showtime56678 0 #1 December 6, 2017 Hello Everyone, We're using a Juki 1508NH to sew nylon webbing ranging from a few to many layers, sewing precise high quality stitches. Bought it new and it has ran great for a few years. Recently, the needle impacted a piece of metal (operator error) that was being sewn into the webbing (at slow speed), then shortly after broke a needle and the machine got jammed up. Took some convincing to free up the jam but got it working again, after the fact noticed some skipped stitches and that the timing was off. At this point I wanted to go through the entire machine to make sure it was in adjustment, following the engineers manual. Link to Engineer's Manual: http://semsi.com.mx/Manuales/JUKI/LU-1500N%20%20SEM02_.pdf I have run into a few discrepancies / issues with obtaining some of the specified settings outlined in the manual. Here is an overview of what I have done, but the one's with a red status indicate a problem area. I have summed up some questions at the end of the post. If you have this machine or something similar you may be able to assist me by letting me know how your machine is set up. On to the details... 1.) Needle Entry Position - Slight Adjustment Clearance between presser and walker bar should be 8.0mm +/- 0.1mm, my machine was set at 7.78mm so I adjusted it to 8.0mm. 2 & 3.) Longitudinal & Lateral Position of Feed Dog - Slight Adjustment Mine was slightly off, so I fine tuned it so the hole is centered with the needle. 4.) Height of Feed Dog - Already Correct Mine was correct at 0.84mm. 5.) Height of Hook - Already Correct Mine was correct at 1.0mm between top of the hook stopper tab and bottom of throat plate (slot). 6.) Adjusting Inner Hook Guide - Already Correct Mine was correct having a clearance of 0.2mm between guide and bobbing basket. 7.) Needle to Hook Timing (& Needle Bar) - Corrected Hook Rotation Timing Hook timing was retarded. Adjusted it so the hook tip meets center of needle once the needle rises 2.3mm, needle bar is set to 52.3mm, and hook tip meets needle 2.5mm above top of needle eyelet. Also, hook to needle distance is set correctly along with the deflection from the needle guard. 8.) Lift of the Presser Feet - Already Correct Mine are correct, they lift 9.0mm with the hand lever and 16.0mm with the knee lifter. 9.) Timing between Upper & Lower Shaft - Not able to adjust correctly? This is where it starts to get interesting... Per the manual the timing should be checked when the needle is at it's lowest dead point and feed is set to 0mm. With those conditions the orientation of the two set screws on the bottom shaft belt pulley should be parallel and perpendicular to the machine bed (manual image attached). In my case, the pulley was slightly advanced from that position. At this point in time I thought it must be close enough, because retarding the pulley by one tooth on the belt would go past the targeted position in the opposite direction. Since I received the machine new and didn't expect that the dealer would have changed this when setting up the machine, I figured it must be correct. More on this later... 10.) Feed Cam Timing 10.1) Horizontal Feed Cam Timing - Was never adjusted correctly? Another interesting observation... The manual states that the machine should again be rotated where the needle is at it's lowest dead point, and in this case the feed set to maximum. With these conditions the manual states that the feed dog should not move when the reverse lever is operated. My machine was not set up like this, and it wasn't set up like this since the day I received it from the dealer. I know because I always made it a point to active reverse at the point during the needle stroke in which the feed dogs would not shift, in my machine's case this was after the needle has slightly risen (maybe 1.0 - 2.0 mm). I went ahead and adjusted the machine per the manual, I'm assuming the manual is right but it seems odd that the feed motion would be centered at the point in time in which the hook tip has not yet reached the needle, more questions about this summed up at the end of this post... 10.2) Top Feed Cam Timing - Not able to adjust correctly Can't achieve the specifications outlined in the manual... This adjustment times the up and down movement of the inner foot. The manual states that the following things should all come into alignment at the same time when this is adjusted correctly: Needle tip Bottom if inner presser foot Top of throat plate Top of feed dog (not explicitly said in manual, but confirmed by Juki - more on that later) Image from manual attached. In my case, it is impossible for me to achieve alignment of all of these since my feed dog rises out of the throat plate before the needle arrives (needle is 9.0mm above throat plate when feed dog is level with throat plate). 11.) Feed Motion 11.1) Amount of Alternate Vertical Movement - Already Correct This setting basically translates to how high the feet lift. My machine is set to the standard setting in the manual of approx. 3.0mm. 11.2) Alternate Momentum - Already Correct This translates to setting the difference between the inner foot lift amount and the outer foot lift amount. My machine is set to the standard setting where the inner and outer feet have the same amount of lift. 12.) Needle Sway - Not applicable Not applicable to my machine. 