Importance of machine maintenance

Maintaining machine productivity is vital to the overall profitability of your embroidery operations. Coats Embroidery have developed a highly effective method of highlighting defects and inefficiencies which takes less than an hour to complete.

The method uses the principle that stoppages and thread breaks do not occur randomly - but that they indicate a problem area which requires attention; by noting on which head the problem occurs and the type of fault - we can quickly build up a picture of the problem areas on the mahcine. This information provides machine maintenance engineers with all the information they require to effect the necessary repairs.

Method:

• download the productivity form below and print out a couple of copies
• note down the machine number and the start time of the test period
• run the machine at normal speed during a typical job
• note down details of every stoppage; the type (see key) and head #
• run trial for 2 hours or 30 stoppages - whichever is quicker

Category of stoppage:

• T = thread break
• N = needle break
• B = bobbin run-out
• J = bobbin jam (birds nest)
• P = ply run-back (single ply break)

Example of completed form:

enlarge photo

Interpretation of results:

Thread breaks: excessive and random thread breaks indicate that the timing requires adjustment or that the bobbin case is scratched - normally the thread should break on a 15-head machine only around 2-3 times per hour; if a particular head is breaking much more frequently then it is better to switch that head off until it can be repaired; a head should be switched off after 3 consecutive thread breaks.

Another cause of thread breakage is applying the incorrect tension (see section on 'Tension' on this site). Breaks caused by friction build-up when embroidering thick fabric such as denim or leather & plastic can be solved by use of wax paper underneath the piece during embroidery

If thread (or needle) breakage occuring at the same point in each design indicates a fault in the digitising; normally too great a stitch density in bthe area causing the breaks; reducing the number of stitches in that area will remove the problem

Needle breaks: indicates a problem with the timing - it is best to switch off that head if it occurs more than twice in an hour because it could damage the stitch plate or bobbin case which becomes much more expensive to repair. If embroidering a course piece of fabric or leather sometimes a needle break can be caused by using the wrong type of needle - for example using a DB1 needle type when the machine's timing is set up for a DBxK5 type - to pantograph moving before the needle is fully withdrawn from the material or scratching along the surface of the fabric

Bobbin run-out: if this becomes a frequent cause of stoppage - for example when making badges with large stitch-counts - many operators use the '3 strikes and you are out' principle; on the third bobbin run-out they change all the remaining bobbins whether they have run out or not; this strikes a balance between some wastage vs. constant stopping of the machine. You may consider using a pre-wound-bobbin on important jobs due to greater length/bobbin (over 30% more than a self-wind) and also the precision wind and smooth offtake of the pre-wound

Bobbin Jam: this can be caused by a number of factors; the most common is the presence of some kind of glue on the fabric; this causes the top thread to become stuck underneath the stitchplate; the only way to stop this happening is to eliminate the cause of the stickiness. Alternatively a scratch on the bobbin case can cause mis-stitches leading to a bobbin jam; a scratch on the edge of the bobbin reel itself; if more than two occur on the same head change the bobbin reel or use a pre-wound. Lastly a build-up of 'fluff' under the checkspring on the bobbin case can restrict the smooth flow of thread - check for 'fluff' once per day (flick a thin knife under the checkspring)

Ply run-back: incorrect tension is the most common cause of this type of break - normally when using polyester thread on a machine used to working with rayon (see 'Tension' section): alternatively it can be caused by a scratch on the outside of the bobbin case; lastly poor quality thread (especially polyester) exhibits this tendancy more often; this is due to poor or uneven twisting of the plies during manufacture. Finally ply run-backs can indicate that the cutters (either top or bottom) are not sharp enough - polyester thread tends to blunt them so they require attention more often than for rayon threads

Summary:

The Productivity analysis is an invaluable tool for telling you about the state of your embroidery machine; in the hands of machine engineers & mechanics it will invoke a higher level of understanding of the problems - they can advise you over the telephone or be better prepared for maintenance visits - bring with them the tools and spare parts required to fix the relevant problems

As a general rule; if an embroidery head has more than 3 or 4 of the same types of stoppage within a short space of time - switch off that head until a qualified mechanic can sort out the problem; every time a machine stops will affect the qoverall quality of the embroidery on the other heads; the Three Musketeer's phrase 'all-for-one' and 'one-for-all' applies to embroidery quality as well.

These tests should be run on each machine on a typical job every 2-4 days to check the general health of the machine; more frequently if a machine is stopping more than usual

Dowloading Productivity Analysis sheet:

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