs a long belt loop to run a z-axis plate up and down. Since it is a repstrap, it's the quick and dirty way to do it.by criswilson10 - Mechanics
I can't say I've ever tried hot bluing a rod in a mechanical device, but now I find myself asking why not? Especially if it is cheaper than stainless or nitriding. Of course, you will still have to keep it oiled. I would suggest trying it on one part first, evaluate how well it works and holds up, and if it works then do all of the other parts.by criswilson10 - General
The silicon tubing method mentioned above works well. There are dual dimension shaft couplers available, but they are not cheap. If you have the tools and patience you can make your own with a piece of scrap 9/16" rod about an 1" long. Just drill a 3/8" hole in one end, a 3/16" hole in the other and a couple of small set screw holes to secure the coupler to the shafts. The trick is getting thoseby criswilson10 - Mechanics
I don't have my reprap in front of me, but for the number of gear teeth there is always the mark 1 tooth with a pen and start counting. You can use a ruler to get the the overall diameter of the gears that were sent to you. Or you can read a bunch of stuff at Basically though: Pitch Diameter = (Number of Teeth)/(Outer gear diameter) Hopefully someone with the info at hand will post it soon, iby criswilson10 - Mechanics
I wouldn't expect a reprap to be able to print a completed smart material unless it was one of the smart plastics - even then I'm not sure, but I only know about smart plastics from brief article skimming. It may be possible for reprap to print out some base structure that could later be sintered. I know someone was doing something with printing ceramics. Or reprap could do a wax mold for castinby criswilson10 - Mechanics
The way to get by the tooth spacing without a jig is to first make your cuts very carefully and then second use a scrap piece of belt to line up the teeth before clamping. Glue doesn't stick well to neoprene so that scrap piece will peel off easily once everything is dry.by criswilson10 - Mechanics
You don't necessarily have to have the belt jig. I have used vises, c-clamps, visegrips, and hemostats to glue belts together over the years. You just have to make sure that belt lines up straight when you clamp it. The best glue that I have found is the E6000 flexible glue put out by Eclectic Products. It is strong and flexible - but it has to cure overnight and has a strong odor while curing.by criswilson10 - Mechanics
You could just buy and wear a full chemical suit with built in respiratory system if you want to cover all of your bases, but seriously, just don't print abs or anything that you are unsure of without lots of ventilation. Once you do a print with it the first time you can then decided how tolerable the fumes are and then decided how much ventilation is necessary. Regardless of what you are printby criswilson10 - General
For quick and dirty fume extraction, you can always use a shop vac duct taped or zip tied to the body and with a long exhaust hose to outside. I run mine in a garage where I can open the door and run a fan on the other side of the garage to blow the fumes out. It's pretty much the same thing that I do when I'm doing a bunch of soldering.by criswilson10 - General
I guess I'll step up and say it and be that one that gets possibly flamed. :-) ABS is more dangerous than PLA. With that being said, now let me qualify it. Printing with either at the proper temperature with proper ventilation should not cause any problems (IMHO). But if you mess the temperature up and start over heating the plastic then the fumes from ABS are more toxic than PLA (Not that anby criswilson10 - General
The notes that I use on that motor tell me that to run it in bipolor mode. I need to join orange and black together and join red and yellow together. The wiring then becomes Blue (A), Brown (, Green (A|), White (B|) I've never had Keling send me a motor with the wrong wire colors on it, but there is always a first time. Wire it up. If it jitters then you probably have one or more coil wires conby criswilson10 - Stepper Motors, Servo Motors, DC Motors
DOH! Why haven't I ever thought of doing that??? Beats the heck out of the tension spring loaded idler pulley design that I typically use. And I'm going to try it tonight on a design I've been working on. Thanksby criswilson10 - General
Is it doable yes - look in a plumbing store for PEX fittings. Lots of simple plastic connectors Is it cheaper than a metal outdoor spigot/faucet, yes. Is it cheaper than a PEX spigot - I'm not sure, but I'm willing to bet it is.by criswilson10 - General
I thought of something that may be civil engineering, emergency housing, and reprap related - or maybe not. Water valves/manifolds for 55 gallon drum emergency/low tech water supplies. The majority of the 55 gallon type water supplies that I have seen have a metal outdoor faucet welded into the side of them with a hose pipe connected to them for bathing, washing, and I guess drinking water. Theby criswilson10 - General
I talked with our architect students that use a zcorp powder printer and for more solid output they undersize the print and oversize holes, coat the output with 2 ton epoxy, hang it to dry overnight, and then file off the excess drip marks. It sounds messy and expensive, but it might be an option for you. I'm not so sure how that would work for the pully teeth, but it could definitely strengthenby criswilson10 - General
For the zcorp powder printer, the plastic and epoxy parts that come out them are not very strong. I suppose you could try doing a UV cure on them, but I doubt that they would be able to handle the shear stress forces in a reprap. It would also be extremely expensive to create the parts that way. I think you could buy a whole reprap kit cheaper than the zcorp resin. For FEA, I don't know if anyonby criswilson10 - General
One option to do reduce some of the friction is to drill out the backside of the tip as well. I've used the welding tips for other extrusions and found that I could use a dremel 30 degree conical tip to clear out and taper the inside of the tips a bit more. You do need to leave a millimeter or two that is untapered at the tip to get a clean extrusion. The trick is figuring out how much untaperedby criswilson10 - Mechanics
I've fixed alot of so called "dead" plotters, and often it is something simple like a blown optoswitch or buldging power capacitor. You might want to give it a good once over to see what the problem is, then fix the problem, then you will know which parts are working for any electronics hacking.by criswilson10 - Controllers
All of the plumber's solder pastes that I have used were lead free, which means a higher temperature (than lead based solder) is needed. When doing plumbing repair it melts like regular solder - but I'm usually using an acetylene torch which is considerably hotter than pcb toaster oven or soldering iron. My guess on the grittiness (is that a word) is that you didn't get it hot enough to melt allby criswilson10 - Controllers
Make sure your threaded rods are straight. Take them out and roll them on a table and make sure that they are not bowed anywhere. I fought with mine for several days before ripping it apart to see what was wrong, and only then did I find out that one of my rods had a slight bow in it. I replaced it with a new straight one and everything ran fine.by criswilson10 - Mechanics
ok, so here is a write up a did a few years ago for a hobby robotics group to cover the basics. Let me know if I need to add more details. If you want the design tables, you can download the standard for free from NEMA after you create an account (free) with them. NEMA is short for "National Electrical Manufacturers Association". The standards that NEMA creates are developed by the manufacturersby criswilson10 - Mechanics
I'll try and get it written up this weekby criswilson10 - Mechanics
A NEMA 24 is 2.4 x 2.4, whoever made the webpage made a mistake. NEMA is a US based association that attempts to set standards for manufacturing. For stepper motors, they have chosen a label that lists the size first. So a NEMA 17 is a 1.7" cube and any NEMA 17 motor will mount in the same mount holes of another NEMA 17. This gives the manufacturers more flexibility with their designs because thby criswilson10 - Mechanics