13.) Stitch length of Normal & Reverse Feed - Not yet adjusted I haven't touched this yet because it is dependent on the horizontal feed cam adjustment, which I haven't finalized / committed to yet. 14.) Balancer - Not applicable Not applicable to my machine. There are some additional steps that I haven't explicitly checked but the operation of those items seems to be functioning as intended, or the step itself does not apply to my machine. After going through these steps...now I'm a little confused, I am not able to obtain some of the settings specified in the manual. To recap: Upper and lower shaft timing can not be set exactly as specified in the manual (half a tooth off, and can only adjust in one tooth increments) Timing of top feed cannot be obtained as specified (needle tip, throat plate, feed dog, and bottom of inner foot aligned). Problem is the feed dog rises out of the throat plate before the needle arrives. If focusing on the second issue it seems that the vertical movement of the feed dog is ahead of the needle, it's important to know that with this machine the eccentric for the feed dog vertical movement is clocked / fixed to the bottom shaft and cannot be adjusted. As such, the vertical movement of the feed dog is completely regulated by the timing between the upper and bottom shaft. Hmm, makes sense that my upper and bottom shaft timing doesn't seem perfect (again, bottom shaft is advanced slightly, which makes sense that the feed dog vertical movement is advanced). I went ahead and tried retarding the bottom shaft by one tooth on the pulley (in relation to the belt / upper shaft)... This improved the condition of the feed dog to needle timing (them meeting at the top of the throat plate), but it still wasn't quite perfect. In addition, the lower pulley position seemed to still not be correct per the manual - but this time the discrepancy is in the opposite direction. See attached image showing the condition of the feed dog rise / top timing, along with the orientation of the lower to upper shaft timing. The top row in the image shows what the machine looked like with the existing top / bottom shaft timing, the bottom shows after a 1 tooth change... In contact with Juki... At this point I'm not sure if the manual is incorrect or if something else in the machine is knocked out of whack which is not allowing me to obtain some of these adjustments. I have been in contact with Juki and so far they agree that something doesn't look right. So far they have confirmed with their own machines / pictures that the manual is correct, those adjustments should be able to be obtained. They are still investigating what may be causing my discrepancies. The only thing I can think of at this point is the needle counterweight on the end of the upper shaft being shifted out of position. I suspect that it would be clocked to the shaft with a flat for the set screw or something similar rendering that impossible, however in the parts book it shows no such thing (but the parts book has been misleading before.) However, I don't want to start messing with that until I know more. I feel that I would be able to get to the bottom of all of this if I just had a new / properly adjusted machine of the same model to reference. As an alternative, if anyone has a 1508NH or 1500 series maybe you could help me out by answering a few questions: Does the top of your feed dog, top of your throat plate, point of needle, and bottom of inner foot all come into alignment on the down stroke (per the manual)? Or, does your feed dog rise out of the throat plate before the needle arrives? Does your bottom shaft timing belt pulley align perfectly with the machine bed as specified in the manual when the needle is at dead bottom? When your needle is at dead bottom and you actuate the reverse lever, does the feed dog remain stationary? Alternatively, does the feed dog remain stationary when using the reverse lever only after the needle has slightly risen? General Questions: I noticed the 1541 specifies centering the horizontal feed (feed dog doesn't move when actuating reverse lever) when the hook tip meets the needle. The 1508NH (my machine) specifies when the needle is at bottom dead center. The 1541 seems to make more sense to me since the hook to needle timing would be the same in forward and reverse (I presume). When centering at needle bottom dead center (before hook arrives), it seems to make the hook timing retarded when operating in reverse. Any idea why the difference in the specifications between these similar machines? Does it make sense to center the feed timing before the hook meets the needle (when needle is at bottom dead center - as specified for the 1508 models)? Our contact at Juki is telling us that the stitch quality will be the best when the feed dog doesn't rise out of the throat plate before the needle arrives (they should meet at the same time). It makes sense, is this how most walking foot machines are set up? Is there the possibility that this particular machine (1508NH) is supposed to have the feed dog rise out before the needle arrives? Quote Share this post Link to post Share on other sites
