Let the mods begin....

Running MDF thru my machine resulted in some slippage somewhere along the X axis I think...

Tried running up the current on the stepper but it just made it run hot so I put it back and came up with another solution.

I had some 1" heat shrink on hand (red and white) so I took the pivot arms out and put the heat shrink on them and shrunk them down. It is a 2 to 1 shrinkage so it worked out pretty good although I would rather had some 3/4" stuff on hand as the shrinkage was not as tight and smooth as I would like. Next trip to Skycraft, I will replace it with something a little smaller and tighter.

I have a bad habit of wanting to lean on the pivot arm handle. This will definitely cause the X axis to miss steps!

Also, while running Depron along the X axis, I noticed the pivot arm springs putting a lot more pressure on the foam than I would like, so I slightly raised up on the pivot arms to take the slack out (just high enough that the spring was ready to start tugging). I marked the position of the pivot arms and drilled a hole in both sides of the cabinet to attach some shelf supports from an old Saunders desk. A dowel or even a screw would have worked, but I had a couple of these left over and they are simple to remove if I wish to have the arms lower below 1/4" for balsa or whatever.

I inserted the shelf supports and lowered the pivot arms onto them. There is still pressure on the Depron and FFF and MDF, but not quite the full force that was there before.

The heat shrink gives the pivot arm rollers a bit more grip and the MDF cut great after doing both mods.

Before the shrink tape was put on the roller, the roller would not turn much of the time, but the shrink wrap grips the MDF now and both rollers turn instead of sliding over the surface. Attached files

 

No static that I have noticed and yes I have cut foam with it. The foam dust does stick to it pretty good though. I really think it helped a great deal. The pivot arm rollers used to slide across the surface of balsa when I would cut it, but now they roll like they were intended to do.

I was thinking the same thing about the different pressure settings. The placement that I have there now works perfect for Depron which was my biggest concern since it costs so much. I don't want the foam to get mashed down, yet I want there to be enough pressure to guide the foam without slipping.

Too much pressure can actually cause missed steps. I can easily cause the belt to slip teeth by holding the foam back with a bit of pressure.

I had a larger stepper motor on my MK1.5 so I exchanged it for the X axis stepper just to see if it was the stepper not holding or if the pulley was jumping a tooth when I held back the foam. I could still jam it up so I think the belt is jumping teeth. I think if the belt were the full width of the pulley there would less of an opportunity for that to happen.

 

(TT, I've never seen a triplicate post before. I deleted the other copies)

 

I removed the shrink wrap because at the time all I had was 1" and it does not do a great job of shrinking down to 1/2". Left a few bubbles that I did not like.

I ordered some smaller shrink tubing which ironically just came in today, so I have not had a chance to try it out.

I had been trying to solve a problem with skewing which is the biggest reason why I removed it, but it did not make any difference, so I will be putting it back on with the smaller diameter tubing this time.

I recently completed a pair of PVC rollers (Mod) to replace the lower drive rollers and covered them with 1/32" neoprene rubber. It protects the surface of Balsa and Depron and from initial testing, it appears to grip very well. I have run MDF and foam thru it with no slippage.

I still have some more testing to do and much video and pics to post, but my computer died in the midst of Christmas and I am still recovering from that so have not had time to get back in the shop. That is about to change. I am nearing completion of getting my computer back together and should be able to start processing the video maybe tonight or tomorrow.

The good thing about using the heat shrink tubing for the pressure rollers is that you can cut it off easily if you find it doesn't suit you.

That won't solve the problem of the bottom drive rollers gouging your foam or balsa, but you can put a carrier on the machine to isolate the material from the grip tape there.




Dorsal: I have seen the triplicate posts a few times... I just delete the duplicates. Could be from accelerator add ons... who knows.

 

Oh heavens no! It was my home Desktop machine with 2 years of accumulated files taking up a fully loaded 1TB drive.

That is why it is taking such a long time to recover from the damage...

 

Same here. Did not want to shrink very tight and left bubbles. I ordered some new stuff from HobbyKing. It came yesterday and I put it on this evening.

This one shrunk down all the way although I had to work it awhile, let it cool and work it some more. Started from the center and at the folds and worked out to the ends.

http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=13838

Did a nice job!

 

The reason you're having problem with the shrinking is because it is a solid piece of metal you are shrinking it on which takes away the heat and cools down the plastic. The warmer you can preheat the roller before you put on the heatshrink the better will the results be.

P.S. Just a crazy thought. it might work best if you hook up a car battery to the rod. It will heat up and shrink the plastic. You better do it in short zaps, though.