一.為什麼 大孔中要加小孔(即卸力孔) 

   這其實跟鑽刀的排屑有關了,當鑽刀越大孔,排屑量也越大(當然這也得跟轉速,下刀速的引數有關係),通常當鑽刀越大,轉速越慢,下刀速也越慢(因為要保證它的排屑通暢)。

    這裡科普一下鑽刀的【進刀速度】,【轉速】,【進刀量】之間的關係是怎樣的.

    進刀速度、轉速之間的關係對於鑽頭來講，切削量越大，產生的粉塵顆粒就會更大，部分切屑尤其是銅絲，會纏繞到鑽頭，從而嚴重影響孔壁的質量。相應的，切削量越小，在鑽孔時，鑽頭停留在孔內的時間就會越長，產生的鑽汙就會越多。

   進刀量、轉速之間的關係

   為了保證大孔的排屑效能好，PCB行業作法是,在鑽大孔之前,提前在大孔中間鑽幾個小孔,先小孔排除一定孔屑,等再鑽大孔時,孔屑變少了。不會再造成大孔排屑不暢。

二.大孔加小孔實現原理

求解方法:（具體可以看下方函式）
1.通過已知大孔6.0mm，小孔與小孔間距:0.2mm
小孔個數,求出最大內切孔尺寸=2.585mm

三.C#簡易程式碼實現:

    1.大孔加小孔程式碼

            #region 大孔加卸力孔  ydkdrl
            List<gP> MaxHoleList = glayer.Plist.Where(tt => tt.width >= 3200 && tt.width <= 6300
 
).ToList();
            if (MaxHoleList.Count() > 0)
            {
                for (int i = 0; i < MaxHoleList.Count; i++)
                {
             //求內切孔函式共6引數 大孔尺寸  小孔尺寸  小孔個數   小孔與小孔間距    小孔與大孔間距   旋轉角度
             //當小孔尺寸不填，由函式自動計算小孔孔徑，否則以填寫小孔孔徑為準
                    List<gP> smallHoleList = calc2.p_small_hole_Plist(MaxHoleList[i], 0, 3, 0.2, 0.1,30);
                    addCOM.pad(smallHoleList);
                }
            }
            #endregion

     2.計算函式(關鍵在於此函式實現)

        /// <summary>
        /// 求點P【內切圓Plist座標】
        /// </summary>
        /// <param name="p">點P</param>
        /// <param name="small_hole_size">內切圓尺寸,填寫為0時自動計算</param>
        /// <param name="small_hole_count">內切圓個數</param>
        /// <param name="small2small">內切圓與內切圓間距</param>
        /// <param name="small2big">內切圓與外圓間距</param>
        /// <param name="ang_rotate">內切圓轉旋角度</param>
        /// <param name="units">單位:mm/inch</param>
        /// <returns>返回:【內切圓Plist座標】</returns>
        public List<gP> p_small_hole_Plist(gP p, double small_hole_size, double small_hole_count = 3, double small2small = 0, double small2big = 0, double ang_rotate = 0)
        {
            List<gP> list_p = new List<gP>();
            double ang_single, ang_sum, dia_hole;
            gP tempP;
            tempP.mirror = false;
            tempP.attribut = "";
            tempP.angle = 0;
            tempP.negative = false;
            tempP.symbols = "";
            dia_hole = p.width / 1000 - small2big * 2; //units mm
            p.width = p.width - small2big * 2000;      //units um
            if (small_hole_size < 0.001)
                    small_hole_size = Math.Floor(p_small_hole_size(p, small2small, small_hole_count) / 0.05) * 0.05; //um-->mm
            ang_single = 360 / small_hole_count;
            ang_sum = 90 - ang_rotate;
            for (int i = 0; i <= small_hole_count - 1; i++)
            {
                tempP.p = p_val_ang(p.p, (dia_hole - small_hole_size) * 0.5, ang_sum);
                tempP.width = small_hole_size * 1000;
                tempP.symbols = "r" + tempP.width.ToString();
                ang_sum += ang_single;
                list_p.Add(tempP);
            }
            return list_p;
        }
        /// <summary>
        /// 求點P【最大內切圓尺寸】
        /// </summary>
        /// <param name="p">點P</param>
        /// <param name="small_hole_space">內切圓與內切圓間距</param>
        /// <param name="small_hole_count">內切圓個數</param>
        /// <returns>返回:【內切圓尺寸】</returns>
        public double p_small_hole_size(gP p, double small_hole_space = 0, double small_hole_count = 3)
        {
            double sin_val = Math.Sin(180 / small_hole_count * Math.PI / 180);
            return (sin_val * p.width * 0.0005 - 0.5 * small_hole_space) / (1 + sin_val) * 2;
        }
        /// <summary>
        /// 求增量座標
        /// </summary>
        /// <param name="ps">起點</param>
        /// <param name="val">增量值</param>
        /// <param name="ang_direction">角度</param>
        /// <returns></returns>
        public gPoint p_val_ang(gPoint ps, double val, double ang_direction)
        {
            gPoint pe;
            pe.x = ps.x + val * Math.Cos(ang_direction * Math.PI / 180);
            pe.y = ps.y + val * Math.Sin(ang_direction * Math.PI / 180);
            return pe;
        }

   3.Point,PAD資料結構

    /// <summary>
    /// PAD  資料型別
    /// </summary>
    public struct gP
    {
        public gP(double x_val, double y_val, double width_)
        {
            this.p = new gPoint(x_val, y_val);
            this.negative = false;
            this.angle = 0;
            this.mirror = false;
            this.symbols = "r";
            this.attribut = string.Empty;
            this.width = width_;
        }
        public gPoint p;
        public bool negative;//polarity-- positive  negative
        public double angle;
        public bool mirror;
        public string symbols;
        public string attribut;
        public double width;
        public static gP operator +(gP p1, gP p2)
        {
            p1.p += p2.p;
            return p1;
        }
        public static gP operator -(gP p1, gP p2)
        {
            p1.p -= p2.p;
            return p1;
        }
    }
    /// <summary>
    /// 點  資料型別 (XY)
    /// </summary>
    public struct gPoint
    {
        public gPoint(gPoint p_)
        {
            this.x = p_.x;
            this.y = p_.y;
        }
        public gPoint(double x_val, double y_val)
        {
            this.x = x_val;
            this.y = y_val;
        }
        public double x;
        public double y;
        public static gPoint operator +(gPoint p1, gPoint p2)
        {
            p1.x += p2.x;
            p1.y += p2.y;
            return p1;
        }
        public static gPoint operator -(gPoint p1, gPoint p2)
        {
            p1.x -= p2.x;
            p1.y -= p2.y;
            return p1;
        }


    }

四.大孔加小孔指令碼UI

五.實現效果