many opportunities for poor welds, undercuts and rework of the weld in both manual and automated processes.


• Dies are not built to produce defect free parts, meaning no flash, etc.


• Typical Die, injection runners and gating runners tend to be pretty non-standard. Rather, they are ideas an engineer tried one time before coming up with a new unique solution


• Injection feeds are secondary to pattern shape having dramatic impacts on fill and quality.


First Steps first, Automating the Assembly


Although this may sound a bit counterintuitive, starting the automation project with the whole assembly is often the simplest and most clear cut automation project for a job shop. Automating assemblies are where we often see the biggest return on investment since most manual assemblies contain lots of variation.


Reducing variation


in the assembly can create gains both in the wax room as well as unforeseen gains and savings in all downstream processes.


The part we focused on


first is reference part #1 (See Figure 5 through 7) and a baseline was recorded for injection, inspection, assembly, metal scrap and metal yield.


information on injection improvements you may reference our second paper in


this series “Overcoming Common


Wax Injection Problems: The First Step Toward Automation”. As you can see from the chart


above, making minor modifications to the injection die and optimizing the injection process and parameters resulted in a dramatic reduction in the defect rate. Overall, the defect rate was reduced from 67.5% (pre-optimization) down to 1% with the optimized recipe run on the die after modification. This represents a 98.52% decrease in defect rate. It also resulted in a significant improvement in cycle time per batch of parts. The original recipe provided by the customer produced 19 acceptable


® For


parts per hour prior to optimization. After injection modification and a minor die modification, the run rate was increased to 98 parts per hour. This is a total improvement of 516% in acceptable parts per hour. The process changes and die modification combined achieved a throughput gain of more than 5 times on this machine with this part. Consequently, there was a significant reduction


in the required inspection requirements. pattern Inspection


savings were directly proportional to the defect rate in injection. The reduction in injection defects reduced the manual inspection from 100% inspection of every single part to a rate of only 1 in 50, greatly reducing operator handling time and the need for machine tending. Assembly of


this part historically


took between 11 and 20 minutes, and averaged 14 minutes over the range of assembly operators and the life of this product. Much of the variation found in the manual building of this assembly was attributed to operator turnover and the resulting variation in training and proficiency.


As alluded to earlier in order to automate the assembly of a process such as the assembly shown in figures 4 and 8 some changes where required. Typically this has been done through die and part modification to achieve pattern quality runners and parts with common features. Because of the customer constraints and challenges it was clear development of a new process would be required. Cooling processes for runners were developed to allow them to cool in a manner that guaranteed repeatable runners


that provide working surface. a consistent This process varied


depending on runner geometry always reducing variation without adding additional cost to the base line process. In addition, given the variety of part and gate geometry a new generation of specialized and easily customized tooling was developed to allow for a wide variety of parts to be manipulated with minimal cost.


After the assembly


process was successfully automated, the resulting cycle time of the finished


Figure 2: Part #3, Patterns to be automated


Figure 3: Part #2, Patterns to be automated


automated assembly including loading and unloading the machine is between 8.5 minutes yielding a 41% decrease in overall cycle time.


to note that until this point we had not focused on anything more than proving the capability of the automated system by building the assembly with the same spacing and number of parts per row as the proven manual process that resulted in 42 parts per assembly. Now that the process was proven on


this part, the real fun of finding additional process improvements and casting yield increases was ready to begin. Because of the flexibility of the End of Arm tooling, we were able to produce


January 2017 ❘ 27


It is important


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