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Lab talk, the good, the bad, and the ugly
Dental-CAM
Wieland Zenotec select PMMA milling
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<blockquote data-quote="brayks" data-source="post: 282921" data-attributes="member: 11275"><p>CHL speaks the truth. another thing to consider is that as your spindle speed increases your programmed feed rate needs to increase to maintain the proper surface feed (SFM) as recommended for the tool and material. This will help as the "burning" of material will be less of an issue. However, even if your spindle can produce the torque required, if your machine and fixturing is not rigid enough, the resultant increased vibration will drastically decrease your tool life, significantly decrease restoration finish quality, and almost certainly cause chipping of the margins.</p><p></p><p>Spindle torque at operating RPM and machine/fixture rigidity are among the most important machine characteristics when evaluating performance of any milling machine and often the most misunderstood and overlooked.</p><p></p><p>In machining any material, the heat generated by the cutting process must be "absorbed" in the chip (not the work-piece or cutting tool) with the resultant chip being cleared and not allowed to remain in the cutting area to be accumulated, re-cut and transferred to the tool. Therefore proper cutting parameters (rpm, feed rate, depth & width of cut) must be maintained. In high-speed machining, these parameters, including <a href="https://www.tormach.com/blog/chip-thinning-cut-aggressively/" target="_blank">radial chip thinning</a> must be taken into account.</p></blockquote><p></p>
[QUOTE="brayks, post: 282921, member: 11275"] CHL speaks the truth. another thing to consider is that as your spindle speed increases your programmed feed rate needs to increase to maintain the proper surface feed (SFM) as recommended for the tool and material. This will help as the "burning" of material will be less of an issue. However, even if your spindle can produce the torque required, if your machine and fixturing is not rigid enough, the resultant increased vibration will drastically decrease your tool life, significantly decrease restoration finish quality, and almost certainly cause chipping of the margins. Spindle torque at operating RPM and machine/fixture rigidity are among the most important machine characteristics when evaluating performance of any milling machine and often the most misunderstood and overlooked. In machining any material, the heat generated by the cutting process must be "absorbed" in the chip (not the work-piece or cutting tool) with the resultant chip being cleared and not allowed to remain in the cutting area to be accumulated, re-cut and transferred to the tool. Therefore proper cutting parameters (rpm, feed rate, depth & width of cut) must be maintained. In high-speed machining, these parameters, including [URL='https://www.tormach.com/blog/chip-thinning-cut-aggressively/']radial chip thinning[/URL] must be taken into account. [/QUOTE]
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Lab talk, the good, the bad, and the ugly
Dental-CAM
Wieland Zenotec select PMMA milling
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